queue/powerpc-kernel-Use-kprobe-blacklist-for-asm-function.patch

From 7891f34ac45a3dfcc387959954e66f9df9ee7b65 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Fri, 16 Sep 2016 20:48:17 +1000
Subject: [PATCH] powerpc/kernel: Use kprobe blacklist for asm functions

commit 6f698df10cb24d466b9a790b9daedb9e7bcd5d2a upstream.

Rather than forcing the whole function into the ".kprobes.text" section,
just add the symbol's address to the kprobe blacklist.

This also lets us drop the three versions of the_KPROBE macro, in
exchange for just one version of _ASM_NOKPROBE_SYMBOL - which is a good
cleanup.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index d5d5b5e348f2..cd39ac127786 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -217,13 +217,6 @@ name: \
 	addi r2,r2,(.TOC.-0b)@l; \
 	.localentry name,.-name
 
-#define _KPROBE(name) \
-	.section ".kprobes.text","a"; \
-	.align 2 ; \
-	.type name,@function; \
-	.globl name; \
-name:
-
 #define DOTSYM(a)	a
 
 #else
@@ -247,20 +240,6 @@ GLUE(.,name):
 
 #define _GLOBAL_TOC(name) _GLOBAL(name)
 
-#define _KPROBE(name) \
-	.section ".kprobes.text","a"; \
-	.align 2 ; \
-	.globl name; \
-	.globl GLUE(.,name); \
-	.section ".opd","aw"; \
-name: \
-	.quad GLUE(.,name); \
-	.quad .TOC.@tocbase; \
-	.quad 0; \
-	.previous; \
-	.type GLUE(.,name),@function; \
-GLUE(.,name):
-
 #define DOTSYM(a)	GLUE(.,a)
 
 #endif
@@ -279,13 +258,22 @@ n:
 
 #define _GLOBAL_TOC(name) _GLOBAL(name)
 
-#define _KPROBE(n)	\
-	.section ".kprobes.text","a";	\
-	.globl	n;	\
-n:
-
 #endif
 
+/*
+ * __kprobes (the C annotation) puts the symbol into the .kprobes.text
+ * section, which gets emitted at the end of regular text.
+ *
+ * _ASM_NOKPROBE_SYMBOL and NOKPROBE_SYMBOL just adds the symbol to
+ * a blacklist. The former is for core kprobe functions/data, the
+ * latter is for those that incdentially must be excluded from probing
+ * and allows them to be linked at more optimal location within text.
+ */
+#define _ASM_NOKPROBE_SYMBOL(entry)			\
+	.pushsection "_kprobe_blacklist","aw";		\
+	PPC_LONG (entry) ;				\
+	.popsection
+
 #define FUNC_START(name)	_GLOBAL(name)
 #define FUNC_END(name)
 
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index f2f787ec3cd6..e3d9d5562e01 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -328,7 +328,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_UNIFIED_ID_CACHE)
  *
  * flush_icache_range(unsigned long start, unsigned long stop)
  */
-_KPROBE(flush_icache_range)
+_GLOBAL(flush_icache_range)
 BEGIN_FTR_SECTION
 	PURGE_PREFETCHED_INS
 	blr				/* for 601, do nothing */
@@ -358,6 +358,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
 	sync				/* additional sync needed on g4 */
 	isync
 	blr
+_ASM_NOKPROBE_SYMBOL(flush_icache_range)
+
 /*
  * Flush a particular page from the data cache to RAM.
  * Note: this is necessary because the instruction cache does *not*
diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index cb195157b318..5d7e583f1588 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -66,7 +66,7 @@ PPC64_CACHES:
  *   flush all bytes from start through stop-1 inclusive
  */
 
-_KPROBE(flush_icache_range)
+_GLOBAL(flush_icache_range)
 BEGIN_FTR_SECTION
 	PURGE_PREFETCHED_INS
 	blr
@@ -109,7 +109,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
 	bdnz	2b
 	isync
 	blr
-	.previous .text
+_ASM_NOKPROBE_SYMBOL(flush_icache_range)
+
 /*
  * Like above, but only do the D-cache.
  *
-- 
2.12.0