From 9af9dcf11bda3e2c0e24c1acaacb8685ad974e93 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 24 Jun 2021 11:41:00 +0200
Subject: x86/xen: Mark cpu_bringup_and_idle() as dead_end_function

The asm_cpu_bringup_and_idle() function is required to push the return
value on the stack in order to make ORC happy, but the only reason
objtool doesn't complain is because of a happy accident.

The thing is that asm_cpu_bringup_and_idle() doesn't return, so
validate_branch() never terminates and falls through to the next
function, which in the normal case is the hypercall_page. And that, as
it happens, is 4095 NOPs and a RET.

Make asm_cpu_bringup_and_idle() terminate on it's own, by making the
function it calls as a dead-end. This way we no longer rely on what
code happens to come after.

Fixes: c3881eb58d56 ("x86/xen: Make the secondary CPU idle tasks reliable")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/20210624095147.693801717@infradead.org
---
 tools/objtool/check.c | 1 +
 1 file changed, 1 insertion(+)

(limited to 'tools/objtool')

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index e5947fbb9e7a..0e3981d91afc 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -173,6 +173,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"rewind_stack_do_exit",
 		"kunit_try_catch_throw",
 		"xen_start_kernel",
+		"cpu_bringup_and_idle",
 	};
 
 	if (!func)
-- 
cgit v1.2.3


From 8b946cc38e063f0f7bb67789478c38f6d7d457c9 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 24 Jun 2021 11:41:01 +0200
Subject: objtool: Introduce CFI hash

Andi reported that objtool on vmlinux.o consumes more memory than his
system has, leading to horrific performance.

This is in part because we keep a struct instruction for every
instruction in the file in-memory. Shrink struct instruction by
removing the CFI state (which includes full register state) from it
and demand allocating it.

Given most instructions don't actually change CFI state, there's lots
of repetition there, so add a hash table to find previous CFI
instances.

Reduces memory consumption (and runtime) for processing an
x86_64-allyesconfig:

  pre:  4:40.84 real,   143.99 user,    44.18 sys,      30624988 mem
  post: 2:14.61 real,   108.58 user,    25.04 sys,      16396184 mem

Suggested-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210624095147.756759107@infradead.org
---
 tools/objtool/arch/x86/decode.c       |  20 ++---
 tools/objtool/check.c                 | 154 ++++++++++++++++++++++++++++++----
 tools/objtool/include/objtool/arch.h  |   2 +-
 tools/objtool/include/objtool/cfi.h   |   2 +
 tools/objtool/include/objtool/check.h |   2 +-
 tools/objtool/orc_gen.c               |  15 +++-
 6 files changed, 160 insertions(+), 35 deletions(-)

(limited to 'tools/objtool')

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index bc821056aba9..3435a32afbd1 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -779,34 +779,32 @@ int arch_rewrite_retpolines(struct objtool_file *file)
 	return 0;
 }
 
-int arch_decode_hint_reg(struct instruction *insn, u8 sp_reg)
+int arch_decode_hint_reg(u8 sp_reg, int *base)
 {
-	struct cfi_reg *cfa = &insn->cfi.cfa;
-
 	switch (sp_reg) {
 	case ORC_REG_UNDEFINED:
-		cfa->base = CFI_UNDEFINED;
+		*base = CFI_UNDEFINED;
 		break;
 	case ORC_REG_SP:
-		cfa->base = CFI_SP;
+		*base = CFI_SP;
 		break;
 	case ORC_REG_BP:
-		cfa->base = CFI_BP;
+		*base = CFI_BP;
 		break;
 	case ORC_REG_SP_INDIRECT:
-		cfa->base = CFI_SP_INDIRECT;
+		*base = CFI_SP_INDIRECT;
 		break;
 	case ORC_REG_R10:
-		cfa->base = CFI_R10;
+		*base = CFI_R10;
 		break;
 	case ORC_REG_R13:
-		cfa->base = CFI_R13;
+		*base = CFI_R13;
 		break;
 	case ORC_REG_DI:
-		cfa->base = CFI_DI;
+		*base = CFI_DI;
 		break;
 	case ORC_REG_DX:
-		cfa->base = CFI_DX;
+		*base = CFI_DX;
 		break;
 	default:
 		return -1;
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0e3981d91afc..d9f32739b433 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -5,6 +5,7 @@
 
 #include <string.h>
 #include <stdlib.h>
+#include <sys/mman.h>
 
 #include <arch/elf.h>
 #include <objtool/builtin.h>
@@ -26,7 +27,11 @@ struct alternative {
 	bool skip_orig;
 };
 
-struct cfi_init_state initial_func_cfi;
+static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
+
+static struct cfi_init_state initial_func_cfi;
+static struct cfi_state init_cfi;
+static struct cfi_state func_cfi;
 
 struct instruction *find_insn(struct objtool_file *file,
 			      struct section *sec, unsigned long offset)
@@ -266,6 +271,78 @@ static void init_insn_state(struct insn_state *state, struct section *sec)
 		state->noinstr = sec->noinstr;
 }
 
+static struct cfi_state *cfi_alloc(void)
+{
+	struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
+	if (!cfi) {
+		WARN("calloc failed");
+		exit(1);
+	}
+	nr_cfi++;
+	return cfi;
+}
+
+static int cfi_bits;
+static struct hlist_head *cfi_hash;
+
+static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
+{
+	return memcmp((void *)cfi1 + sizeof(cfi1->hash),
+		      (void *)cfi2 + sizeof(cfi2->hash),
+		      sizeof(struct cfi_state) - sizeof(struct hlist_node));
+}
+
+static inline u32 cfi_key(struct cfi_state *cfi)
+{
+	return jhash((void *)cfi + sizeof(cfi->hash),
+		     sizeof(*cfi) - sizeof(cfi->hash), 0);
+}
+
+static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
+{
+	struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
+	struct cfi_state *obj;
+
+	hlist_for_each_entry(obj, head, hash) {
+		if (!cficmp(cfi, obj)) {
+			nr_cfi_cache++;
+			return obj;
+		}
+	}
+
+	obj = cfi_alloc();
+	*obj = *cfi;
+	hlist_add_head(&obj->hash, head);
+
+	return obj;
+}
+
+static void cfi_hash_add(struct cfi_state *cfi)
+{
+	struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
+
+	hlist_add_head(&cfi->hash, head);
+}
+
+static void *cfi_hash_alloc(unsigned long size)
+{
+	cfi_bits = max(10, ilog2(size));
+	cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
+			PROT_READ|PROT_WRITE,
+			MAP_PRIVATE|MAP_ANON, -1, 0);
+	if (cfi_hash == (void *)-1L) {
+		WARN("mmap fail cfi_hash");
+		cfi_hash = NULL;
+	}  else if (stats) {
+		printf("cfi_bits: %d\n", cfi_bits);
+	}
+
+	return cfi_hash;
+}
+
+static unsigned long nr_insns;
+static unsigned long nr_insns_visited;
+
 /*
  * Call the arch-specific instruction decoder for all the instructions and add
  * them to the global instruction list.
@@ -276,7 +353,6 @@ static int decode_instructions(struct objtool_file *file)
 	struct symbol *func;
 	unsigned long offset;
 	struct instruction *insn;
-	unsigned long nr_insns = 0;
 	int ret;
 
 	for_each_sec(file, sec) {
@@ -302,7 +378,6 @@ static int decode_instructions(struct objtool_file *file)
 			memset(insn, 0, sizeof(*insn));
 			INIT_LIST_HEAD(&insn->alts);
 			INIT_LIST_HEAD(&insn->stack_ops);
-			init_cfi_state(&insn->cfi);
 
 			insn->sec = sec;
 			insn->offset = offset;
@@ -1137,7 +1212,6 @@ static int handle_group_alt(struct objtool_file *file,
 		memset(nop, 0, sizeof(*nop));
 		INIT_LIST_HEAD(&nop->alts);
 		INIT_LIST_HEAD(&nop->stack_ops);
-		init_cfi_state(&nop->cfi);
 
 		nop->sec = special_alt->new_sec;
 		nop->offset = special_alt->new_off + special_alt->new_len;
@@ -1546,10 +1620,11 @@ static void set_func_state(struct cfi_state *state)
 
 static int read_unwind_hints(struct objtool_file *file)
 {
+	struct cfi_state cfi = init_cfi;
 	struct section *sec, *relocsec;
-	struct reloc *reloc;
 	struct unwind_hint *hint;
 	struct instruction *insn;
+	struct reloc *reloc;
 	int i;
 
 	sec = find_section_by_name(file->elf, ".discard.unwind_hints");
@@ -1587,19 +1662,24 @@ static int read_unwind_hints(struct objtool_file *file)
 		insn->hint = true;
 
 		if (hint->type == UNWIND_HINT_TYPE_FUNC) {
-			set_func_state(&insn->cfi);
+			insn->cfi = &func_cfi;
 			continue;
 		}
 
