powerpc: Use kprobe blacklist for exception handlers

Currently we mark the C implementations of some exception handlers as
__kprobes. This has the effect of putting them in the ".kprobes.text"
section, which separates them from the rest of the text.

Instead we can use the blacklist macros to add the symbols to a
blacklist which kprobes will check. This allows the linker to move
exception handler functions close to callers and avoids trampolines in
larger kernels.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Reword change log a bit]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 14 insertions, 7 deletions

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 0bab80e64ff9..6b108ed29c20 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -117,7 +117,7 @@ static int die_owner = -1;
 static unsigned int die_nest_count;
 static int die_counter;
 
-static unsigned __kprobes long oops_begin(struct pt_regs *regs)
+static unsigned long oops_begin(struct pt_regs *regs)
 {
 	int cpu;
 	unsigned long flags;
@@ -144,8 +144,9 @@ static unsigned __kprobes long oops_begin(struct pt_regs *regs)
 		pmac_backlight_unblank();
 	return flags;
 }
+NOKPROBE_SYMBOL(oops_begin);
 
-static void __kprobes oops_end(unsigned long flags, struct pt_regs *regs,
+static void oops_end(unsigned long flags, struct pt_regs *regs,
 			       int signr)
 {
 	bust_spinlocks(0);
@@ -196,8 +197,9 @@ static void __kprobes oops_end(unsigned long flags, struct pt_regs *regs,
 		panic("Fatal exception");
 	do_exit(signr);
 }
+NOKPROBE_SYMBOL(oops_end);
 
-static int __kprobes __die(const char *str, struct pt_regs *regs, long err)
+static int __die(const char *str, struct pt_regs *regs, long err)
 {
 	printk("Oops: %s, sig: %ld [#%d]\n", str, err, ++die_counter);
 #ifdef CONFIG_PREEMPT
@@ -221,6 +223,7 @@ static int __kprobes __die(const char *str, struct pt_regs *regs, long err)
 
 	return 0;
 }
+NOKPROBE_SYMBOL(__die);
 
 void die(const char *str, struct pt_regs *regs, long err)
 {
@@ -802,7 +805,7 @@ void RunModeException(struct pt_regs *regs)
 	_exception(SIGTRAP, regs, 0, 0);
 }
 
-void __kprobes single_step_exception(struct pt_regs *regs)
+void single_step_exception(struct pt_regs *regs)
 {
 	enum ctx_state prev_state = exception_enter();
 
@@ -819,6 +822,7 @@ void __kprobes single_step_exception(struct pt_regs *regs)
 bail:
 	exception_exit(prev_state);
 }
+NOKPROBE_SYMBOL(single_step_exception);
 
 /*
  * After we have successfully emulated an instruction, we have to
@@ -1140,7 +1144,7 @@ static int emulate_math(struct pt_regs *regs)
 static inline int emulate_math(struct pt_regs *regs) { return -1; }
 #endif
 
-void __kprobes program_check_exception(struct pt_regs *regs)
+void program_check_exception(struct pt_regs *regs)
 {
 	enum ctx_state prev_state = exception_enter();
 	unsigned int reason = get_reason(regs);
@@ -1260,16 +1264,18 @@ sigill:
 bail:
 	exception_exit(prev_state);
 }
+NOKPROBE_SYMBOL(program_check_exception);
 
 /*
  * This occurs when running in hypervisor mode on POWER6 or later
  * and an illegal instruction is encountered.
  */
-void __kprobes emulation_assist_interrupt(struct pt_regs *regs)
+void emulation_assist_interrupt(struct pt_regs *regs)
 {
 	regs->msr |= REASON_ILLEGAL;
 	program_check_exception(regs);
 }
+NOKPROBE_SYMBOL(emulation_assist_interrupt);
 
 void alignment_exception(struct pt_regs *regs)
 {
@@ -1668,7 +1674,7 @@ static void handle_debug(struct pt_regs *regs, unsigned long debug_status)
 		mtspr(SPRN_DBCR0, current->thread.debug.dbcr0);
 }
 
-void __kprobes DebugException(struct pt_regs *regs, unsigned long debug_status)
+void DebugException(struct pt_regs *regs, unsigned long debug_status)
 {
 	current->thread.debug.dbsr = debug_status;
 
@@ -1729,6 +1735,7 @@ void __kprobes DebugException(struct pt_regs *regs, unsigned long debug_status)
 	} else
 		handle_debug(regs, debug_status);
 }
+NOKPROBE_SYMBOL(DebugException);
 #endif /* CONFIG_PPC_ADV_DEBUG_REGS */
 
 #if !defined(CONFIG_TAU_INT)