From 24ff652573754fe4c03213ebd26b17e86842feb3 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 30 Sep 2021 12:43:10 +0200 Subject: objtool: Teach get_alt_entry() about more relocation types Occasionally objtool encounters symbol (as opposed to section) relocations in .altinstructions. Typically they are the alternatives written by elf_add_alternative() as encountered on a noinstr validation run on vmlinux after having already ran objtool on the individual .o files. Basically this is the counterpart of commit 44f6a7c0755d ("objtool: Fix seg fault with Clang non-section symbols"), because when these new assemblers (binutils now also does this) strip the section symbols, elf_add_reloc_to_insn() is forced to emit symbol based relocations. As such, teach get_alt_entry() about different relocation types. Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Reported-by: Stephen Rothwell Reported-by: Borislav Petkov Signed-off-by: Peter Zijlstra (Intel) Acked-by: Josh Poimboeuf Tested-by: Nathan Chancellor Link: https://lore.kernel.org/r/YVWUvknIEVNkPvnP@hirez.programming.kicks-ass.net --- tools/objtool/special.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) (limited to 'tools/objtool') diff --git a/tools/objtool/special.c b/tools/objtool/special.c index bc925cf19e2d..f58ecc50fb10 100644 --- a/tools/objtool/special.c +++ b/tools/objtool/special.c @@ -58,6 +58,24 @@ void __weak arch_handle_alternative(unsigned short feature, struct special_alt * { } +static bool reloc2sec_off(struct reloc *reloc, struct section **sec, unsigned long *off) +{ + switch (reloc->sym->type) { + case STT_FUNC: + *sec = reloc->sym->sec; + *off = reloc->sym->offset + reloc->addend; + return true; + + case STT_SECTION: + *sec = reloc->sym->sec; + *off = reloc->addend; + return true; + + default: + return false; + } +} + static int get_alt_entry(struct elf *elf, struct special_entry *entry, struct section *sec, int idx, struct special_alt *alt) @@ -91,15 +109,12 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry, WARN_FUNC("can't find orig reloc", sec, offset + entry->orig); return -1; } - if (orig_reloc->sym->type != STT_SECTION) { - WARN_FUNC("don't know how to handle non-section reloc symbol %s", + if (!reloc2sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off)) { + WARN_FUNC("don't know how to handle reloc symbol type: %s", sec, offset + entry->orig, orig_reloc->sym->name); return -1; } - alt->orig_sec = orig_reloc->sym->sec; - alt->orig_off = orig_reloc->addend; - if (!entry->group || alt->new_len) { new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new); if (!new_reloc) { @@ -116,8 +131,11 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry, if (arch_is_retpoline(new_reloc->sym)) return 1; - alt->new_sec = new_reloc->sym->sec; - alt->new_off = (unsigned int)new_reloc->addend; + if (!reloc2sec_off(new_reloc, &alt->new_sec, &alt->new_off)) { + WARN_FUNC("don't know how to handle reloc symbol type: %s", + sec, offset + entry->new, new_reloc->sym->name); + return -1; + } /* _ASM_EXTABLE_EX hack */ if (alt->new_off >= 0x7ffffff0) -- cgit v1.2.3 From 7fab1c12bde926c5a8c7d5984c551d0854d7e0b3 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 3 Oct 2021 13:45:48 -0700 Subject: objtool: print out the symbol type when complaining about it The objtool warning that the kvm instruction emulation code triggered wasn't very useful: arch/x86/kvm/emulate.o: warning: objtool: __ex_table+0x4: don't know how to handle reloc symbol type: kvm_fastop_exception in that it helpfully tells you which symbol name it had trouble figuring out the relocation for, but it doesn't actually say what the unknown symbol type was that triggered it all. In this case it was because of missing type information (type 0, aka STT_NOTYPE), but on the whole it really should just have printed that out as part of the message. Because if this warning triggers, that's very much the first thing you want to know - why did reloc2sec_off() return failure for that symbol? So rather than just saying you can't handle some type of symbol without saying what the type _was_, just print out the type number too. Fixes: 24ff65257375 ("objtool: Teach get_alt_entry() about more relocation types") Link: https://lore.kernel.org/lkml/CAHk-=wiZwq-0LknKhXN4M+T8jbxn_2i9mcKpO+OaBSSq_Eh7tg@mail.gmail.com/ Signed-off-by: Linus Torvalds --- tools/objtool/special.