-		if (arch_decode_hint_reg(insn, hint->sp_reg)) {
+		if (insn->cfi)
+			cfi = *(insn->cfi);
+
+		if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
 			WARN_FUNC("unsupported unwind_hint sp base reg %d",
 				  insn->sec, insn->offset, hint->sp_reg);
 			return -1;
 		}
 
-		insn->cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
-		insn->cfi.type = hint->type;
-		insn->cfi.end = hint->end;
+		cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
+		cfi.type = hint->type;
+		cfi.end = hint->end;
+
+		insn->cfi = cfi_hash_find_or_add(&cfi);
 	}
 
 	return 0;
@@ -2453,13 +2533,18 @@ static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn
 	if (!insn->alt_group)
 		return 0;
 
+	if (!insn->cfi) {
+		WARN("CFI missing");
+		return -1;
+	}
+
 	alt_cfi = insn->alt_group->cfi;
 	group_off = insn->offset - insn->alt_group->first_insn->offset;
 
 	if (!alt_cfi[group_off]) {
-		alt_cfi[group_off] = &insn->cfi;
+		alt_cfi[group_off] = insn->cfi;
 	} else {
-		if (memcmp(alt_cfi[group_off], &insn->cfi, sizeof(struct cfi_state))) {
+		if (cficmp(alt_cfi[group_off], insn->cfi)) {
 			WARN_FUNC("stack layout conflict in alternatives",
 				  insn->sec, insn->offset);
 			return -1;
@@ -2510,9 +2595,14 @@ static int handle_insn_ops(struct instruction *insn,
 
 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
 {
-	struct cfi_state *cfi1 = &insn->cfi;
+	struct cfi_state *cfi1 = insn->cfi;
 	int i;
 
+	if (!cfi1) {
+		WARN("CFI missing");
+		return false;
+	}
+
 	if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
 
 		WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
@@ -2697,7 +2787,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 			   struct instruction *insn, struct insn_state state)
 {
 	struct alternative *alt;
-	struct instruction *next_insn;
+	struct instruction *next_insn, *prev_insn = NULL;
 	struct section *sec;
 	u8 visited;
 	int ret;
@@ -2726,15 +2816,25 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 
 			if (insn->visited & visited)
 				return 0;
+		} else {
+			nr_insns_visited++;
 		}
 
 		if (state.noinstr)
 			state.instr += insn->instr;
 
-		if (insn->hint)
-			state.cfi = insn->cfi;
-		else
-			insn->cfi = state.cfi;
+		if (insn->hint) {
+			state.cfi = *insn->cfi;
+		} else {
+			/* XXX track if we actually changed state.cfi */
+
+			if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
+				insn->cfi = prev_insn->cfi;
+				nr_cfi_reused++;
+			} else {
+				insn->cfi = cfi_hash_find_or_add(&state.cfi);
+			}
+		}
 
 		insn->visited |= visited;
 
@@ -2884,6 +2984,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 			return 1;
 		}
 
+		prev_insn = insn;
 		insn = next_insn;
 	}
 
@@ -3139,10 +3240,20 @@ int check(struct objtool_file *file)
 	int ret, warnings = 0;
 
 	arch_initial_func_cfi_state(&initial_func_cfi);
+	init_cfi_state(&init_cfi);
+	init_cfi_state(&func_cfi);
+	set_func_state(&func_cfi);
+
+	if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
+		goto out;
+
+	cfi_hash_add(&init_cfi);
+	cfi_hash_add(&func_cfi);
 
 	ret = decode_sections(file);
 	if (ret < 0)
 		goto out;
+
 	warnings += ret;
 
 	if (list_empty(&file->insn_list))
@@ -3193,6 +3304,13 @@ int check(struct objtool_file *file)
 		warnings += ret;
 	}
 
+	if (stats) {
+		printf("nr_insns_visited: %ld\n", nr_insns_visited);
+		printf("nr_cfi: %ld\n", nr_cfi);
+		printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
+		printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
+	}
+
 out:
 	/*
 	 *  For now, don't fail the kernel build on fatal warnings.  These
diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h
index 062bb6e9b865..a5ab6829511f 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -83,7 +83,7 @@ unsigned long arch_dest_reloc_offset(int addend);
 
 const char *arch_nop_insn(int len);
 
-int arch_decode_hint_reg(struct instruction *insn, u8 sp_reg);
+int arch_decode_hint_reg(u8 sp_reg, int *base);
 
 bool arch_is_retpoline(struct symbol *sym);
 
diff --git a/tools/objtool/include/objtool/cfi.h b/tools/objtool/include/objtool/cfi.h
index fd5cb0bed9bf..f11d1ac1dadf 100644
--- a/tools/objtool/include/objtool/cfi.h
+++ b/tools/objtool/include/objtool/cfi.h
@@ -7,6 +7,7 @@
 #define _OBJTOOL_CFI_H
 
 #include <arch/cfi_regs.h>
+#include <linux/list.h>
 
 #define CFI_UNDEFINED		-1
 #define CFI_CFA			-2
@@ -24,6 +25,7 @@ struct cfi_init_state {
 };
 
 struct cfi_state {
+	struct hlist_node hash; /* must be first, cficmp() */
 	struct cfi_reg regs[CFI_NUM_REGS];
 	struct cfi_reg vals[CFI_NUM_REGS];
 	struct cfi_reg cfa;
diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index 56d50bc50c10..07e99c25c7ac 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -60,7 +60,7 @@ struct instruction {
 	struct list_head alts;
 	struct symbol *func;
 	struct list_head stack_ops;
-	struct cfi_state cfi;
+	struct cfi_state *cfi;
 };
 
 static inline bool is_static_jump(struct instruction *insn)
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index dc9b7dd314b0..ddacb4215748 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -13,13 +13,19 @@
 #include <objtool/warn.h>
 #include <objtool/endianness.h>
 
-static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi)
+static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
+			  struct instruction *insn)
 {
-	struct instruction *insn = container_of(cfi, struct instruction, cfi);
 	struct cfi_reg *bp = &cfi->regs[CFI_BP];
 
 	memset(orc, 0, sizeof(*orc));
 
+	if (!cfi) {
+		orc->end = 0;
+		orc->sp_reg = ORC_REG_UNDEFINED;
+		return 0;
+	}
+
 	orc->end = cfi->end;
 
 	if (cfi->cfa.base == CFI_UNDEFINED) {
@@ -162,7 +168,7 @@ int orc_create(struct objtool_file *file)
 			int i;
 
 			if (!alt_group) {
-				if (init_orc_entry(&orc, &insn->cfi))
+				if (init_orc_entry(&orc, insn->cfi, insn))
 					return -1;
 				if (!memcmp(&prev_orc, &orc, sizeof(orc)))
 					continue;
@@ -186,7 +192,8 @@ int orc_create(struct objtool_file *file)
 				struct cfi_state *cfi = alt_group->cfi[i];
 				if (!cfi)
 					continue;
-				if (init_orc_entry(&orc, cfi))
+				/* errors are reported on the original insn */
+				if (init_orc_entry(&orc, cfi, insn))
 					return -1;
 				if (!memcmp(&prev_orc, &orc, sizeof(orc)))
 					continue;
-- 
cgit v1.2.3


From f56dae88a81fded66adf2bea9922d1d98d1da14f Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 24 Jun 2021 11:41:02 +0200
Subject: objtool: Handle __sanitize_cov*() tail calls

Turns out the compilers also generate tail calls to __sanitize_cov*(),
make sure to also patch those out in noinstr code.

