[ Upstream commit bad6722e47 ]
Consolidate the machine_kexec_mask_interrupts implementation into a common
function located in a new file: kernel/irq/kexec.c. This removes duplicate
implementations from architecture-specific files in arch/arm, arch/arm64,
arch/powerpc, and arch/riscv, reducing code duplication and improving
maintainability.
The new implementation retains architecture-specific behavior for
CONFIG_GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD, which was previously implemented
for ARM64. When enabled (currently for ARM64), it clears the active state
of interrupts forwarded to virtual machines (VMs) before handling other
interrupt masking operations.
Signed-off-by: Eliav Farber <farbere@amazon.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241204142003.32859-2-farbere@amazon.com
Stable-dep-of: 20197b967a ("powerpc/kexec/core: use big-endian types for crash variables")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit ef3ff40346 ]
The vstate in thread_struct is zeroed when the vector context is
initialized. That includes read-only register vlenb, which holds
the vector register length in bytes. Zeroed state persists until
mstatus.VS becomes 'dirty' and a context switch saves the actual
hardware values.
This can expose the zero vlenb value to the user-space in early
debug scenarios, e.g. when ptrace attaches to a traced process
early, before any vector instruction except the first one was
executed.
Fix this by specifying proper vlenb on vector context init.
Signed-off-by: Sergey Matyukevich <geomatsi@gmail.com>
Reviewed-by: Andy Chiu <andybnac@gmail.com>
Tested-by: Andy Chiu <andybnac@gmail.com>
Link: https://patch.msgid.link/20251214163537.1054292-3-geomatsi@gmail.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 974555d6e4 ]
When executing HLV* instructions at the HS mode, a guest page fault
may occur when a g-stage page table migration between triggering the
virtual instruction exception and executing the HLV* instruction.
This may be a corner case, and one simpler way to handle this is to
re-execute the instruction where the virtual instruction exception
occurred, and the guest page fault will be automatically handled.
Fixes: b91f0e4cb8 ("RISC-V: KVM: Factor-out instruction emulation into separate sources")
Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251121133543.46822-1-fangyu.yu@linux.alibaba.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 69a8b62a7a ]
Similar to the ARM64 commit 3505f30fb6a9s ("ARM64 / ACPI: If we chose
to boot from acpi then disable FDT"), let's not do DT hardware probing
if ACPI is enabled in early boot. This avoids errors caused by
repeated driver probing.
Signed-off-by: Han Gao <rabenda.cn@gmail.com>
Link: https://lore.kernel.org/r/20250910112401.552987-1-rabenda.cn@gmail.com
[pjw@kernel.org: cleaned up patch description and subject]
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit ae9e9f3d67 ]
openSBI v1.7 adds harts checks for ipi operations. Especially it
adds comparison between hmask passed as an argument from linux
and mask of online harts (from openSBI side). If they don't
fit each other the error occurs.
When cpu is offline, cpu_online_mask is explicitly cleared in
__cpu_disable. However, there is no explicit clearing of
mm_cpumask. mm_cpumask is used for rfence operations that
call openSBI RFENCE extension which uses ipi to remote harts.
If hart is offline there may be error if mask of linux is not
as mask of online harts in openSBI.
this patch adds explicit clearing of mm_cpumask for offline hart.
Signed-off-by: Danil Skrebenkov <danil.skrebenkov@cloudbear.ru>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20250919132849.31676-1-danil.skrebenkov@cloudbear.ru
[pjw@kernel.org: rewrote subject line for clarity]
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit a74f038fa5 ]
The pt_dump_seq_puts() macro incorrectly uses seq_printf() instead of
seq_puts(). This is both a performance issue and conceptually wrong,
as the macro name suggests plain string output (puts) but the
implementation uses formatted output (printf).
The macro is used in ptdump.c:301 to output a newline character. Using
seq_printf() adds unnecessary overhead for format string parsing when
outputting this constant string.
