Re: [PATCH v1 1/6] objtool/powerpc: Add build-time fixup of alternate feature branch targets
From: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Date: 2026-05-05 15:48:43
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Le 05/05/2026 à 16:49, Peter Zijlstra a écrit :
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 ?
No, it is bc/bca/bcl/bcla, it is quite similar to type 18 which is b/ba/bl/bla, but that's a conditional branch to a 14-bit offset while type 18 is a non-conditional branch to a 24-bit offset (10 bits are the conditional in the bc, hence the reduced offset size).
Also, isn't that typically used for return, suggesting at least something should have INSN_RETURN on?
bclr (which is the return INSN_RETURN) has type 19 By the way you can have a look at https://patchwork.ozlabs.org/project/linuxppc-dev/patch/bfa8364da047d8610a09458a1cd924a0566aedbb.1736955567.git.christophe.leroy@csgroup.eu/ That patch has all the objtool decoding. By the way objtool is missing a INSN_CONDITIONAL_RETURN, also see https://patchwork.ozlabs.org/project/linuxppc-dev/patch/537e5d8f181b1f1c2b8918f1aefa1dba3f972c03.1736955567.git.christophe.leroy@csgroup.eu/
quoted
quoted
+ if (ins & 1) + typ = INSN_OTHER; + else + typ = INSN_JUMP_CONDITIONAL; + imm = ins & 0xfffc; + if (imm & 0x8000) + imm -= 0x10000; + insn->immediate = imm | aa; + break; + case 18: /* b[l][a] */ if (ins == 0x48000005) /* bl .+4 */ typ = INSN_OTHER;