Fixes: 0f1441b44e82 ("objtool: Fix noinstr vs KCOV")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20210624095147.818783799@infradead.org
---
 tools/objtool/arch/x86/decode.c      |  20 +++++
 tools/objtool/check.c                | 158 +++++++++++++++++++----------------
 tools/objtool/include/objtool/arch.h |   1 +
 3 files changed, 105 insertions(+), 74 deletions(-)

(limited to 'tools/objtool')

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 3435a32afbd1..340a3dce94a0 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -659,6 +659,26 @@ const char *arch_nop_insn(int len)
 	return nops[len-1];
 }
 
+#define BYTE_RET	0xC3
+
+const char *arch_ret_insn(int len)
+{
+	static const char ret[5][5] = {
+		{ BYTE_RET },
+		{ BYTE_RET, BYTES_NOP1 },
+		{ BYTE_RET, BYTES_NOP2 },
+		{ BYTE_RET, BYTES_NOP3 },
+		{ BYTE_RET, BYTES_NOP4 },
+	};
+
+	if (len < 1 || len > 5) {
+		WARN("invalid RET size: %d\n", len);
+		return NULL;
+	}
+
+	return ret[len-1];
+}
+
 /* asm/alternative.h ? */
 
 #define ALTINSTR_FLAG_INV	(1 << 15)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index d9f32739b433..c6f206fee8ff 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -904,6 +904,79 @@ static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *i
 	return insn->reloc;
 }
 
+static void remove_insn_ops(struct instruction *insn)
+{
+	struct stack_op *op, *tmp;
+
+	list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
+		list_del(&op->list);
+		free(op);
+	}
+}
+
+static void add_call_dest(struct objtool_file *file, struct instruction *insn,
+			  struct symbol *dest, bool sibling)
+{
+	struct reloc *reloc = insn_reloc(file, insn);
+
+	insn->call_dest = dest;
+	if (!dest)
+		return;
+
+	if (insn->call_dest->static_call_tramp) {
+		list_add_tail(&insn->call_node,
+			      &file->static_call_list);
+	}
+
+	/*
+	 * Many compilers cannot disable KCOV with a function attribute
+	 * so they need a little help, NOP out any KCOV calls from noinstr
+	 * text.
+	 */
+	if (insn->sec->noinstr &&
+	    !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
+		if (reloc) {
+			reloc->type = R_NONE;
+			elf_write_reloc(file->elf, reloc);
+		}
+
+		elf_write_insn(file->elf, insn->sec,
+			       insn->offset, insn->len,
+			       sibling ? arch_ret_insn(insn->len)
+			               : arch_nop_insn(insn->len));
+
+		insn->type = sibling ? INSN_RETURN : INSN_NOP;
+	}
+
+	if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) {
+		if (sibling)
+			WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
+
+		if (reloc) {
+			reloc->type = R_NONE;
+			elf_write_reloc(file->elf, reloc);
+		}
+
+		elf_write_insn(file->elf, insn->sec,
+			       insn->offset, insn->len,
+			       arch_nop_insn(insn->len));
+
+		insn->type = INSN_NOP;
+
+		list_add_tail(&insn->mcount_loc_node,
+			      &file->mcount_loc_list);
+	}
+
+	/*
+	 * Whatever stack impact regular CALLs have, should be undone
+	 * by the RETURN of the called function.
+	 *
+	 * Annotated intra-function calls retain the stack_ops but
+	 * are converted to JUMP, see read_intra_function_calls().
+	 */
+	remove_insn_ops(insn);
+}
+
 /*
  * Find the destination instructions for all jumps.
  */
@@ -942,11 +1015,7 @@ static int add_jump_destinations(struct objtool_file *file)
 			continue;
 		} else if (insn->func) {
 			/* internal or external sibling call (with reloc) */
-			insn->call_dest = reloc->sym;
-			if (insn->call_dest->static_call_tramp) {
-				list_add_tail(&insn->call_node,
-					      &file->static_call_list);
-			}
+			add_call_dest(file, insn, reloc->sym, true);
 			continue;
 		} else if (reloc->sym->sec->idx) {
 			dest_sec = reloc->sym->sec;
@@ -1002,13 +1071,8 @@ static int add_jump_destinations(struct objtool_file *file)
 
 			} else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
 				   insn->jump_dest->offset == insn->jump_dest->func->offset) {
-
 				/* internal sibling call (without reloc) */
-				insn->call_dest = insn->jump_dest->func;
-				if (insn->call_dest->static_call_tramp) {
-					list_add_tail(&insn->call_node,
-						      &file->static_call_list);
-				}
+				add_call_dest(file, insn, insn->jump_dest->func, true);
 			}
 		}
 	}
@@ -1016,16 +1080,6 @@ static int add_jump_destinations(struct objtool_file *file)
 	return 0;
 }
 
-static void remove_insn_ops(struct instruction *insn)
-{
-	struct stack_op *op, *tmp;
-
-	list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
-		list_del(&op->list);
-		free(op);
-	}
-}
-
 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
 {
 	struct symbol *call_dest;
@@ -1044,6 +1098,7 @@ static int add_call_destinations(struct objtool_file *file)
 {
 	struct instruction *insn;
 	unsigned long dest_off;
+	struct symbol *dest;
 	struct reloc *reloc;
 
 	for_each_insn(file, insn) {
@@ -1053,7 +1108,9 @@ static int add_call_destinations(struct objtool_file *file)
 		reloc = insn_reloc(file, insn);
 		if (!reloc) {
 			dest_off = arch_jump_destination(insn);
-			insn->call_dest = find_call_destination(insn->sec, dest_off);
+			dest = find_call_destination(insn->sec, dest_off);
+
+			add_call_dest(file, insn, dest, false);
 
 			if (insn->ignore)
 				continue;
@@ -1071,9 +1128,8 @@ static int add_call_destinations(struct objtool_file *file)
 
 		} else if (reloc->sym->type == STT_SECTION) {
 			dest_off = arch_dest_reloc_offset(reloc->addend);
-			insn->call_dest = find_call_destination(reloc->sym->sec,
-								dest_off);
-			if (!insn->call_dest) {
+			dest = find_call_destination(reloc->sym->sec, dest_off);
+			if (!dest) {
 				WARN_FUNC("can't find call dest symbol at %s+0x%lx",
 					  insn->sec, insn->offset,
 					  reloc->sym->sec->name,
@@ -1081,6 +1137,8 @@ static int add_call_destinations(struct objtool_file *file)
 				return -1;
 			}
 
+			add_call_dest(file, insn, dest, false);
+
 		} else if (arch_is_retpoline(reloc->sym)) {
 			/*
 			 * Retpoline calls are really dynamic calls in
@@ -1096,55 +1154,7 @@ static int add_call_destinations(struct objtool_file *file)
 			continue;
 
