linux-dev/arch/um/kernel/skas, branch master

Merge tag 'locking_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-01-12T01:24:45Z

Pull locking updates from Borislav Petkov: "Lots of cleanups and preparation. Highlights: - futex: Cleanup and remove runtime futex_cmpxchg detection - rtmutex: Some fixes for the PREEMPT_RT locking infrastructure - kcsan: Share owner_on_cpu() between mutex,rtmutex and rwsem and annotate the racy owner->on_cpu access *once*. - atomic64: Dead-Code-Elemination" [ Description above by Peter Zijlstra ] * tag 'locking_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: locking/atomic: atomic64: Remove unusable atomic ops futex: Fix additional regressions locking: Allow to include asm/spinlock_types.h from linux/spinlock_types_raw.h x86/mm: Include spinlock_t definition in pgtable. locking: Mark racy reads of owner->on_cpu locking: Make owner_on_cpu() into lockdep/selftests: Adapt ww-tests for PREEMPT_RT lockdep/selftests: Skip the softirq related tests on PREEMPT_RT lockdep/selftests: Unbalanced migrate_disable() & rcu_read_lock(). lockdep/selftests: Avoid using local_lock_{acquire|release}(). lockdep: Remove softirq accounting on PREEMPT_RT. locking/rtmutex: Add rt_mutex_lock_nest_lock() and rt_mutex_lock_killable(). locking/rtmutex: Squash self-deadlock check for ww_rt_mutex. locking: Remove rt_rwlock_is_contended(). sched: Trigger warning if ->migration_disabled counter underflows. futex: Fix sparc32/m68k/nds32 build regression futex: Remove futex_cmpxchg detection futex: Ensure futex_atomic_cmpxchg_inatomic() is present kernel/locking: Use a pointer in ww_mutex_trylock().

um: remove set_fs

2021-12-22T16:56:56Z

Remove address space overrides using set_fs() for User Mode Linux. Note that just like the existing kernel access case of the uaccess routines the new nofault kernel handlers do not actually have any exception handling. This is probably broken, but not change to the status quo. Signed-off-by: Christoph Hellwig Signed-off-by: Richard Weinberger

futex: Remove futex_cmpxchg detection

2021-11-24T23:02:28Z

Now that all architectures have a working futex implementation in any configuration, remove the runtime detection code. Signed-off-by: Arnd Bergmann Signed-off-by: Thomas Gleixner Reviewed-by: Russell King (Oracle) Acked-by: Vineet Gupta Acked-by: Max Filippov Acked-by: Christian Borntraeger Link: https://lore.kernel.org/r/20211026100432.1730393-2-arnd@kernel.org

Merge tag 'for-linus-5.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml

2021-09-09T20:45:26Z

Pull UML updates from Richard Weinberger: - Support for VMAP_STACK - Support for splice_write in hostfs - Fixes for virt-pci - Fixes for virtio_uml - Various fixes * tag 'for-linus-5.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml: um: fix stub location calculation um: virt-pci: fix uapi documentation um: enable VMAP_STACK um: virt-pci: don't do DMA from stack hostfs: support splice_write um: virtio_uml: fix memory leak on init failures um: virtio_uml: include linux/virtio-uml.h lib/logic_iomem: fix sparse warnings um: make PCI emulation driver init/exit static

um: fix stub location calculation

2021-08-26T20:28:03Z

In commit 9f0b4807a44f ("um: rework userspace stubs to not hard-code stub location") I changed stub_segv_handler() to do a calculation with a pointer to a stack variable to find the data page that we're using for the stack and the rest of the data. This same commit was meant to do it as well for stub_clone_handler(), but the change inadvertently went into commit 84b2789d6115 ("um: separate child and parent errors in clone stub") instead. This was reported to not be compiled correctly by gcc 5, causing the code to crash here. I'm not sure why, perhaps it's UB because the var isn't initialized? In any case, this trick always seemed bad, so just create a new inline function that does the calculation in assembly. Reported-by: subashab@codeaurora.org Fixes: 9f0b4807a44f ("um: rework userspace stubs to not hard-code stub location") Fixes: 84b2789d6115 ("um: separate child and parent errors in clone stub") Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

asm-generic/uaccess.h: remove __strncpy_from_user/__strnlen_user

2021-07-23T12:39:56Z

This is a preparation for changing over architectures to the generic implementation one at a time. As there are no callers of either __strncpy_from_user() or __strnlen_user(), fold these into the strncpy_from_user() and strnlen_user() functions to make each implementation independent of the others. Many of these implementations have known bugs, but the intention here is to not change behavior at all and stay compatible with those bugs for the moment. Reviewed-by: Christoph Hellwig Signed-off-by: Arnd Bergmann

