Messages in this thread | | | Date | Wed, 1 Jul 2009 12:54:41 -0400 (EDT) | From | Steven Rostedt <> | Subject | [BUG] gcov causes vread_tsc to increment kernel memory |
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On bootup of the latest kernel my init segfaults. Debugging it, I found that vread_tsc (a vsyscall) increments some strange kernel memory:
0000000000000000 <vread_tsc>: 0: 55 push %rbp 1: 48 ff 05 00 00 00 00 incq 0(%rip) # 8 <vread_tsc+0x8> 4: R_X86_64_PC32 .bss+0x3c 8: 48 89 e5 mov %rsp,%rbp b: 66 66 90 xchg %ax,%ax e: 48 ff 05 00 00 00 00 incq 0(%rip) # 15 <vread_tsc+0x15> 11: R_X86_64_PC32 .bss+0x44 15: 66 66 90 xchg %ax,%ax 18: 48 ff 05 00 00 00 00 incq 0(%rip) # 1f <vread_tsc+0x1f> 1b: R_X86_64_PC32 .bss+0x4c 1f: 0f 31 rdtsc
Those "incq" is very bad to happen in vsyscall memory, since userspace can not modify it. You need to make something prevent profiling of vsyscall memory (like I do with ftrace).
-- Steve
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