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) (limited to 'tools/objtool') diff --git a/tools/objtool/special.c b/tools/objtool/special.c index f58ecc50fb10..f1428e32a505 100644 --- a/tools/objtool/special.c +++ b/tools/objtool/special.c @@ -110,8 +110,10 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry, return -1; } if (!reloc2sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off)) { - WARN_FUNC("don't know how to handle reloc symbol type: %s", - sec, offset + entry->orig, orig_reloc->sym->name); + WARN_FUNC("don't know how to handle reloc symbol type %d: %s", + sec, offset + entry->orig, + orig_reloc->sym->type, + orig_reloc->sym->name); return -1; } @@ -132,8 +134,10 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry, return 1; if (!reloc2sec_off(new_reloc, &alt->new_sec, &alt->new_off)) { - WARN_FUNC("don't know how to handle reloc symbol type: %s", - sec, offset + entry->new, new_reloc->sym->name); + WARN_FUNC("don't know how to handle reloc symbol type %d: %s", + sec, offset + entry->new, + new_reloc->sym->type, + new_reloc->sym->name); return -1; } -- cgit v1.2.3 From 4d8b35968bbf9e42b6b202eedb510e2c82ad8b38 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 4 Oct 2021 10:07:50 -0700 Subject: objtool: Remove reloc symbol type checks in get_alt_entry() Converting a special section's relocation reference to a symbol is straightforward. No need for objtool to complain that it doesn't know how to handle it. Just handle it. This fixes the following warning: arch/x86/kvm/emulate.o: warning: objtool: __ex_table+0x4: don't know how to handle reloc symbol type: kvm_fastop_exception Fixes: 24ff65257375 ("objtool: Teach get_alt_entry() about more relocation types") Reported-by: Linus Torvalds Signed-off-by: Josh Poimboeuf Link: https://lore.kernel.org/r/feadbc3dfb3440d973580fad8d3db873cbfe1694.1633367242.git.jpoimboe@redhat.com Cc: Peter Zijlstra Cc: x86@kernel.org Cc: Miroslav Benes Cc: linux-kernel@vger.kernel.org --- tools/objtool/special.c | 36 +++++++----------------------------- 1 file changed, 7 insertions(+), 29 deletions(-) (limited to 'tools/objtool') diff --git a/tools/objtool/special.c b/tools/objtool/special.c index f1428e32a505..83d5f969bcb0 100644 --- a/tools/objtool/special.c +++ b/tools/objtool/special.c @@ -58,22 +58,11 @@ void __weak arch_handle_alternative(unsigned short feature, struct special_alt * { } -static bool reloc2sec_off(struct reloc *reloc, struct section **sec, unsigned long *off) +static void reloc_to_sec_off(struct reloc *reloc, struct section **sec, + unsigned long *off) { - switch (reloc->sym->type) { - case STT_FUNC: - *sec = reloc->sym->sec; - *off = reloc->sym->offset + reloc->addend; - return true; - - case STT_SECTION: - *sec = reloc->sym->sec; - *off = reloc->addend; - return true; - - default: - return false; - } + *sec = reloc->sym->sec; + *off = reloc->sym->offset + reloc->addend; } static int get_alt_entry(struct elf *elf, struct special_entry *entry, @@ -109,13 +98,8 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry, WARN_FUNC("can't find orig reloc", sec, offset + entry->orig); return -1; } - if (!reloc2sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off)) { - WARN_FUNC("don't know how to handle reloc symbol type %d: %s", - sec, offset + entry->orig, - orig_reloc->sym->type, - orig_reloc->sym->name); - return -1; - } + + reloc_to_sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off); if (!entry->group || alt->new_len) { new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new); @@ -133,13 +117,7 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry, if (arch_is_retpoline(new_reloc->sym)) return 1; - if (!reloc2sec_off(new_reloc, &alt->new_sec, &alt->new_off)) { - WARN_FUNC("don't