This bug was introduced in commit 59c4da8640 ("riscv: Add support to
dump the kernel page tables") in 2020, which copied the implementation
pattern from other architectures that had the same bug.
Fixes: 59c4da8640 ("riscv: Add support to dump the kernel page tables")
Signed-off-by: Josephine Pfeiffer <hi@josie.lol>
Link: https://lore.kernel.org/r/20251018170451.3355496-1-hi@josie.lol
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 060ea84a48 ]
Unwinding the stack of a task other than current, KASAN would report
"BUG: KASAN: out-of-bounds in walk_stackframe+0x41c/0x460"
There is a same issue on x86 and has been resolved by the commit
84936118bd ("x86/unwind: Disable KASAN checks for non-current tasks")
The solution could be applied to RISC-V too.
This patch also can solve the issue:
https://seclists.org/oss-sec/2025/q4/23
Fixes: 5d8544e2d0 ("RISC-V: Generic library routines and assembly")
Co-developed-by: Jiakai Xu <xujiakai2025@iscas.ac.cn>
Signed-off-by: Jiakai Xu <xujiakai2025@iscas.ac.cn>
Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
Link: https://lore.kernel.org/r/20251022072608.743484-1-zhangchunyan@iscas.ac.cn
[pjw@kernel.org: clean up checkpatch issues]
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit d0bf7cd5df ]
In the __arch_prepare_bpf_trampoline() function, retval_off is only
meaningful when save_ret is true, so the current logic is correct.
However, in the original logic, retval_off is only initialized under
certain conditions; for example, in the fmod_ret logic, the compiler is
not aware that the flags of the fmod_ret program (prog) have set
BPF_TRAMP_F_CALL_ORIG, which results in an uninitialized symbol
compilation warning.
So initialize retval_off unconditionally to fix it.
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Link: https://lore.kernel.org/r/20250922062244.822937-2-duanchenghao@kylinos.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 35561bab76 ]
The include/generated/asm-offsets.h is generated in Kbuild during
compiling from arch/SRCARCH/kernel/asm-offsets.c. When we want to
generate another similar offset header file, circular dependency can
happen.
For example, we want to generate a offset file include/generated/test.h,
which is included in include/sched/sched.h. If we generate asm-offsets.h
first, it will fail, as include/sched/sched.h is included in asm-offsets.c
and include/generated/test.h doesn't exist; If we generate test.h first,
it can't success neither, as include/generated/asm-offsets.h is included
by it.
In x86_64, the macro COMPILE_OFFSETS is used to avoid such circular
dependency. We can generate asm-offsets.h first, and if the
COMPILE_OFFSETS is defined, we don't include the "generated/test.h".
And we define the macro COMPILE_OFFSETS for all the asm-offsets.c for this
purpose.
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit b7776a802f ]
Resolve this smatch warning:
arch/riscv/kernel/sys_hwprobe.c:50 hwprobe_arch_id() error: uninitialized symbol 'cpu_id'.
This could happen if hwprobe_arch_id() was called with a key ID of
something other than MVENDORID, MIMPID, and MARCHID. This does not
happen in the current codebase. The only caller of hwprobe_arch_id()
is a function that only passes one of those three key IDs.
For the sake of reducing static analyzer warning noise, and in the
unlikely event that hwprobe_arch_id() is someday called with some
other key ID, validate hwprobe_arch_id()'s input to ensure that
'cpu_id' is always initialized before use.
Fixes: ea3de9ce8a ("RISC-V: Add a syscall for HW probing")
Cc: Evan Green <evan@rivosinc.com>
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Link: https://lore.kernel.org/r/cf5a13ec-19d0-9862-059b-943f36107bf3@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit ca525d53f9 ]
The pgprot_dmacoherent() is used when allocating memory for
non-coherent devices and by default pgprot_dmacoherent() is
same as pgprot_noncached() unless architecture overrides it.
Currently, there is no pgprot_dmacoherent() definition for
RISC-V hence non-coherent device memory is being mapped as
IO thereby making CPU access to such memory slow.
