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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Feb 29, 2024 at 11:16:20PM +0000, Puranjay Mohan wrote: > Make arch_kunwind_consume_entry() as __always_inline otherwise the > compiler might not inline it and allow attaching probes to it. > > Without this, just probing arch_kunwind_consume_entry() via > /kprobe_events will crash the kernel on arm64. > > The crash can be reproduced using the following compiler and kernel > combination: > clang version 19.0.0git (https://github.com/llvm/llvm-project.git d68d29516102252f6bf6dc23fb22cef144ca1cb3) > commit 87adedeba51a ("Merge tag 'net-6.8-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net") > > [root@localhost ~]# echo 'p arch_kunwind_consume_entry' > /sys/kernel/debug/tracing/kprobe_events > [root@localhost ~]# echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable > > Modules linked in: aes_ce_blk aes_ce_cipher ghash_ce sha2_ce virtio_net sha256_arm64 sha1_ce arm_smccc_trng net_failover failover virtio_mmio uio_pdrv_genirq uio sch_fq_codel dm_mod dax configfs > CPU: 3 PID: 1405 Comm: bash Not tainted 6.8.0-rc6+ #14 > Hardware name: linux,dummy-virt (DT) > pstate: 604003c5 (nZCv DAIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : kprobe_breakpoint_handler+0x17c/0x258 > lr : kprobe_breakpoint_handler+0x17c/0x258 > sp : ffff800085d6ab60 > x29: ffff800085d6ab60 x28: ffff0000066f0040 x27: ffff0000066f0b20 > x26: ffff800081fa7b0c x25: 0000000000000002 x24: ffff00000b29bd18 > x23: ffff00007904c590 x22: ffff800081fa6590 x21: ffff800081fa6588 > x20: ffff00000b29bd18 x19: ffff800085d6ac40 x18: 0000000000000079 > x17: 0000000000000001 x16: ffffffffffffffff x15: 0000000000000004 > x14: ffff80008277a940 x13: 0000000000000003 x12: 0000000000000003 > x11: 00000000fffeffff x10: c0000000fffeffff x9 : aa95616fdf80cc00 > x8 : aa95616fdf80cc00 x7 : 205d343137373231 x6 : ffff800080fb48ec > x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000 > x2 : 0000000000000000 x1 : ffff800085d6a910 x0 : 0000000000000079 > Call trace: > kprobes: Failed to recover from reentered kprobes. > kprobes: Dump kprobe: > .symbol_name = arch_kunwind_consume_entry, .offset = 0, .addr = arch_kunwind_consume_entry+0x0/0x40 > ------------[ cut here ]------------ > kernel BUG at arch/arm64/kernel/probes/kprobes.c:241! > kprobes: Failed to recover from reentered kprobes. > kprobes: Dump kprobe: > .symbol_name = arch_kunwind_consume_entry, .offset = 0, .addr = arch_kunwind_consume_entry+0x0/0x40 > > Fixes: 1aba06e7b2b49 ("arm64: stacktrace: factor out kunwind_stack_walk()") > Signed-off-by: Puranjay Mohan Thanks for this! Whoops; I had meant to make this __always_inline (or noinstr), but I evidently messed that up. I don't recall any problem with making this __always_inline, and that's preferable here to allow the compiler to fold some of the indirection. >From a scan of stacktrace.c I don't see anything else that needs similar treatment; the other functions lacking __always_inline and noinstr are safe to instrument as they aren't core to the unwinder, and won't recurse into themselves in a problematic way. Given all the above: Reviewed-by: Mark Rutland Catalin, Will, are you happy to queue this as a fix? Mark. > --- > arch/arm64/kernel/stacktrace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index 7f88028a00c0..b2a60e0bcfd2 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -247,7 +247,7 @@ struct kunwind_consume_entry_data { > void *cookie; > }; > > -static bool > +static __always_inline bool > arch_kunwind_consume_entry(const struct kunwind_state *state, void *cookie) > { > struct kunwind_consume_entry_data *data = cookie; > > base-commit: 87adedeba51a822533649b143232418b9e26d08b > -- > 2.40.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel