From: Peter Zijlstra <peterz@infradead.org>
To: mingo@kernel.org
Cc: tglx@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com,
x86@kernel.org, hpa@zytor.com, peterz@infradead.org,
jpoimboe@kernel.org, jbaron@akamai.com, rostedt@goodmis.org,
ardb@kernel.org, linux-kernel@vger.kernel.org,
erhard_f@mailbox.org, ndesaulniers@google.com,
mhiramat@kernel.org, sandipan.das@amd.com
Subject: [PATCH 0/3] static_call/x86: Handle clang's conditional tail calls
Date: Mon, 23 Jan 2023 21:59:15 +0100 [thread overview]
Message-ID: <20230123205915.751729592@infradead.org> (raw)
Erhard reported boot fails on this AMD machine when using clang and bisected it
to a commit introducing a few static_call()s. Turns out that when using clang
with -Os it it very likely to generate conditional tail calls like:
0000000000000350 <amd_pmu_add_event>:
350: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 351: R_X86_64_NONE __fentry__-0x4
355: 48 83 bf 20 01 00 00 00 cmpq $0x0,0x120(%rdi)
35d: 0f 85 00 00 00 00 jne 363 <amd_pmu_add_event+0x13> 35f: R_X86_64_PLT32 __SCT__amd_pmu_branch_add-0x4
363: e9 00 00 00 00 jmp 368 <amd_pmu_add_event+0x18> 364: R_X86_64_PLT32 __x86_return_thunk-0x4
And our inline static_call() patching code can't deal with those and BUG
happens -- really early.
These patches borrow the kprobe Jcc emulation to implement text_poke_bp() Jcc
support, which is then used to teach inline static_call() about this form.
---
arch/x86/include/asm/text-patching.h | 31 ++++++++++++++++++
arch/x86/kernel/alternative.c | 62 +++++++++++++++++++++++++++---------
arch/x86/kernel/kprobes/core.c | 38 +++++-----------------
arch/x86/kernel/static_call.c | 50 +++++++++++++++++++++++++++--
4 files changed, 133 insertions(+), 48 deletions(-)
next reply other threads:[~2023-01-23 21:07 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-23 20:59 Peter Zijlstra [this message]
2023-01-23 20:59 ` [PATCH 1/3] x86/alternative: Introduce int3_emulate_jcc() Peter Zijlstra
2023-01-31 14:22 ` [tip: x86/alternatives] x86/alternatives: " tip-bot2 for Peter Zijlstra
2023-01-23 20:59 ` [PATCH 2/3] x86/alternative: Teach text_poke_bp() to patch Jcc.d32 instructions Peter Zijlstra
2023-01-31 14:22 ` [tip: x86/alternatives] x86/alternatives: " tip-bot2 for Peter Zijlstra
2023-01-23 20:59 ` [PATCH 3/3] x86/static_call: Add support for Jcc tail-calls Peter Zijlstra
2023-01-23 22:44 ` Steven Rostedt
2023-01-24 13:06 ` Peter Zijlstra
2023-01-24 15:07 ` Steven Rostedt
2023-01-26 15:34 ` [PATCH v1.1 " Peter Zijlstra
2023-01-26 18:14 ` Nick Desaulniers
2023-02-06 16:07 ` Steven Rostedt
2023-01-31 14:22 ` [tip: x86/alternatives] " tip-bot2 for Peter Zijlstra
2023-02-08 22:36 ` [PATCH 0/3] static_call/x86: Handle clang's conditional tail calls Nathan Chancellor
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