 		} else
-			insn->call_dest = reloc->sym;
-
-		if (insn->call_dest && insn->call_dest->static_call_tramp) {
-			list_add_tail(&insn->call_node,
-				      &file->static_call_list);
-		}
-
-		/*
-		 * Many compilers cannot disable KCOV with a function attribute
-		 * so they need a little help, NOP out any KCOV calls from noinstr
-		 * text.
-		 */
-		if (insn->sec->noinstr &&
-		    !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
-			if (reloc) {
-				reloc->type = R_NONE;
-				elf_write_reloc(file->elf, reloc);
-			}
-
-			elf_write_insn(file->elf, insn->sec,
-				       insn->offset, insn->len,
-				       arch_nop_insn(insn->len));
-			insn->type = INSN_NOP;
-		}
-
-		if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) {
-			if (reloc) {
-				reloc->type = R_NONE;
-				elf_write_reloc(file->elf, reloc);
-			}
-
-			elf_write_insn(file->elf, insn->sec,
-				       insn->offset, insn->len,
-				       arch_nop_insn(insn->len));
-
-			insn->type = INSN_NOP;
-
-			list_add_tail(&insn->mcount_loc_node,
-				      &file->mcount_loc_list);
-		}
-
-		/*
-		 * Whatever stack impact regular CALLs have, should be undone
-		 * by the RETURN of the called function.
-		 *
-		 * Annotated intra-function calls retain the stack_ops but
-		 * are converted to JUMP, see read_intra_function_calls().
-		 */
-		remove_insn_ops(insn);
+			add_call_dest(file, insn, reloc->sym, false);
 	}
 
 	return 0;
diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h
index a5ab6829511f..6f482ae2d7d8 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -82,6 +82,7 @@ unsigned long arch_jump_destination(struct instruction *insn);
 unsigned long arch_dest_reloc_offset(int addend);
 
 const char *arch_nop_insn(int len);
+const char *arch_ret_insn(int len);
 
 int arch_decode_hint_reg(u8 sp_reg, int *base);
 
-- 
cgit v1.2.3


From db2b0c5d7b6f19b3c2cab08c531b65342eb5252b Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 24 Jun 2021 11:41:23 +0200
Subject: objtool: Support pv_opsindirect calls for noinstr

Normally objtool will now follow indirect calls; there is no need.

However, this becomes a problem with noinstr validation; if there's an
indirect call from noinstr code, we very much need to know it is to
another noinstr function. Luckily there aren't many indirect calls in
entry code with the obvious exception of paravirt. As such, noinstr
validation didn't work with paravirt kernels.

In order to track pv_ops[] call targets, objtool reads the static
pv_ops[] tables as well as direct assignments to the pv_ops[] array,
provided the compiler makes them a single instruction like:

  bf87:       48 c7 05 00 00 00 00 00 00 00 00        movq   $0x0,0x0(%rip)
    bf92 <xen_init_spinlocks+0x5f>
    bf8a: R_X86_64_PC32     pv_ops+0x268

There are, as of yet, no warnings for when this goes wrong :/

Using the functions found with the above means, all pv_ops[] calls are
now subject to noinstr validation.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210624095149.118815755@infradead.org
---
 lib/Kconfig.debug                       |   2 +-
 tools/objtool/arch/x86/decode.c         |  34 ++++++-
 tools/objtool/check.c                   | 151 +++++++++++++++++++++++++++++---
 tools/objtool/include/objtool/arch.h    |   2 +-
 tools/objtool/include/objtool/elf.h     |   1 +
 tools/objtool/include/objtool/objtool.h |   9 ++
 tools/objtool/objtool.c                 |  22 +++++
 7 files changed, 208 insertions(+), 13 deletions(-)

(limited to 'tools/objtool')

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ed4a31e34098..63a4735cef66 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -458,7 +458,7 @@ config STACK_VALIDATION
 
 config VMLINUX_VALIDATION
 	bool
-	depends on STACK_VALIDATION && DEBUG_ENTRY && !PARAVIRT
+	depends on STACK_VALIDATION && DEBUG_ENTRY
 	default y
 
 config VMLINUX_MAP
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 340a3dce94a0..3172983bf808 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -20,6 +20,7 @@
 #include <objtool/arch.h>
 #include <objtool/warn.h>
 #include <objtool/endianness.h>
+#include <objtool/builtin.h>
 #include <arch/elf.h>
 
 static int is_x86_64(const struct elf *elf)
@@ -102,12 +103,13 @@ unsigned long arch_jump_destination(struct instruction *insn)
 #define rm_is_mem(reg)	(mod_is_mem() && !is_RIP() && rm_is(reg))
 #define rm_is_reg(reg)	(mod_is_reg() && modrm_rm == (reg))
 
-int arch_decode_instruction(const struct elf *elf, const struct section *sec,
+int arch_decode_instruction(struct objtool_file *file, const struct section *sec,
 			    unsigned long offset, unsigned int maxlen,
 			    unsigned int *len, enum insn_type *type,
 			    unsigned long *immediate,
 			    struct list_head *ops_list)
 {
+	const struct elf *elf = file->elf;
 	struct insn insn;
 	int x86_64, ret;
 	unsigned char op1, op2,
@@ -544,6 +546,36 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 		*type = INSN_RETURN;
 		break;
 
+	case 0xc7: /* mov imm, r/m */
+		if (!noinstr)
+			break;
+
+		if (insn.length == 3+4+4 && !strncmp(sec->name, ".init.text", 10)) {
+			struct reloc *immr, *disp;
+			struct symbol *func;
+			int idx;
+
+			immr = find_reloc_by_dest(elf, (void *)sec, offset+3);
+			disp = find_reloc_by_dest(elf, (void *)sec, offset+7);
+
+			if (!immr || strcmp(immr->sym->name, "pv_ops"))
+				break;
+
+			idx = (immr->addend + 8) / sizeof(void *);
+
+			func = disp->sym;
+			if (disp->sym->type == STT_SECTION)
+				func = find_symbol_by_offset(disp->sym->sec, disp->addend);
+			if (!func) {
+				WARN("no func for pv_ops[]");
+				return -1;
+			}
+
+			objtool_pv_add(file, idx, func);
+		}
+
+		break;
+
 	case 0xcf: /* iret */
 		/*
 		 * Handle sync_core(), which has an IRET to self.
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index c6f206fee8ff..84e59a97bab6 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -382,7 +382,7 @@ static int decode_instructions(struct objtool_file *file)
 			insn->sec = sec;
 			insn->offset = offset;
 
-			ret = arch_decode_instruction(file->elf, sec, offset,
+			ret = arch_decode_instruction(file, sec, offset,
 						      sec->len - offset,
 						      &insn->len, &insn->type,
 						      &insn->immediate,
@@ -420,6 +420,82 @@ err:
 	return ret;
 }
 
+/*
+ * Read the pv_ops[] .data table to find the static initialized values.
+ */
+static int add_pv_ops(struct objtool_file *file, const char *symname)
+{
+	struct symbol *sym, *func;
+	unsigned long off, end;
+	struct reloc *rel;
+	int idx;
+
+	sym = find_symbol_by_name(file->elf, symname);
+	if (!sym)
+		return 0;
+
+	off = sym->offset;
+	end = off + sym->len;
+	for (;;) {
+		rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
+		if (!rel)
+			break;
+
+		func = rel->sym;
+		if (func->type == STT_SECTION)
+			func = find_symbol_by_offset(rel->sym->sec, rel->addend);
+
+		idx = (rel->offset - sym->offset) / sizeof(unsigned long);
+
+		objtool_pv_add(file, idx, func);
+
+		off = rel->offset + 1;
+		if (off > end)
+			break;
+	}
+
+	return 0;
+}
+
+/*
+ * Allocate and initialize file->pv_ops[].
+ */
+static int init_pv_ops(struct objtool_file *file)
+{
+	static const char *pv_ops_tables[] = {
+		"pv_ops",
+		"xen_cpu_ops",
+		"xen_irq_ops",
+		"xen_mmu_ops",
+		NULL,
+	};
+	const char *pv_ops;
+	struct symbol *sym;
+	int idx, nr;
+
+	if (!noinstr)
+		return 0;
+
+	file->pv_ops = NULL;
+
+	sym = find_symbol_by_name(file->elf, "pv_ops");
+	if (!sym)
+		return 0;
+
+	nr = sym->len / sizeof(unsigned long);
+	file->pv_ops = calloc(sizeof(struct pv_state), nr);
+	if (!file->pv_ops)
+		return -1;
+
+	for (idx = 0; idx < nr; idx++)
+		INIT_LIST_HEAD(&file->pv_ops[idx].targets);
+
+	for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
+		add_pv_ops(file, pv_ops);
+
+	return 0;
+}
+
 static struct instruction *find_last_insn(struct objtool_file *file,
 					  struct section *sec)
 {
@@ -893,6 +969,9 @@ static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *i
 		return NULL;
 
 	if (!insn->reloc) {
+		if (!file)
+			return NULL;
+
 		insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
 						       insn->offset, insn->len);
 		if (!insn->reloc) {
@@ -1882,6 +1961,10 @@ static int decode_sections(struct objtool_file *file)
 
 	mark_rodata(file);
 
