powerpc/kernel: Use kprobe blacklist for asm functions

commit 6f698df1 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>

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 @@ GLUE(.,name):
 
 #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'

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

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.
  *