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12051b318b
linux/arch/mips/kernel
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Nick Desaulniers 12051b318b
mips: avoid explicit UB in assignment of mips_io_port_base 
The code in question is modifying a variable declared const through
pointer manipulation.  Such code is explicitly undefined behavior, and
is the lone issue preventing malta_defconfig from booting when built
with Clang:

If an attempt is made to modify an object defined with a const-qualified
type through use of an lvalue with non-const-qualified type, the
behavior is undefined.

LLVM is removing such assignments. A simple fix is to not declare
variables const that you plan on modifying.  Limiting the scope would be
a better method of preventing unwanted writes to such a variable.

Further, the code in question mentions "compiler bugs" without any links
to bug reports, so it is difficult to know if the issue is resolved in
GCC. The patch was authored in 2006, which would have been GCC 4.0.3 or
4.1.1. The minimal supported version of GCC in the Linux kernel is
currently 4.6.

For what its worth, there was UB before the commit in question, it just
added a barrier and got lucky IRT codegen. I don't think there's any
actual compiler bugs related, just runtime bugs due to UB.

Link: https://github.com/ClangBuiltLinux/linux/issues/610
Fixes: 966f4406d9 ("[MIPS] Work around bad code generation for <asm/io.h>.")
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Debugged-by: Nathan Chancellor <natechancellor@gmail.com>
Suggested-by: Eli Friedman <efriedma@quicinc.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: ralf@linux-mips.org
Cc: jhogan@kernel.org
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Hassan Naveed <hnaveed@wavecomp.com>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Serge Semin <fancer.lancer@gmail.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: clang-built-linux@googlegroups.com
2019-08-24 15:10:58 +01:00
..
syscalls mips: remove nargs from __SYSCALL 2019-07-30 10:50:30 -07:00
.gitignore
8250-platform.c
asm-offsets.c MIPS: Remove struct task_struct fpu state when CONFIG_MIPS_FP_SUPPORT=n 2018-11-09 10:23:19 -08:00
binfmt_elfn32.c y2038: globally rename compat_time to old_time32 2018-08-27 14:48:48 +02:00
binfmt_elfo32.c y2038: globally rename compat_time to old_time32 2018-08-27 14:48:48 +02:00
bmips_5xxx_init.S MIPS: BCM5xxx: Remove dead init_fpu code 2018-11-08 11:20:57 -08:00
bmips_vec.S MIPS: BMIPS: Add Whirlwind (BMIPS5200) initialization code 2016-05-09 12:00:01 +02:00
branch.c MIPS: Don't use bc_false uninitialized in __mm_isBranchInstr 2019-08-11 21:44:24 -07:00
cacheinfo.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 252 2019-06-05 17:30:27 +02:00
cevt-bcm1480.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
cevt-ds1287.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 1 2019-05-21 11:28:39 +02:00
cevt-gt641xx.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 1 2019-05-21 11:28:39 +02:00
cevt-r4k.c MIPS: cevt-r4k: Fix out-of-bounds array access 2017-04-10 13:31:12 +02:00
cevt-sb1250.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
cevt-txx9.c MIPS: clockevent drivers: Set ->min_delta_ticks and ->max_delta_ticks 2017-04-14 13:11:16 -07:00
cmpxchg.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cps-vec-ns16550.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cps-vec.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cpu-bugs64.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cpu-probe.c MIPS: Ingenic: Disable broken BTB lookup optimization. 2019-08-05 18:30:45 -07:00
crash_dump.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
crash.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
csrc-bcm1480.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
csrc-ioasic.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
csrc-r4k.c clocksource: Use a plain u64 instead of cycle_t 2016-12-25 11:04:12 +01:00
csrc-sb1250.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
early_printk_8250.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 1 2019-05-21 11:28:39 +02:00
early_printk.c mips: unify prom_putchar() declarations 2018-07-17 09:40:17 -07:00
elf.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
entry.S MIPS: entry: Remove unneeded need_resched() loop 2019-03-19 15:25:45 -07:00
ftrace.c MIPS: ftrace: Reword prepare_ftrace_return() comment block 2019-06-11 15:46:21 -07:00
genex.S MIPS: Remove unused R5432_CP0_INTERRUPT_WAR 2019-07-23 14:33:44 -07:00
gpio_txx9.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
head.S MIPS/head: Store ELF appended dtb in a global variable too 2018-09-25 16:27:24 -07:00
i8253.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
idle.c MIPS: Remove unused R4300 CPU support 2019-07-23 14:33:23 -07:00
irq_txx9.c
irq-gt641xx.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 1 2019-05-21 11:28:39 +02:00
irq-msc01.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
irq-rm7000.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
irq.c MIPS: irq: Allocate accurate order pages for irq stack 2019-02-19 12:45:01 -08:00
