Re: [Crash-utility] invalid regs display in bt

Richard J Moore wrote: > On looking at the code in entry.S at page_fault and the other

> entry points I see no attempt to save regs to create a pt_regs struct.

> The fact that do_page_fault takes pt_regs as the first arg is a hack

> get at CS:EIP and SS:ESP at the time of exception. KPROBE_ENTRY(page_fault) RING0_EC_FRAME pushl $do_page_fault CFI_ADJUST_CFA_OFFSET 4 ALIGN error_code: /* the function address is in %fs's slot on the stack */ pushl %es CFI_ADJUST_CFA_OFFSET 4 /*CFI_REL_OFFSET es, 0*/ pushl %ds CFI_ADJUST_CFA_OFFSET 4 /*CFI_REL_OFFSET ds, 0*/ pushl %eax CFI_ADJUST_CFA_OFFSET 4 CFI_REL_OFFSET eax, 0 pushl %ebp CFI_ADJUST_CFA_OFFSET 4 CFI_REL_OFFSET ebp, 0 pushl %edi CFI_ADJUST_CFA_OFFSET 4 CFI_REL_OFFSET edi, 0 pushl %esi CFI_ADJUST_CFA_OFFSET 4 CFI_REL_OFFSET esi, 0 pushl %edx CFI_ADJUST_CFA_OFFSET 4 CFI_REL_OFFSET edx, 0 pushl %ecx CFI_ADJUST_CFA_OFFSET 4 CFI_REL_OFFSET ecx, 0 pushl %ebx CFI_ADJUST_CFA_OFFSET 4 CFI_REL_OFFSET ebx, 0 cld pushl %fs CFI_ADJUST_CFA_OFFSET 4 /*CFI_REL_OFFSET fs, 0*/ movl $(__KERNEL_PERCPU), %ecx movl %ecx, %fs UNWIND_ESPFIX_STACK popl %ecx CFI_ADJUST_CFA_OFFSET -4 /*CFI_REGISTER es, ecx*/ movl PT_FS(%esp), %edi # get the function address movl PT_ORIG_EAX(%esp), %edx # get the error code movl $-1, PT_ORIG_EAX(%esp) # no syscall to restart mov %ecx, PT_FS(%esp) /*CFI_REL_OFFSET fs, ES*/ movl $(__USER_DS), %ecx movl %ecx, %ds movl %ecx, %es movl %esp,%eax # pt_regs pointer call *%edi jmp ret_from_exception CFI_ENDPROC KPROBE_END(page_fault)