kernel/arch/s390, branch linux-5.10.y

s390/perf: Disable register readout on sampling events

2026-03-04T12:19:54Z

[ Upstream commit b2c04fc1239062b39ddfdd8731ee1a10810dfb74 ] Running commands # ./perf record -IR0,R1 -a sleep 1 extracts and displays register value of general purpose register r1 and r0. However the value displayed of any register is random and does not reflect the register value recorded at the time of the sample interrupt. The sampling device driver on s390 creates a very large buffer for the hardware to store the samples. Only when that large buffer gets full an interrupt is generated and many hundreds of sample entries are processed and copied to the kernel ring buffer and eventually get copied to the perf tool. It is during the copy to the kernel ring buffer that each sample is processed (on s390) and at that time the register values are extracted. This is not the original goal, the register values should be read when the samples are created not when the samples are copied to the kernel ring buffer. Prevent this event from being installed in the first place and return -EOPNOTSUPP. This is already the case for PERF_SAMPLE_REGS_USER. Signed-off-by: Thomas Richter Reviewed-by: Jan Polensky Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin

s390/purgatory: Add -Wno-default-const-init-unsafe to KBUILD_CFLAGS

2026-03-04T12:19:52Z

[ Upstream commit b4780fe4ddf04b51127a33d705f4a2e224df00fa ] Add -Wno-default-const-init-unsafe to purgatory KBUILD_CFLAGS, similar to scripts/Makefile.extrawarn, since clang generates warnings for the dummy variable in typecheck(): CC arch/s390/purgatory/purgatory.o arch/s390/include/asm/ptrace.h:221:9: warning: default initialization of an object of type 'typeof (regs->psw)' (aka 'const psw_t') leaves the object uninitialized [-Wdefault-const-init-var-unsafe] 221 | return psw_bits(regs->psw).pstate; | ^ arch/s390/include/asm/ptrace.h:98:2: note: expanded from macro 'psw_bits' 98 | typecheck(psw_t, __psw); \ | ^ include/linux/typecheck.h:11:12: note: expanded from macro 'typecheck' 11 | typeof(x) __dummy2; \ | ^ Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin

s390/smp: Fix fallback CPU detection

2026-01-19T12:11:28Z

[ Upstream commit 07a75d08cfa1b883a6e1256666e5f0617ee99231 ] In case SCLP CPU detection does not work a fallback mechanism using SIGP is in place. Since a cleanup this does not work correctly anymore: new CPUs are only considered if their type matches the boot CPU. Before the cleanup the information if a CPU type should be considered was also part of a structure generated by the fallback mechanism and indicated that a CPU type should not be considered when adding CPUs. Since the rework a global SCLP state is used instead. If the global SCLP state indicates that the CPU type should be considered and the fallback mechanism is used, there may be a mismatch with CPU types if CPUs are added. This can lead to a system with only a single CPU even tough there are many more CPUs. Address this by simply copying the boot cpu type into the generated data structure from the fallback mechanism. Reported-by: Alexander Egorenkov Fixes: d08d94306e90 ("s390/smp: cleanup core vs. cpu in the SCLP interface") Reviewed-by: Mete Durlu Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin

Makefile.compiler: replace cc-ifversion with compiler-specific macros

2025-12-06T21:08:21Z

commit 88b61e3bff93f99712718db785b4aa0c1165f35c upstream. cc-ifversion is GCC specific. Replace it with compiler specific variants. Update the users of cc-ifversion to use these new macros. Link: https://github.com/ClangBuiltLinux/linux/issues/350 Link: https://lore.kernel.org/llvm/CAGG=3QWSAUakO42kubrCap8fp-gm1ERJJAYXTnP1iHk_wrH=BQ@mail.gmail.com/ Suggested-by: Bill Wendling Reviewed-by: Nathan Chancellor Signed-off-by: Nick Desaulniers Signed-off-by: Masahiro Yamada [nathan: Backport to 5.10 and eliminate instances of cc-ifversion that did not exist upstream when this change was original created] Signed-off-by: Nathan Chancellor Signed-off-by: Greg Kroah-Hartman

