[PATCH] uml: use correct register file size everywhere

This patch uses MAX_REG_NR consistently to refer to the register file size.
 FRAME_SIZE isn't sufficient because on x86_64, it is smaller than the
ptrace register file size.  MAX_REG_NR was introduced as a consistent way
to get the number of registers, but wasn't used everywhere it should be.

When this causes a problem, it makes PTRACE_SETREGS fail on x86_64 because
of a corrupted segment register value in the known-good register file.  The
patch also adds a register dump at that point in case there are any future
problems here.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/arch/um/os-Linux/skas/mem.c b/arch/um/os-Linux/skas/mem.c
index b3c11cfa995a..9383e8751ae7 100644
--- a/arch/um/os-Linux/skas/mem.c
+++ b/arch/um/os-Linux/skas/mem.c
@@ -48,7 +48,7 @@ int multi_op_count = 0;
 static inline long do_syscall_stub(struct mm_id * mm_idp, void **addr)
 {
         unsigned long regs[MAX_REG_NR];
-        int n;
+        int n, i;
         long ret, offset;
         unsigned long * data;
         unsigned long * syscall;
@@ -66,9 +66,13 @@ static inline long do_syscall_stub(struct mm_id * mm_idp, void **addr)
                  (unsigned long) &__syscall_stub_start);
 
         n = ptrace_setregs(pid, regs);
-        if(n < 0)
+        if(n < 0){
+                printk("Registers - \n");
+                for(i = 0; i < MAX_REG_NR; i++)
+                        printk("\t%d\t0x%lx\n", i, regs[i]);
                 panic("do_syscall_stub : PTRACE_SETREGS failed, errno = %d\n",
-                      n);
+                      -n);
+        }
 
         wait_stub_done(pid, 0, "do_syscall_stub");