kernel.git/arch/arm/kernel/signal.c, branch linux-6.0.y

signal: Deliver SIGTRAP on perf event asynchronously if blocked

2022-04-22T10:14:05Z

With SIGTRAP on perf events, we have encountered termination of processes due to user space attempting to block delivery of SIGTRAP. Consider this case: ... sigset_t s; sigemptyset(&s); sigaddset(&s, SIGTRAP | ); sigprocmask(SIG_BLOCK, &s, ...); ... When the perf event triggers, while SIGTRAP is blocked, force_sig_perf() will force the signal, but revert back to the default handler, thus terminating the task. This makes sense for error conditions, but not so much for explicitly requested monitoring. However, the expectation is still that signals generated by perf events are synchronous, which will no longer be the case if the signal is blocked and delivered later. To give user space the ability to clearly distinguish synchronous from asynchronous signals, introduce siginfo_t::si_perf_flags and TRAP_PERF_FLAG_ASYNC (opted for flags in case more binary information is required in future). The resolution to the problem is then to (a) no longer force the signal (avoiding the terminations), but (b) tell user space via si_perf_flags if the signal was synchronous or not, so that such signals can be handled differently (e.g. let user space decide to ignore or consider the data imprecise). The alternative of making the kernel ignore SIGTRAP on perf events if the signal is blocked may work for some usecases, but likely causes issues in others that then have to revert back to interception of sigprocmask() (which we want to avoid). [ A concrete example: when using breakpoint perf events to track data-flow, in a region of code where signals are blocked, data-flow can no longer be tracked accurately. When a relevant asynchronous signal is received after unblocking the signal, the data-flow tracking logic needs to know its state is imprecise. ] Fixes: 97ba62b27867 ("perf: Add support for SIGTRAP on perf events") Reported-by: Dmitry Vyukov Signed-off-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Acked-by: Geert Uytterhoeven Tested-by: Dmitry Vyukov Link: https://lore.kernel.org/r/20220404111204.935357-1-elver@google.com

resume_user_mode: Move to resume_user_mode.h

2022-03-10T22:51:50Z

Move set_notify_resume and tracehook_notify_resume into resume_user_mode.h. While doing that rename tracehook_notify_resume to resume_user_mode_work. Update all of the places that included tracehook.h for these functions to include resume_user_mode.h instead. Update all of the callers of tracehook_notify_resume to call resume_user_mode_work. Reviewed-by: Kees Cook Link: https://lkml.kernel.org/r/20220309162454.123006-12-ebiederm@xmission.com Signed-off-by: "Eric W. Biederman"

ARM: Snapshot thread flags

2021-11-30T23:06:43Z

Some thread flags can be set remotely, and so even when IRQs are disabled, the flags can change under our feet. Generally this is unlikely to cause a problem in practice, but it is somewhat unsound, and KCSAN will legitimately warn that there is a data race. To avoid such issues, a snapshot of the flags has to be taken prior to using them. Some places already use READ_ONCE() for that, others do not. Convert them all to the new flag accessor helpers. Signed-off-by: Mark Rutland Signed-off-by: Thomas Gleixner Acked-by: Paul E. McKenney Cc: Russell King Link: https://lore.kernel.org/r/20211129130653.2037928-6-mark.rutland@arm.com

entry: rseq: Call rseq_handle_notify_resume() in tracehook_notify_resume()

2021-09-22T14:24:01Z

Invoke rseq_handle_notify_resume() from tracehook_notify_resume() now that the two function are always called back-to-back by architectures that have rseq. The rseq helper is stubbed out for architectures that don't support rseq, i.e. this is a nop across the board. Note, tracehook_notify_resume() is horribly named and arguably does not belong in tracehook.h as literally every line of code in it has nothing to do with tracing. But, that's been true since commit a42c6ded827d ("move key_repace_session_keyring() into tracehook_notify_resume()") first usurped tracehook_notify_resume() back in 2012. Punt cleaning that mess up to future patches. No functional change intended. Acked-by: Mathieu Desnoyers Signed-off-by: Sean Christopherson Message-Id: <20210901203030.1292304-3-seanjc@google.com> Signed-off-by: Paolo Bonzini

