x86: x86 core dump TLS

This makes ELF core dumps of 32-bit processes include a new
note type NT_386_TLS (0x200) giving the contents of the TLS
slots in struct user_desc format.  This lets post mortem
examination figure out what the segment registers mean like
the debugger does with get_thread_area on a live process.
Signed-off-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/ptrace.c

@@ -1313,6 +1313,7 @@ static const struct user_regset x86_32_regsets[] = {
 		.active = xfpregs_active, .get = xfpregs_get, .set = xfpregs_set
 	},
 	[REGSET_TLS] = {
+		.core_note_type = NT_386_TLS,
 		.n = GDT_ENTRY_TLS_ENTRIES, .bias = GDT_ENTRY_TLS_MIN,
 		.size = sizeof(struct user_desc),
 		.align = sizeof(struct user_desc),

include/linux/elf.h

@@ -355,6 +355,7 @@ typedef struct elf64_shdr {
 #define NT_AUXV		6
 #define NT_PRXFPREG     0x46e62b7f      /* copied from gdb5.1/include/elf/common.h */
 #define NT_PPC_VMX	0x100		/* PowerPC Altivec/VMX registers */
+#define NT_386_TLS	0x200		/* i386 TLS slots (struct user_desc) */
 
 
 /* Note header in a PT_NOTE section */