From 867ac9d737094e46a6c33213f16dd1ec9e8bd5d5 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 24 Jul 2017 18:34:14 -0500 Subject: [PATCH] objtool: Fix gcov check for older versions of GCC Objtool tries to silence 'unreachable instruction' warnings when it detects gcov is enabled, because gcov produces a lot of unreachable instructions and they don't really matter. However, the 0-day bot is still reporting some unreachable instruction warnings with CONFIG_GCOV_KERNEL=y on GCC 4.6.4. As it turns out, objtool's gcov detection doesn't work with older versions of GCC because they don't create a bunch of symbols with the 'gcov.' prefix like newer versions of GCC do. Move the gcov check out of objtool and instead just create a new '--no-unreachable' flag which can be passed in by the kernel Makefile when CONFIG_GCOV_KERNEL is defined. Also rename the 'nofp' variable to 'no_fp' for consistency with the new 'no_unreachable' variable. Reported-by: kbuild test robot Signed-off-by: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 9cfffb116887 ("objtool: Skip all "unreachable instruction" warnings for gcov kernels") Link: http://lkml.kernel.org/r/c243dc78eb2ffdabb6e927844dea39b6033cd395.1500939244.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- scripts/Makefile.build | 3 +++ tools/objtool/builtin-check.c | 7 ++++--- tools/objtool/builtin-orc.c | 4 ++-- tools/objtool/check.c | 36 +++++++---------------------------- tools/objtool/check.h | 2 +- 5 files changed, 17 insertions(+), 35 deletions(-) diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 4a9a2cec0a1b..854608d42e85 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -262,6 +262,9 @@ objtool_args = check ifndef CONFIG_FRAME_POINTER objtool_args += --no-fp endif +ifdef CONFIG_GCOV_KERNEL +objtool_args += --no-unreachable +endif # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c index eedf089b1495..57254f5b2779 100644 --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -29,7 +29,7 @@ #include "builtin.h" #include "check.h" -bool nofp; +bool no_fp, no_unreachable; static const char * const check_usage[] = { "objtool check [] file.o", @@ -37,7 +37,8 @@ static const char * const check_usage[] = { }; const struct option check_options[] = { - OPT_BOOLEAN('f', "no-fp", &nofp, "Skip frame pointer validation"), + OPT_BOOLEAN('f', "no-fp", &no_fp, "Skip frame pointer validation"), + OPT_BOOLEAN('u', "no-unreachable", &no_unreachable, "Skip 'unreachable instruction' warnings"), OPT_END(), }; @@ -52,5 +53,5 @@ int cmd_check(int argc, const char **argv) objname = argv[0]; - return check(objname, nofp, false); + return check(objname, no_fp, no_unreachable, false); } diff --git a/tools/objtool/builtin-orc.c b/tools/objtool/builtin-orc.c index 5ca41ab0df48..4c6b5c9ef073 100644 --- a/tools/objtool/builtin-orc.c +++ b/tools/objtool/builtin-orc.c @@ -37,7 +37,7 @@ static const char *orc_usage[] = { }; extern const struct option check_options[]; -extern bool nofp; +extern bool no_fp, no_unreachable; int cmd_orc(int argc, const char **argv) { @@ -51,7 +51,7 @@ int cmd_orc(int argc, const char **argv) objname = argv[0]; - return check(objname, nofp, true); + return check(objname, no_fp, no_unreachable, true); } diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 368275de5f23..3436a942b606 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -33,7 +33,7 @@ struct alternative { }; const char *objname; -static bool nofp; +static bool no_fp; struct cfi_state initial_func_cfi; struct instruction *find_insn(struct objtool_file *file, @@ -59,19 +59,6 @@ static struct instruction *next_insn_same_sec(struct objtool_file *file, return next; } -static bool gcov_enabled(struct objtool_file *file) -{ - struct section *sec; - struct symbol *sym; - - for_each_sec(file, sec) - list_for_each_entry(sym, &sec->symbol_list, list) - if (!strncmp(sym->name, "__gcov_.", 8)) - return true; - - return false; -} - #define func_for_each_insn(file, func, insn) \ for (insn = find_insn(file, func->sec, func->offset); \ insn && &insn->list != &file->insn_list && \ @@ -1174,7 +1161,7 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state) regs[CFI_BP].base = CFI_BP; regs[CFI_BP].offset = -state->stack_size; state->bp_scratch = false; - } else if (!nofp) { + } else if (!no_fp) { WARN_FUNC("unknown stack-related register move", insn->sec, insn->offset); @@ -1345,7 +1332,7 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state) } /* detect when asm code uses rbp as a scratch register */ - if (!nofp && insn->func && op->src.reg == CFI_BP && + if (!no_fp && insn->func && op->src.reg == CFI_BP && cfa->base != CFI_BP) state->bp_scratch = true; break; @@ -1593,7 +1580,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, /* fallthrough */ case INSN_CALL_DYNAMIC: - if (!nofp && func && !has_valid_stack_frame(&state)) { + if (!no_fp && func && !has_valid_stack_frame(&state)) { WARN_FUNC("call without frame pointer save/setup", sec, insn->offset); return 1; @@ -1779,15 +1766,6 @@ static int validate_reachable_instructions(struct objtool_file *file) if (insn->visited || ignore_unreachable_insn(insn)) continue; - /* - * gcov produces a lot of unreachable instructions. If we get - * an unreachable warning and the file has gcov enabled, just - * ignore it, and all other such warnings for the file. Do - * this here because this is an expensive function. - */ - if (gcov_enabled(file)) - return 0; - WARN_FUNC("unreachable instruction", insn->sec, insn->offset); return 1; } @@ -1812,13 +1790,13 @@ static void cleanup(struct objtool_file *file) elf_close(file->elf); } -int check(const char *_objname, bool _nofp, bool orc) +int check(const char *_objname, bool _no_fp, bool no_unreachable, bool orc) { struct objtool_file file; int ret, warnings = 0; objname = _objname; - nofp = _nofp; + no_fp = _no_fp; file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY); if (!file.elf) @@ -1829,7 +1807,7 @@ int check(const char *_objname, bool _nofp, bool orc) file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard"); file.rodata = find_section_by_name(file.elf, ".rodata"); file.c_file = find_section_by_name(file.elf, ".comment"); - file.ignore_unreachables = false; + file.ignore_unreachables = no_unreachable; file.hints = false; arch_initial_func_cfi_state(&initial_func_cfi); diff --git a/tools/objtool/check.h b/tools/objtool/check.h index ac3d4b13f17b..c9af11f0c8af 100644 --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -61,7 +61,7 @@ struct objtool_file { bool ignore_unreachables, c_file, hints; }; -int check(const char *objname, bool nofp, bool orc); +int check(const char *objname, bool no_fp, bool no_unreachable, bool orc); struct instruction *find_insn(struct objtool_file *file, struct section *sec, unsigned long offset); -- 2.30.2