From 11dbc963a8f6128595d0f6ecf138dc369e144997 Mon Sep 17 00:00:00 2001
From: TAKADA Yoshihito <takada@mbf.nifty.com>
Date: Mon, 30 Jun 2008 13:44:45 +0900
Subject: [PATCH] ptrace GET/SET FPXREGS broken

When I update kernel 2.6.25 from 2.6.24, gdb does not work.
On 2.6.25, ptrace(PTRACE_GETFPXREGS, ...) returns ENODEV.

But 2.6.24 kernel's ptrace() returns EIO.
It is issue of compatibility.

I attached test program as pt.c and patch for fix it.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <sys/ptrace.h>
#include <sys/types.h>

struct user_fxsr_struct {
	unsigned short	cwd;
	unsigned short	swd;
	unsigned short	twd;
	unsigned short	fop;
	long	fip;
	long	fcs;
	long	foo;
	long	fos;
	long	mxcsr;
	long	reserved;
	long	st_space[32];	/* 8*16 bytes for each FP-reg = 128 bytes */
	long	xmm_space[32];	/* 8*16 bytes for each XMM-reg = 128 bytes */
	long	padding[56];
};

int main(void)
{
  pid_t pid;

  pid = fork();

  switch(pid){
  case -1:/*  error */
    break;
  case 0:/*  child */
    child();
    break;
  default:
    parent(pid);
    break;
  }
  return 0;
}

int child(void)
{
  ptrace(PTRACE_TRACEME);
  kill(getpid(), SIGSTOP);
  sleep(10);
  return 0;
}
int parent(pid_t pid)
{
  int ret;
  struct user_fxsr_struct fpxregs;

  ret = ptrace(PTRACE_GETFPXREGS, pid, 0, &fpxregs);
  if(ret < 0){
    printf("%d: %s.\n", errno, strerror(errno));
  }
  kill(pid, SIGCONT);
  wait(pid);
  return 0;
}

/* in the kerel, at kernel/i387.c get_fpxregs() */

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/i387.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index eb9ddd8efb8..95e80e5033c 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -162,7 +162,7 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 	int ret;
 
 	if (!cpu_has_fxsr)
-		return -ENODEV;
+		return -EIO;
 
 	ret = init_fpu(target);
 	if (ret)
@@ -179,7 +179,7 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 	int ret;
 
 	if (!cpu_has_fxsr)
-		return -ENODEV;
+		return -EIO;
 
 	ret = init_fpu(target);
 	if (ret)
-- 
2.41.1