Merge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm

2021-09-09T20:25:49Z

Pull ARM development updates from Russell King: - Rename "mod_init" and "mod_exit" so that initcall debug output is actually useful (Randy Dunlap) - Update maintainers entries for linux-arm-kernel to indicate it is moderated for non-subscribers (Randy Dunlap) - Move install rules to arch/arm/Makefile (Masahiro Yamada) - Drop unnecessary ARCH_NR_GPIOS definition (Linus Walleij) - Don't warn about atags_to_fdt() stack size (David Heidelberg) - Speed up unaligned copy_{from,to}_kernel_nofault (Arnd Bergmann) - Get rid of set_fs() usage (Arnd Bergmann) - Remove checks for GCC prior to v4.6 (Geert Uytterhoeven) * tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm: ARM: 9118/1: div64: Remove always-true __div64_const32_is_OK() duplicate ARM: 9117/1: asm-generic: div64: Remove always-true __div64_const32_is_OK() ARM: 9116/1: unified: Remove check for gcc < 4 ARM: 9110/1: oabi-compat: fix oabi epoll sparse warning ARM: 9113/1: uaccess: remove set_fs() implementation ARM: 9112/1: uaccess: add __{get,put}_kernel_nofault ARM: 9111/1: oabi-compat: rework fcntl64() emulation ARM: 9114/1: oabi-compat: rework sys_semtimedop emulation ARM: 9108/1: oabi-compat: rework epoll_wait/epoll_pwait emulation ARM: 9107/1: syscall: always store thread_info->abi_syscall ARM: 9109/1: oabi-compat: add epoll_pwait handler ARM: 9106/1: traps: use get_kernel_nofault instead of set_fs() ARM: 9115/1: mm/maccess: fix unaligned copy_{from,to}_kernel_nofault ARM: 9105/1: atags_to_fdt: don't warn about stack size ARM: 9103/1: Drop ARCH_NR_GPIOS definition ARM: 9102/1: move theinstall rules to arch/arm/Makefile ARM: 9100/1: MAINTAINERS: mark all linux-arm-kernel@infradead list as moderated ARM: 9099/1: crypto: rename 'mod_init' & 'mod_exit' functions to be module-specific

Merge tag 'soc-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc

2021-09-01T22:19:43Z

Pull ARM SoC updates from Arnd Bergmann: "There are three noteworthy updates for 32-bit arm platforms this time: - The Microchip SAMA7 family based on Cortex-A7 gets introduced, a new cousin to the older SAM9 (ARM9xx based) and SAMA5 (Cortex-A5 based) SoCs. - The ixp4xx platform (based on Intel XScale) is finally converted to device tree, and all the old board files are getting removed now. - The Cirrus Logic EP93xx platform loses support for the old MaverickCrunch FPU. Support for compiling user space applications was already removed in gcc-4.9, and the kernel support for old applications could not be built with clang ias. After confirming that there are no remaining users, removing this from the kernel seemed better than adding support for unused features to clang. There are minor updates to the aspeed, omap and samsung platforms" * tag 'soc-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (48 commits) soc: aspeed-lpc-ctrl: Fix clock cleanup in error path ARM: s3c: delete unneed local variable "delay" soc: aspeed: Re-enable FWH2AHB on AST2600 soc: aspeed: socinfo: Add AST2625 variant soc: aspeed: p2a-ctrl: Fix boundary check for mmap soc: aspeed: lpc-ctrl: Fix boundary check for mmap ARM: ixp4xx: Delete the Freecom FSG-3 boardfiles ARM: ixp4xx: Delete GTWX5715 board files ARM: ixp4xx: Delete Coyote and IXDPG425 boardfiles ARM: ixp4xx: Delete Intel reference design boardfiles ARM: ixp4xx: Delete Avila boardfiles ARM: ixp4xx: Delete the Arcom Vulcan boardfiles ARM: ixp4xx: Delete Gateway WG302v2 boardfiles ARM: ixp4xx: Delete Omicron boardfiles ARM: ixp4xx: Delete the D-Link DSM-G600 boardfiles ARM: ixp4xx: Delete NAS100D boardfiles ARM: ixp4xx: Delete NSLU2 boardfiles arm: omap2: Drop the unused OMAP_PACKAGE_* KConfig entries arm: omap2: Drop obsolete MACH_OMAP3_PANDORA entry ARM: ep93xx: remove MaverickCrunch support ...

