[PATCH] x86_64: fix 32-bit thread debugging

The IA32 ptrace emulation currently returns the wrong registers for fs/gs;
it's returning what x86_64 calls gs_base. We need regs.gsindex in order
for GDB to correctly locate the TLS area. Without this patch, the 32-bit
GDB testsuite bombs on a 64-bit kernel. With it, results look about like
I'd expect, although there are still a handful of kernel-related failures
(vsyscall related?).

Signed-off-by: Daniel Jacobowitz <[e-mail]>
Acked-by: Andi Kleen <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/x86_64/ia32/ptrace32.c

···
 	switch (regno) {
 	case offsetof(struct user32, regs.fs):
 		if (val && (val & 3) != 3) return -EIO; 
-		child->thread.fs = val & 0xffff; 
+		child->thread.fsindex = val & 0xffff;
 		break;
 	case offsetof(struct user32, regs.gs):
 		if (val && (val & 3) != 3) return -EIO; 
-		child->thread.gs = val & 0xffff;
+		child->thread.gsindex = val & 0xffff;
 		break;
 	case offsetof(struct user32, regs.ds):
 		if (val && (val & 3) != 3) return -EIO; 
···
 
 	switch (regno) {
 	case offsetof(struct user32, regs.fs):
-	        *val = child->thread.fs; 
+	        *val = child->thread.fsindex;
 		break;
 	case offsetof(struct user32, regs.gs):
-		*val = child->thread.gs;
+		*val = child->thread.gsindex;
 		break;
 	case offsetof(struct user32, regs.ds):
 		*val = child->thread.ds;