On Wed, Feb 10, 2021 at 08:01:23PM -0000, tip-bot2 for Peter Zijlstra wrote: > objtool: Support stack-swizzle --- Subject: objtool: Fix stack-swizzle for FRAME_POINTER=y From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Date: Thu Feb 18 17:14:10 CET 2021 When objtool encounters the stack-swizzle: mov %rsp, (%[tos]) mov %[tos], %rsp ... pop %rsp Inside a FRAME_POINTER=y build, things go a little screwy because clearly we're not adjusting the cfa->base. This then results in the pop %rsp not being detected as a restore of cfa->base so it will turn into a regular POP and offset the stack, resulting in: kernel/softirq.o: warning: objtool: do_softirq()+0xdb: return with modified stack frame Therefore, have "mov %[tos], %rsp" act like a PUSH (it sorta is anyway) to balance the things out. We're not too concerned with the actual stack_size for frame-pointer builds, since we don't generate ORC data for them anyway. Fixes: aafeb14e9da2 ("objtool: Support stack-swizzle") Reported-by: kernel test robot <lkp@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> --- tools/objtool/check.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1996,6 +1996,20 @@ static int update_cfi_state(struct instr } } + else if (op->dest.reg == CFI_SP && + cfi->vals[op->src.reg].base == CFI_SP_INDIRECT && + cfi->vals[op->src.reg].offset == cfa->offset) { + + /* + * The same stack swizzle case 2) as above. But + * because we can't change cfa->base, case 3) + * will become a regular POP. Pretend we're a + * PUSH so things don't go unbalanced. + */ + cfi->stack_size += 8; + } + + break; case OP_SRC_ADD:
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