arch: back to -std=gnu89 in < v5.18

2025-12-06T21:08:08Z

Recent fixes have been backported to < v5.18 to fix build issues with GCC 5.15. They all force -std=gnu11 in the CFLAGS, "because [the kernel] requests the gnu11 standard via '-std=' in the main Makefile". This is true for >= 5.18 versions, but not before. This switch to -std=gnu11 has been done in commit e8c07082a810 ("Kbuild: move to -std=gnu11"). For a question of uniformity, force -std=gnu89, similar to what is done in the main Makefile. Note: the fixes tags below refers to upstream commits, but this fix is only for kernels not having commit e8c07082a810 ("Kbuild: move to -std=gnu11"). Fixes: 7cbb015e2d3d ("parisc: fix building with gcc-15") Fixes: 3b8b80e99376 ("s390: Add '-std=gnu11' to decompressor and purgatory CFLAGS") Fixes: b3bee1e7c3f2 ("x86/boot: Compile boot code with -std=gnu11 too") Fixes: ee2ab467bddf ("x86/boot: Use '-std=gnu11' to fix build with GCC 15") Fixes: 8ba14d9f490a ("efi: libstub: Use '-std=gnu11' to fix build with GCC 15") Signed-off-by: Matthieu Baerts (NGI0) Cc: Nathan Chancellor Cc: Ard Biesheuvel Cc: Alexey Dobriyan Cc: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman

s390/hypfs: Enable limited access during lockdown

2025-08-28T14:22:59Z

[ Upstream commit 3868f910440c47cd5d158776be4ba4e2186beda7 ] When kernel lockdown is active, debugfs_locked_down() blocks access to hypfs files that register ioctl callbacks, even if the ioctl interface is not required for a function. This unnecessarily breaks userspace tools that only rely on read operations. Resolve this by registering a minimal set of file operations during lockdown, avoiding ioctl registration and preserving access for affected tooling. Note that this change restores hypfs functionality when lockdown is active from early boot (e.g. via lockdown=integrity kernel parameter), but does not apply to scenarios where lockdown is enabled dynamically while Linux is running. Tested-by: Mete Durlu Reviewed-by: Vasily Gorbik Fixes: 5496197f9b08 ("debugfs: Restrict debugfs when the kernel is locked down") Signed-off-by: Peter Oberparleiter Signed-off-by: Alexander Gordeev Signed-off-by: Sasha Levin

s390/hypfs: Avoid unnecessary ioctl registration in debugfs

2025-08-28T14:22:59Z

[ Upstream commit fec7bdfe7f8694a0c39e6c3ec026ff61ca1058b9 ] Currently, hypfs registers ioctl callbacks for all debugfs files, despite only one file requiring them. This leads to unintended exposure of unused interfaces to user space and can trigger side effects such as restricted access when kernel lockdown is enabled. Restrict ioctl registration to only those files that implement ioctl functionality to avoid interface clutter and unnecessary access restrictions. Tested-by: Mete Durlu Reviewed-by: Vasily Gorbik Fixes: 5496197f9b08 ("debugfs: Restrict debugfs when the kernel is locked down") Signed-off-by: Peter Oberparleiter Signed-off-by: Alexander Gordeev Signed-off-by: Sasha Levin

mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd()

2025-08-28T14:22:55Z

[ Upstream commit 59305202c67fea50378dcad0cc199dbc13a0e99a ] 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: bbd6ec605c0f ("arm64/mm: Enable memory hot remove") Signed-off-by: Anshuman Khandual Acked-by: David Hildenbrand Reviewed-by: Dev Jain Acked-by: Alexander Gordeev [s390] Cc: Catalin Marinas Cc: Will Deacon Cc: Ryan Roberts Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Alexander Gordeev Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: Sven Schnelle Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

s390/stp: Remove udelay from stp_sync_clock()

2025-08-28T14:22:43Z

[ Upstream commit b367017cdac21781a74eff4e208d3d38e1f38d3f ] When an stp sync check is handled on a system with multiple cpus each cpu gets a machine check but only the first one actually handles the sync operation. All other CPUs spin waiting for the first one to finish with a short udelay(). But udelay can't be used here as the first CPU modifies tod_clock_base before performing the sync op. During this timeframe get_tod_clock_monotonic() might return a non-monotonic time. The time spent waiting should be very short and udelay is a busy loop anyways, therefore simply remove the udelay. Reviewed-by: Heiko Carstens Signed-off-by: Sven Schnelle Signed-off-by: Alexander Gordeev Signed-off-by: Sasha Levin

s390/time: Use monotonic clock in get_cycles()

2025-08-28T14:22:42Z

[ Upstream commit 09e7e29d2b49ba84bcefb3dc1657726d2de5bb24 ] Otherwise the code might not work correctly when the clock is changed. Signed-off-by: Sven Schnelle Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Sasha Levin