On Mon, Nov 09, 2020 at 08:48:01PM -0800, Sami Tolvanen wrote: > On Mon, Nov 9, 2020 at 6:29 PM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > > How would I recreate all these warnings? > > You can reproduce all of these using a normal gcc build without any of > the LTO patches by running objtool check -arfld vmlinux.o. However, > with gcc you'll see even more warnings due to duplicate symbol names, > as Peter pointed out elsewhere in the thread, so I looked at only the > warnings that objtool also prints with LTO. > > Note that the LTO series contains a patch to split noinstr validation > from --vmlinux, as we need to run objtool here even if > CONFIG_VMLINUX_VALIDATION isn't selected, so I have not looked at the > noinstr warnings. The latest LTO tree is available here: > > https://github.com/samitolvanen/linux/commits/clang-lto > > > Here's the patch for hopefully making the warnings more helpful: > > Thanks, I'll give it a try. Here's the version without the nonsensical debug warning :-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 4e1d7460574b..ced7e4754cba 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -217,6 +217,21 @@ struct symbol *find_func_containing(struct section *sec, unsigned long offset) return NULL; } +struct symbol *find_symbol_preceding(struct section *sec, unsigned long offset) +{ + struct symbol *sym; + + /* + * This is slow, but used for warning messages. + */ + while (1) { + sym = find_symbol_by_offset(sec, offset); + if (sym || !offset) + return sym; + offset--; + } +} + struct symbol *find_symbol_by_name(const struct elf *elf, const char *name) { struct symbol *sym; diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h index 807f8c670097..841902ed381e 100644 --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -136,10 +136,11 @@ struct symbol *find_func_by_offset(struct section *sec, unsigned long offset); struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset); struct symbol *find_symbol_by_name(const struct elf *elf, const char *name); struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset); +struct symbol *find_func_containing(struct section *sec, unsigned long offset); +struct symbol *find_symbol_preceding(struct section *sec, unsigned long offset); struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset); struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec, unsigned long offset, unsigned int len); -struct symbol *find_func_containing(struct section *sec, unsigned long offset); int elf_rebuild_reloc_section(struct elf *elf, struct section *sec); #define for_each_sec(file, sec) \ diff --git a/tools/objtool/warn.h b/tools/objtool/warn.h index 7799f60de80a..33da0f2ed9d5 100644 --- a/tools/objtool/warn.h +++ b/tools/objtool/warn.h @@ -22,6 +22,8 @@ static inline char *offstr(struct section *sec, unsigned long offset) unsigned long name_off; func = find_func_containing(sec, offset); + if (!func) + func = find_symbol_preceding(sec, offset); if (func) { name = func->name; name_off = offset - func->offset;