know how to handle reloc symbol type %d: %s", - sec, offset + entry->new, - new_reloc->sym->type, - new_reloc->sym->name); - return -1; - } + reloc_to_sec_off(new_reloc, &alt->new_sec, &alt->new_off); /* _ASM_EXTABLE_EX hack */ if (alt->new_off >= 0x7ffffff0) -- cgit v1.2.3 From dc02368164bd0ec603e3f5b3dd8252744a667b8a Mon Sep 17 00:00:00 2001 From: Joe Lawrence Date: Sun, 22 Aug 2021 18:50:36 -0400 Subject: objtool: Make .altinstructions section entry size consistent Commit e31694e0a7a7 ("objtool: Don't make .altinstructions writable") aligned objtool-created and kernel-created .altinstructions section flags, but there remains a minor discrepency in their use of a section entry size: objtool sets one while the kernel build does not. While sh_entsize of sizeof(struct alt_instr) seems intuitive, this small deviation can cause failures with external tooling (kpatch-build). Fix this by creating new .altinstructions sections with sh_entsize of 0 and then later updating sec->sh_size as alternatives are added to the section. An added benefit is avoiding the data descriptor and buffer created by elf_create_section(), but previously unused by elf_add_alternative(). Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls") Signed-off-by: Joe Lawrence Reviewed-by: Miroslav Benes Signed-off-by: Josh Poimboeuf Link: https://lore.kernel.org/r/20210822225037.54620-2-joe.lawrence@redhat.com Cc: Andy Lavr Cc: Peter Zijlstra Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- tools/objtool/arch/x86/decode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'tools/objtool') diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index bc821056aba9..0893436cc09f 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -684,7 +684,7 @@ static int elf_add_alternative(struct elf *elf, sec = find_section_by_name(elf, ".altinstructions"); if (!sec) { sec = elf_create_section(elf, ".altinstructions", - SHF_ALLOC, size, 0); + SHF_ALLOC, 0, 0); if (!sec) { WARN_ELF("elf_create_section"); -- cgit v1.2.3 From fe255fe6ad97685e5a4be0d871f43288dbc10ad6 Mon Sep 17 00:00:00 2001 From: Joe Lawrence Date: Sun, 22 Aug 2021 18:50:37 -0400 Subject: objtool: Remove redundant 'len' field from struct section The section structure already contains sh_size, so just remove the extra 'len' member that requires extra mirroring and potential confusion. Suggested-by: Josh Poimboeuf Signed-off-by: Joe Lawrence Reviewed-by: Miroslav Benes Signed-off-by: Josh Poimboeuf Link: https://lore.kernel.org/r/20210822225037.54620-3-joe.lawrence@redhat.com Cc: Andy Lavr Cc: Peter Zijlstra Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- tools/objtool/check.c | 16 ++++++++-------- tools/objtool/elf.c | 14 ++++++-------- tools/objtool/include/objtool/elf.h | 1 - tools/objtool/orc_gen.c | 2 +- tools/objtool/special.c | 4 ++-- 5 files changed, 17 insertions(+), 20 deletions(-) (limited to 'tools/objtool') diff --git a/tools/objtool/check.c b/tools/objtool/check.c index e5947fbb9e7a..06b5c164ae93 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -292,7 +292,7 @@ static int decode_instructions(struct objtool_file *file) !strcmp(sec->name, ".entry.text")) sec->noinstr = true; - for (offset = 0; offset < sec->len; offset += insn->len) { + for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) { insn = malloc(sizeof(*insn)); if (!insn) { WARN("malloc failed"); @@ -307,7 +307,7 @@ static int decode_instructions(struct objtool_file *file) insn->offset = offset; ret = arch_decode_instruction(file->elf, sec, offset, - sec->len - offset, + sec->sh.sh_size - offset, &insn->len, &insn->type, &insn->immediate, &insn->stack_ops); @@ -349,9 +349,9 @@ static struct instruction *find_last_insn(struct objtool_file *file, { struct instruction *insn = NULL; unsigned int offset; - unsigned int end = (sec->len > 10) ? sec->len - 10 : 0; + unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0; - for (offset = sec->len - 1; offset >= end && !insn; offset--) + for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--) insn = find_insn(file, sec, offset); return