This is a note to let you know that I've just added the patch titled
ftrace: Have recordmcount use w8 to read relp->r_info in arm64_is_fake_mcount
to the 5.4-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:
ftrace-have-recordmcount-use-w8-to-read-relp-r_info-.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f2d6b07be181053a49c56c56bff100d1c46b663a
Author: Chen Jun <chenjun102@xxxxxxxxxx>
Date: Mon Feb 22 13:58:40 2021 +0000
ftrace: Have recordmcount use w8 to read relp->r_info in arm64_is_fake_mcount
[ Upstream commit 999340d51174ce4141dd723105d4cef872b13ee9 ]
On little endian system, Use aarch64_be(gcc v7.3) downloaded from
linaro.org to build image with CONFIG_CPU_BIG_ENDIAN = y,
CONFIG_FTRACE = y, CONFIG_DYNAMIC_FTRACE = y.
gcc will create symbols of _mcount but recordmcount can not create
mcount_loc for *.o.
aarch64_be-linux-gnu-objdump -r fs/namei.o | grep mcount
00000000000000d0 R_AARCH64_CALL26 _mcount
...
0000000000007190 R_AARCH64_CALL26 _mcount
The reason is than funciton arm64_is_fake_mcount can not work correctly.
A symbol of _mcount in *.o compiled with big endian compiler likes:
00 00 00 2d 00 00 01 1b
w(rp->r_info) will return 0x2d instead of 0x011b. Because w() takes
uint32_t as parameter, which truncates rp->r_info.
Use w8() instead w() to read relp->r_info
Link: https://lkml.kernel.org/r/20210222135840.56250-1-chenjun102@xxxxxxxxxx
Fixes: ea0eada45632 ("recordmcount: only record relocation of type R_AARCH64_CALL26 on arm64.")
Acked-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Chen Jun <chenjun102@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index b9c2ee7ab43f..cce12e1971d8 100644
--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -438,7 +438,7 @@ static int arm_is_fake_mcount(Elf32_Rel const *rp)
static int arm64_is_fake_mcount(Elf64_Rel const *rp)
{
- return ELF64_R_TYPE(w(rp->r_info)) != R_AARCH64_CALL26;
+ return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26;
}
/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