Define pgprot_dmacoherent() to be same as pgprot_writecombine()
for RISC-V so that CPU access non-coherent device memory as
NOCACHE which is better than accessing it as IO.
Fixes: ff689fd21c ("riscv: add RISC-V Svpbmt extension support")
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Tested-by: Han Gao <rabenda.cn@gmail.com>
Tested-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
Link: https://lore.kernel.org/r/20250820152316.1012757-1-apatel@ventanamicro.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 9e68bd803f ]
When adding a kprobe such as "p:probe/tcp_sendmsg _text+15392192",
arch_check_kprobe would start iterating all instructions starting from
_text until the probed address. Not only is this very inefficient, but
literal values in there (e.g. left by function patching) are
misinterpreted in a way that causes a desync.
Fix this by doing it like x86: start the iteration at the closest
preceding symbol instead of the given starting point.
Fixes: 87f48c7ccc ("riscv: kprobe: Fixup kernel panic when probing an illegal position")
Signed-off-by: Fabian Vogt <fvogt@suse.de>
Signed-off-by: Marvin Friedrich <marvin.friedrich@suse.com>
Acked-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/6191817.lOV4Wx5bFT@fvogt-thinkpad
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 8d4f1e05ff ]
Without this I get a bunch of build errors like
In file included from ./include/linux/sched/task_stack.h:12,
from ./arch/riscv/include/asm/compat.h:12,
from ./arch/riscv/include/asm/pgtable.h:115,
from ./include/linux/pgtable.h:6,
from ./include/linux/mm.h:30,
from arch/riscv/kernel/asm-offsets.c:8:
./include/linux/kasan.h:50:37: error: ‘MAX_PTRS_PER_PTE’ undeclared here (not in a function); did you mean ‘PTRS_PER_PTE’?
50 | extern pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS];
| ^~~~~~~~~~~~~~~~
| PTRS_PER_PTE
./include/linux/kasan.h:51:8: error: unknown type name ‘pmd_t’; did you mean ‘pgd_t’?
51 | extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
| ^~~~~
| pgd_t
./include/linux/kasan.h:51:37: error: ‘MAX_PTRS_PER_PMD’ undeclared here (not in a function); did you mean ‘PTRS_PER_PGD’?
51 | extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
| ^~~~~~~~~~~~~~~~
| PTRS_PER_PGD
./include/linux/kasan.h:52:8: error: unknown type name ‘pud_t’; did you mean ‘pgd_t’?
52 | extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
| ^~~~~
| pgd_t
./include/linux/kasan.h:52:37: error: ‘MAX_PTRS_PER_PUD’ undeclared here (not in a function); did you mean ‘PTRS_PER_PGD’?
52 | extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
| ^~~~~~~~~~~~~~~~
| PTRS_PER_PGD
./include/linux/kasan.h:53:8: error: unknown type name ‘p4d_t’; did you mean ‘pgd_t’?
53 | extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
| ^~~~~
| pgd_t
./include/linux/kasan.h:53:37: error: ‘MAX_PTRS_PER_P4D’ undeclared here (not in a function); did you mean ‘PTRS_PER_PGD’?
53 | extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
| ^~~~~~~~~~~~~~~~
| PTRS_PER_PGD
Link: https://lore.kernel.org/r/20241126143250.29708-1-palmer@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 41f9049cff upstream.
When building with CONFIG_CMODEL_MEDLOW and CONFIG_LTO_CLANG, there is a
series of errors due to some files being unconditionally compiled with
'-mcmodel=medany', mismatching with the rest of the kernel built with
'-mcmodel=medlow':
ld.lld: error: Function Import: link error: linking module flags 'Code Model': IDs have conflicting values: 'i32 3' from vmlinux.a(init.o at 899908), and 'i32 1' from vmlinux.a(net-traces.o at 1014628)
Only allow LTO to be performed when CONFIG_CMODEL_MEDANY is enabled to
ensure there will be no code model mismatch errors. An alternative
solution would be disabling LTO for the files with a different code
model than the main kernel like some specialized areas of the kernel do
but doing that for individual files is not as sustainable than
forbidding the combination altogether.
