diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2018-05-20 20:01:38 +0300 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-05-20 20:01:38 +0300 |
commit | 583dbad34098fd2891dcc850744e7c80063dd8a4 (patch) | |
tree | 6c1041c3eaf761d414bd81f6f12ad58fcd3a7b3d /tools | |
parent | 203ec2fed17ade9582277570eb234be52085f8c5 (diff) | |
parent | 7dec80ccbe310fb7e225bf21c48c672bb780ce7b (diff) | |
download | linux-583dbad34098fd2891dcc850744e7c80063dd8a4.tar.xz |
Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core fixes from Thomas Gleixner:
- Unbreak the BPF compilation which got broken by the unconditional
requirement of asm-goto, which is not supported by clang.
- Prevent probing on exception masking instructions in uprobes and
kprobes to avoid the issues of the delayed exceptions instead of
having an ugly workaround.
- Prevent a double free_page() in the error path of do_kexec_load()
- A set of objtool updates addressing various issues mostly related to
switch tables and the noreturn detection for recursive sibling calls
- Header sync for tools.
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
objtool: Detect RIP-relative switch table references, part 2
objtool: Detect RIP-relative switch table references
objtool: Support GCC 8 switch tables
objtool: Support GCC 8's cold subfunctions
objtool: Fix "noreturn" detection for recursive sibling calls
objtool, kprobes/x86: Sync the latest <asm/insn.h> header with tools/objtool/arch/x86/include/asm/insn.h
x86/cpufeature: Guard asm_volatile_goto usage for BPF compilation
uprobes/x86: Prohibit probing on MOV SS instruction
kprobes/x86: Prohibit probing on exception masking instructions
x86/kexec: Avoid double free_page() upon do_kexec_load() failure
Diffstat (limited to 'tools')
-rw-r--r-- | tools/objtool/arch/x86/include/asm/insn.h | 18 | ||||
-rw-r--r-- | tools/objtool/check.c | 167 | ||||
-rw-r--r-- | tools/objtool/elf.c | 42 | ||||
-rw-r--r-- | tools/objtool/elf.h | 2 |
4 files changed, 155 insertions, 74 deletions
diff --git a/tools/objtool/arch/x86/include/asm/insn.h b/tools/objtool/arch/x86/include/asm/insn.h index b3e32b010ab1..c2c01f84df75 100644 --- a/tools/objtool/arch/x86/include/asm/insn.h +++ b/tools/objtool/arch/x86/include/asm/insn.h @@ -208,4 +208,22 @@ static inline int insn_offset_immediate(struct insn *insn) return insn_offset_displacement(insn) + insn->displacement.nbytes; } +#define POP_SS_OPCODE 0x1f +#define MOV_SREG_OPCODE 0x8e + +/* + * Intel SDM Vol.3A 6.8.3 states; + * "Any single-step trap that would be delivered following the MOV to SS + * instruction or POP to SS instruction (because EFLAGS.TF is 1) is + * suppressed." + * This function returns true if @insn is MOV SS or POP SS. On these + * instructions, single stepping is suppressed. + */ +static inline int insn_masking_exception(struct insn *insn) +{ + return insn->opcode.bytes[0] == POP_SS_OPCODE || + (insn->opcode.bytes[0] == MOV_SREG_OPCODE && + X86_MODRM_REG(insn->modrm.bytes[0]) == 2); +} + #endif /* _ASM_X86_INSN_H */ diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 5409f6f6c48d..3a31b238f885 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -59,6 +59,31 @@ static struct instruction *next_insn_same_sec(struct objtool_file *file, return next; } +static struct instruction *next_insn_same_func(struct objtool_file *file, + struct instruction *insn) +{ + struct instruction *next = list_next_entry(insn, list); + struct symbol *func = insn->func; + + if (!func) + return NULL; + + if (&next->list != &file->insn_list && next->func == func) + return next; + + /* Check if we're already in the subfunction: */ + if (func == func->cfunc) + return NULL; + + /* Move to the subfunction: */ + return find_insn(file, func->cfunc->sec, func->cfunc->offset); +} + +#define func_for_each_insn_all(file, func, insn) \ + for (insn = find_insn(file, func->sec, func->offset); \ + insn; \ + insn = next_insn_same_func(file, insn)) + #define func_for_each_insn(file, func, insn) \ for (insn = find_insn(file, func->sec, func->offset); \ insn && &insn->list != &file->insn_list && \ @@ -149,10 +174,14 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func, if (!strcmp(func->name, global_noreturns[i])) return 1; - if (!func->sec) + if (!func->len) return 0; - func_for_each_insn(file, func, insn) { + insn = find_insn(file, func->sec, func->offset); + if (!insn->func) + return 0; + + func_for_each_insn_all(file, func, insn) { empty = false; if (insn->type == INSN_RETURN) @@ -167,35 +196,28 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func, * case, the function's dead-end status depends on whether the target * of the sibling call returns. */ - func_for_each_insn(file, func, insn) { - if (insn->sec != func->sec || - insn->offset >= func->offset + func->len) - break; - + func_for_each_insn_all(file, func, insn) { if (insn->type == INSN_JUMP_UNCONDITIONAL) { struct instruction *dest = insn->jump_dest; - struct symbol *dest_func; if (!dest) /* sibling call to another file */ return 0; - if (dest->sec != func->sec || - dest->offset < func->offset || - dest->offset >= func->offset + func->len) { - /* local sibling call */ - dest_func = find_symbol_by_offset(dest->sec, - dest->offset); - if (!dest_func) - continue; + if (dest->func && dest->func->pfunc != insn->func->pfunc) { + /* local sibling call */ if (recursion == 5) { - WARN_FUNC("infinite recursion (objtool bug!)", - dest->sec, dest->offset); - return -1; + /* + * Infinite recursion: two functions + * have sibling calls to each other. + * This is a very rare case. It means + * they aren't dead ends. + */ + return 0; } - return __dead_end_function(file, dest_func, + return __dead_end_function(file, dest->func, recursion + 1); } } @@ -422,7 +444,7 @@ static void add_ignores(struct objtool_file *file) if (!ignore_func(file, func)) continue; - func_for_each_insn(file, func, insn) + func_for_each_insn_all(file, func, insn) insn->ignore = true; } } @@ -782,30 +804,35 @@ out: return ret; } -static int add_switch_table(struct objtool_file *file, struct symbol *func, - struct instruction *insn, struct rela *table, - struct rela *next_table) +static int add_switch_table(struct objtool_file *file, struct instruction *insn, + struct rela *table, struct rela *next_table) { struct rela *rela = table; struct instruction *alt_insn; struct alternative *alt; + struct symbol *pfunc = insn->func->pfunc; + unsigned int prev_offset = 0; list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) { if (rela == next_table) break; - if (rela->sym->sec != insn->sec || - rela->addend <= func->offset || - rela->addend >= func->offset + func->len) + /* Make sure the switch table entries are consecutive: */ + if (prev_offset && rela->offset != prev_offset + 8) break; - alt_insn = find_insn(file, insn->sec, rela->addend); - if (!alt_insn) { - WARN("%s: can't find instruction at %s+0x%x", - file->rodata->rela->name, insn->sec->name, - rela->addend); - return -1; - } + /* Detect function pointers from contiguous objects: */ + if (rela->sym->sec == pfunc->sec && + rela->addend == pfunc->offset) + break; + + alt_insn = find_insn(file, rela->sym->sec, rela->addend); + if (!alt_insn) + break; + + /* Make sure the jmp dest is in the function or subfunction: */ + if (alt_insn->func->pfunc != pfunc) + break; alt = malloc(sizeof(*alt)); if (!alt) { @@ -815,6 +842,13 @@ static int add_switch_table(struct objtool_file *file, struct symbol *func, alt->insn = alt_insn; list_add_tail(&alt->list, &insn->alts); + prev_offset = rela->offset; + } + + if (!prev_offset) { + WARN_FUNC("can't find switch jump table", + insn->sec, insn->offset); + return -1; } return 0; @@ -869,40 +903,21 @@ static struct rela *find_switch_table(struct objtool_file *file, { struct rela *text_rela, *rodata_rela; struct instruction *orig_insn = insn; + unsigned long table_offset; - text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); - if (text_rela && text_rela->sym == file->rodata->sym) { - /* case 1 */ - rodata_rela = find_rela_by_dest(file->rodata, - text_rela->addend); - if (rodata_rela) - return rodata_rela; - - /* case 2 */ - rodata_rela = find_rela_by_dest(file->rodata, - text_rela->addend + 4); - if (!rodata_rela) - return NULL; - - file->ignore_unreachables = true; - return rodata_rela; - } - - /* case 3 */ /* * Backward search using the @first_jump_src links, these help avoid * much of the 'in between' code. Which avoids us getting confused by * it. */ - for (insn = list_prev_entry(insn, list); - + for (; &insn->list != &file->insn_list && insn->sec == func->sec && insn->offset >= func->offset; insn = insn->first_jump_src ?: list_prev_entry(insn, list)) { - if (insn->type == INSN_JUMP_DYNAMIC) + if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) break; /* allow small jumps within the range */ @@ -918,18 +933,29 @@ static struct rela *find_switch_table(struct objtool_file *file, if (!text_rela || text_rela->sym != file->rodata->sym) continue; + table_offset = text_rela->addend; + if (text_rela->type == R_X86_64_PC32) + table_offset += 4; + /* * Make sure the .rodata address isn't associated with a * symbol. gcc jump tables are anonymous data. */ - if (find_symbol_containing(file->rodata, text_rela->addend)) + if (find_symbol_containing(file->rodata, table_offset)) continue; - rodata_rela = find_rela_by_dest(file->rodata, text_rela->addend); - if (!rodata_rela) - continue; + rodata_rela = find_rela_by_dest(file->rodata, table_offset); + if (rodata_rela) { + /* + * Use of RIP-relative switch jumps is quite rare, and + * indicates a rare GCC quirk/bug which can leave dead + * code