+	ret = init_pv_ops(file);
+	if (ret)
+		return ret;
+
 	ret = decode_instructions(file);
 	if (ret)
 		return ret;
@@ -2663,20 +2746,64 @@ static inline bool func_uaccess_safe(struct symbol *func)
 
 static inline const char *call_dest_name(struct instruction *insn)
 {
+	static char pvname[16];
+	struct reloc *rel;
+	int idx;
+
 	if (insn->call_dest)
 		return insn->call_dest->name;
 
+	rel = insn_reloc(NULL, insn);
+	if (rel && !strcmp(rel->sym->name, "pv_ops")) {
+		idx = (rel->addend / sizeof(void *));
+		snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
+		return pvname;
+	}
+
 	return "{dynamic}";
 }
 
-static inline bool noinstr_call_dest(struct symbol *func)
+static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
+{
+	struct symbol *target;
+	struct reloc *rel;
+	int idx;
+
+	rel = insn_reloc(file, insn);
+	if (!rel || strcmp(rel->sym->name, "pv_ops"))
+		return false;
+
+	idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
+
+	if (file->pv_ops[idx].clean)
+		return true;
+
+	file->pv_ops[idx].clean = true;
+
+	list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
+		if (!target->sec->noinstr) {
+			WARN("pv_ops[%d]: %s", idx, target->name);
+			file->pv_ops[idx].clean = false;
+		}
+	}
+
+	return file->pv_ops[idx].clean;
+}
+
+static inline bool noinstr_call_dest(struct objtool_file *file,
+				     struct instruction *insn,
+				     struct symbol *func)
 {
 	/*
 	 * We can't deal with indirect function calls at present;
 	 * assume they're instrumented.
 	 */
-	if (!func)
+	if (!func) {
+		if (file->pv_ops)
+			return pv_call_dest(file, insn);
+
 		return false;
+	}
 
 	/*
 	 * If the symbol is from a noinstr section; we good.
@@ -2695,10 +2822,12 @@ static inline bool noinstr_call_dest(struct symbol *func)
 	return false;
 }
 
-static int validate_call(struct instruction *insn, struct insn_state *state)
+static int validate_call(struct objtool_file *file,
+			 struct instruction *insn,
+			 struct insn_state *state)
 {
 	if (state->noinstr && state->instr <= 0 &&
-	    !noinstr_call_dest(insn->call_dest)) {
+	    !noinstr_call_dest(file, insn, insn->call_dest)) {
 		WARN_FUNC("call to %s() leaves .noinstr.text section",
 				insn->sec, insn->offset, call_dest_name(insn));
 		return 1;
@@ -2719,7 +2848,9 @@ static int validate_call(struct instruction *insn, struct insn_state *state)
 	return 0;
 }
 
-static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
+static int validate_sibling_call(struct objtool_file *file,
+				 struct instruction *insn,
+				 struct insn_state *state)
 {
 	if (has_modified_stack_frame(insn, state)) {
 		WARN_FUNC("sibling call from callable instruction with modified stack frame",
@@ -2727,7 +2858,7 @@ static int validate_sibling_call(struct instruction *insn, struct insn_state *st
 		return 1;
 	}
 
-	return validate_call(insn, state);
+	return validate_call(file, insn, state);
 }
 
 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
@@ -2880,7 +3011,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 
 		case INSN_CALL:
 		case INSN_CALL_DYNAMIC:
-			ret = validate_call(insn, &state);
+			ret = validate_call(file, insn, &state);
 			if (ret)
 				return ret;
 
@@ -2899,7 +3030,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 		case INSN_JUMP_CONDITIONAL:
 		case INSN_JUMP_UNCONDITIONAL:
 			if (is_sibling_call(insn)) {
-				ret = validate_sibling_call(insn, &state);
+				ret = validate_sibling_call(file, insn, &state);
 				if (ret)
 					return ret;
 
@@ -2921,7 +3052,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 		case INSN_JUMP_DYNAMIC:
 		case INSN_JUMP_DYNAMIC_CONDITIONAL:
 			if (is_sibling_call(insn)) {
-				ret = validate_sibling_call(insn, &state);
+				ret = validate_sibling_call(file, insn, &state);
 				if (ret)
 					return ret;
 			}
diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h
index 6f482ae2d7d8..589ff58426ab 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -69,7 +69,7 @@ struct instruction;
 
 void arch_initial_func_cfi_state(struct cfi_init_state *state);
 
-int arch_decode_instruction(const struct elf *elf, const struct section *sec,
+int arch_decode_instruction(struct objtool_file *file, const struct section *sec,
 			    unsigned long offset, unsigned int maxlen,
 			    unsigned int *len, enum insn_type *type,
 			    unsigned long *immediate,
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index e34395047530..c3857fadee7a 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -57,6 +57,7 @@ struct symbol {
 	struct symbol *pfunc, *cfunc, *alias;
 	bool uaccess_safe;
 	bool static_call_tramp;
+	struct list_head pv_target;
 };
 
 struct reloc {
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index 24fa83634de4..f99fbc6078d5 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -14,6 +14,11 @@
 
 #define __weak __attribute__((weak))
 
+struct pv_state {
+	bool clean;
+	struct list_head targets;
+};
+
 struct objtool_file {
 	struct elf *elf;
 	struct list_head insn_list;
@@ -25,10 +30,14 @@ struct objtool_file {
 
 	unsigned long jl_short, jl_long;
 	unsigned long jl_nop_short, jl_nop_long;
+
+	struct pv_state *pv_ops;
 };
 
 struct objtool_file *objtool_open_read(const char *_objname);
 
+void objtool_pv_add(struct objtool_file *file, int idx, struct symbol *func);
+
 int check(struct objtool_file *file);
 int orc_dump(const char *objname);
 int orc_create(struct objtool_file *file);
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index e21db8bce493..c90c7084e45a 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -135,6 +135,28 @@ struct objtool_file *objtool_open_read(const char *_objname)
 	return &file;
 }
 
+void objtool_pv_add(struct objtool_file *f, int idx, struct symbol *func)
+{
+	if (!noinstr)
+		return;
+
+	if (!f->pv_ops) {
+		WARN("paravirt confusion");
+		return;
+	}
+
+	/*
+	 * These functions will be patched into native code,
+	 * see paravirt_patch().
+	 */
+	if (!strcmp(func->name, "_paravirt_nop") ||
+	    !strcmp(func->name, "_paravirt_ident_64"))
+		return;
+
+	list_add(&func->pv_target, &f->pv_ops[idx].targets);
+	f->pv_ops[idx].clean = false;
+}
+
 static void cmd_usage(void)
 {
 	unsigned int i, longest = 0;
-- 
cgit v1.2.3


From 1739c66eb7bd5f27f1b69a5a26e10e8327d1e136 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 26 Oct 2021 14:01:33 +0200
Subject: objtool: Classify symbols

In order to avoid calling str*cmp() on symbol names, over and over, do
them all once upfront and store the result.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211026120309.658539311@infradead.org
---
 tools/objtool/check.c               | 34 ++++++++++++++++++++++------------
 tools/objtool/include/objtool/elf.h |  7 +++++--
 2 files changed, 27 insertions(+), 14 deletions(-)

(limited to 'tools/objtool')

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 7c865a10372a..fdbc6d2c5597 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1012,8 +1012,7 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn,
 	 * so they need a little help, NOP out any KCOV calls from noinstr
 	 * text.
 	 */
-	if (insn->sec->noinstr &&
-	    !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
+	if (insn->sec->noinstr && insn->call_dest->kcov) {
 		if (reloc) {
 			reloc->type = R_NONE;
 			elf_write_reloc(file->elf, reloc);
@@ -1027,7 +1026,7 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn,
 		insn->type = sibling ? INSN_RETURN : INSN_NOP;
 	}
 