ARM: 9113/1: uaccess: remove set_fs() implementation

2021-08-20T10:39:27Z

There are no remaining callers of set_fs(), so just remove it along with all associated code that operates on thread_info->addr_limit. There are still further optimizations that can be done: - In get_user(), the address check could be moved entirely into the out of line code, rather than passing a constant as an argument, - I assume the DACR handling can be simplified as we now only change it during user access when CONFIG_CPU_SW_DOMAIN_PAN is set, but not during set_fs(). Acked-by: Christoph Hellwig Signed-off-by: Arnd Bergmann Signed-off-by: Russell King (Oracle)

ARM: ep93xx: remove MaverickCrunch support

2021-08-04T11:30:04Z

The MaverickCrunch support for ep93xx never made it into glibc and was removed from gcc in its 4.8 release in 2012. It is now one of the last parts of arch/arm/ that fails to build with the clang integrated assembler, which is unlikely to ever want to support it. The two alternatives are to force the use of binutils/gas when building the crunch support, or to remove it entirely. According to Hartley Sweeten: "Martin Guy did a lot of work trying to get the maverick crunch working but I was never able to successfully use it for anything. It "kind" of works but depending on the EP93xx silicon revision there are still a number of hardware bugs that either give imprecise or garbage results. I have no problem with removing the kernel support for the maverick crunch." Unless someone else comes up with a good reason to keep it around, remove it now. This touches mostly the ep93xx platform, but removes a bit of code from ARM common ptrace and signal frame handling as well. If there are remaining users of MaverickCrunch, they can use LTS kernels for at least another five years before kernel support ends. Link: https://lore.kernel.org/linux-arm-kernel/20210802141245.1146772-1-arnd@kernel.org/ Link: https://lore.kernel.org/linux-arm-kernel/20210226164345.3889993-1-arnd@kernel.org/ Link: https://github.com/ClangBuiltLinux/linux/issues/1272 Link: https://gcc.gnu.org/legacy-ml/gcc/2008-03/msg01063.html Cc: "Martin Guy" Signed-off-by: Arnd Bergmann

signal: Verify the alignment and size of siginfo_t

2021-07-23T18:15:31Z

Update the static assertions about siginfo_t to also describe it's alignment and size. While investigating if it was possible to add a 64bit field into siginfo_t[1] it became apparent that the alignment of siginfo_t is as much a part of the ABI as the size of the structure. If the alignment changes siginfo_t when embedded in another structure can move to a different offset. Which is not acceptable from an ABI structure. So document that fact and add static assertions to notify developers if they change change the alignment by accident. [1] https://lkml.kernel.org/r/YJEZdhe6JGFNYlum@elver.google.com Acked-by: Marco Elver v1: https://lkml.kernel.org/r/20210505141101.11519-4-ebiederm@xmission.co Link: https://lkml.kernel.org/r/875yxaxmyl.fsf_-_@disp2133 Signed-off-by: "Eric W. Biederman"

arm: Add compile-time asserts for siginfo_t offsets

2021-07-23T16:56:54Z

To help catch ABI breaks at compile-time, add compile-time assertions to verify the siginfo_t layout. This could have caught that we cannot portably add 64-bit integers to siginfo_t on 32-bit architectures like Arm before reaching -next: https://lkml.kernel.org/r/20210422191823.79012-1-elver@google.com Link: https://lkml.kernel.org/r/20210429190734.624918-2-elver@google.com Link: https://lkml.kernel.org/r/20210505141101.11519-2-ebiederm@xmission.com Link: https://lkml.kernel.org/r/87y2a7xx9q.fsf_-_@disp2133 Signed-off-by: Marco Elver Signed-off-by: Eric W. Biederman