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-rw-r--r--Documentation/admin-guide/kernel-parameters.txt3
-rw-r--r--arch/s390/Kconfig17
-rw-r--r--arch/s390/include/asm/alternative.h163
-rw-r--r--arch/s390/kernel/Makefile1
-rw-r--r--arch/s390/kernel/alternative.c110
-rw-r--r--arch/s390/kernel/module.c17
-rw-r--r--arch/s390/kernel/setup.c3
-rw-r--r--arch/s390/kernel/vmlinux.lds.S23
8 files changed, 337 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 05496622b4ef..464f60c50c36 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2548,6 +2548,9 @@
noalign [KNL,ARM]
+ noaltinstr [S390] Disables alternative instructions patching
+ (CPU alternatives feature).
+
noapic [SMP,APIC] Tells the kernel to not make use of any
IOAPICs that may be present in the system.
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 5fd4a67c93b3..080a3fcc3cb8 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -537,6 +537,22 @@ config ARCH_RANDOM
If unsure, say Y.
+config ALTERNATIVES
+ def_bool y
+ prompt "Patch optimized instructions for running CPU type"
+ help
+ When enabled the kernel code is compiled with additional
+ alternative instructions blocks optimized for newer CPU types.
+ These alternative instructions blocks are patched at kernel boot
+ time when running CPU supports them. This mechanism is used to
+ optimize some critical code paths (i.e. spinlocks) for newer CPUs
+ even if kernel is build to support older machine generations.
+
+ This mechanism could be disabled by appending "noaltinstr"
+ option to the kernel command line.
+
+ If unsure, say Y.
+
endmenu
menu "Memory setup"
@@ -811,6 +827,7 @@ config PFAULT
config SHARED_KERNEL
bool "VM shared kernel support"
depends on !JUMP_LABEL
+ depends on !ALTERNATIVES
help
Select this option, if you want to share the text segment of the
Linux kernel between different VM guests. This reduces memory
diff --git a/arch/s390/include/asm/alternative.h b/arch/s390/include/asm/alternative.h
new file mode 100644
index 000000000000..6c268f6a51d3
--- /dev/null
+++ b/arch/s390/include/asm/alternative.h
@@ -0,0 +1,163 @@
+#ifndef _ASM_S390_ALTERNATIVE_H
+#define _ASM_S390_ALTERNATIVE_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+#include <linux/stddef.h>
+#include <linux/stringify.h>
+
+struct alt_instr {
+ s32 instr_offset; /* original instruction */
+ s32 repl_offset; /* offset to replacement instruction */
+ u16 facility; /* facility bit set for replacement */
+ u8 instrlen; /* length of original instruction */
+ u8 replacementlen; /* length of new instruction */
+} __packed;
+
+#ifdef CONFIG_ALTERNATIVES
+extern void apply_alternative_instructions(void);
+extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
+#else
+static inline void apply_alternative_instructions(void) {};
+static inline void apply_alternatives(struct alt_instr *start,
+ struct alt_instr *end) {};
+#endif
+/*
+ * |661: |662: |6620 |663:
+ * +-----------+---------------------+
+ * | oldinstr | oldinstr_padding |
+ * | +----------+----------+
+ * | | | |
+ * | | >6 bytes |6/4/2 nops|
+ * | |6 bytes jg----------->
+ * +-----------+---------------------+
+ * ^^ static padding ^^
+ *
+ * .altinstr_replacement section
+ * +---------------------+-----------+
+ * |6641: |6651:
+ * | alternative instr 1 |
+ * +-----------+---------+- - - - - -+
+ * |6642: |6652: |
+ * | alternative instr 2 | padding