-	if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) {
+	if (mcount && insn->call_dest->fentry) {
 		if (sibling)
 			WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
 
@@ -1077,7 +1076,7 @@ static int add_jump_destinations(struct objtool_file *file)
 		} else if (reloc->sym->type == STT_SECTION) {
 			dest_sec = reloc->sym->sec;
 			dest_off = arch_dest_reloc_offset(reloc->addend);
-		} else if (arch_is_retpoline(reloc->sym)) {
+		} else if (reloc->sym->retpoline_thunk) {
 			/*
 			 * Retpoline jumps are really dynamic jumps in
 			 * disguise, so convert them accordingly.
@@ -1218,7 +1217,7 @@ static int add_call_destinations(struct objtool_file *file)
 
 			add_call_dest(file, insn, dest, false);
 
-		} else if (arch_is_retpoline(reloc->sym)) {
+		} else if (reloc->sym->retpoline_thunk) {
 			/*
 			 * Retpoline calls are really dynamic calls in
 			 * disguise, so convert them accordingly.
@@ -1907,17 +1906,28 @@ static int read_intra_function_calls(struct objtool_file *file)
 	return 0;
 }
 
-static int read_static_call_tramps(struct objtool_file *file)
+static int classify_symbols(struct objtool_file *file)
 {
 	struct section *sec;
 	struct symbol *func;
 
 	for_each_sec(file, sec) {
 		list_for_each_entry(func, &sec->symbol_list, list) {
-			if (func->bind == STB_GLOBAL &&
-			    !strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
+			if (func->bind != STB_GLOBAL)
+				continue;
+
+			if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
 				     strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
 				func->static_call_tramp = true;
+
+			if (arch_is_retpoline(func))
+				func->retpoline_thunk = true;
+
+			if (!strcmp(func->name, "__fentry__"))
+				func->fentry = true;
+
+			if (!strncmp(func->name, "__sanitizer_cov_", 16))
+				func->kcov = true;
 		}
 	}
 
@@ -1983,7 +1993,7 @@ static int decode_sections(struct objtool_file *file)
 	/*
 	 * Must be before add_{jump_call}_destination.
 	 */
-	ret = read_static_call_tramps(file);
+	ret = classify_symbols(file);
 	if (ret)
 		return ret;
 
@@ -2041,9 +2051,9 @@ static int decode_sections(struct objtool_file *file)
 
 static bool is_fentry_call(struct instruction *insn)
 {
-	if (insn->type == INSN_CALL && insn->call_dest &&
-	    insn->call_dest->type == STT_NOTYPE &&
-	    !strcmp(insn->call_dest->name, "__fentry__"))
+	if (insn->type == INSN_CALL &&
+	    insn->call_dest &&
+	    insn->call_dest->fentry)
 		return true;
 
 	return false;
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index c48c1067797d..c2dbf53528c5 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -54,8 +54,11 @@ struct symbol {
 	unsigned long offset;
 	unsigned int len;
 	struct symbol *pfunc, *cfunc, *alias;
-	bool uaccess_safe;
-	bool static_call_tramp;
+	u8 uaccess_safe      : 1;
+	u8 static_call_tramp : 1;
+	u8 retpoline_thunk   : 1;
+	u8 fentry            : 1;
+	u8 kcov              : 1;
 	struct list_head pv_target;
 };
 
-- 
cgit v1.2.3


From dd003edeffa3cb87bc9862582004f405d77d7670 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 26 Oct 2021 14:01:34 +0200
Subject: objtool: Explicitly avoid self modifying code in
 .altinstr_replacement

Assume ALTERNATIVE()s know what they're doing and do not change, or
cause to change, instructions in .altinstr_replacement sections.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211026120309.722511775@infradead.org
---
 tools/objtool/check.c | 42 +++++++++++++++++++++++++++++++-----------
 1 file changed, 31 insertions(+), 11 deletions(-)

(limited to 'tools/objtool')

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index fdbc6d2c5597..8ab6f24f8753 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -993,18 +993,27 @@ static void remove_insn_ops(struct instruction *insn)
 	}
 }
 
-static void add_call_dest(struct objtool_file *file, struct instruction *insn,
-			  struct symbol *dest, bool sibling)
+static void annotate_call_site(struct objtool_file *file,
+			       struct instruction *insn, bool sibling)
 {
 	struct reloc *reloc = insn_reloc(file, insn);
+	struct symbol *sym = insn->call_dest;
 
-	insn->call_dest = dest;
-	if (!dest)
+	if (!sym)
+		sym = reloc->sym;
+
+	/*
+	 * Alternative replacement code is just template code which is
+	 * sometimes copied to the original instruction. For now, don't
+	 * annotate it. (In the future we might consider annotating the
+	 * original instruction if/when it ever makes sense to do so.)
+	 */
+	if (!strcmp(insn->sec->name, ".altinstr_replacement"))
 		return;
 
-	if (insn->call_dest->static_call_tramp) {
-		list_add_tail(&insn->call_node,
-			      &file->static_call_list);
+	if (sym->static_call_tramp) {
+		list_add_tail(&insn->call_node, &file->static_call_list);
+		return;
 	}
 
 	/*
@@ -1012,7 +1021,7 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn,
 	 * so they need a little help, NOP out any KCOV calls from noinstr
 	 * text.
 	 */
-	if (insn->sec->noinstr && insn->call_dest->kcov) {
+	if (insn->sec->noinstr && sym->kcov) {
 		if (reloc) {
 			reloc->type = R_NONE;
 			elf_write_reloc(file->elf, reloc);
@@ -1024,9 +1033,10 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn,
 			               : arch_nop_insn(insn->len));
 
 		insn->type = sibling ? INSN_RETURN : INSN_NOP;
+		return;
 	}
 
-	if (mcount && insn->call_dest->fentry) {
+	if (mcount && sym->fentry) {
 		if (sibling)
 			WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
 
@@ -1041,9 +1051,17 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn,
 
 		insn->type = INSN_NOP;
 
-		list_add_tail(&insn->mcount_loc_node,
-			      &file->mcount_loc_list);
+		list_add_tail(&insn->mcount_loc_node, &file->mcount_loc_list);
+		return;
 	}
+}
+
+static void add_call_dest(struct objtool_file *file, struct instruction *insn,
+			  struct symbol *dest, bool sibling)
+{
+	insn->call_dest = dest;
+	if (!dest)
+		return;
 
 	/*
 	 * Whatever stack impact regular CALLs have, should be undone
@@ -1053,6 +1071,8 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn,
 	 * are converted to JUMP, see read_intra_function_calls().
 	 */
 	remove_insn_ops(insn);
+
+	annotate_call_site(file, insn, sibling);
 }
 
 /*
-- 
cgit v1.2.3


From c509331b41b7365e17396c246e8c5797bccc8074 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 26 Oct 2021 14:01:35 +0200
Subject: objtool: Shrink struct instruction

Any one instruction can only ever call a single function, therefore
insn->mcount_loc_node is superfluous and can use insn->call_node.

