13e165baf6
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>
124 lines
3.1 KiB
C
124 lines
3.1 KiB
C
/*
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* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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* Licensed under the GPL
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*/
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#ifndef __UM_ELF_I386_H
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#define __UM_ELF_I386_H
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#include <asm/user.h>
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#include "skas.h"
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#define R_386_NONE 0
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#define R_386_32 1
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#define R_386_PC32 2
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#define R_386_GOT32 3
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#define R_386_PLT32 4
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#define R_386_COPY 5
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#define R_386_GLOB_DAT 6
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#define R_386_JMP_SLOT 7
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#define R_386_RELATIVE 8
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#define R_386_GOTOFF 9
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#define R_386_GOTPC 10
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#define R_386_NUM 11
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typedef unsigned long elf_greg_t;
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#define ELF_NGREG (sizeof (struct user_regs_struct) / sizeof(elf_greg_t))
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typedef elf_greg_t elf_gregset_t[ELF_NGREG];
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typedef struct user_i387_struct elf_fpregset_t;
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/*
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* This is used to ensure we don't load something for the wrong architecture.
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*/
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#define elf_check_arch(x) \
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(((x)->e_machine == EM_386) || ((x)->e_machine == EM_486))
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#define ELF_CLASS ELFCLASS32
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#define ELF_DATA ELFDATA2LSB
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#define ELF_ARCH EM_386
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#define ELF_PLAT_INIT(regs, load_addr) do { \
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PT_REGS_EBX(regs) = 0; \
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PT_REGS_ECX(regs) = 0; \
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PT_REGS_EDX(regs) = 0; \
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PT_REGS_ESI(regs) = 0; \
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PT_REGS_EDI(regs) = 0; \
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PT_REGS_EBP(regs) = 0; \
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PT_REGS_EAX(regs) = 0; \
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} while (0)
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#define ELF_EXEC_PAGESIZE 4096
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#define ELF_ET_DYN_BASE (2 * TASK_SIZE / 3)
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/* Shamelessly stolen from include/asm-i386/elf.h */
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#define ELF_CORE_COPY_REGS(pr_reg, regs) do { \
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pr_reg[0] = PT_REGS_EBX(regs); \
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pr_reg[1] = PT_REGS_ECX(regs); \
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pr_reg[2] = PT_REGS_EDX(regs); \
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pr_reg[3] = PT_REGS_ESI(regs); \
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pr_reg[4] = PT_REGS_EDI(regs); \
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pr_reg[5] = PT_REGS_EBP(regs); \
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pr_reg[6] = PT_REGS_EAX(regs); \
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pr_reg[7] = PT_REGS_DS(regs); \
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pr_reg[8] = PT_REGS_ES(regs); \
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/* fake once used fs and gs selectors? */ \
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pr_reg[9] = PT_REGS_DS(regs); \
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pr_reg[10] = PT_REGS_DS(regs); \
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pr_reg[11] = PT_REGS_SYSCALL_NR(regs); \
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pr_reg[12] = PT_REGS_IP(regs); \
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pr_reg[13] = PT_REGS_CS(regs); \
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pr_reg[14] = PT_REGS_EFLAGS(regs); \
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pr_reg[15] = PT_REGS_SP(regs); \
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pr_reg[16] = PT_REGS_SS(regs); \
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} while (0);
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#define task_pt_regs(t) (&(t)->thread.regs)
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struct task_struct;
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extern int elf_core_copy_fpregs(struct task_struct *t, elf_fpregset_t *fpu);
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#define ELF_CORE_COPY_FPREGS(t, fpu) elf_core_copy_fpregs(t, fpu)
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extern long elf_aux_hwcap;
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#define ELF_HWCAP (elf_aux_hwcap)
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extern char * elf_aux_platform;
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#define ELF_PLATFORM (elf_aux_platform)
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#define SET_PERSONALITY(ex) do { } while (0)
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extern unsigned long vsyscall_ehdr;
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extern unsigned long vsyscall_end;
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extern unsigned long __kernel_vsyscall;
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#define VSYSCALL_BASE vsyscall_ehdr
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#define VSYSCALL_END vsyscall_end
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/*
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* This is the range that is readable by user mode, and things
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* acting like user mode such as get_user_pages.
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*/
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#define FIXADDR_USER_START VSYSCALL_BASE
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#define FIXADDR_USER_END VSYSCALL_END
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/*
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* Architecture-neutral AT_ values in 0-17, leave some room
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* for more of them, start the x86-specific ones at 32.
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*/
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#define AT_SYSINFO 32
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#define AT_SYSINFO_EHDR 33
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#define ARCH_DLINFO \
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do { \
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if ( vsyscall_ehdr ) { \
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NEW_AUX_ENT(AT_SYSINFO, __kernel_vsyscall); \
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NEW_AUX_ENT(AT_SYSINFO_EHDR, vsyscall_ehdr); \
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} \
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} while (0)
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#endif
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