Re: [uml-devel] Kernel panic - not syncing: do_syscall_stub : PTRACE_SETREGS failed, errno = 5

["Peter Teoh" <htmldeveloper@gmail.com>]

The problem lies in the function:

static inline long do_syscall_stub(struct mm_id * mm_idp, void **addr)
{
        int n, i;
        long ret, offset;
        unsigned long * data;
        unsigned long * syscall;
        int err, pid = mm_idp->u.pid;

        if (proc_mm)
                /* FIXME: Need to look up userspace_pid by cpu */
                pid = userspace_pid[0];

        multi_count++;

        n = ptrace_setregs(pid, syscall_regs);
        if (n < 0) {
                printk(UM_KERN_ERR "Registers - \n");
                for (i = 0; i < MAX_REG_NR; i++)
                        printk(UM_KERN_ERR "\t%d\t0x%lx\n", i, syscall_regs[i]);
                panic("do_syscall_stub : PTRACE_SETREGS failed, errno = %d\n",
                      -n);
        }

Where the ptrace_setregs() above returned a value less than zero.

Breakpoint 2, do_syscall_stub (mm_idp=0xfdaee9c, addr=0xfc5ce44) at
/mnt/hd0/download/linux-2.6-latest/arch/um/os-Linux/skas/mem.c:76
76                              printk(UM_KERN_ERR "\t%d\t0x%lx\n", i,
syscall_regs[i]);
(gdb)
        16      0x0
75                      for (i = 0; i < MAX_REG_NR; i++)
(gdb)
77                      panic("do_syscall_stub : PTRACE_SETREGS
failed, errno = %d\n",
(gdb)
Kernel panic - not syncing: do_syscall_stub : PTRACE_SETREGS failed, errno = 5

And ptrace_setregs() calling ptrace() seemed to returned -errno almost
immediately:

(gdb) s
ptrace_setregs (pid=19131, regs=0x820aae0) at
/mnt/hd0/download/linux-2.6-latest/arch/um/sys-i386/ptrace_user.c:18
18              if (ptrace(PTRACE_SETREGS, pid, 0, regs) < 0)
(gdb) s
19                      return -errno;
(gdb) s

Why is it so?

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