This shrinks struct instruction, which is by far the most numerous
structure objtool creates.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211026120309.785456706@infradead.org
---
 tools/objtool/check.c                 | 6 +++---
 tools/objtool/include/objtool/check.h | 1 -
 2 files changed, 3 insertions(+), 4 deletions(-)

(limited to 'tools/objtool')

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 8ab6f24f8753..ce3c25fec2a6 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -701,7 +701,7 @@ static int create_mcount_loc_sections(struct objtool_file *file)
 		return 0;
 
 	idx = 0;
-	list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node)
+	list_for_each_entry(insn, &file->mcount_loc_list, call_node)
 		idx++;
 
 	sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
@@ -709,7 +709,7 @@ static int create_mcount_loc_sections(struct objtool_file *file)
 		return -1;
 
 	idx = 0;
-	list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node) {
+	list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
 
 		loc = (unsigned long *)sec->data->d_buf + idx;
 		memset(loc, 0, sizeof(unsigned long));
@@ -1051,7 +1051,7 @@ static void annotate_call_site(struct objtool_file *file,
 
 		insn->type = INSN_NOP;
 
-		list_add_tail(&insn->mcount_loc_node, &file->mcount_loc_list);
+		list_add_tail(&insn->call_node, &file->mcount_loc_list);
 		return;
 	}
 }
diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index 07e99c25c7ac..6cfff078897f 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -40,7 +40,6 @@ struct instruction {
 	struct list_head list;
 	struct hlist_node hash;
 	struct list_head call_node;
-	struct list_head mcount_loc_node;
 	struct section *sec;
 	unsigned long offset;
 	unsigned int len;
-- 
cgit v1.2.3


From 134ab5bd1883312d7a4b3033b05c6b5a1bb8889b Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 26 Oct 2021 14:01:36 +0200
Subject: objtool,x86: Replace alternatives with .retpoline_sites

Instead of writing complete alternatives, simply provide a list of all
the retpoline thunk calls. Then the kernel is free to do with them as
it pleases. Simpler code all-round.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211026120309.850007165@infradead.org
---
 arch/x86/kernel/vmlinux.lds.S       |  14 ++++
 tools/objtool/arch/x86/decode.c     | 120 --------------------------------
 tools/objtool/check.c               | 132 +++++++++++++++++++++++++-----------
 tools/objtool/elf.c                 |  84 -----------------------
 tools/objtool/include/objtool/elf.h |   1 -
 tools/objtool/special.c             |   8 ---
 6 files changed, 107 insertions(+), 252 deletions(-)

(limited to 'tools/objtool')

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index efd9e9ea17f2..3d6dc12d198f 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -272,6 +272,20 @@ SECTIONS
 		__parainstructions_end = .;
 	}
 
+#ifdef CONFIG_RETPOLINE
+	/*
+	 * List of instructions that call/jmp/jcc to retpoline thunks
+	 * __x86_indirect_thunk_*(). These instructions can be patched along
+	 * with alternatives, after which the section can be freed.
+	 */
+	. = ALIGN(8);
+	.retpoline_sites : AT(ADDR(.retpoline_sites) - LOAD_OFFSET) {
+		__retpoline_sites = .;
+		*(.retpoline_sites)
+		__retpoline_sites_end = .;
+	}
+#endif
+
 	/*
 	 * struct alt_inst entries. From the header (alternative.h):
 	 * "Alternative instructions for different CPU types or capabilities"
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 1f2ae708b223..4d6d7fc13255 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -711,126 +711,6 @@ const char *arch_ret_insn(int len)
 	return ret[len-1];
 }
 
-/* asm/alternative.h ? */
-
-#define ALTINSTR_FLAG_INV	(1 << 15)
-#define ALT_NOT(feat)		((feat) | ALTINSTR_FLAG_INV)
-
-struct alt_instr {
-	s32 instr_offset;	/* original instruction */
-	s32 repl_offset;	/* offset to replacement instruction */
-	u16 cpuid;		/* cpuid bit set for replacement */
-	u8  instrlen;		/* length of original instruction */
-	u8  replacementlen;	/* length of new instruction */
-} __packed;
-
-static int elf_add_alternative(struct elf *elf,
-			       struct instruction *orig, struct symbol *sym,
-			       int cpuid, u8 orig_len, u8 repl_len)
-{
-	const int size = sizeof(struct alt_instr);
-	struct alt_instr *alt;
-	struct section *sec;
-	Elf_Scn *s;
-
-	sec = find_section_by_name(elf, ".altinstructions");
-	if (!sec) {
-		sec = elf_create_section(elf, ".altinstructions",
-					 SHF_ALLOC, 0, 0);
-
-		if (!sec) {
-			WARN_ELF("elf_create_section");
-			return -1;
-		}
-	}
-
-	s = elf_getscn(elf->elf, sec->idx);
-	if (!s) {
-		WARN_ELF("elf_getscn");
-		return -1;
-	}
-
-	sec->data = elf_newdata(s);
-	if (!sec->data) {
-		WARN_ELF("elf_newdata");
-		return -1;
-	}
-
-	sec->data->d_size = size;
-	sec->data->d_align = 1;
-
-	alt = sec->data->d_buf = malloc(size);
-	if (!sec->data->d_buf) {
-		perror("malloc");
-		return -1;
-	}
-	memset(sec->data->d_buf, 0, size);
-
-	if (elf_add_reloc_to_insn(elf, sec, sec->sh.sh_size,
-				  R_X86_64_PC32, orig->sec, orig->offset)) {
-		WARN("elf_create_reloc: alt_instr::instr_offset");
-		return -1;
-	}
-
-	if (elf_add_reloc(elf, sec, sec->sh.sh_size + 4,
-			  R_X86_64_PC32, sym, 0)) {
-		WARN("elf_create_reloc: alt_instr::repl_offset");
-		return -1;
-	}
-
-	alt->cpuid = bswap_if_needed(cpuid);
-	alt->instrlen = orig_len;
-	alt->replacementlen = repl_len;
-
-	sec->sh.sh_size += size;
-	sec->changed = true;
-
-	return 0;
-}
-
-#define X86_FEATURE_RETPOLINE                ( 7*32+12)
-
-int arch_rewrite_retpolines(struct objtool_file *file)
-{
-	struct instruction *insn;
-	struct reloc *reloc;
-	struct symbol *sym;
-	char name[32] = "";
-
-	list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
-
-		if (insn->type != INSN_JUMP_DYNAMIC &&
-		    insn->type != INSN_CALL_DYNAMIC)
-			continue;
-
-		if (!strcmp(insn->sec->name, ".text.__x86.indirect_thunk"))
-			continue;
-
-		reloc = insn->reloc;
-
-		sprintf(name, "__x86_indirect_alt_%s_%s",
-			insn->type == INSN_JUMP_DYNAMIC ? "jmp" : "call",
-			reloc->sym->name + 21);
-
-		sym = find_symbol_by_name(file->elf, name);
-		if (!sym) {
-			sym = elf_create_undef_symbol(file->elf, name);
-			if (!sym) {
-				WARN("elf_create_undef_symbol");
-				return -1;
-			}
-		}
-
-		if (elf_add_alternative(file->elf, insn, sym,
-					ALT_NOT(X86_FEATURE_RETPOLINE), 5, 5)) {
-			WARN("elf_add_alternative");
-			return -1;
-		}
-	}
-
-	return 0;
-}
-
 int arch_decode_hint_reg(u8 sp_reg, int *base)
 {
 	switch (sp_reg) {
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index ce3c25fec2a6..fb3f251ea021 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -683,6 +683,52 @@ static int create_static_call_sections(struct objtool_file *file)
 	return 0;
 }
 
+static int create_retpoline_sites_sections(struct objtool_file *file)
+{
+	struct instruction *insn;
+	struct section *sec;
+	int idx;
+
+	sec = find_section_by_name(file->elf, ".retpoline_sites");
+	if (sec) {
+		WARN("file already has .retpoline_sites, skipping");
+		return 0;
+	}
+
+	idx = 0;
+	list_for_each_entry(insn, &file->retpoline_call_list, call_node)
+		idx++;
+
+	if (!idx)
+		return 0;
+
+	sec = elf_create_section(file->elf, ".retpoline_sites", 0,
+				 sizeof(int), idx);
+	if (!sec) {
+		WARN("elf_create_section: .retpoline_sites");
+		return -1;
+	}
+
+	idx = 0;
+	list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
+
+		int *site = (int *)sec->data->d_buf + idx;
+		*site = 0;
+
+		if (elf_add_reloc_to_insn(file->elf, sec,
+					  idx * sizeof(int),
+					  R_X86_64_PC32,
+					  insn->sec, insn->offset)) {
+			WARN("elf_add_reloc_to_insn: .retpoline_sites");
+			return -1;
+		}
+
+		idx++;
+	}
+
+	return 0;
+}
+
 static int create_mcount_loc_sections(struct objtool_file *file)
 {
 	struct section *sec;
@@ -1016,6 +1062,11 @@ static void annotate_call_site(struct objtool_file *file,
 		return;
 	}
 
