On Tue, Feb 09, 2021 at 10:32:55AM -0600, Josh Poimboeuf wrote: > On Tue, Feb 09, 2021 at 10:16:02AM +0100, Peter Zijlstra wrote: > > Where we already decode: mov %rsp, %reg, also decode mov %rsp, (%reg). > > > > Nothing should match for this new stack-op. > > > > Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> > > --- > > tools/objtool/arch/x86/decode.c | 23 ++++++++++++++++++----- > > 1 file changed, 18 insertions(+), 5 deletions(-) > > > > --- a/tools/objtool/arch/x86/decode.c > > +++ b/tools/objtool/arch/x86/decode.c > > @@ -222,14 +222,24 @@ int arch_decode_instruction(const struct > > break; > > > > case 0x89: > > - if (rex_w && !rex_r && modrm_mod == 3 && modrm_reg == 4) { > > + if (rex_w && !rex_r && modrm_reg == 4) { > > > > - /* mov %rsp, reg */ > > + /* mov %rsp, */ > > ADD_OP(op) { > > op->src.type = OP_SRC_REG; > > op->src.reg = CFI_SP; > > - op->dest.type = OP_DEST_REG; > > - op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b]; > > + if (modrm_mod == 3) { > > + > > + /* mov %rsp, reg */ > > + op->dest.type = OP_DEST_REG; > > + op->dest.reg = > > op_to_cfi_reg[modrm_rm][rex_b]; > > + > > + } else if (modrm_mod == 0) { > > + > > + /* mov %rsp, (%reg) */ > > + op->dest.type = OP_DEST_REG_INDIRECT; > > + op->dest.reg = > > op_to_cfi_reg[modrm_rm][rex_b]; > > + } > > What if modrm_mod is 1 or 2? Should 'if' below the 'case' make sure > it's 0 or 3?
For 1,2 we need to look at the SIB byte or something. IIRC you get that encoding for stuff like: mov %rsp, off(%reg). Didn't want to dive too deep into the instruction encoding thing again, this is all we need. > > } > > break; > > } > > @@ -259,8 +269,10 @@ int arch_decode_instruction(const struct > > op->dest.reg = CFI_BP; > > op->dest.offset = insn.displacement.value; > > } > > + break; > > + } > > > > - } else if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) { > > + if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) { > > > > /* mov reg, disp(%rsp) */ > > ADD_OP(op) { > > @@ -270,6 +282,7 @@ int arch_decode_instruction(const struct > > op->dest.reg = CFI_SP; > > op->dest.offset = insn.displacement.value; > > } > > + break; > > } > > > > break; > > > > Did this change have a point? Consistency, but yeah, I see what you mean.