From: Peter Zijlstra <peterz@infradead.org>
To: Lukasz Majczak <lma@semihalf.com>
Cc: "Nathan Chancellor" <nathan@kernel.org>,
"Nick Desaulniers" <ndesaulniers@google.com>,
"Fāng-ruì Sòng" <maskray@google.com>,
"Josh Poimboeuf" <jpoimboe@redhat.com>,
"Guenter Roeck" <groeck@google.com>,
"Juergen Gross" <jgross@suse.com>,
"Łukasz Bartosik" <lb@semihalf.com>,
LKML <linux-kernel@vger.kernel.org>,
mbenes@suse.com, "Radosław Biernacki" <rad@semihalf.com>,
upstream@semihalf.com,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
"Sami Tolvanen" <samitolvanen@google.com>
Subject: Re: [PATCH v3 16/16] objtool,x86: Rewrite retpoline thunk calls
Date: Wed, 9 Jun 2021 17:08:04 +0200 [thread overview]
Message-ID: <20210609150804.GF68208@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <CAFJ_xbodWTQQaJ-3yJ4ZQOiTFFXo6M+cn_F0p157o=80BwrQAw@mail.gmail.com>
On Wed, Jun 09, 2021 at 02:23:28PM +0200, Lukasz Majczak wrote:
> śr., 9 cze 2021 o 09:20 Peter Zijlstra <peterz@infradead.org> napisał(a):
> >
> > On Wed, Jun 09, 2021 at 09:11:18AM +0200, Lukasz Majczak wrote:
> >
> > > I'm sorry I was on vacation last week - do you still need the requested debugs?
> >
> > If the patch here:
> >
> > https://lkml.kernel.org/r/YL3q1qFO9QIRL/BA@hirez.programming.kicks-ass.net
> >
> > does not fix things for you (don't think it actually will), then yes,
> > please send me the information requested.
>
> Ok, it didn't help. Peter, Josh I have sent you a private email with
> requested information.
OK, I think I've found it. Check this one:
5d5: 0f 85 00 00 00 00 jne 5db <cpuidle_reflect+0x22> 5d7: R_X86_64_PLT32 __x86_indirect_thunk_r11-0x4
+Relocation section '.rela.altinstructions' at offset 0 contains 14 entries:
+ Offset Info Type Symbol's Value Symbol's Name + Addend
+0000000000000018 0000000200000002 R_X86_64_PC32 0000000000000000 .text + 5d5
+000000000000001c 0000009200000002 R_X86_64_PC32 0000000000000000 __x86_indirect_alt_call_r11 + 0
Apparently we get conditional branches to retpoline thunks and objtool
completely messes that up. I'm betting this also explains the problems
Nathan is having.
*groan*,.. not sure what to do about this, except return to having
objtool generate code, which everybody hated on. For now I'll make it
skip the conditional branches.
I wonder if the compiler will also generate conditional tail calls, and
what that does with static_call... now I have to check all that.
---
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 24295d39713b..523aa4157f80 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -747,6 +747,10 @@ int arch_rewrite_retpolines(struct objtool_file *file)
list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
+ if (insn->type != INSN_JUMP_DYNAMIC &&
+ insn->type != INSN_CALL_DYNAMIC)
+ continue;
+
if (!strcmp(insn->sec->name, ".text.__x86.indirect_thunk"))
continue;
next prev parent reply other threads:[~2021-06-09 15:08 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-26 15:11 [PATCH v3 00/16] x86,objtool: Optimize !RETPOLINE Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 01/16] x86: Add insn_decode_kernel() Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 02/16] x86/alternatives: Optimize optimize_nops() Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:11 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 03/16] x86/retpoline: Simplify retpolines Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-04-06 8:56 ` David Laight
2021-03-26 15:12 ` [PATCH v3 04/16] objtool: Correctly handle retpoline thunk calls Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 05/16] objtool: Per arch retpoline naming Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] objtool: Handle per " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 06/16] objtool: Fix static_call list generation Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 07/16] objtool: Rework rebuild_reloc logic Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` [tip: x86/core] objtool: Rework the elf_rebuild_reloc_section() logic tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 08/16] objtool: Add elf_create_reloc() helper Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 09/16] objtool: Implicitly create reloc sections Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` [tip: x86/core] objtool: Create reloc sections implicitly tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 10/16] objtool: Extract elf_strtab_concat() Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 11/16] objtool: Extract elf_symbol_add() Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 12/16] objtool: Add elf_create_undef_symbol() Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 13/16] objtool: Keep track of retpoline call sites Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 14/16] objtool: Cache instruction relocs Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 15/16] objtool: Skip magical retpoline .altinstr_replacement Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-26 15:12 ` [PATCH v3 16/16] objtool,x86: Rewrite retpoline thunk calls Peter Zijlstra
2021-03-29 16:38 ` Josh Poimboeuf
2021-06-02 15:51 ` Lukasz Majczak
2021-06-02 16:56 ` Peter Zijlstra
2021-06-02 17:10 ` Peter Zijlstra
2021-06-02 20:43 ` Josh Poimboeuf
2021-06-04 20:50 ` Nick Desaulniers
2021-06-04 23:27 ` Nick Desaulniers
2021-06-04 23:50 ` Fangrui Song
2021-06-05 10:38 ` Peter Zijlstra
2021-06-06 1:58 ` Fāng-ruì Sòng
2021-06-07 7:56 ` Peter Zijlstra
2021-06-07 9:22 ` Peter Zijlstra
2021-06-07 9:45 ` Peter Zijlstra
2021-06-07 17:23 ` Fāng-ruì Sòng
2021-06-07 18:25 ` Peter Zijlstra
2021-06-07 20:54 ` Nick Desaulniers
2021-06-08 9:56 ` Peter Zijlstra
2021-06-08 16:58 ` Nathan Chancellor
2021-06-08 17:22 ` Peter Zijlstra
2021-06-08 17:29 ` Nathan Chancellor
2021-06-08 18:17 ` Peter Zijlstra
2021-06-08 18:49 ` Nathan Chancellor
2021-06-09 7:11 ` Lukasz Majczak
2021-06-09 7:20 ` Peter Zijlstra
2021-06-09 12:23 ` Lukasz Majczak
2021-06-09 15:08 ` Peter Zijlstra [this message]
2021-06-09 15:11 ` Peter Zijlstra
2021-06-09 15:56 ` Nathan Chancellor
2021-06-08 18:18 ` Nick Desaulniers
2021-06-07 18:19 ` Peter Zijlstra
2021-06-07 18:27 ` Fāng-ruì Sòng
2021-06-07 18:47 ` Peter Zijlstra
2021-04-01 15:08 ` [tip: x86/core] objtool/x86: " tip-bot2 for Peter Zijlstra
2021-04-03 11:10 ` tip-bot2 for Peter Zijlstra
2021-03-30 15:02 ` [PATCH v3 00/16] x86,objtool: Optimize !RETPOLINE Miroslav Benes
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