Since get_runtime_offset() is executed as a part of reloaction logic,
it cannot have code dependend on any kind of
relocation. Unfortunately, current codebase violates this rule and
linkadr:
.quad get_runtime_offset
ends up producing R_AARCH64_RELATIVE relocation that has to be
resolved at runtime. From tiral and error experimentation it seems
that the simplest way to do this is to drop "a" (allocatable)
attribute fom the section directive in runtime-offset.S
With "a" (see first entry):
aarch64-linux-gnu-objdump -R images/start_zii_imx8mq_dev.pbl
images/start_zii_imx8mq_dev.pbl: file format elf64-littleaarch64
DYNAMIC RELOCATION RECORDS
OFFSET TYPE VALUE
00000000000000b0 R_AARCH64_RELATIVE *ABS*+0x00000000000000a0
0000000000004258 R_AARCH64_RELATIVE *ABS*+0x0000000000028118
0000000000004260 R_AARCH64_RELATIVE *ABS*+0x0000000000028128
00000000000042e0 R_AARCH64_RELATIVE *ABS*
00000000000042e8 R_AARCH64_RELATIVE *ABS*+0x0000000000028118
00000000000042f0 R_AARCH64_RELATIVE *ABS*+0x00000000000042c8
Without "a":
aarch64-linux-gnu-objdump -R images/start_zii_imx8mq_dev.pbl
images/start_zii_imx8mq_dev.pbl: file format elf64-littleaarch64
DYNAMIC RELOCATION RECORDS
OFFSET TYPE VALUE
0000000000004258 R_AARCH64_RELATIVE *ABS*+0x0000000000028100
0000000000004260 R_AARCH64_RELATIVE *ABS*+0x0000000000028110
00000000000042e0 R_AARCH64_RELATIVE *ABS*
00000000000042e8 R_AARCH64_RELATIVE *ABS*+0x0000000000028100
00000000000042f0 R_AARCH64_RELATIVE *ABS*+0x00000000000042c8
Note that on recent toolchains (tested on 8.1.1), this problem is
masked by the fact that
.quad get_runtime_offset
will be initialized with link-time value of "get_runtime_offset" in
addition to having a R_AARCH64_RELATIVE relocation.
00000000000000a0 <get_runtime_offset>:
a0: 10000000 adr x0, a0 <get_runtime_offset>
a4: 58000061 ldr x1, b0 <linkadr>
a8: eb010000 subs x0, x0, x1
ac: d65f03c0 ret
00000000000000b0 <linkadr>:
b0: 000000a0 .word 0x000000a0
b4: 00000000 .word 0x00000000
_However_, older toolchains (tested on 5.5.0), will only issue a
R_AARCH64_RELATIVE, so memory location will contain only zeroes:
00000000000000a0 <get_runtime_offset>:
a0: 10000000 adr x0, a0 <get_runtime_offset>
a4: 58000061 ldr x1, b0 <linkadr>
a8: eb010000 subs x0, x0, x1
ac: d65f03c0 ret
00000000000000b0 <linkadr>:
...
This leads to an very early crash and complete boot failure in the
latter case.
Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
---
Sascha:
Assuming that proposed fix is OK, this should probably got to 'master'
as well as 'next'.
Thanks,
Andrey Smirnov
arch/arm/lib64/runtime-offset.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/lib64/runtime-offset.S b/arch/arm/lib64/runtime-offset.S
index 177ca6478..c90469e66 100644
--- a/arch/arm/lib64/runtime-offset.S
+++ b/arch/arm/lib64/runtime-offset.S
@@ -1,7 +1,7 @@
#include <linux/linkage.h>
#include <asm/assembler.h>
-.section ".text_bare_init","ax"
+.section ".text_bare_init","x"
/*
* Get the offset between the link address and the address
--
2.20.1
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