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 <fengguang.wu@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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 <mingo@kernel.org>
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 368275d..3436a942 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -33,7 +33,7 @@
};
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 @@
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 @@
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 @@
}
/* 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 @@
/* 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 @@
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 @@
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 @@
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);