Re: [Crash-utility] command dis fails to display name of function

Hello Dave, When using dis command on RHEL5.11, I found a weird thing. Please check the following execution. <cut> crash> dis do_wp_page | grep 591 0xffffffff8001115c <do_wp_page+591>: callq 0xffffffff800623d0 <__sched_text_start> crash> dis schedule 0xffffffff800623d0 <__sched_text_start>: push %rbp 0xffffffff800623d1 <schedule+1>: mov %rsp,%rbp ... crash> dis do_wp_page | grep 591 0xffffffff8001115c <do_wp_page+591>: callq 0xffffffff800623d0 <schedule> crash> dis do_wp_page | grep 591 0xffffffff8001115c <do_wp_page+591>: callq 0xffffffff800623d0 <__sched_text_start> <cut> schedule and __sched_text_start are always shifting. After some investigation, I found the following sentences in arch/x86_64/kernel/vmlinux.lds.S <cut> SECTIONS { ... SCHED_TEXT LOCK_TEXT KPROBES_TEXT ... <cut> the SCHED_TEXT is defined like below <cut> #define SCHED_TEXT \ ALIGN_FUNCTION(); \ VMLINUX_SYMBOL(__sched_text_start) = .; \ *(.sched.text) \ VMLINUX_SYMBOL(__sched_text_end) = .; <cut> So symbol __sched_text_start may have the same address as the first function of *(.sched.text). And LOCK_TEXT/KPROBES_TEXT/IRQENTRY_TEXT has the same problems. The attached patch is used to fix this.

diff --git a/symbols.c b/symbols.c index cebff52..461348c 100755 --- a/symbols.c +++ b/symbols.c @@ -4527,6 +4527,15 @@ value_search(ulong value, ulong *offset) (spnext->value == value)) sp = spnext; +#define STRNVEQ(A, B) (string_exists((char *)A) && string_exists((char *)B) && \ + strstr(A, B) && (strstr(A, B) - A) == \ + (strlen((char *)(A)) - strlen((char *)(B))) ) + + if (STRNVEQ(sp->name, "_text_start") && + ((spnext = sp+1) < st->symend) && + (spnext->value == value)) + sp = spnext; + return((struct syment *)sp); } if (sp->value > value) {