+ * +---------------------+- - - - - -+
+ * ^ runtime ^
+ *
+ * .altinstructions section
+ * +---------------------------------+
+ * | alt_instr entries for each |
+ * | alternative instr |
+ * +---------------------------------+
+ */
+
+#define b_altinstr(num) "664"#num
+#define e_altinstr(num) "665"#num
+
+#define e_oldinstr_pad_end "663"
+#define oldinstr_len "662b-661b"
+#define oldinstr_total_len e_oldinstr_pad_end"b-661b"
+#define altinstr_len(num) e_altinstr(num)"b-"b_altinstr(num)"b"
+#define oldinstr_pad_len(num) \
+ "-(((" altinstr_len(num) ")-(" oldinstr_len ")) > 0) * " \
+ "((" altinstr_len(num) ")-(" oldinstr_len "))"
+
+#define INSTR_LEN_SANITY_CHECK(len) \
+ ".if " len " > 254\n" \
+ "\t.error \"cpu alternatives does not support instructions " \
+ "blocks > 254 bytes\"\n" \
+ ".endif\n" \
+ ".if (" len ") %% 2\n" \
+ "\t.error \"cpu alternatives instructions length is odd\"\n" \
+ ".endif\n"
+
+#define OLDINSTR_PADDING(oldinstr, num) \
+ ".if " oldinstr_pad_len(num) " > 6\n" \
+ "\tjg " e_oldinstr_pad_end "f\n" \
+ "6620:\n" \
+ "\t.fill (" oldinstr_pad_len(num) " - (6620b-662b)) / 2, 2, 0x0700\n" \
+ ".else\n" \
+ "\t.fill " oldinstr_pad_len(num) " / 6, 6, 0xc0040000\n" \
+ "\t.fill " oldinstr_pad_len(num) " %% 6 / 4, 4, 0x47000000\n" \
+ "\t.fill " oldinstr_pad_len(num) " %% 6 %% 4 / 2, 2, 0x0700\n" \
+ ".endif\n"
+
+#define OLDINSTR(oldinstr, num) \
+ "661:\n\t" oldinstr "\n662:\n" \
+ OLDINSTR_PADDING(oldinstr, num) \
+ e_oldinstr_pad_end ":\n" \
+ INSTR_LEN_SANITY_CHECK(oldinstr_len)
+
+#define OLDINSTR_2(oldinstr, num1, num2) \
+ "661:\n\t" oldinstr "\n662:\n" \
+ ".if " altinstr_len(num1) " < " altinstr_len(num2) "\n" \
+ OLDINSTR_PADDING(oldinstr, num2) \
+ ".else\n" \
+ OLDINSTR_PADDING(oldinstr, num1) \
+ ".endif\n" \
+ e_oldinstr_pad_end ":\n" \
+ INSTR_LEN_SANITY_CHECK(oldinstr_len)
+
+#define ALTINSTR_ENTRY(facility, num) \
+ "\t.long 661b - .\n" /* old instruction */ \
+ "\t.long " b_altinstr(num)"b - .\n" /* alt instruction */ \
+ "\t.word " __stringify(facility) "\n" /* facility bit */ \
+ "\t.byte " oldinstr_total_len "\n" /* source len */ \
+ "\t.byte " altinstr_len(num) "\n" /* alt instruction len */
+
+#define ALTINSTR_REPLACEMENT(altinstr, num) /* replacement */ \
+ b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n" \
+ INSTR_LEN_SANITY_CHECK(altinstr_len(num))
+
+#ifdef CONFIG_ALTERNATIVES
+/* alternative assembly primitive: */
+#define ALTERNATIVE(oldinstr, altinstr, facility) \
+ ".pushsection .altinstr_replacement, \"ax\"\n" \
+ ALTINSTR_REPLACEMENT(altinstr, 1) \
+ ".popsection\n" \
+ OLDINSTR(oldinstr, 1) \
+ ".pushsection .altinstructions,\"a\"\n" \
+ ALTINSTR_ENTRY(facility, 1) \
+ ".popsection\n"
+
+#define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
+ ".pushsection .altinstr_replacement, \"ax\"\n" \
+ ALTINSTR_REPLACEMENT(altinstr1, 1) \
+ ALTINSTR_REPLACEMENT(altinstr2, 2) \
+ ".popsection\n" \
+ OLDINSTR_2(oldinstr, 1, 2) \
+ ".pushsection .altinstructions,\"a\"\n" \
+ ALTINSTR_ENTRY(facility1, 1) \
+ ALTINSTR_ENTRY(facility2, 2) \
+ ".popsection\n"
+#else
+/* Alternative instructions are disabled, let's put just oldinstr in */
+#define ALTERNATIVE(oldinstr, altinstr, facility) \
+ oldinstr "\n"
+
+#define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
+ oldinstr "\n"
+#endif
+
+/*
+ * Alternative instructions for different CPU types or capabilities.
