From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Kees Cook <keescook@chromium.org>
Subject: Re: Remaining randconfig objtool warnings, linux-next-20200428
Date: Tue, 28 Apr 2020 15:38:55 -0500 [thread overview]
Message-ID: <20200428203855.zapf6jhcp6mbft7i@treble> (raw)
In-Reply-To: <CAK8P3a0X4kMW1BQU6x9A2oo6i3-CMxi1h=0PhQgEbBtYWbJa9A@mail.gmail.com>
On Tue, Apr 28, 2020 at 10:19:46PM +0200, Arnd Bergmann wrote:
> On Tue, Apr 28, 2020 at 6:10 PM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > On Tue, Apr 28, 2020 at 04:49:15PM +0200, Arnd Bergmann wrote:
> > > ==> build/x86/0xFD7B7323_defconfig/log <==
> > > arch/x86/entry/entry_64.o: warning: objtool: .entry.text+0x991: unreachable instruction
> >
> > This warning looks correct, did you make a change to entry_64.S?
>
> I bisected my local patches and found that I had a local hack that turned
> off CONFIG_RETPOLINE for testing something unrelated. I can reproduce
> it on linux-next with this patch:
>
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -447,8 +447,7 @@ config GOLDFISH
> depends on X86_GOLDFISH
>
> config RETPOLINE
> - bool "Avoid speculative indirect branches in kernel"
> - default y
> + def_bool n
> select STACK_VALIDATION if HAVE_STACK_VALIDATION
> help
> Compile kernel with the retpoline compiler options to guard against
Thanks, that worked.
This one makes no sense to me. It looks like the assembler is inserting
a jump as part of the alignment padding??? WTH.
0000000000000980 <common_spurious>:
980: 48 83 04 24 80 addq $0xffffffffffffff80,(%rsp)
985: e8 00 00 00 00 callq 98a <common_spurious+0xa>
986: R_X86_64_PLT32 interrupt_entry-0x4
98a: e8 00 00 00 00 callq 98f <common_spurious+0xf>
98b: R_X86_64_PLT32 smp_spurious_interrupt-0x4
98f: eb 7e jmp a0f <ret_from_intr>
991: eb 6d jmp a00 <common_interrupt>
993: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
99a: 00 00 00 00
99e: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
9a5: 00 00 00 00
9a9: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
9b0: 00 00 00 00
9b4: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
9bb: 00 00 00 00
9bf: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
9c6: 00 00 00 00
9ca: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
9d1: 00 00 00 00
9d5: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
9dc: 00 00 00 00
9e0: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
9e7: 00 00 00 00
9eb: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
9f2: 00 00 00 00
9f6: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
9fd: 00 00 00
0000000000000a00 <common_interrupt>:
a00: 48 83 04 24 80 addq $0xffffffffffffff80,(%rsp)
--
Josh
next prev parent reply other threads:[~2020-04-28 20:39 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 14:49 Arnd Bergmann
2020-04-28 16:10 ` Josh Poimboeuf
2020-04-28 19:11 ` Kees Cook
2020-04-28 20:19 ` Arnd Bergmann
2020-04-28 20:38 ` Josh Poimboeuf [this message]
2020-04-28 21:55 ` Peter Zijlstra
2020-04-28 22:03 ` Josh Poimboeuf
2020-04-28 22:33 ` Peter Zijlstra
2020-04-28 22:48 ` Josh Poimboeuf
2020-04-28 23:08 ` Josh Poimboeuf
2020-04-29 18:55 ` Josh Poimboeuf
2020-04-29 22:46 ` Arnd Bergmann
2020-04-29 23:01 ` Josh Poimboeuf
2020-04-29 23:11 ` Josh Poimboeuf
2020-04-29 23:28 ` Josh Poimboeuf
2020-04-30 13:41 ` Arnd Bergmann
2020-04-30 14:33 ` Josh Poimboeuf
2020-04-30 19:46 ` Josh Poimboeuf
2020-04-30 20:59 ` Arnd Bergmann
2020-04-30 21:10 ` Josh Poimboeuf
2020-04-30 21:08 ` Josh Poimboeuf
2020-04-30 23:02 ` Josh Poimboeuf
2020-04-29 19:18 ` Josh Poimboeuf
2020-05-01 12:23 ` Peter Zijlstra
2020-04-30 14:05 ` Arnd Bergmann
2020-05-01 0:28 ` Josh Poimboeuf
2020-05-01 11:41 ` Arnd Bergmann
2020-05-01 17:16 ` Peter Zijlstra
2020-05-01 12:27 ` Peter Zijlstra
2020-05-01 1:07 ` Josh Poimboeuf
2020-05-01 11:18 ` Arnd Bergmann
2020-05-01 12:33 ` Peter Zijlstra
2020-05-01 13:08 ` Arnd Bergmann
2020-05-01 15:49 ` Josh Poimboeuf
2020-05-01 17:21 ` Arnd Bergmann
2020-05-01 17:26 ` Peter Zijlstra
2020-05-01 17:50 ` Josh Poimboeuf
2020-05-01 19:47 ` Arnd Bergmann
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