insn; @@ -389,7 +389,7 @@ static int add_dead_ends(struct objtool_file *file) insn = find_insn(file, reloc->sym->sec, reloc->addend); if (insn) insn = list_prev_entry(insn, list); - else if (reloc->addend == reloc->sym->sec->len) { + else if (reloc->addend == reloc->sym->sec->sh.sh_size) { insn = find_last_insn(file, reloc->sym->sec); if (!insn) { WARN("can't find unreachable insn at %s+0x%x", @@ -424,7 +424,7 @@ reachable: insn = find_insn(file, reloc->sym->sec, reloc->addend); if (insn) insn = list_prev_entry(insn, list); - else if (reloc->addend == reloc->sym->sec->len) { + else if (reloc->addend == reloc->sym->sec->sh.sh_size) { insn = find_last_insn(file, reloc->sym->sec); if (!insn) { WARN("can't find reachable insn at %s+0x%x", @@ -1561,14 +1561,14 @@ static int read_unwind_hints(struct objtool_file *file) return -1; } - if (sec->len % sizeof(struct unwind_hint)) { + if (sec->sh.sh_size % sizeof(struct unwind_hint)) { WARN("struct unwind_hint size mismatch"); return -1; } file->hints = true; - for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) { + for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) { hint = (struct unwind_hint *)sec->data->d_buf + i; reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint)); diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 8676c7598728..b18f0055b50b 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -286,10 +286,9 @@ static int read_sections(struct elf *elf) return -1; } } - sec->len = sec->sh.sh_size; if (sec->sh.sh_flags & SHF_EXECINSTR) - elf->text_size += sec->len; + elf->text_size += sec->sh.sh_size; list_add_tail(&sec->list, &elf->sections); elf_hash_add(section, &sec->hash, sec->idx); @@ -734,8 +733,8 @@ static int elf_add_string(struct elf *elf, struct section *strtab, char *str) data->d_size = strlen(str) + 1; data->d_align = 1; - len = strtab->len; - strtab->len += data->d_size; + len = strtab->sh.sh_size; + strtab->sh.sh_size += data->d_size; strtab->changed = true; return len; @@ -790,9 +789,9 @@ struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) data->d_align = 1; data->d_type = ELF_T_SYM; - sym->idx = symtab->len / sizeof(sym->sym); + sym->idx = symtab->sh.sh_size / sizeof(sym->sym); - symtab->len += data->d_size; + symtab->sh.sh_size += data->d_size; symtab->changed = true; symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); @@ -814,7 +813,7 @@ struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) data->d_align = 4; data->d_type = ELF_T_WORD; - symtab_shndx->len += 4; + symtab_shndx->sh.sh_size += 4; symtab_shndx->changed = true; } @@ -855,7 +854,6 @@ struct section *elf_create_section(struct elf *elf, const char *name, } sec->idx = elf_ndxscn(s); - sec->len = size; sec->changed = true; sec->data = elf_newdata(s); diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h index e34395047530..075d8291b854 100644 --- a/tools/objtool/include/objtool/elf.h +++ b/tools/objtool/include/objtool/elf.h @@ -38,7 +38,6 @@ struct section { Elf_Data *data; char *name; int idx; - unsigned int len; bool changed, text, rodata, noinstr; }; diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c index dc9b7dd314b0..b5865e2450cb 100644 --- a/tools/objtool/orc_gen.c +++ b/tools/objtool/orc_gen.c @@ -204,7 +204,7 @@ int orc_create(struct objtool_file *file) /* Add a section terminator */ if (!empty) { - orc_list_add(&orc_list, &null, sec, sec->len); + orc_list_add(&orc_list, &null, sec, sec->sh.sh_size); nr++; } } diff --git a/tools/objtool/special.c b/tools/objtool/special.c index 83d5f969bcb0..06c3eacab3d5 100644 --- a/tools/objtool/special.c +++ b/tools/objtool/special.c @@ -159,13 +159,13 @@ int special_get_alts(struct elf *elf, struct list_head *alts) if (!sec) continue; - if (sec->len % entry->size != 0) { + if (sec->sh.sh_size % entry->size != 0) { WARN("%s size not a multiple of %d", sec->name, entry->size); return -1; } - nr_entries = sec->len / entry->size; + nr_entries = sec->sh.sh_size / entry->size; for (idx = 0; idx < nr_entries; idx++) { alt = malloc(sizeof(*alt)); -- cgit v1.2.3