+ *
+ * This allows to use optimized instructions even on generic binary
+ * kernels.
+ *
+ * oldinstr is padded with jump and nops at compile time if altinstr is
+ * longer. altinstr is padded with jump and nops at run-time during patching.
+ *
+ * For non barrier like inlines please define new variants
+ * without volatile and memory clobber.
+ */
+#define alternative(oldinstr, altinstr, facility) \
+ asm volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
+
+#define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
+ asm volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1, \
+ altinstr2, facility2) ::: "memory")
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_S390_ALTERNATIVE_H */
diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index 7b742ffac7d3..addf61024153 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
obj-$(CONFIG_UPROBES) += uprobes.o
+obj-$(CONFIG_ALTERNATIVES) += alternative.o
obj-$(CONFIG_PERF_EVENTS) += perf_event.o perf_cpum_cf.o perf_cpum_sf.o
obj-$(CONFIG_PERF_EVENTS) += perf_cpum_cf_events.o
diff --git a/arch/s390/kernel/alternative.c b/arch/s390/kernel/alternative.c
new file mode 100644
index 000000000000..315986a06cf5
--- /dev/null
+++ b/arch/s390/kernel/alternative.c
@@ -0,0 +1,110 @@
+#include <linux/module.h>
+#include <asm/alternative.h>
+#include <asm/facility.h>
+
+#define MAX_PATCH_LEN (255 - 1)
+
+static int __initdata_or_module alt_instr_disabled;
+
+static int __init disable_alternative_instructions(char *str)
+{
+ alt_instr_disabled = 1;
+ return 0;
+}
+
+early_param("noaltinstr", disable_alternative_instructions);
+
+struct brcl_insn {
+ u16 opc;
+ s32 disp;
+} __packed;
+
+static u16 __initdata_or_module nop16 = 0x0700;
+static u32 __initdata_or_module nop32 = 0x47000000;
+static struct brcl_insn __initdata_or_module nop48 = {
+ 0xc004, 0
+};
+
+static const void *nops[] __initdata_or_module = {
+ &nop16,
+ &nop32,
+ &nop48
+};
+
+static void __init_or_module add_jump_padding(void *insns, unsigned int len)
+{
+ struct brcl_insn brcl = {
+ 0xc0f4,
+ len / 2
+ };
+
+ memcpy(insns, &brcl, sizeof(brcl));
+ insns += sizeof(brcl);
+ len -= sizeof(brcl);
+
+ while (len > 0) {
+ memcpy(insns, &nop16, 2);
+ insns += 2;
+ len -= 2;
+ }
+}
+
+static void __init_or_module add_padding(void *insns, unsigned int len)
+{
+ if (len > 6)
+ add_jump_padding(insns, len);
+ else if (len >= 2)
+ memcpy(insns, nops[len / 2 - 1], len);
+}
+
+static void __init_or_module __apply_alternatives(struct alt_instr *start,
+ struct alt_instr *end)
+{
+ struct alt_instr *a;
+ u8 *instr, *replacement;
+ u8 insnbuf[MAX_PATCH_LEN];
+
+ /*
+ * The scan order should be from start to end. A later scanned
+ * alternative code can overwrite previously scanned alternative code.