Merge tag 'for-linus-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml

2021-07-09T17:19:13Z

Pull UML updates from Richard Weinberger: - Support for optimized routines based on the host CPU - Support for PCI via virtio - Various fixes * tag 'for-linus-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml: um: remove unneeded semicolon in um_arch.c um: Remove the repeated declaration um: fix error return code in winch_tramp() um: fix error return code in slip_open() um: Fix stack pointer alignment um: implement flush_cache_vmap/flush_cache_vunmap um: add a UML specific futex implementation um: enable the use of optimized xor routines in UML um: Add support for host CPU flags and alignment um: allow not setting extra rpaths in the linux binary um: virtio/pci: enable suspend/resume um: add PCI over virtio emulation driver um: irqs: allow invoking time-travel handler multiple times um: time-travel/signals: fix ndelay() in interrupt um: expose time-travel mode to userspace side um: export signals_enabled directly um: remove unused smp_sigio_handler() declaration lib: add iomem emulation (logic_iomem) um: allow disabling NO_IOMEM

um: Fix stack pointer alignment

2021-06-17T20:08:31Z

GCC assumes that stack is aligned to 16-byte on call sites [1]. Since GCC 8, GCC began using 16-byte aligned SSE instructions to implement assignments to structs on stack. When CC_OPTIMIZE_FOR_PERFORMANCE is enabled, this affects os-Linux/sigio.c, write_sigio_thread: struct pollfds *fds, tmp; tmp = current_poll; Note that struct pollfds is exactly 16 bytes in size. GCC 8+ generates assembly similar to: movdqa (%rdi),%xmm0 movaps %xmm0,-0x50(%rbp) This is an issue, because movaps will #GP if -0x50(%rbp) is not aligned to 16 bytes [2], and how rbp gets assigned to is via glibc clone thread_start, then function prologue, going though execution trace similar to (showing only relevant instructions): sub $0x10,%rsi mov %rcx,0x8(%rsi) mov %rdi,(%rsi) syscall pop %rax pop %rdi callq *%rax push %rbp mov %rsp,%rbp The stack pointer always points to the topmost element on stack, rather then the space right above the topmost. On push, the pointer decrements first before writing to the memory pointed to by it. Therefore, there is no need to have the stack pointer pointer always point to valid memory unless the stack is poped; so the `- sizeof(void *)` in the code is unnecessary. On the other hand, glibc reserves the 16 bytes it needs on stack and pops itself, so by the call instruction the stack pointer is exactly the caller-supplied sp. It then push the 16 bytes of the return address and the saved stack pointer, so the base pointer will be 16-byte aligned if and only if the caller supplied sp is 16-byte aligned. Therefore, the caller must supply a 16-byte aligned pointer, which `stack + UM_KERN_PAGE_SIZE` already satisfies. On a side note, musl is unaffected by this issue because it forces 16 byte alignment via `and $-16,%rsi` in its clone wrapper. Similarly, glibc i386 is also unaffected because it has `andl $0xfffffff0, %ecx`. To reproduce this bug, enable CONFIG_UML_RTC and CC_OPTIMIZE_FOR_PERFORMANCE. uml_rtc will call add_sigio_fd which will then cause write_sigio_thread to either go into segfault loop or panic with "Segfault with no mm". Similarly, signal stacks will be aligned by the host kernel upon signal delivery. `- sizeof(void *)` to sigaltstack is unconventional and extraneous. On a related note, initialization of longjmp buffers do require `- sizeof(void *)`. This is to account for the return address that would have been pushed to the stack at the call site. The reason for uml to respect 16-byte alignment, rather than telling GCC to assume 8-byte alignment like the host kernel since commit d9b0cde91c60 ("x86-64, gcc: Use -mpreferred-stack-boundary=3 if supported"), is because uml links against libc. There is no reason to assume libc is also compiled with that flag and assumes 8-byte alignment rather than 16-byte. [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40838 [2] https://c9x.me/x86/html/file_module_x86_id_180.html Signed-off-by: YiFei Zhu Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reviewed-by: Johannes Berg Signed-off-by: Richard Weinberger

um: add a UML specific futex implementation

2021-06-17T20:01:45Z

The generic asm futex implementation emulates atomic access to memory by doing a get_user followed by put_user. These translate to two mapping operations on UML with paging enabled in the meantime. This, in turn may end up changing interrupts, invoking the signal loop, etc. This replaces the generic implementation by a mapping followed by an operation on the mapped segment. Signed-off-by: Anton Ivanov Signed-off-by: Richard Weinberger

x86/syscalls: Use __NR_syscalls instead of __NR_syscall_max

2021-05-20T13:03:59Z

__NR_syscall_max is only used by x86 and UML. In contrast, __NR_syscalls is widely used by all the architectures. Convert __NR_syscall_max to __NR_syscalls and adjust the usage sites. This prepares x86 to switch to the generic syscallhdr.sh script. Signed-off-by: Masahiro Yamada Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210517073815.97426-6-masahiroy@kernel.org