Messages in this thread Patch in this message | | | Subject | [PATCH RT] Don't call mcount from vsyscall_fn's | From | Steven Rostedt <> | Date | Mon, 18 Jun 2007 22:41:09 -0400 |
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This bit me in the butt.
I couldn't understand why my init app was segfaulting, with a kernel address, but a user RIP and RSP. Well, the RIP I think was bogus, but the kernel address was always the start of "mcount". Looking deeper, I printed out what was in the RSP (even though it was a user stack). It ended up showing me that the calling address was from the VDSO area. Looking even further, I found the offending culprit, which was vread_hpet.
Looking at the assembly dump, I saw the vread_hpet was calling mcount, but I could not see it in the code. Nor could I see it in hpet.i (-E option of compiling).
Well, I guess Ingo is a magician when it comes to compiler tricks, and has the mcount being called by "every!!" function, unless you add the "notrace" option.
This patch adds the notrace to vsyscall_fn, so that we don't have user land apps calling mcount and crashing!
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Index: linux-2.6-rt-test/include/asm-x86_64/vsyscall.h =================================================================== --- linux-2.6-rt-test.orig/include/asm-x86_64/vsyscall.h +++ linux-2.6-rt-test/include/asm-x86_64/vsyscall.h @@ -22,7 +22,7 @@ enum vsyscall_num { /* Definitions for CONFIG_GENERIC_TIME definitions */ #define __section_vsyscall_gtod_data __attribute__ \ ((unused, __section__ (".vsyscall_gtod_data"),aligned(16))) -#define __vsyscall_fn __attribute__ ((unused,__section__(".vsyscall_fn"))) +#define __vsyscall_fn __attribute__ ((unused,__section__(".vsyscall_fn"))) notrace #define VGETCPU_RDTSCP 1 #define VGETCPU_LSL 2
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