Patch "recordmcount: arm64: Replace the ignored mcount call into nop" has been added to the 4.3-stable tree

Patch "recordmcount: arm64: Replace the ignored mcount call into nop" has been added to the 4.3-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    recordmcount: arm64: Replace the ignored mcount call into nop

to the 4.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     recordmcount-arm64-replace-the-ignored-mcount-call-into-nop.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 2ee8a74f2a5da913637f75a19a0da0e7a08c0f86 Mon Sep 17 00:00:00 2001
From: Li Bin <huawei.libin@huawei.com>
Date: Fri, 30 Oct 2015 16:31:04 +0800
Subject: recordmcount: arm64: Replace the ignored mcount call into nop

From: Li Bin <huawei.libin@huawei.com>

commit 2ee8a74f2a5da913637f75a19a0da0e7a08c0f86 upstream.

By now, the recordmcount only records the function that in
following sections:
.text/.ref.text/.sched.text/.spinlock.text/.irqentry.text/
.kprobes.text/.text.unlikely

For the function that not in these sections, the call mcount
will be in place and not be replaced when kernel boot up. And
it will bring performance overhead, such as do_mem_abort (in
.exception.text section). This patch make the call mcount to
nop for this case in recordmcount.

Link: http://lkml.kernel.org/r/1446019445-14421-1-git-send-email-huawei.libin@huawei.com
Link: http://lkml.kernel.org/r/1446193864-24593-4-git-send-email-huawei.libin@huawei.com

Cc: <lkp@intel.com>
Cc: <catalin.marinas@arm.com>
Cc: <takahiro.akashi@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Li Bin <huawei.libin@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 scripts/recordmcount.c |   24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -42,6 +42,7 @@
 
 #ifndef EM_AARCH64
 #define EM_AARCH64	183
+#define R_AARCH64_NONE		0
 #define R_AARCH64_ABS64	257
 #endif
 
@@ -160,6 +161,22 @@ static int make_nop_x86(void *map, size_
 	return 0;
 }
 
+static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
+static int make_nop_arm64(void *map, size_t const offset)
+{
+	uint32_t *ptr;
+
+	ptr = map + offset;
+	/* bl <_mcount> is 0x94000000 before relocation */
+	if (*ptr != 0x94000000)
+		return -1;
+
+	/* Convert to nop */
+	ulseek(fd_map, offset, SEEK_SET);
+	uwrite(fd_map, ideal_nop, 4);
+	return 0;
+}
+
 /*
  * Get the whole file as a programming convenience in order to avoid
  * malloc+lseek+read+free of many pieces.  If successful, then mmap
@@ -353,7 +370,12 @@ do_file(char const *const fname)
 			 altmcount = "__gnu_mcount_nc";
 			 break;
 	case EM_AARCH64:
-			 reltype = R_AARCH64_ABS64; gpfx = '_'; break;
+			reltype = R_AARCH64_ABS64;
+			make_nop = make_nop_arm64;
+			rel_type_nop = R_AARCH64_NONE;
+			ideal_nop = ideal_nop4_arm64;
+			gpfx = '_';
+			break;
 	case EM_IA_64:	 reltype = R_IA64_IMM64;   gpfx = '_'; break;
 	case EM_METAG:	 reltype = R_METAG_ADDR32;
 			 altmcount = "_mcount_wrapper";


Patches currently in stable-queue which might be from huawei.libin@huawei.com are

queue-4.3/recordmcount-arm64-replace-the-ignored-mcount-call-into-nop.patch