Because find_symbol_by_name() traverses the same lists as read_symbols() changing sym->name in place without copying it affects the result of find_symbol_by_name() and, in case when ".cold" function precedes it's parent in sec->symbol_list, can result in function being considered a parent of itself. This leads to function length being set to 0 and other consequent side-effects including a segfault in add_switch_table(). The effects of this bug are only visible when building with -ffunction-sections in KCFLAGS.
Fix by copying the search string instead of modifying it in place. Signed-off-by: Artem Savkov <[email protected]> --- tools/objtool/elf.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 6dbb9fae0f9d..781c8afb29b9 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -298,6 +298,7 @@ static int read_symbols(struct elf *elf) /* 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) { + char *pname; if (sym->type != STT_FUNC) continue; sym->pfunc = sym->cfunc = sym; @@ -305,9 +306,9 @@ static int read_symbols(struct elf *elf) if (!coldstr) continue; - coldstr[0] = '\0'; - pfunc = find_symbol_by_name(elf, sym->name); - coldstr[0] = '.'; + pname = strndup(sym->name, coldstr - sym->name); + pfunc = find_symbol_by_name(elf, pname); + free(pname); if (!pfunc) { WARN("%s(): can't find parent function", -- 2.17.2
