mirror of
https://github.com/openwrt/openwrt.git
synced 2024-12-25 16:31:13 +00:00
2932b4d05e
The malta subtargets for mips64 and mips64el fail to start the init process
at boot, resulting in a boot loop. The issue was raised and analyzed within
FS#3277. Investigation suggested code near the [vdso] memory area of the
process was long jumping into a region inaccessible to the process, e.g.
init: - preinit -
init: Launched preinit instance, pid=522
do_page_fault(): sending SIGSEGV to init for invalid read access from 0000000000000360
epc = 0000000000000360 in init[aaab42b000+4000]
ra = 000000fffee385e0 in
Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
Rebooting in 1 seconds..
Note the low-memory read access and epc are the same. Upstream kernel 5.6
included a relevant patch and discussion:
* d3f703c4359f ("mips: vdso: fix 'jalr t9' crash in vdso code")
Disassembly of the failing kernel's vdso.so confirmed presence of the
telltale long jumps, e.g.:
00000000000007c0 <__vdso_clock_getres@@LINUX_2.6>:
[...]
7dc: 0320f809 jalr t9
[...]
Restore booting mips64/mips64el malta by backporting the above commit:
* 310-v5.6-mips-vdso-fix-jalr-t9-crash-in-vdso-code.patch
Fixes: 54310a3aa0 ("malta: add kernel 5.4 config")
Fixes: FS#3277
Ref: https://bugs.openwrt.org/index.php?do=details&task_id=3277
Signed-off-by: Tony Ambardar <itugrok@yahoo.com>
60 lines
2.6 KiB
Diff
60 lines
2.6 KiB
Diff
From d3f703c4359ff06619b2322b91f69710453e6b6d Mon Sep 17 00:00:00 2001
|
|
From: Victor Kamensky <kamensky@cisco.com>
|
|
Date: Tue, 11 Feb 2020 11:24:33 -0800
|
|
Subject: [PATCH] mips: vdso: fix 'jalr t9' crash in vdso code
|
|
|
|
Observed that when kernel is built with Yocto mips64-poky-linux-gcc,
|
|
and mips64-poky-linux-gnun32-gcc toolchain, resulting vdso contains
|
|
'jalr t9' instructions in its code and since in vdso case nobody
|
|
sets GOT table code crashes when instruction reached. On other hand
|
|
observed that when kernel is built mips-poky-linux-gcc toolchain, the
|
|
same 'jalr t9' instruction are replaced with PC relative function
|
|
calls using 'bal' instructions.
|
|
|
|
The difference boils down to -mrelax-pic-calls and -mexplicit-relocs
|
|
gcc options that gets different default values depending on gcc
|
|
target triplets and corresponding binutils. -mrelax-pic-calls got
|
|
enabled by default only in mips-poky-linux-gcc case. MIPS binutils
|
|
ld relies on R_MIPS_JALR relocation to convert 'jalr t9' into 'bal'
|
|
and such relocation is generated only if -mrelax-pic-calls option
|
|
is on.
|
|
|
|
Please note 'jalr t9' conversion to 'bal' can happen only to static
|
|
functions. These static PIC calls use mips local GOT entries that
|
|
are supposed to be filled with start of DSO value by run-time linker
|
|
(missing in VDSO case) and they do not have dynamic relocations.
|
|
Global mips GOT entries must have dynamic relocations and they should
|
|
be prevented by cmd_vdso_check Makefile rule.
|
|
|
|
Solution call out -mrelax-pic-calls and -mexplicit-relocs options
|
|
explicitly while compiling MIPS vdso code. That would get correct
|
|
and consistent between different toolchains behaviour.
|
|
|
|
Reported-by: Bruce Ashfield <bruce.ashfield@gmail.com>
|
|
Signed-off-by: Victor Kamensky <kamensky@cisco.com>
|
|
Signed-off-by: Paul Burton <paulburton@kernel.org>
|
|
Cc: linux-mips@vger.kernel.org
|
|
Cc: Ralf Baechle <ralf@linux-mips.org>
|
|
Cc: James Hogan <jhogan@kernel.org>
|
|
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
|
|
Cc: richard.purdie@linuxfoundation.org
|
|
---
|
|
arch/mips/vdso/Makefile | 1 +
|
|
1 file changed, 1 insertion(+)
|
|
|
|
diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
|
|
index aa89a41dc5dd..848baeaef1f8 100644
|
|
--- a/arch/mips/vdso/Makefile
|
|
+++ b/arch/mips/vdso/Makefile
|
|
@@ -33,6 +33,7 @@ endif
|
|
cflags-vdso := $(ccflags-vdso) \
|
|
$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
|
|
-O3 -g -fPIC -fno-strict-aliasing -fno-common -fno-builtin -G 0 \
|
|
+ -mrelax-pic-calls -mexplicit-relocs \
|
|
-fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
|
|
$(call cc-option, -fno-asynchronous-unwind-tables) \
|
|
$(call cc-option, -fno-stack-protector)
|
|
--
|
|
2.17.1
|
|
|