jump_label.c MIPS: jump_label: Use compact branches for >= r6 2019-04-09 16:21:30 -07:00
kgdb.c MIPS: KGDB: fix kgdb support for SMP platforms. 2019-03-28 11:35:58 -07:00
kprobes.c mm, kprobes: generalize and rename notify_page_fault() as kprobe_page_fault() 2019-07-16 19:23:22 -07:00
linux32.c MIPS: Delete unused code in linux32.c 2018-08-01 13:20:27 -07:00
machine_kexec.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230 2019-06-19 17:09:06 +02:00
Makefile mips: rename scall64-64.S to scall64-n64.S 2018-12-14 11:19:01 -08:00
mcount.S mips: ftrace: fix static function graph tracing 2018-06-19 15:00:12 -07:00
mips_machine.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
mips-cm.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
mips-cpc.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
mips-mt-fpaff.c sched/core: Provide a pointer to the valid CPU mask 2019-06-03 11:49:37 +02:00
mips-mt.c MIPS: MT: Remove norps command line parameter 2018-11-26 22:49:14 -08:00
mips-r2-to-r6-emul.c mips: kernel: no need to check return value of debugfs_create functions 2019-01-22 11:17:20 -08:00
module.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
octeon_switch.S Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables 2018-06-14 12:21:18 +09:00
perf_event_mipsxx.c The main MIPS changes for a pretty light v5.3 cycle, including: 2019-07-17 09:42:03 -07:00
perf_event.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
pm-cps.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
pm.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
probes-common.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
proc.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
process.c MIPS: Remove function size check in get_frame_info() 2019-02-04 15:15:34 -08:00
prom.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
ptrace32.c MIPS: ptrace: Remove FP support when CONFIG_MIPS_FP_SUPPORT=n 2018-11-09 10:23:17 -08:00
ptrace.c audit/stable-5.2 PR 20190507 2019-05-07 19:06:04 -07:00
r4k_fpu.S MIPS: Simplify FP context initialization 2018-11-09 10:23:13 -08:00
r4k_switch.S Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables 2018-06-14 12:21:18 +09:00
r2300_fpu.S MIPS: Simplify FP context initialization 2018-11-09 10:23:13 -08:00
r2300_switch.S Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables 2018-06-14 12:21:18 +09:00
relocate_kernel.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230 2019-06-19 17:09:06 +02:00
relocate.c MIPS: Remove no-op/identity casts 2018-08-31 11:49:20 -07:00
reset.c MIPS: Hang more efficiently on halt/powerdown/restart 2018-03-09 11:22:43 +00:00
rtlx-cmp.c
rtlx-mt.c
rtlx.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
scall32-o32.S mips: remove nargs from __SYSCALL 2019-07-30 10:50:30 -07:00
scall64-n32.S mips: remove nargs from __SYSCALL 2019-07-30 10:50:30 -07:00
scall64-n64.S mips: remove nargs from __SYSCALL 2019-07-30 10:50:30 -07:00
scall64-o32.S mips: remove nargs from __SYSCALL 2019-07-30 10:50:30 -07:00
segment.c mips: kernel: no need to check return value of debugfs_create functions 2019-01-22 11:17:20 -08:00
setup.c mips: avoid explicit UB in assignment of mips_io_port_base 2019-08-24 15:10:58 +01:00
signal32.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
signal_n32.c Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2019-07-08 21:48:15 -07:00
signal_o32.c signal: Remove task parameter from force_sig 2019-05-27 09:36:28 -05:00
signal-common.h
signal.c signal: Remove task parameter from force_sig 2019-05-27 09:36:28 -05:00
smp-bmips.c MIPS: kexec: Make a framework for both jumping and halting on nonboot CPUs 2018-09-22 10:31:50 -07:00
smp-cmp.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 182 2019-05-30 11:29:20 -07:00
smp-cps.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
smp-mt.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 182 2019-05-30 11:29:20 -07:00
smp-up.c MIPS: SMP: Allow boot_secondary SMP op to return errors 2017-08-30 00:57:27 +02:00
smp.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
spinlock_test.c mips: kernel: no need to check return value of debugfs_create functions 2019-01-22 11:17:20 -08:00
spram.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
stacktrace.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
sync-r4k.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
syscall.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
sysrq.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
time.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
topology.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
traps.c Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2019-07-08 21:48:15 -07:00
unaligned.c signal: Remove task parameter from force_sig 2019-05-27 09:36:28 -05:00
uprobes.c MIPS: uprobes: remove set but not used variable 'epc' 2019-05-29 13:20:30 -07:00
vdso.c mips: Add support for generic vDSO 2019-07-25 21:45:05 -07:00
vmlinux.lds.S MIPS: Ensure ELF appended dtb is relocated 2019-03-11 11:08:31 -07:00
vpe-cmp.c
vpe-mt.c
vpe.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
watch.c mips: annotate implicit fall throughs 2018-12-03 13:42:38 -08:00