Cc: stable@vger.kernel.org
Fixes: 021d23428b ("RISC-V: build: Allow LTO to be selected")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506290255.KBVM83vZ-lkp@intel.com/
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250710-riscv-restrict-lto-to-medany-v1-1-b1dac9871ecf@kernel.org
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 59305202c6 upstream.
Memory hot remove unmaps and tears down various kernel page table regions
as required. The ptdump code can race with concurrent modifications of
the kernel page tables. When leaf entries are modified concurrently, the
dump code may log stale or inconsistent information for a VA range, but
this is otherwise not harmful.
But when intermediate levels of kernel page table are freed, the dump code
will continue to use memory that has been freed and potentially
reallocated for another purpose. In such cases, the ptdump code may
dereference bogus addresses, leading to a number of potential problems.
To avoid the above mentioned race condition, platforms such as arm64,
riscv and s390 take memory hotplug lock, while dumping kernel page table
via the sysfs interface /sys/kernel/debug/kernel_page_tables.
Similar race condition exists while checking for pages that might have
been marked W+X via /sys/kernel/debug/kernel_page_tables/check_wx_pages
which in turn calls ptdump_check_wx(). Instead of solving this race
condition again, let's just move the memory hotplug lock inside generic
ptdump_check_wx() which will benefit both the scenarios.
Drop get_online_mems() and put_online_mems() combination from all existing
platform ptdump code paths.
Link: https://lkml.kernel.org/r/20250620052427.2092093-1-anshuman.khandual@arm.com
Fixes: bbd6ec605c ("arm64/mm: Enable memory hot remove")
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com> [s390]
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 969f028bf2 ]
force_sig_fault() takes a spinlock, which is a sleeping lock with
CONFIG_PREEMPT_RT=y. However, exception handling calls force_sig_fault()
with interrupt disabled, causing a sleeping in atomic context warning.
This can be reproduced using userspace programs such as:
int main() { asm ("ebreak"); }
or
int main() { asm ("unimp"); }
There is no reason that interrupt must be disabled while handling
exceptions from userspace.
Enable interrupt while handling user exceptions. This also has the added
benefit of avoiding unnecessary delays in interrupt handling.
Fixes: f0bddf5058 ("riscv: entry: Convert to generic entry")
Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20250625085630.3649485-1-namcao@linutronix.de
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit e0eb1b6b0c ]
.rodata is implicitly included in the PT_DYNAMIC segment due to
inheriting the segment of the preceding .dynamic section (in both GNU ld
and LLD). When the .rodata section's size is not a multiple of 16
bytes on riscv64, llvm-readelf will report a "PT_DYNAMIC dynamic table
is invalid" warning. Note: in the presence of the .dynamic section, GNU
readelf and llvm-readelf's -d option decodes the dynamic section using
the section.
This issue arose after commit 8f8c1ff879
("riscv: vdso.lds.S: remove hardcoded 0x800 .text start addr"), which
placed .rodata directly after .dynamic by removing .eh_frame.
This patch resolves the implicit inclusion into PT_DYNAMIC by explicitly
specifying the :text output section phdr.
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/2093
Signed-off-by: Fangrui Song <i@maskray.me>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250602-riscv-vdso-v1-1-0620cf63cff0@maskray.me
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 1898300abf ]
Sign extend also an unsigned compare value to match what lr.w is doing.
Otherwise try_cmpxchg may spuriously return true when used on a u32 value
that has the sign bit set, as it happens often in inode_set_ctime_current.
Do this in three conversion steps. The first conversion to long is needed
to avoid a -Wpointer-to-int-cast warning when arch_cmpxchg is used with a
pointer type. Then convert to int and back to long to always sign extend
the 32-bit value to 64-bit.
