diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2022-05-01 19:34:54 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-05-01 19:34:54 +0300 |
commit | b70ed23c238af025153cb0f5b3c1d0ae5bc30f73 (patch) | |
tree | 0effdfc6282165b5372773bb1f0e09862de93699 /tools | |
parent | d4af0c17235fbf992f5023bbfb84303e082e45a6 (diff) | |
parent | 4abff6d48dbcea8200c7ea35ba70c242d128ebf3 (diff) | |
download | linux-b70ed23c238af025153cb0f5b3c1d0ae5bc30f73.tar.xz |
Merge tag 'objtool_urgent_for_v5.18_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull objtool fixes from Borislav Petkov:
"A bunch of objtool fixes to improve unwinding, sibling call detection,
fallthrough detection and relocation handling of weak symbols when the
toolchain strips section symbols"
* tag 'objtool_urgent_for_v5.18_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
objtool: Fix code relocs vs weak symbols
objtool: Fix type of reloc::addend
objtool: Fix function fallthrough detection for vmlinux
objtool: Fix sibling call detection in alternatives
objtool: Don't set 'jump_dest' for sibling calls
x86/uaccess: Don't jump between functions
Diffstat (limited to 'tools')
-rw-r--r-- | tools/objtool/check.c | 81 | ||||
-rw-r--r-- | tools/objtool/elf.c | 189 | ||||
-rw-r--r-- | tools/objtool/include/objtool/elf.h | 4 | ||||
-rw-r--r-- | tools/objtool/include/objtool/objtool.h | 2 | ||||
-rw-r--r-- | tools/objtool/objtool.c | 1 |
5 files changed, 213 insertions, 64 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index bd0c2c828940..3f6785415894 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -559,12 +559,12 @@ static int add_dead_ends(struct objtool_file *file) 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", + WARN("can't find unreachable insn at %s+0x%lx", reloc->sym->sec->name, reloc->addend); return -1; } } else { - WARN("can't find unreachable insn at %s+0x%x", + WARN("can't find unreachable insn at %s+0x%lx", reloc->sym->sec->name, reloc->addend); return -1; } @@ -594,12 +594,12 @@ reachable: 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", + WARN("can't find reachable insn at %s+0x%lx", reloc->sym->sec->name, reloc->addend); return -1; } } else { - WARN("can't find reachable insn at %s+0x%x", + WARN("can't find reachable insn at %s+0x%lx", reloc->sym->sec->name, reloc->addend); return -1; } @@ -1271,12 +1271,19 @@ static bool is_first_func_insn(struct objtool_file *file, struct instruction *in */ static int add_jump_destinations(struct objtool_file *file) { - struct instruction *insn; + struct instruction *insn, *jump_dest; struct reloc *reloc; struct section *dest_sec; unsigned long dest_off; for_each_insn(file, insn) { + if (insn->jump_dest) { + /* + * handle_group_alt() may have previously set + * 'jump_dest' for some alternatives. + */ + continue; + } if (!is_static_jump(insn)) continue; @@ -1291,7 +1298,10 @@ static int add_jump_destinations(struct objtool_file *file) add_retpoline_call(file, insn); continue; } else if (insn->func) { - /* internal or external sibling call (with reloc) */ + /* + * External sibling call or internal sibling call with + * STT_FUNC reloc. + */ add_call_dest(file, insn, reloc->sym, true); continue; } else if (reloc->sym->sec->idx) { @@ -1303,17 +1313,8 @@ static int add_jump_destinations(struct objtool_file *file) continue; } - insn->jump_dest = find_insn(file, dest_sec, dest_off); - if (!insn->jump_dest) { - - /* - * This is a special case where an alt instruction - * jumps past the end of the section. These are - * handled later in handle_group_alt(). - */ - if (!strcmp(insn->sec->name, ".altinstr_replacement")) - continue; - + jump_dest = find_insn(file, dest_sec, dest_off); + if (!jump_dest) { WARN_FUNC("can't find jump dest instruction at %s+0x%lx", insn->sec, insn->offset, dest_sec->name, dest_off); @@ -1323,8 +1324,8 @@ static int add_jump_destinations(struct objtool_file *file) /* * Cross-function jump. */ - if (insn->func && insn->jump_dest->func && - insn->func != insn->jump_dest->func) { + if (insn->func && jump_dest->func && + insn->func != jump_dest->func) { /* * For GCC 8+, create parent/child links for any cold @@ -1342,16 +1343,22 @@ static int add_jump_destinations(struct objtool_file *file) * subfunction is through a jump table. */ if (!strstr(insn->func->name, ".cold") && - strstr(insn->jump_dest->func->name, ".cold")) { - insn->func->cfunc = insn->jump_dest->func; - insn->jump_dest->func->pfunc = insn->func; + strstr(jump_dest->func->name, ".cold")) { + insn->func->cfunc = jump_dest->func; + jump_dest->func->pfunc = insn->func; - } else if (!same_function(insn, insn->jump_dest) && - is_first_func_insn(file, insn->jump_dest)) { - /* internal sibling call (without reloc) */ - add_call_dest(file, insn, insn->jump_dest->func, true); + } else if (!same_function(insn, jump_dest) && + is_first_func_insn(file, jump_dest)) { + /* + * Internal sibling call without reloc or with + * STT_SECTION reloc. + */ + add_call_dest(file, insn, jump_dest->func, true); + continue; } } + + insn->jump_dest = jump_dest; } return 0; @@ -1540,13 +1547,13 @@ static int handle_group_alt(struct objtool_file *file, continue; dest_off = arch_jump_destination(insn); - if (dest_off == special_alt->new_off + special_alt->new_len) + if (dest_off == special_alt->new_off + special_alt->new_len) { insn->jump_dest = next_insn_same_sec(file, last_orig_insn); - - if (!insn->jump_dest) { - WARN_FUNC("can't find alternative jump destination", - insn->sec, insn->offset); - return -1; + if (!insn->jump_dest) { + WARN_FUNC("can't find alternative jump destination", + insn->sec, insn->offset); + return -1; + } } } @@ -2245,14 +2252,14 @@ static int decode_sections(struct objtool_file *file) return ret; /* - * Must be before add_special_section_alts() as that depends on - * jump_dest being set. + * Must be before add_jump_destinations(), which depends on 'func' + * being set for alternatives, to enable proper sibling call detection. */ - ret = add_jump_destinations(file); + ret = add_special_section_alts(file); if (ret) return ret; - ret = add_special_section_alts(file); + ret = add_jump_destinations(file); if (ret) return ret; @@ -3303,7 +3310,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, while (1) { next_insn = next_insn_to_validate(file, insn); - if (file->c_file && func && insn->func && func != insn->func->pfunc) { + if (func && insn->func && func != insn->func->pfunc) { WARN("%s() falls through to next function %s()", func->name, insn->func->name); return 1; diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index d7b99a737496..ebf2ba5755c1 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -546,7 +546,7 @@ static struct section *elf_create_reloc_section(struct elf *elf, int reltype); int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset, - unsigned int type, struct symbol *sym, int addend) + unsigned int type, struct symbol *sym, long addend) { struct reloc *reloc; @@ -575,37 +575,180 @@ int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset, return 0; } -int elf_add_reloc_to_insn(struct elf *elf, struct section *sec, - unsigned long offset, unsigned int type, - struct section *insn_sec, unsigned long insn_off) +/* + * Ensure that any reloc section containing references to @sym is marked + * changed such that it will get re-generated in elf_rebuild_reloc_sections() + * with the new symbol index. + */ +static void elf_dirty_reloc_sym(struct elf *elf, struct symbol *sym) +{ + struct section *sec; + + list_for_each_entry(sec, &elf->sections, list) { + struct reloc *reloc; + + if (sec->changed) + continue; + + list_for_each_entry(reloc, &sec->reloc_list, list) { + if (reloc->sym == sym) { + sec->changed = true; + break; + } + } + } +} + +/* + * Move the first global symbol, as per sh_info, into a new, higher symbol + * index. This fees up the shndx for a new local symbol. + */ +static int elf_move_global_symbol(struct elf *elf, struct section *symtab, + struct section *symtab_shndx) { + Elf_Data *data, *shndx_data = NULL; + Elf32_Word first_non_local; struct symbol *sym; - int addend; + Elf_Scn *s; - if (insn_sec->sym) { - sym = insn_sec->sym; - addend = insn_off; + first_non_local = symtab->sh.sh_info; - } else { - /* - * The Clang assembler strips section symbols, so we have to - * reference the function symbol instead: - */ - sym = find_symbol_containing(insn_sec, insn_off); - if (!sym) { - /* - * Hack alert. This happens when we need to reference - * the NOP pad insn immediately after the function. - */ - sym = find_symbol_containing(insn_sec, insn_off - 1); + sym = find_symbol_by_index(elf, first_non_local); + if (!sym) { + WARN("no non-local symbols !?"); + return first_non_local; + } + + s = elf_getscn(elf->elf, symtab->idx); + if (!s) { + WARN_ELF("elf_getscn"); + return -1; + } + + data = elf_newdata(s); + if (!data) { + WARN_ELF("elf_newdata"); + return -1; + } + + 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); + elf_dirty_reloc_sym(elf, sym); + + symtab->sh.sh_info += 1; + symtab->sh.sh_size += data->d_size; + symtab->changed = true; + + if (symtab_shndx) { + s = elf_getscn(elf->elf, symtab_shndx->idx); + if (!s) { + WARN_ELF("elf_getscn"); + return -1; } - if (!sym) { - WARN("can't find symbol containing %s+0x%lx", insn_sec->name, insn_off); + shndx_data = elf_newdata(s); + if (!shndx_data) { + WARN_ELF("elf_newshndx_data"); return -1; } - addend = insn_off - sym->offset; + shndx_data->d_buf = &sym->sec->idx; + shndx_data->d_size = sizeof(Elf32_Word); + shndx_data->d_align = 4; + shndx_data->d_type = ELF_T_WORD; + + symtab_shndx->sh.sh_size += 4; + symtab_shndx->changed = true; + } + + return first_non_local; +} + +static struct symbol * +elf_create_section_symbol(struct elf *elf, struct section *sec) +{ + struct section *symtab, *symtab_shndx; + Elf_Data *shndx_data = NULL; + struct symbol *sym; + Elf32_Word shndx; + + symtab = find_section_by_name(elf, ".symtab"); + if (symtab) { + symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); + if (symtab_shndx) + shndx_data = symtab_shndx->data; + } else { + WARN("no .symtab"); + return NULL; + } + + sym = malloc(sizeof(*sym)); + if (!sym) { + perror("malloc"); + return NULL; + } + memset(sym, 0, sizeof(*sym)); + + sym->idx = elf_move_global_symbol(elf, symtab, symtab_shndx); + if (sym->idx < 0) { + WARN("elf_move_global_symbol"); + return NULL; + } + + sym->name = sec->name; + sym->sec = sec; + + // st_name 0 + sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION); + // st_other 0 + // st_value 0 + // st_size 0 + shndx = sec->idx; + if (shndx >= SHN_UNDEF && shndx < SHN_LORESERVE) { + sym->sym.st_shndx = shndx; + if (!shndx_data) + shndx = 0; + } else { + sym->sym.st_shndx = SHN_XINDEX; + if (!shndx_data) { + WARN("no .symtab_shndx"); + return NULL; + } + } + + if (!gelf_update_symshndx(symtab->data, shndx_data, sym->idx, &sym->sym, shndx)) { + WARN_ELF("gelf_update_symshndx"); + return NULL; + } + + elf_add_symbol(elf, sym); + + return sym; +} + +int elf_add_reloc_to_insn(struct elf *elf, struct section *sec, + unsigned long offset, unsigned int type, + struct section *insn_sec, unsigned long insn_off) +{ + struct symbol *sym = insn_sec->sym; + int addend = insn_off; + + if (!sym) { + /* + * Due to how weak functions work, we must use section based + * relocations. Symbol based relocations would result in the + * weak and non-weak function annotations being overlaid on the + * non-weak function after linking. + */ + sym = elf_create_section_symbol(elf, insn_sec); + if (!sym) + return -1; + + insn_sec->sym = sym; } return elf_add_reloc(elf, sec, offset, type, sym, addend); diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h index 22ba7e2b816e..9b36802ed86f 100644 --- a/tools/objtool/include/objtool/elf.h +++ b/tools/objtool/include/objtool/elf.h @@ -73,7 +73,7 @@ struct reloc { struct symbol *sym; unsigned long offset; unsigned int type; - int addend; + long addend; int idx; bool jump_table_start; }; @@ -135,7 +135,7 @@ struct elf *elf_open_read(const char *name, int flags); struct section *elf_create_section(struct elf *elf, const char *name, unsigned int sh_flags, size_t entsize, int nr); int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset, - unsigned int type, struct symbol *sym, int addend); + unsigned int type, struct symbol *sym, long addend); int elf_add_reloc_to_insn(struct elf *elf, struct section *sec, unsigned long offset, unsigned int type, struct section *insn_sec, unsigned long insn_off); diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h index 7a5c13a78f87..a6e72d916807 100644 --- a/tools/objtool/include/objtool/objtool.h +++ b/tools/objtool/include/objtool/objtool.h @@ -27,7 +27,7 @@ struct objtool_file { struct list_head static_call_list; struct list_head mcount_loc_list; struct list_head endbr_list; - bool ignore_unreachables, c_file, hints, rodata; + bool ignore_unreachables, hints, rodata; unsigned int nr_endbr; unsigned int nr_endbr_int; diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c index b09946f4e1d6..843ff3c2f28e 100644 --- a/tools/objtool/objtool.c +++ b/tools/objtool/objtool.c @@ -129,7 +129,6 @@ struct objtool_file *objtool_open_read(const char *_objname) INIT_LIST_HEAD(&file.static_call_list); INIT_LIST_HEAD(&file.mcount_loc_list); INIT_LIST_HEAD(&file.endbr_list); - file.c_file = !vmlinux && find_section_by_name(file.elf, ".comment"); file.ignore_unreachables = no_unreachable; file.hints = false; |