kgdbts: unify/generalize gdb breakpoint adjustment

The Blackfin arch, like the x86 arch, needs to adjust the PC manually
after a breakpoint is hit as normally this is handled by the remote gdb.
However, rather than starting another arch ifdef mess, create a common
GDB_ADJUSTS_BREAK_OFFSET define for any arch to opt-in via their kgdb.h.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Dongdong Deng <dongdong.deng@windriver.com>
Cc: Sergei Shtylyov <sshtylyov@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/blackfin/include/asm/kgdb.h

@@ -108,6 +108,7 @@ static inline void arch_kgdb_breakpoint(void)
 #else
 # define CACHE_FLUSH_IS_SAFE	1
 #endif
+#define GDB_ADJUSTS_BREAK_OFFSET
 #define HW_INST_WATCHPOINT_NUM	6
 #define HW_WATCHPOINT_NUM	8
 #define TYPE_INST_WATCHPOINT	0

arch/sh/include/asm/kgdb.h

@@ -34,5 +34,6 @@ static inline void arch_kgdb_breakpoint(void)
 
 #define CACHE_FLUSH_IS_SAFE	1
 #define BREAK_INSTR_SIZE	2
+#define GDB_ADJUSTS_BREAK_OFFSET
 
 #endif /* __ASM_SH_KGDB_H */

arch/x86/include/asm/kgdb.h

@@ -77,6 +77,7 @@ static inline void arch_kgdb_breakpoint(void)
 }
 #define BREAK_INSTR_SIZE	1
 #define CACHE_FLUSH_IS_SAFE	1
+#define GDB_ADJUSTS_BREAK_OFFSET
 
 extern int kgdb_ll_trap(int cmd, const char *str,
 			struct pt_regs *regs, long err, int trap, int sig);

drivers/misc/kgdbts.c

@@ -285,33 +285,26 @@ static void hw_break_val_write(void)
 static int check_and_rewind_pc(char *put_str, char *arg)
 {
 	unsigned long addr = lookup_addr(arg);
+	unsigned long ip;
 	int offset = 0;
 
 	kgdb_hex2mem(&put_str[1], (char *)kgdbts_gdb_regs,
 		 NUMREGBYTES);
 	gdb_regs_to_pt_regs(kgdbts_gdb_regs, &kgdbts_regs);
-	v2printk("Stopped at IP: %lx\n", instruction_pointer(&kgdbts_regs));
-#ifdef CONFIG_X86
-	/* On x86 a breakpoint stop requires it to be decremented */
-	if (addr + 1 == kgdbts_regs.ip)
-		offset = -1;
-#elif defined(CONFIG_SUPERH)
-	/* On SUPERH a breakpoint stop requires it to be decremented */
-	if (addr + 2 == kgdbts_regs.pc)
-		offset = -2;
+	ip = instruction_pointer(&kgdbts_regs);
+	v2printk("Stopped at IP: %lx\n", ip);
+#ifdef GDB_ADJUSTS_BREAK_OFFSET
+	/* On some arches, a breakpoint stop requires it to be decremented */
+	if (addr + BREAK_INSTR_SIZE == ip)
+		offset = -BREAK_INSTR_SIZE;
 #endif
-	if (strcmp(arg, "silent") &&
-		instruction_pointer(&kgdbts_regs) + offset != addr) {
+	if (strcmp(arg, "silent") && ip + offset != addr) {
 		eprintk("kgdbts: BP mismatch %lx expected %lx\n",
-			   instruction_pointer(&kgdbts_regs) + offset, addr);
+			   ip + offset, addr);
 		return 1;
 	}
-#ifdef CONFIG_X86
-	/* On x86 adjust the instruction pointer if needed */
-	kgdbts_regs.ip += offset;
-#elif defined(CONFIG_SUPERH)
-	kgdbts_regs.pc += offset;
-#endif
+	/* Readjust the instruction pointer if needed */
+	instruction_pointer_set(&kgdbts_regs, ip + offset);
 	return 0;
 }