Re: [PATCH v1 1/6] objtool/powerpc: Add build-time fixup of alternate feature branch targets
From: Peter Zijlstra <peterz@infradead.org>
Date: 2026-05-06 07:12:54
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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:quoted
On Tue, May 05, 2026 at 02:16:23PM +0530, Sathvika Vasireddy wrote:quoted
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.