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authorPaul Pluzhnikov <ppluzhnikov@google.com>2011-03-22 16:33:46 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-03-22 17:44:09 -0700
commit13e165baf6ada9f427c319bd41a1c7a9c7b4f0a6 (patch)
tree8ff1d630ca686f6f1ad6c2a5931f731a2d1140c7 /arch/um/sys-i386
parent3dd7ae8ec0ef399bfea347f297d2a95504d35571 (diff)
uml: kernels on {i386,x86_64} produce bad coredumps
One of our users reported that when a user-level program SIGSEGVs under UML kernel, the resulting core dump is not very usable. I have reproduced that with the latest kernel: make ARCH=um defconfig; make ARCH=um Run the resulting kernel, then "inside" run this program: #include <pthread.h> void *fn(void *p) { abort(); } int main() { pthread_t tid; pthread_create(&tid, 0, fn, 0); pthread_join(tid, 0); return 0; } Analyze the coredump with GDB. Here is what you'll see: sudo gdb -q -ex 'set solib-absolute-prefix ../root_fs' -ex 'file ../root_fs/var/tmp/mt-abort' -ex 'core ../root_fs/var/tmp/core.762' Reading symbols from /usr/local/google/root_fs/var/tmp/mt-abort...done. [New Thread 763] [New Thread 762] Core was generated by `./mt-abort'. Program terminated with signal 6, Aborted. #0 0x0000000040255250 in raise () from ../root_fs/lib64/libc.so.6 (gdb) info thread 2 Thread 762 0x0000000000000000 in ?? () * 1 Thread 763 0x0000000040255250 in raise () from ../root_fs/lib64/libc.so.6 Note that thread#2 looks funny. (gdb) thread 2 [Switching to thread 2 (Thread 762)]#0 0x0000000000000000 in ?? () (gdb) info reg rax 0x0 0 rbx 0x0 0 rcx 0x0 0 rdx 0x0 0 rsi 0x0 0 rdi 0x0 0 rbp 0x0 0x0 rsp 0x0 0x0 r8 0x0 0 r9 0x0 0 r10 0x0 0 r11 0x0 0 r12 0x0 0 r13 0x0 0 r14 0x0 0 r15 0x0 0 rip 0x0 0 eflags 0x0 [ ] cs 0x0 0 ss 0x0 0 ds 0x0 0 es 0x0 0 fs 0x0 0 gs 0x0 0 Examining the core shows that NT_PRSTATUS notes for all threads other than the one that crashed are zeroed out. I believe this is happening because neither ELF_CORE_COPY_TASK_REGS nor task_pt_regs are defined under ARCH=um, and so elf_core_copy_task_regs() becomes a no-op. Attached patch fixes this for SUBARCH={x86_64,i386}. Signed-off-by: Paul Pluzhnikov <ppluzhnikov@google.com> Cc: Jeff Dike <jdike@addtoit.com> Acked-by: WANG Cong <xiyou.wangcong@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/um/sys-i386')
-rw-r--r--arch/um/sys-i386/asm/elf.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/um/sys-i386/asm/elf.h b/arch/um/sys-i386/asm/elf.h
index a979a22a8d9f..d964a4111ac6 100644
--- a/arch/um/sys-i386/asm/elf.h
+++ b/arch/um/sys-i386/asm/elf.h
@@ -75,6 +75,8 @@ typedef struct user_i387_struct elf_fpregset_t;
pr_reg[16] = PT_REGS_SS(regs); \
} while (0);
+#define task_pt_regs(t) (&(t)->thread.regs)
+
struct task_struct;
extern int elf_core_copy_fpregs(struct task_struct *t, elf_fpregset_t *fpu);

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