From: Peter Zijlstra <peterz@infradead.org>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Sathvika Vasireddy <sv@linux.ibm.com>,
nathan@kernel.org, nsc@kernel.org, maddy@linux.ibm.com,
mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org,
jpoimboe@kernel.org, ojeda@kernel.org, masahiroy@kernel.org,
lossin@kernel.org, tamird@kernel.org,
thomas.weissschuh@linutronix.de, rostedt@goodmis.org,
ihor.solodrai@linux.dev, thuth@redhat.com, pmladek@suse.com,
aliceryhl@google.com, elver@google.com, kees@kernel.org,
legion@kernel.org, ardb@kernel.org, yuxuan.zuo@outlook.com,
alexghiti@rivosinc.com, alexandre.chartre@oracle.com,
bp@alien8.de, linux-kbuild@vger.kernel.org,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v1 1/6] objtool/powerpc: Add build-time fixup of alternate feature branch targets
Date: Wed, 6 May 2026 09:00:00 +0200 [thread overview]
Message-ID: <20260506070000.GZ3126523@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <afoTSvawD4CXCCy1@gate>
On Tue, May 05, 2026 at 10:56:58AM -0500, Segher Boessenkool wrote:
> Hi!
>
> On Tue, May 05, 2026 at 04:45:39PM +0200, Peter Zijlstra wrote:
> > On Tue, May 05, 2026 at 02:16:23PM +0530, Sathvika Vasireddy wrote:
> > > switch (opcode) {
> > > + case 16:
> >
> > Like case 18 below, this wants a comment describing which instruction
> > this is; bclr ?
>
> Yes. It is 19/16, b[c]lr (primary opcode 19, secondary opcode 16).
>
> Where is it described what INSN_RETURN actually means for objtool? Not
> in the header file :-(
Yeah, nowhere much I'm afraid, it is very much organic growth that is
firmly rooted in x86.
RETURN, along with sibling/tail CALLs validate things like the stack
frame being in identical state as on function entry and a few other
sanity checks (DF flag not set, no uaccess).
There is also a pile of hacks around the whole return thunk mitigation
thing. But that might be less relevant for other archs.
next prev parent reply other threads:[~2026-05-06 7:12 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-05 8:46 [PATCH v1 0/6] objtool: Fixup alternate feature relative addresses Sathvika Vasireddy
2026-05-05 8:46 ` [PATCH v1 1/6] objtool/powerpc: Add build-time fixup of alternate feature branch targets Sathvika Vasireddy
2026-05-05 14:45 ` Peter Zijlstra
2026-05-05 14:49 ` Peter Zijlstra
2026-05-05 15:48 ` Christophe Leroy (CS GROUP)
2026-05-06 7:17 ` Peter Zijlstra
2026-05-06 14:28 ` Segher Boessenkool
2026-05-05 15:56 ` Segher Boessenkool
2026-05-06 7:00 ` Peter Zijlstra [this message]
2026-05-06 13:58 ` Segher Boessenkool
2026-05-06 14:22 ` Peter Zijlstra
2026-05-06 14:42 ` Segher Boessenkool
2026-05-05 8:46 ` [PATCH v1 2/6] objtool: Set ELF_F_LAYOUT flag to preserve vmlinux segment layout Sathvika Vasireddy
2026-05-05 8:46 ` [PATCH v1 3/6] objtool: Fix "can't find starting instruction" warnings on vmlinux Sathvika Vasireddy
2026-05-05 8:46 ` [PATCH v1 4/6] objtool/powerpc: Skip jump destination analysis and unnanotated intra-function call warnings for --ftr-fixup Sathvika Vasireddy
2026-05-05 8:46 ` [PATCH v1 5/6] kbuild: Add objtool integration for PowerPC feature fixups Sathvika Vasireddy
2026-05-05 8:46 ` [PATCH v1 6/6] powerpc: Enable build-time feature fixup processing by default Sathvika Vasireddy
2026-05-05 9:05 ` [PATCH v1 0/6] objtool: Fixup alternate feature relative addresses Christophe Leroy (CS GROUP)
2026-05-05 11:40 ` Peter Zijlstra
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