Re: [Crash-utility] [PATCH v3] x86_64_exception_frame only performs EFRAME_VERIFY if it is the only flag

Hi David, Thanks for the update. > -----Original Message----- > x86_64_exception_frame() called with combined flags including > EFRAME_VERIFY does not perform the verify. It's only done when > EFRAME_VERIFY is the only flag set. > > Correct the condition to EFRAME_VERIFY if the flag is set. Verify > requests are always performed. Fixes stack overrun "seek errors" seen on > an x86_64 core when backtracing a PID at an IRQ stack where the > interrupt handler doesn't save a pt_regs. Higher layers than the top > frame on the IRQ stack were not displayed. Fixed by this change. > > But it breaks bt -e and bt -E for exceptions on userspace stacks. Those > use the constant 0 as the kvaddr argument to x86_64_exception_frame() > and pass the userspace stack position in the local argument. > x86_64_exception_frame() only verifies the kvaddr argument. Zero is not > accessible and EFRAME_VERIFY always fails for those cases. > > Modify the EFRAME_VERIFY block in x86_64_exception_frame() to choose > kvaddr or local to verify using the same condition used to assign one of > them to pt_regs_buf later in the same function. Add verify_addr to > locals to hold the choice. Modify the accessible tests to use it instead > of kvaddr. Type of the new variable is the same as the type of kvaddr. > > If verifying local argument, translate to a kernel address range using > the stackbuf and stackbase members of the bt argument the same way used > for EFRAME_SEARCH later in x86_64_exception_frame(). local and > bt->stackbuf are char *, the assignment destination and bt->stackbase > are ulong. Cast the char * variables to uintptr_t for the assignment > arithmetic using the local argument to prevent gcc 10.2 errors assigning > char * to ulong...the sum is okay without casts in the uses for function > arguments later. sorry for nitpicking, but I may need some study, what errors do you see? If you replace uintptr_t with ulong, what do you see? I cannot see any errors with Fedora gcc 10.2 without the casts. and uintptr_t looks same as ulong. In the crash source code, we usually use ulong for pointer value.

The patch logic looks good and tested OK.