+	if (sym->retpoline_thunk) {
+		list_add_tail(&insn->call_node, &file->retpoline_call_list);
+		return;
+	}
+
 	/*
 	 * Many compilers cannot disable KCOV with a function attribute
 	 * so they need a little help, NOP out any KCOV calls from noinstr
@@ -1075,6 +1126,39 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn,
 	annotate_call_site(file, insn, sibling);
 }
 
+static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
+{
+	/*
+	 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
+	 * so convert them accordingly.
+	 */
+	switch (insn->type) {
+	case INSN_CALL:
+		insn->type = INSN_CALL_DYNAMIC;
+		break;
+	case INSN_JUMP_UNCONDITIONAL:
+		insn->type = INSN_JUMP_DYNAMIC;
+		break;
+	case INSN_JUMP_CONDITIONAL:
+		insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
+		break;
+	default:
+		return;
+	}
+
+	insn->retpoline_safe = true;
+
+	/*
+	 * Whatever stack impact regular CALLs have, should be undone
+	 * by the RETURN of the called function.
+	 *
+	 * Annotated intra-function calls retain the stack_ops but
+	 * are converted to JUMP, see read_intra_function_calls().
+	 */
+	remove_insn_ops(insn);
+
+	annotate_call_site(file, insn, false);
+}
 /*
  * Find the destination instructions for all jumps.
  */
@@ -1097,19 +1181,7 @@ static int add_jump_destinations(struct objtool_file *file)
 			dest_sec = reloc->sym->sec;
 			dest_off = arch_dest_reloc_offset(reloc->addend);
 		} else if (reloc->sym->retpoline_thunk) {
-			/*
-			 * Retpoline jumps are really dynamic jumps in
-			 * disguise, so convert them accordingly.
-			 */
-			if (insn->type == INSN_JUMP_UNCONDITIONAL)
-				insn->type = INSN_JUMP_DYNAMIC;
-			else
-				insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
-
-			list_add_tail(&insn->call_node,
-				      &file->retpoline_call_list);
-
-			insn->retpoline_safe = true;
+			add_retpoline_call(file, insn);
 			continue;
 		} else if (insn->func) {
 			/* internal or external sibling call (with reloc) */
@@ -1238,18 +1310,7 @@ static int add_call_destinations(struct objtool_file *file)
 			add_call_dest(file, insn, dest, false);
 
 		} else if (reloc->sym->retpoline_thunk) {
-			/*
-			 * Retpoline calls are really dynamic calls in
-			 * disguise, so convert them accordingly.
-			 */
-			insn->type = INSN_CALL_DYNAMIC;
-			insn->retpoline_safe = true;
-
-			list_add_tail(&insn->call_node,
-				      &file->retpoline_call_list);
-
-			remove_insn_ops(insn);
-			continue;
+			add_retpoline_call(file, insn);
 
 		} else
 			add_call_dest(file, insn, reloc->sym, false);
@@ -1980,11 +2041,6 @@ static void mark_rodata(struct objtool_file *file)
 	file->rodata = found;
 }
 
-__weak int arch_rewrite_retpolines(struct objtool_file *file)
-{
-	return 0;
-}
-
 static int decode_sections(struct objtool_file *file)
 {
 	int ret;
@@ -2057,15 +2113,6 @@ static int decode_sections(struct objtool_file *file)
 	if (ret)
 		return ret;
 
-	/*
-	 * Must be after add_special_section_alts(), since this will emit
-	 * alternatives. Must be after add_{jump,call}_destination(), since
-	 * those create the call insn lists.
-	 */
-	ret = arch_rewrite_retpolines(file);
-	if (ret)
-		return ret;
-
 	return 0;
 }
 
@@ -3468,6 +3515,13 @@ int check(struct objtool_file *file)
 		goto out;
 	warnings += ret;
 
+	if (retpoline) {
+		ret = create_retpoline_sites_sections(file);
+		if (ret < 0)
+			goto out;
+		warnings += ret;
+	}
+
 	if (mcount) {
 		ret = create_mcount_loc_sections(file);
 		if (ret < 0)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index b18f0055b50b..5c029355c38c 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -740,90 +740,6 @@ static int elf_add_string(struct elf *elf, struct section *strtab, char *str)
 	return len;
 }
 
-struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name)
-{
-	struct section *symtab, *symtab_shndx;
-	struct symbol *sym;
-	Elf_Data *data;
-	Elf_Scn *s;
-
-	sym = malloc(sizeof(*sym));
-	if (!sym) {
-		perror("malloc");
-		return NULL;
-	}
-	memset(sym, 0, sizeof(*sym));
-
-	sym->name = strdup(name);
-
-	sym->sym.st_name = elf_add_string(elf, NULL, sym->name);
-	if (sym->sym.st_name == -1)
-		return NULL;
-
-	sym->sym.st_info = GELF_ST_INFO(STB_GLOBAL, STT_NOTYPE);
-	// st_other 0
-	// st_shndx 0
-	// st_value 0
-	// st_size 0
-
-	symtab = find_section_by_name(elf, ".symtab");
-	if (!symtab) {
-		WARN("can't find .symtab");
-		return NULL;
-	}
-
-	s = elf_getscn(elf->elf, symtab->idx);
-	if (!s) {
-		WARN_ELF("elf_getscn");
-		return NULL;
-	}
-
-	data = elf_newdata(s);
-	if (!data) {
-		WARN_ELF("elf_newdata");
-		return NULL;
-	}
-
-	data->d_buf = &sym->sym;
-	data->d_size = sizeof(sym->sym);
-	data->d_align = 1;
-	data->d_type = ELF_T_SYM;
-
-	sym->idx = symtab->sh.sh_size / sizeof(sym->sym);
-
-	symtab->sh.sh_size += data->d_size;
-	symtab->changed = true;
-
-	symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
-	if (symtab_shndx) {
-		s = elf_getscn(elf->elf, symtab_shndx->idx);
-		if (!s) {
-			WARN_ELF("elf_getscn");
-			return NULL;
-		}
-
-		data = elf_newdata(s);
-		if (!data) {
-			WARN_ELF("elf_newdata");
-			return NULL;
-		}
-
-		data->d_buf = &sym->sym.st_size; /* conveniently 0 */
-		data->d_size = sizeof(Elf32_Word);
-		data->d_align = 4;
-		data->d_type = ELF_T_WORD;
-
-		symtab_shndx->sh.sh_size += 4;
-		symtab_shndx->changed = true;
-	}
-
-	sym->sec = find_section_by_index(elf, 0);
-
-	elf_add_symbol(elf, sym);
-
-	return sym;
-}
-
 struct section *elf_create_section(struct elf *elf, const char *name,
 				   unsigned int sh_flags, size_t entsize, int nr)
 {
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index c2dbf53528c5..cdc739fa9a6f 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -144,7 +144,6 @@ int elf_write_insn(struct elf *elf, struct section *sec,
 		   unsigned long offset, unsigned int len,
 		   const char *insn);
 int elf_write_reloc(struct elf *elf, struct reloc *reloc);
-struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name);
 int elf_write(struct elf *elf);
 void elf_close(struct elf *elf);
 
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index 06c3eacab3d5..e2223dd91c37 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -109,14 +109,6 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
 			return -1;
 		}
 
-		/*
-		 * Skip retpoline .altinstr_replacement... we already rewrite the
-		 * instructions for retpolines anyway, see arch_is_retpoline()
-		 * usage in add_{call,jump}_destinations().
-		 */
-		if (arch_is_retpoline(new_reloc->sym))
-			return 1;
-
 		reloc_to_sec_off(new_reloc, &alt->new_sec, &alt->new_off);
 
 		/* _ASM_EXTABLE_EX hack */
-- 
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