Fixes: 6c58f25e69 ("riscv/atomic: Fix sign extension for RV64I")
Signed-off-by: Andreas Schwab <schwab@suse.de>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Tested-by: Xi Ruoyao <xry111@xry111.site>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/mvmed0k4prh.fsf@suse.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 890ba5be63 upstream.
This reverts commit ad5643cf2f ("riscv: Define TASK_SIZE_MAX for
__access_ok()").
This commit changes TASK_SIZE_MAX to be LONG_MAX to optimize access_ok(),
because the previous TASK_SIZE_MAX (default to TASK_SIZE) requires some
computation.
The reasoning was that all user addresses are less than LONG_MAX, and all
kernel addresses are greater than LONG_MAX. Therefore access_ok() can
filter kernel addresses.
Addresses between TASK_SIZE and LONG_MAX are not valid user addresses, but
access_ok() let them pass. That was thought to be okay, because they are
not valid addresses at hardware level.
Unfortunately, one case is missed: get_user_pages_fast() happily accepts
addresses between TASK_SIZE and LONG_MAX. futex(), for instance, uses
get_user_pages_fast(). This causes the problem reported by Robert [1].
Therefore, revert this commit. TASK_SIZE_MAX is changed to the default:
TASK_SIZE.
This unfortunately reduces performance, because TASK_SIZE is more expensive
to compute compared to LONG_MAX. But correctness first, we can think about
optimization later, if required.
Reported-by: <rtm@csail.mit.edu>
Closes: https://lore.kernel.org/linux-riscv/77605.1750245028@localhost/
Signed-off-by: Nam Cao <namcao@linutronix.de>
Cc: stable@vger.kernel.org
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Fixes: ad5643cf2f ("riscv: Define TASK_SIZE_MAX for __access_ok()")
Link: https://lore.kernel.org/r/20250619155858.1249789-1-namcao@linutronix.de
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit ca358692de ]
RISC-V spec explicitly calls out that a local fence.i is not enough for
the code modification to be visble from a remote hart. In fact, it
states:
To make a store to instruction memory visible to all RISC-V harts, the
writing hart also has to execute a data FENCE before requesting that all
remote RISC-V harts execute a FENCE.I.
Although current riscv drivers for IPI use ordered MMIO when sending IPIs
in order to synchronize the action between previous csd writes, riscv
does not restrict itself to any particular flavor of IPI. Any driver or
firmware implementation that does not order data writes before the IPI
may pose a risk for code-modifying race.
Thus, add a fence here to order data writes before making the IPI.
Signed-off-by: Andy Chiu <andybnac@gmail.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250407180838.42877-8-andybnac@gmail.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit a79be02bba upstream.
This was triggered by one of my mis-uses causing odd build warnings on
sparc in linux-next, but while figuring out why the "obviously correct"
use of cc-option caused such odd breakage, I found eight other cases of
the same thing in the tree.
The root cause is that 'cc-option' doesn't work for checking negative
warning options (ie things like '-Wno-stringop-overflow') because gcc
will silently accept options it doesn't recognize, and so 'cc-option'
ends up thinking they are perfectly fine.
And it all works, until you have a situation where _another_ warning is
emitted. At that point the compiler will go "Hmm, maybe the user
intended to disable this warning but used that wrong option that I
didn't recognize", and generate a warning for the unrecognized negative
option.
Which explains why we have several cases of this in the tree: the
'cc-option' test really doesn't work for this situation, but most of the
time it simply doesn't matter that ity doesn't work.
The reason my recently added case caused problems on sparc was pointed
out by Thomas Weißschuh: the sparc build had a previous explicit warning
that then triggered the new one.
I think the best fix for this would be to make 'cc-option' a bit smarter
about this sitation, possibly by adding an intentional warning to the
test case that then triggers the unrecognized option warning reliably.
But the short-term fix is to replace 'cc-option' with an existing helper
designed for this exact case: 'cc-disable-warning', which picks the
negative warning but uses the positive form for testing the compiler
support.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/all/20250422204718.0b4e3f81@canb.auug.org.au/
Explained-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