+ */
+ for (a = start; a < end; a++) {
+ int insnbuf_sz = 0;
+
+ instr = (u8 *)&a->instr_offset + a->instr_offset;
+ replacement = (u8 *)&a->repl_offset + a->repl_offset;
+
+ if (!test_facility(a->facility))
+ continue;
+
+ if (unlikely(a->instrlen % 2 || a->replacementlen % 2)) {
+ WARN_ONCE(1, "cpu alternatives instructions length is "
+ "odd, skipping patching\n");
+ continue;
+ }
+
+ memcpy(insnbuf, replacement, a->replacementlen);
+ insnbuf_sz = a->replacementlen;
+
+ if (a->instrlen > a->replacementlen) {
+ add_padding(insnbuf + a->replacementlen,
+ a->instrlen - a->replacementlen);
+ insnbuf_sz += a->instrlen - a->replacementlen;
+ }
+
+ s390_kernel_write(instr, insnbuf, insnbuf_sz);
+ }
+}
+
+void __init_or_module apply_alternatives(struct alt_instr *start,
+ struct alt_instr *end)
+{
+ if (!alt_instr_disabled)
+ __apply_alternatives(start, end);
+}
+
+extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
+void __init apply_alternative_instructions(void)
+{
+ apply_alternatives(__alt_instructions, __alt_instructions_end);
+}
diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index 1a27f307a920..6d9f73bb4142 100644
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -31,6 +31,7 @@
#include <linux/kernel.h>
#include <linux/moduleloader.h>
#include <linux/bug.h>
+#include <asm/alternative.h>
#if 0
#define DEBUGP printk
@@ -429,6 +430,22 @@ int module_finalize(const Elf_Ehdr *hdr,
const Elf_Shdr *sechdrs,
struct module *me)
{
+ const Elf_Shdr *s;
+ char *secstrings;
+
+ if (IS_ENABLED(CONFIG_ALTERNATIVES)) {
+ secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
+ for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
+ if (!strcmp(".altinstructions",
+ secstrings + s->sh_name)) {
+ /* patch .altinstructions */
+ void *aseg = (void *)s->sh_addr;
+
+ apply_alternatives(aseg, aseg + s->sh_size);
+ }
+ }
+ }
+
jump_label_apply_nops(me);
return 0;
}
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index b2c9af9b88d5..c07e6d6a91cc 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -66,6 +66,7 @@
#include <asm/sclp.h>
#include <asm/sysinfo.h>
#include <asm/numa.h>
+#include <asm/alternative.h>
#include "entry.h"
/*
@@ -957,6 +958,8 @@ void __init setup_arch(char **cmdline_p)
conmode_default();
set_preferred_console();
+ apply_alternative_instructions();
+
/* Setup zfcpdump support */
setup_zfcpdump();
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 6e2c42bd1c3b..7c9fcf7cb43d 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -104,6 +104,29 @@ SECTIONS
EXIT_DATA
}
+ /*
+ * struct alt_inst entries. From the header (alternative.h):
+ * "Alternative instructions for different CPU types or capabilities"
+ * Think locking instructions on spinlocks.
+ * Note, that it is a part of __init region.
+ */
+ . = ALIGN(8);
+ .altinstructions : {
+ __alt_instructions = .;
+ *(.altinstructions)
+ __alt_instructions_end = .;
+ }
+
+ /*
+ * And here are the replacement instructions. The linker sticks
+ * them as binary blobs. The .altinstructions has enough data to
+ * get the address and the length of them to patch the kernel safely.
+ * Note, that it is a part of __init region.
+ */
+ .altinstr_replacement : {
+ *(.altinstr_replacement)
+ }
+
/* early.c uses stsi, which requires page aligned data. */
. = ALIGN(PAGE_SIZE);
INIT_DATA_SECTION(0x100)
generated by cgit v1.2.3 (git 2.39.0) at 2024-12-14 16:29:48 +0300