[PATCH] ptrace GET/SET FPXREGS broken

[TAKADA Yoshihito]

Hi
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() */
--- a/arch/x86/kernel/i387.c	2008-04-17 11:49:44.000000000 +0900
+++ b/arch/x86/kernel/i387.c	2008-06-30 13:22:57.000000000 +0900
@@ -130,7 +130,7 @@
 		void *kbuf, void __user *ubuf)
 {
 	if (!cpu_has_fxsr)
-		return -ENODEV;
+		return -EIO;
 
 	init_fpu(target);
 
@@ -145,7 +145,7 @@
 	int ret;
 
 	if (!cpu_has_fxsr)
-		return -ENODEV;
+		return -EIO;
 
 	init_fpu(target);
 	set_stopped_child_used_math(target);