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Message-Id: <20250828131049.3feb168ab25f564b8e3b24e6@kernel.org>
Date: Thu, 28 Aug 2025 13:10:49 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Borislav Petkov
<bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, Ingo Molnar
<mingo@...hat.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, Masami
Hiramatsu <mhiramat@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>, Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-trace-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] init/main.c: fix boot time tracing crash
On Sun, 24 Aug 2025 16:07:59 +0300
Mike Rapoport <rppt@...nel.org> wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>
>
> Steven Rostedt reported a crash with "ftrace=function" kernel command
> line:
>
> [ 0.159269] BUG: kernel NULL pointer dereference, address: 000000000000001c
> [ 0.160254] #PF: supervisor read access in kernel mode
> [ 0.160975] #PF: error_code(0x0000) - not-present page
> [ 0.161697] PGD 0 P4D 0
> [ 0.162055] Oops: Oops: 0000 [#1] SMP PTI
> [ 0.162619] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.17.0-rc2-test-00006-g48d06e78b7cb-dirty #9 PREEMPT(undef)
> [ 0.164141] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> [ 0.165439] RIP: 0010:kmem_cache_alloc_noprof (mm/slub.c:4237)
> [ 0.166186] Code: 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 49 89 fc 53 48 83 e4 f0 48 83 ec 20 8b 05 c9 b6 7e 01 <44> 8b 77 1c 65 4c 8b 2d b5 ea 20 02 4c 89 6c 24 18 41 89 f5 21 f0
> [ 0.168811] RSP: 0000:ffffffffb2e03b30 EFLAGS: 00010086
> [ 0.169545] RAX: 0000000001fff33f RBX: 0000000000000000 RCX: 0000000000000000
> [ 0.170544] RDX: 0000000000002800 RSI: 0000000000002800 RDI: 0000000000000000
> [ 0.171554] RBP: ffffffffb2e03b80 R08: 0000000000000004 R09: ffffffffb2e03c90
> [ 0.172549] R10: ffffffffb2e03c90 R11: 0000000000000000 R12: 0000000000000000
> [ 0.173544] R13: ffffffffb2e03c90 R14: ffffffffb2e03c90 R15: 0000000000000001
> [ 0.174542] FS: 0000000000000000(0000) GS:ffff9d2808114000(0000) knlGS:0000000000000000
> [ 0.175684] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 0.176486] CR2: 000000000000001c CR3: 000000007264c001 CR4: 00000000000200b0
> [ 0.177483] Call Trace:
> [ 0.177828] <TASK>
> [ 0.178123] mas_alloc_nodes (lib/maple_tree.c:176 (discriminator 2) lib/maple_tree.c:1255 (discriminator 2))
> [ 0.178692] mas_store_gfp (lib/maple_tree.c:5468)
> [ 0.179223] execmem_cache_add_locked (mm/execmem.c:207)
> [ 0.179870] execmem_alloc (mm/execmem.c:213 mm/execmem.c:313 mm/execmem.c:335 mm/execmem.c:475)
> [ 0.180397] ? ftrace_caller (arch/x86/kernel/ftrace_64.S:169)
> [ 0.180922] ? __pfx_ftrace_caller (arch/x86/kernel/ftrace_64.S:158)
> [ 0.181517] execmem_alloc_rw (mm/execmem.c:487)
> [ 0.182052] arch_ftrace_update_trampoline (arch/x86/kernel/ftrace.c:266 arch/x86/kernel/ftrace.c:344 arch/x86/kernel/ftrace.c:474)
> [ 0.182778] ? ftrace_caller_op_ptr (arch/x86/kernel/ftrace_64.S:182)
> [ 0.183388] ftrace_update_trampoline (kernel/trace/ftrace.c:7947)
> [ 0.184024] __register_ftrace_function (kernel/trace/ftrace.c:368)
> [ 0.184682] ftrace_startup (kernel/trace/ftrace.c:3048)
> [ 0.185205] ? __pfx_function_trace_call (kernel/trace/trace_functions.c:210)
> [ 0.185877] register_ftrace_function_nolock (kernel/trace/ftrace.c:8717)
> [ 0.186595] register_ftrace_function (kernel/trace/ftrace.c:8745)
> [ 0.187254] ? __pfx_function_trace_call (kernel/trace/trace_functions.c:210)
> [ 0.187924] function_trace_init (kernel/trace/trace_functions.c:170)
> [ 0.188499] tracing_set_tracer (kernel/trace/trace.c:5916 kernel/trace/trace.c:6349)
> [ 0.189088] register_tracer (kernel/trace/trace.c:2391)
> [ 0.189642] early_trace_init (kernel/trace/trace.c:11075 kernel/trace/trace.c:11149)
> [ 0.190204] start_kernel (init/main.c:970)
> [ 0.190732] x86_64_start_reservations (arch/x86/kernel/head64.c:307)
> [ 0.191381] x86_64_start_kernel (??:?)
> [ 0.191955] common_startup_64 (arch/x86/kernel/head_64.S:419)
> [ 0.192534] </TASK>
> [ 0.192839] Modules linked in:
> [ 0.193267] CR2: 000000000000001c
> [ 0.193730] ---[ end trace 0000000000000000 ]---
>
> The crash happens because on x86 ftrace allocations from execmem require
> maple tree to be initialized.
>
> Move maple tree initialization that depends only on slab availability
> earlier in boot so that it will happen right after mm_core_init().
>
Looks good to me.
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Thanks,
> Fixes: 5d79c2be5081 ("x86/ftrace: enable EXECMEM_ROX_CACHE for ftrace allocations")
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
> ---
> init/main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/init/main.c b/init/main.c
> index 0ee0ee7b7c2c..5753e9539ae6 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -956,6 +956,7 @@ void start_kernel(void)
> sort_main_extable();
> trap_init();
> mm_core_init();
> + maple_tree_init();
> poking_init();
> ftrace_init();
>
> @@ -973,7 +974,6 @@ void start_kernel(void)
> "Interrupts were enabled *very* early, fixing it\n"))
> local_irq_disable();
> radix_tree_init();
> - maple_tree_init();
>
> /*
> * Set up housekeeping before setting up workqueues to allow the unbound
>
> base-commit: c17b750b3ad9f45f2b6f7e6f7f4679844244f0b9
> --
> 2.50.1
>
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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