in kernel/ptrace.c [123:215]
long arch_ptrace(struct task_struct *child, long request,
unsigned long addr, unsigned long data)
{
unsigned long __user *datap = (unsigned long __user *)data;
unsigned long tmp;
long ret = -EIO;
switch (request) {
/* Read the word at location addr in the USER area. For ptraced
processes, the kernel saves all regs on a syscall. */
case PTRACE_PEEKUSR:
if ((addr & (sizeof(unsigned long)-1)) ||
addr >= sizeof(struct pt_regs))
break;
tmp = *(unsigned long *) ((char *) task_regs(child) + addr);
ret = put_user(tmp, datap);
break;
/* Write the word at location addr in the USER area. This will need
to change when the kernel no longer saves all regs on a syscall.
FIXME. There is a problem at the moment in that r3-r18 are only
saved if the process is ptraced on syscall entry, and even then
those values are overwritten by actual register values on syscall
exit. */
case PTRACE_POKEUSR:
/* Some register values written here may be ignored in
* entry.S:syscall_restore_rfi; e.g. iaoq is written with
* r31/r31+4, and not with the values in pt_regs.
*/
if (addr == PT_PSW) {
/* Allow writing to Nullify, Divide-step-correction,
* and carry/borrow bits.
* BEWARE, if you set N, and then single step, it won't
* stop on the nullified instruction.
*/
data &= USER_PSW_BITS;
task_regs(child)->gr[0] &= ~USER_PSW_BITS;
task_regs(child)->gr[0] |= data;
ret = 0;
break;
}
if ((addr & (sizeof(unsigned long)-1)) ||
addr >= sizeof(struct pt_regs))
break;
if (addr == PT_IAOQ0 || addr == PT_IAOQ1) {
data |= 3; /* ensure userspace privilege */
}
if ((addr >= PT_GR1 && addr <= PT_GR31) ||
addr == PT_IAOQ0 || addr == PT_IAOQ1 ||
(addr >= PT_FR0 && addr <= PT_FR31 + 4) ||
addr == PT_SAR) {
*(unsigned long *) ((char *) task_regs(child) + addr) = data;
ret = 0;
}
break;
case PTRACE_GETREGS: /* Get all gp regs from the child. */
return copy_regset_to_user(child,
task_user_regset_view(current),
REGSET_GENERAL,
0, sizeof(struct user_regs_struct),
datap);
case PTRACE_SETREGS: /* Set all gp regs in the child. */
return copy_regset_from_user(child,
task_user_regset_view(current),
REGSET_GENERAL,
0, sizeof(struct user_regs_struct),
datap);
case PTRACE_GETFPREGS: /* Get the child FPU state. */
return copy_regset_to_user(child,
task_user_regset_view(current),
REGSET_FP,
0, sizeof(struct user_fp_struct),
datap);
case PTRACE_SETFPREGS: /* Set the child FPU state. */
return copy_regset_from_user(child,
task_user_regset_view(current),
REGSET_FP,
0, sizeof(struct user_fp_struct),
datap);
default:
ret = ptrace_request(child, request, addr, data);
break;
}
return ret;
}