Paul Pluzhnikov 13e165baf6 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>		2011-03-22 17:44:09 -07:00
..
asm	uml: kernels on {i386,x86_64} produce bad coredumps	2011-03-22 17:44:09 -07:00
shared/sysdep	Add generic sys_old_mmap()	2010-03-12 15:52:32 -08:00
bug.c
bugs.c
checksum.S
delay.c
elfcore.c
fault.c
ksyms.c
ldt.c	include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h	2010-03-30 22:02:32 +09:00
Makefile
ptrace_user.c
ptrace.c	ptrace: change signature of arch_ptrace()	2010-10-27 18:03:10 -07:00
setjmp.S
signal.c
stub_segv.c
stub.S
sys_call_table.S	Add generic sys_old_mmap()	2010-03-12 15:52:32 -08:00
syscalls.c	Add generic sys_ipc wrapper	2010-03-12 15:52:32 -08:00
sysrq.c
tls.c
user-offsets.c