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authorLi Bin <huawei.libin@huawei.com>2015-10-30 16:31:04 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-01-31 11:23:39 -0800
commit8831ded35abdb2ff1eaaa10c3e756a8d45a9d171 (patch)
tree8f23ae44f62f5b112c03ee6ee25ea2e45ab3614f
parenta33b8ff3d6cb996ae964dc04a99c536f31fc463f (diff)
downloadlwn-8831ded35abdb2ff1eaaa10c3e756a8d45a9d171.tar.gz
lwn-8831ded35abdb2ff1eaaa10c3e756a8d45a9d171.zip
recordmcount: arm64: Replace the ignored mcount call into nop
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>
-rw-r--r--scripts/recordmcount.c24
1 files changed, 23 insertions, 1 deletions
diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index 3d1984e59a30..e00bcd129336 100644
--- 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_t const offset)
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";