Re: [Crash-utility] [PATCH v2] Determine the ARM64 kernel's Pointer Authentication mask value by reading the new KERNELPACMASK vmcoreinfo entry.

----- 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