behind. + */ + if (text_rela->type == R_X86_64_PC32) + file->ignore_unreachables = true; - return rodata_rela; + return rodata_rela; + } } return NULL; @@ -943,7 +969,7 @@ static int add_func_switch_tables(struct objtool_file *file, struct rela *rela, *prev_rela = NULL; int ret; - func_for_each_insn(file, func, insn) { + func_for_each_insn_all(file, func, insn) { if (!last) last = insn; @@ -974,8 +1000,7 @@ static int add_func_switch_tables(struct objtool_file *file, * the beginning of another switch table in the same function. */ if (prev_jump) { - ret = add_switch_table(file, func, prev_jump, prev_rela, - rela); + ret = add_switch_table(file, prev_jump, prev_rela, rela); if (ret) return ret; } @@ -985,7 +1010,7 @@ static int add_func_switch_tables(struct objtool_file *file, } if (prev_jump) { - ret = add_switch_table(file, func, prev_jump, prev_rela, NULL); + ret = add_switch_table(file, prev_jump, prev_rela, NULL); if (ret) return ret; } @@ -1749,15 +1774,13 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, while (1) { next_insn = next_insn_same_sec(file, insn); - - if (file->c_file && func && insn->func && func != insn->func) { + if (file->c_file && func && insn->func && func != insn->func->pfunc) { WARN("%s() falls through to next function %s()", func->name, insn->func->name); return 1; } - if (insn->func) - func = insn->func; + func = insn->func ? insn->func->pfunc : NULL; if (func && insn->ignore) { WARN_FUNC("BUG: why am I validating an ignored function?", @@ -1778,7 +1801,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, i = insn; save_insn = NULL; - func_for_each_insn_continue_reverse(file, func, i) { + func_for_each_insn_continue_reverse(file, insn->func, i) { if (i->save) { save_insn = i; break; @@ -1865,7 +1888,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, case INSN_JUMP_UNCONDITIONAL: if (insn->jump_dest && (!func || !insn->jump_dest->func || - func == insn->jump_dest->func)) { + insn->jump_dest->func->pfunc == func)) { ret = validate_branch(file, insn->jump_dest, state); if (ret) @@ -2060,7 +2083,7 @@ static int validate_functions(struct objtool_file *file) for_each_sec(file, sec) { list_for_each_entry(func, &sec->symbol_list, list) { - if (func->type != STT_FUNC) + if (func->type != STT_FUNC || func->pfunc != func) continue; insn = find_insn(file, sec, func->offset); diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index c1c338661699..4e60e105583e 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -79,6 +79,19 @@ struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset) return NULL; } +struct symbol *find_symbol_by_name(struct elf *elf, const char *name) +{ + struct section *sec; + struct symbol *sym; + + list_for_each_entry(sec, &elf->sections, list) + list_for_each_entry(sym, &sec->symbol_list, list) + if (!strcmp(sym->name, name)) + return sym; + + return NULL; +} + struct symbol *find_symbol_containing(struct section *sec, unsigned long offset) { struct symbol *sym; @@ -203,10 +216,11 @@ static int read_sections(struct elf *elf) static int read_symbols(struct elf *elf) { - struct section *symtab; - struct symbol *sym; + struct section *symtab, *sec; + struct symbol *sym, *pfunc; struct list_head *entry, *tmp; int symbols_nr, i; + char *coldstr; symtab = find_section_by_name(elf, ".symtab"); if (!symtab) { @@ -281,6 +295,30 @@ static int read_symbols(struct elf *elf) hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx); } + /* Create parent/child links for any cold subfunctions */ + list_for_each_entry(sec, &elf->sections, list) { + list_for_each_entry(sym, &sec->symbol_list, list) { + if (sym->type != STT_FUNC) + continue; + sym->pfunc = sym->cfunc = sym; + coldstr = strstr(sym->name, ".cold."); + if (coldstr) { + coldstr[0] = '\0'; + pfunc = find_symbol_by_name(elf, sym->name); + coldstr[0] = '.'; + + if (!pfunc) { + WARN("%s(): can't find parent function", + sym->name); + goto err; + } + + sym->pfunc = pfunc; + pfunc->cfunc = sym; + } + } + } + return 0; err: diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h index d86e2ff14466..de5cd2ddded9 100644 --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -61,6 +61,7 @@ struct symbol { unsigned char bind, type; unsigned long offset; unsigned int len; + struct symbol *pfunc, *cfunc; }; struct rela { @@ -86,6 +87,7 @@ struct elf { struct elf *elf_open(const char *name, int flags); struct section *find_section_by_name(struct elf *elf, const char *name); struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset); +struct symbol *find_symbol_by_name(struct elf *elf, const char *name); struct symbol *find_symbol_containing(struct section *sec, unsigned long offset); struct rela *find_rela_by_dest(struct section *sec, unsigned long offset); struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset, |