[POWERPC] Allow ptrace write to pt_regs trap and orig_r3

This patch allows a ptracer to write to the "trap" and "orig_r3" words
of the pt_regs.

This, along with a subsequent patch to the signal restart code, should
enable gdb to properly handle syscall restarting after executing a separate
function (at least when there's no restart block).

This patch also removes ptrace32.c code toying directly with the registers
and makes it use the ptrace_get/put_reg() accessors for everything so that
the logic for checking what is permitted is in only one place.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index c9c330d35c17..dd4837c4a68a 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -75,10 +75,15 @@ int ptrace_put_reg(struct task_struct *task, int regno, unsigned long data)
         if (task->thread.regs == NULL)
                 return -EIO;
 
-        if (regno <= PT_MAX_PUT_REG) {
+        if (regno <= PT_MAX_PUT_REG || regno == PT_TRAP) {
                 if (regno == PT_MSR)
                         data = (data & MSR_DEBUGCHANGE)
                                 | (task->thread.regs->msr & ~MSR_DEBUGCHANGE);
+                /* We prevent mucking around with the reserved area of trap
+                 * which are used internally by the kernel
+                 */
+                if (regno == PT_TRAP)
+                        data &= 0xfff0;
                 ((unsigned long *)task->thread.regs)[regno] = data;
                 return 0;
         }
@@ -409,8 +414,6 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                         break;
 
                 CHECK_FULL_REGS(child->thread.regs);
-                if (index == PT_ORIG_R3)
-                        break;
                 if (index < PT_FPR0) {
                         ret = ptrace_put_reg(child, index, data);
                 } else {