From 4d8b35968bbf9e42b6b202eedb510e2c82ad8b38 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 4 Oct 2021 10:07:50 -0700 Subject: [PATCH 1/3] 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(-) 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) From dc02368164bd0ec603e3f5b3dd8252744a667b8a Mon Sep 17 00:00:00 2001 From: Joe Lawrence Date: Sun, 22 Aug 2021 18:50:36 -0400 Subject: [PATCH 2/3] 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(-) 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"); From fe255fe6ad97685e5a4be0d871f43288dbc10ad6 Mon Sep 17 00:00:00 2001 From: Joe Lawrence Date: Sun, 22 Aug 2021 18:50:37 -0400 Subject: [PATCH 3/3] 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(-) 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));