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.
--
Regards
Qiao Nuohan
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) {
--
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