[PATCH 7/8] powerpc/livepatch: Clarify location of mcount call site

[Naveen N. Rao]

The existing comment around the location of mcount() call site in a
function is a bit confusing.

Depending on the gcc version, the mcount() call can either be the fourth
(gcc v6 and later) or the fifth instruction (gcc v5 and earlier) into a
function. So, the mcount call is actually within the first _20_ bytes of
a function.

However, ftrace_location_range() does an inclusive search and hence
passing (addr + 16) is still accurate.

Clarify the same by updating comments around this.

Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/livepatch.h | 4 ++--
 arch/powerpc/kernel/kprobes.c        | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/livepatch.h b/arch/powerpc/include/asm/livepatch.h
index 47a03b9b528b..62f98d977f59 100644
--- a/arch/powerpc/include/asm/livepatch.h
+++ b/arch/powerpc/include/asm/livepatch.h
@@ -37,8 +37,8 @@ static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 static inline unsigned long klp_get_ftrace_location(unsigned long faddr)
 {
 	/*
-	 * Live patch works only with -mprofile-kernel on PPC. In this case,
-	 * the ftrace location is always within the first 16 bytes.
+	 * Live patch only works with -mprofile-kernel on PPC. In this case, the
+	 * ftrace location always starts within the first 16 bytes (inclusive).
 	 */
 	return ftrace_location_range(faddr, faddr + 16);
 }
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 562d18f456d7..4398ea60b4e0 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -62,8 +62,8 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
 #ifdef CONFIG_KPROBES_ON_FTRACE
 		unsigned long faddr;
 		/*
-		 * Per livepatch.h, ftrace location is always within the first
-		 * 16 bytes of a function on powerpc with -mprofile-kernel.
+		 * Per livepatch.h, ftrace location always starts within the first
+		 * 16 bytes (inclusive) of a function with -mprofile-kernel.
 		 */
 		faddr = ftrace_location_range((unsigned long)addr,
 					      (unsigned long)addr + 16);
-- 
2.12.2