From: Borislav Petkov <bp@alien8.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, jpoimboe@redhat.com, andrew.cooper3@citrix.com,
linux-kernel@vger.kernel.org, alexei.starovoitov@gmail.com,
ndesaulniers@google.com, bpf@vger.kernel.org
Subject: Re: [PATCH v3 00/16] x86: Rewrite the retpoline rewrite logic
Date: Thu, 28 Oct 2021 19:43:45 +0200 [thread overview]
Message-ID: <YXrhUQZ5lA70Fhm0@zn.tnic> (raw)
In-Reply-To: <20211026120132.613201817@infradead.org>
On Tue, Oct 26, 2021 at 02:01:32PM +0200, Peter Zijlstra wrote:
> Hi,
>
> These patches rewrite the way retpolines are rewritten. Currently objtool emits
> alternative entries for most retpoline calls. However trying to extend that led
> to trouble (ELF files are horrid).
>
> Therefore completely overhaul this and have objtool emit a .retpoline_sites
> section that lists all compiler generated retpoline thunk calls. Then the
> kernel can do with them as it pleases.
>
> Notably it will:
>
> - rewrite them to indirect instructions for !RETPOLINE
> - rewrite them to lfence; indirect; for RETPOLINE_AMD,
> where size allows (boo clang!)
>
> Specifically, the !RETPOLINE case can now also deal with the clang-special
> conditional-indirect-tail-call:
>
> Jcc __x86_indirect_thunk_\reg.
>
> Finally, also update the x86 BPF jit to catch up to recent times and do these
> same things.
>
> All this should help improve performance by removing an indirection.
>
> Patches can (soon) be found here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git objtool/core
>
> Changes since v2:
>
> - rewrite the __x86_indirect_thunk_array[] stuff again
> - rewrite the retpoline,amd rewrite logic, it now also supports
> rewriting the Jcc case, if the original instruction is long enough, but
> more importantly, it's simpler code.
> - bpf label simplification patch
> - random assorted cleanups
> - actually managed to get bpf selftests working
>
> ---
> arch/um/kernel/um_arch.c | 4 +
> arch/x86/include/asm/GEN-for-each-reg.h | 14 ++-
> arch/x86/include/asm/alternative.h | 1 +
> arch/x86/include/asm/asm-prototypes.h | 18 ---
> arch/x86/include/asm/nospec-branch.h | 72 ++---------
> arch/x86/kernel/alternative.c | 189 ++++++++++++++++++++++++++++-
> arch/x86/kernel/cpu/bugs.c | 7 --
> arch/x86/kernel/module.c | 9 +-
> arch/x86/kernel/vmlinux.lds.S | 14 +++
> arch/x86/lib/retpoline.S | 56 ++-------
> arch/x86/net/bpf_jit_comp.c | 160 +++++++++---------------
> arch/x86/net/bpf_jit_comp32.c | 22 +++-
> tools/objtool/arch/x86/decode.c | 120 ------------------
> tools/objtool/check.c | 208 ++++++++++++++++++++++----------
> tools/objtool/elf.c | 84 -------------
> tools/objtool/include/objtool/check.h | 1 -
> tools/objtool/include/objtool/elf.h | 6 +-
> tools/objtool/special.c | 8 --
> 18 files changed, 472 insertions(+), 521 deletions(-)
Ok, this all looks real nice, thx!
Reviewed-by: Borislav Petkov <bp@suse.de>
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2021-10-28 17:43 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-26 12:01 [PATCH v3 00/16] x86: Rewrite the retpoline rewrite logic Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 01/16] objtool: Classify symbols Peter Zijlstra
2021-10-28 3:58 ` Josh Poimboeuf
2021-10-26 12:01 ` [PATCH v3 02/16] objtool: Explicitly avoid self modifying code in .altinstr_replacement Peter Zijlstra
2021-10-28 4:01 ` Josh Poimboeuf
2021-10-26 12:01 ` [PATCH v3 03/16] objtool: Shrink struct instruction Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 04/16] objtool,x86: Replace alternatives with .retpoline_sites Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 05/16] x86/retpoline: Remove unused replacement symbols Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 06/16] x86/asm: Fix register order Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 07/16] x86/asm: Fixup odd GEN-for-each-reg.h usage Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 08/16] x86/retpoline: Move the retpoline thunk declarations to nospec-branch.h Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 09/16] x86/retpoline: Create a retpoline thunk array Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 10/16] x86/alternative: Implement .retpoline_sites support Peter Zijlstra
2021-10-27 17:38 ` Borislav Petkov
2021-10-27 19:10 ` Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 11/16] x86/alternative: Handle Jcc __x86_indirect_thunk_\reg Peter Zijlstra
2021-10-28 9:29 ` Borislav Petkov
2021-10-26 12:01 ` [PATCH v3 12/16] x86/alternative: Try inline spectre_v2=retpoline,amd Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 13/16] x86/alternative: Add debug prints to apply_retpolines() Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 14/16] x86,bugs: Unconditionally allow spectre_v2=retpoline,amd Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 15/16] bpf, x86: Simplify computing label offsets Peter Zijlstra
2021-10-26 12:01 ` [PATCH v3 16/16] bpf,x86: Respect X86_FEATURE_RETPOLINE* Peter Zijlstra
2021-10-26 18:26 ` [PATCH v3 00/16] x86: Rewrite the retpoline rewrite logic Alexei Starovoitov
2021-10-26 18:45 ` Peter Zijlstra
2021-10-26 20:00 ` Alexei Starovoitov
2021-10-26 21:05 ` Peter Zijlstra
2021-10-26 21:05 ` Alexei Starovoitov
2021-10-27 9:00 ` Peter Zijlstra
2021-10-27 17:32 ` Alexei Starovoitov
2021-10-28 5:17 ` Josh Poimboeuf
2021-10-28 17:43 ` Borislav Petkov [this message]
2021-10-29 12:43 ` Miroslav Benes
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