From: Nicholas Piggin <npiggin@gmail.com>
Date: Fri, 16 Sep 2016 10:48:17 +0000 (+1000)
Subject: powerpc/kernel: Use kprobe blacklist for asm functions
X-Git-Tag: v3.16.46~55
X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=958bc332da6ed174ffb58d19893ad6da08b9e953;p=linux

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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index 7e4612528546..6d23045555c6 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
+
 /* 
  * LOAD_REG_IMMEDIATE(rn, expr)
  *   Loads the value of the constant expression 'expr' into register 'rn'
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index 2c70bbcb006f..0703738d092f 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -345,7 +345,7 @@ 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 */
@@ -376,6 +376,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
 	sync				/* additional sync needed on g4 */
 	isync
 	blr
+_ASM_NOKPROBE_SYMBOL(flush_icache_range)
+
 /*
  * Write any modified data cache blocks out to memory.
  * Does not invalidate the corresponding cache lines (especially for
diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index 4e314b90c75d..7f0f06d788b6 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -65,7 +65,7 @@ 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
@@ -108,7 +108,8 @@ 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.
  *