On Wed, Apr 21, 2021 at 05:11PM +0200, Marco Elver wrote: > +Cc linux-arm-kernel > [...] > > > > I've managed to reproduce this issue with a public Raspberry Pi OS Lite > > rootfs image, even without deploying kernel modules: > > > > https://downloads.raspberrypi.org/raspios_lite_armhf/images/raspios_lite_armhf-2021-03-25/2021-03-04-raspios-buster-armhf-lite.zip > > > > # qemu-system-arm -M virt -smp 2 -m 512 -kernel zImage -append "earlycon > > console=ttyAMA0 root=/dev/vda2 rw rootwait" -serial stdio -display none > > -monitor null -device virtio-blk-device,drive=virtio-blk -drive > > file=/tmp/2021-03-04-raspios-buster-armhf-lite.img,id=virtio-blk,if=none,format=raw > > -netdev user,id=user -device virtio-net-device,netdev=user > > > > The above one doesn't boot if zImage z compiled from commit fb6cc127e0b6 > > and boots if compiled from 2e498d0a74e5. In both cases I've used default > > arm/multi_v7_defconfig and > > gcc-linaro-6.4.1-2017.11-x86_64_arm-linux-gnueabi toolchain. > > Yup, I've narrowed it down to the addition of "__u64 _perf" to > siginfo_t. My guess is the __u64 causes a different alignment for a > bunch of adjacent fields. It seems that x86 and m68k are the only ones > that have compile-time tests for the offsets. Arm should probably add > those -- I have added a bucket of static_assert() in > arch/arm/kernel/signal.c and see that something's off. > > I'll hopefully have a fix in a day or so. Arm and compiler folks: are there some special alignment requirement for __u64 on arm 32-bit? (And if there is for arm64, please shout as well.) With the static-asserts below, the only thing that I can do to fix it is to completely remove the __u64. Padding it before or after with __u32 just does not work. It seems that the use of __u64 shifts everything in __sifields by 4 bytes. diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h index d0bb9125c853..b02a4ac55938 100644 --- a/include/uapi/asm-generic/siginfo.h +++ b/include/uapi/asm-generic/siginfo.h @@ -92,7 +92,10 @@ union __sifields { __u32 _pkey; } _addr_pkey; /* used when si_code=TRAP_PERF */ - __u64 _perf; + struct { + __u32 _perf1; + __u32 _perf2; + } _perf; }; } _sigfault; ^^ works, but I'd hate to have to split this into 2 __u32 because it makes the whole design worse. What alignment trick do we have to do here to fix it for __u64? ------ >8 ------ diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index a3a38d0a4c85..6c558dc314c3 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -725,3 +725,41 @@ asmlinkage void do_rseq_syscall(struct pt_regs *regs) rseq_syscall(regs); } #endif + +/* + * Compile-time tests for siginfo_t offsets. Changes to NSIG* likely come with + * new fields; new fields should be added below. + */ +static_assert(NSIGILL == 11); +static_assert(NSIGFPE == 15); +static_assert(NSIGSEGV == 9); +static_assert(NSIGBUS == 5); +static_assert(NSIGTRAP == 6); +static_assert(NSIGCHLD == 6); +static_assert(NSIGSYS == 2); +static_assert(offsetof(siginfo_t, si_signo) == 0x00); +static_assert(offsetof(siginfo_t, si_errno) == 0x04); +static_assert(offsetof(siginfo_t, si_code) == 0x08); +static_assert(offsetof(siginfo_t, si_pid) == 0x0c); +#if 0 +static_assert(offsetof(siginfo_t, si_uid) == 0x10); +static_assert(offsetof(siginfo_t, si_tid) == 0x0c); +static_assert(offsetof(siginfo_t, si_overrun) == 0x10); +static_assert(offsetof(siginfo_t, si_status) == 0x14); +static_assert(offsetof(siginfo_t, si_utime) == 0x18); +static_assert(offsetof(siginfo_t, si_stime) == 0x1c); +static_assert(offsetof(siginfo_t, si_value) == 0x14); +static_assert(offsetof(siginfo_t, si_int) == 0x14); +static_assert(offsetof(siginfo_t, si_ptr) == 0x14); +static_assert(offsetof(siginfo_t, si_addr) == 0x0c); +static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x10); +static_assert(offsetof(siginfo_t, si_lower) == 0x14); +static_assert(offsetof(siginfo_t, si_upper) == 0x18); +static_assert(offsetof(siginfo_t, si_pkey) == 0x14); +static_assert(offsetof(siginfo_t, si_perf) == 0x10); +static_assert(offsetof(siginfo_t, si_band) == 0x0c); +static_assert(offsetof(siginfo_t, si_fd) == 0x10); +static_assert(offsetof(siginfo_t, si_call_addr) == 0x0c); +static_assert(offsetof(siginfo_t, si_syscall) == 0x10); +static_assert(offsetof(siginfo_t, si_arch) == 0x14); +#endif
