----- Original Message -----
...
>
> A small correction, top bytes are included in KERNELPACMASK but that is
> configurable. Anyway so when autiasp(authentication) instruction fails
> then all obfuscated value is cleared and a error bit pattern is added
> only in top byte.
> As mentioned earlier armv8.6 enhanced PAC will not add bit pattern to
> denote failure but will cause illegal instruction fault with an
> exception class and hence pc will not have extra details. This is work
> in progress so the current crash utility changes should work fine.
Just to be clear then, your v2 patch set should be OK to check in -- except
for this call to is_kernel_text():
> And then when trying to determine whether the current stack pointer is
> pointing to an in-kernel exception frame, the possible regs->pc and regs[30]
> values are both transformed with the mask, so it seems that both of them
> will have been obfuscated by the processor when creating the frame on
> the stack:
>
> static int
> arm64_is_kernel_exception_frame(struct bt_info *bt, ulong stkptr)
> {
> struct arm64_pt_regs *regs;
> struct machine_specific *ms = machdep->machspec;
>
> regs = (struct arm64_pt_regs *)&bt->stackbuf[(ulong)(STACK_OFFSET_TYPE(stkptr))];
>
> if (INSTACK(regs->sp, bt) && INSTACK(regs->regs[29], bt) &&
> !(regs->pstate & (0xffffffff00000000ULL | PSR_MODE32_BIT)) &&
> ========> is_kernel_text(regs->pc | ms->CONFIG_ARM64_KERNELPACMASK) &&
Yes good catch. Masking can be removed from here.
Can you please confirm?
Thanks,
Dave
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