Messages in this thread Patch in this message | | | Date | Tue, 19 Sep 2017 16:39:26 -0500 | From | Josh Poimboeuf <> | Subject | Re: gcc-8 objtool warnings |
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On Tue, Sep 19, 2017 at 10:43:31PM +0200, Arnd Bergmann wrote: > On Tue, Sep 19, 2017 at 9:52 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote: > > On Mon, Sep 11, 2017 at 04:34:52PM +0200, Arnd Bergmann wrote: > >> On Thu, Aug 24, 2017 at 9:19 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote: > >> 1. one configuration causing tons of warnings, on most compiler > >> versions (4.9 and newer), and even a couple of "unreachable > >> instruction warnings on gcc-4.3. > >> > >> arch/x86/mm/pageattr.o: warning: objtool: set_memory_x()+0x3a: call > >> without frame pointer save/setup > >> security/keys/keyring.o: warning: objtool: keyring_read()+0x70: leave > >> instruction with modified stack frame > >> arch/x86/events/intel/pt.o: warning: objtool: > >> pt_event_addr_filters_sync uses BP as a scratch register > > > > I downloaded the tarball, and I see configs/logs for the other problems, > > but not for this one. Did you forget to attach it, or did I miss it? > > I think what I ended up doing was to take the smallest files for that > configuration and packed them up, but the warnings I listed in the > mail don't match the ones for those files. However, it seems the > 0xEBFDB964_defconfig/log file got corrupted. > > I've uploaded a new copy to http://paste.ubuntu.com/25574959/ now. > > I've also experimented with other compiler versions > in the meantime and ran into similar problems on those version but did > not bother to take detailed notes about them since they are likely just > variants of the ones I already reported. If you can work around the > warnings I reported here, I can rerun with all compilers I have to > see if anything else shows up.
Here's the fix for #1 and #2. I still need to work on the GCC 8 warnings.
----- From: Josh Poimboeuf <jpoimboe@redhat.com> Subject: [PATCH] objtool: Support unoptimized frame pointer setup
Arnd Bergmann reported a bunch of warnings like:
crypto/jitterentropy.o: warning: objtool: jent_fold_time()+0x3b: call without frame pointer save/setup crypto/jitterentropy.o: warning: objtool: jent_stuck()+0x1d: call without frame pointer save/setup crypto/jitterentropy.o: warning: objtool: jent_unbiased_bit()+0x15: call without frame pointer save/setup crypto/jitterentropy.o: warning: objtool: jent_read_entropy()+0x32: call without frame pointer save/setup crypto/jitterentropy.o: warning: objtool: jent_entropy_collector_free()+0x19: call without frame pointer save/setup
and
arch/x86/events/core.o: warning: objtool: collect_events uses BP as a scratch register arch/x86/events/core.o: warning: objtool: events_ht_sysfs_show()+0x22: call without frame pointer save/setup
With certain rare configurations, GCC sometimes sets up the frame pointer with:
lea (%rsp),%rbp
instead of:
mov %rsp,%rbp
The instructions are equivalent, so treat the former like the latter.
Reported-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> --- tools/objtool/arch/x86/decode.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index 0e8c8ec4fd4e..97a1fdb3db63 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -284,11 +284,16 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, case 0x8d: if (sib == 0x24 && rex_w && !rex_b && !rex_x) { - /* lea disp(%rsp), reg */ *type = INSN_STACK; - op->src.type = OP_SRC_ADD; + if (!insn.displacement.value) { + /* lea (%rsp), reg */ + op->src.type = OP_SRC_REG; + } else { + /* lea disp(%rsp), reg */ + op->src.type = OP_SRC_ADD; + op->src.offset = insn.displacement.value; + } op->src.reg = CFI_SP; - op->src.offset = insn.displacement.value; op->dest.type = OP_DEST_REG; op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r]; -- 2.13.5
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