ARM: 6798/1: aout-core: zero thread debug registers in a.out core dump

The removal of the single-step emulation from ptrace on ARM means that
thread_struct no longer has software breakpoint fields in its debug
member.

This patch fixes the a.out core dump code so that the debug registers
are zeroed rather than trying to copy from non-existent fields.

Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/a.out-core.h

@@ -32,11 +32,7 @@ static inline void aout_dump_thread(struct pt_regs *regs, struct user *dump)
 	dump->u_dsize = (tsk->mm->brk - tsk->mm->start_data + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	dump->u_ssize = 0;
 
-	dump->u_debugreg[0] = tsk->thread.debug.bp[0].address;
-	dump->u_debugreg[1] = tsk->thread.debug.bp[1].address;
-	dump->u_debugreg[2] = tsk->thread.debug.bp[0].insn.arm;
-	dump->u_debugreg[3] = tsk->thread.debug.bp[1].insn.arm;
-	dump->u_debugreg[4] = tsk->thread.debug.nsaved;
+	memset(dump->u_debugreg, 0, sizeof(dump->u_debugreg));
 
 	if (dump->start_stack < 0x04000000)
 		dump->u_ssize = (0x04000000 - dump->start_stack) >> PAGE_SHIFT;

arch/arm/include/asm/user.h

@@ -71,7 +71,7 @@ struct user{
 				/* the registers. */
   unsigned long magic;		/* To uniquely identify a core file */
   char u_comm[32];		/* User command that was responsible */
-  int u_debugreg[8];
+  int u_debugreg[8];		/* No longer used */
   struct user_fp u_fp;		/* FP state */
   struct user_fp_struct * u_fp0;/* Used by gdb to help find the values for */
   				/* the FP registers. */