Content-Type: multipart/mixed; boundary="===============4952950765313407881==" MIME-Version: 1.0 From: Ingo Molnar To: lkp@lists.01.org Subject: Re: [PATCH] objtool: Detect assembly code falling through to INT3 padding Date: Fri, 18 May 2018 09:24:12 +0200 Message-ID: <20180518072412.GC26358@gmail.com> In-Reply-To: <20180517140118.GT12217@hirez.programming.kicks-ass.net> List-Id: --===============4952950765313407881== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable * Peter Zijlstra wrote: > On Thu, May 17, 2018 at 08:49:34AM -0500, Josh Poimboeuf wrote: > > With the following commit: > > = > > 51bad67ffbce ("x86/asm: Pad assembly functions with INT3 instructions= ") > > = > > ... asm function alignments are padded with INT3, so it's no longer safe > > to fall through to an aligned function. Make sure we catch any such > > cases with objtool. > > = > > Note this only adds checking for 64-bit, since objtool doesn't support > > x86-32. > > = > > Suggested-by: Thomas Gleixner > > Suggested-by: Linus Torvalds > > Signed-off-by: Josh Poimboeuf > > --- > > arch/x86/kernel/head_64.S | 2 -- > > tools/objtool/arch.h | 3 ++- > > tools/objtool/arch/x86/decode.c | 2 +- > > tools/objtool/check.c | 11 ++++++++++- > > 4 files changed, 13 insertions(+), 5 deletions(-) > > = > > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > > index 8344dd2f310a..3ed8cec6e765 100644 > > --- a/arch/x86/kernel/head_64.S > > +++ b/arch/x86/kernel/head_64.S > > @@ -285,11 +285,9 @@ ENTRY(early_idt_handler_array) > > .endif > > pushq $i # 72(%rsp) Vector number > > jmp early_idt_handler_common > > - UNWIND_HINT_IRET_REGS > > i =3D i + 1 > > .fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc > > .endr > > - UNWIND_HINT_IRET_REGS offset=3D16 > > END(early_idt_handler_array) > > = > > early_idt_handler_common: > = > As noted on IRC; I got slightly confused what this was about. > = > Other than that: > = > Acked-by: Peter Zijlstra (Intel) And after talking to you on IRC I added this paragraph to the changelog: Also remove incorrect and unnecessary unwinder hints from head_64.S which caused false positives in the new detection code. Thanks, Ingo --===============4952950765313407881==--