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Howlett" , Masami Hiramatsu , Peter Zijlstra , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH] init/main.c: fix boot time tracing crash Message-Id: <20250828131049.3feb168ab25f564b8e3b24e6@kernel.org> In-Reply-To: <20250824130759.1732736-1-rppt@kernel.org> References: <20250824130759.1732736-1-rppt@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 05DD140007 X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: ksczqmxjqkbw7ktye3snxncnaabt6z54 X-HE-Tag: 1756354253-232158 X-HE-Meta: U2FsdGVkX18VyYeiOVN7ZivntyJgGGe+kutZ1VA3B1kFTEdP4hdbrg3F03FJitheZoiTlqwHdC+qpmYNc54kIYWimG//gpt3WCuZQ4XzFm5uj+5BBVAzGXNDHAHsQDneuSpUd8u+3cQ17WJfe7/l4l3G3oUb9HA1z2uE1VnUsjFjhkGvFD7tHcZrqz9BP8iyo7aXUYPOR32vyqYE2ro3UGceqvy18CjNxccSWHTTezyHHgywA/nOSkmerorOqv7iRn3PYe9363EXsr2abPAn3eHDcQZw1Bh6EmaE7ed7OJF+QX3YLqEb4vSw03ONiYpF0hiAB0Hrhbp71HiTTYEbFlsuefa43gdDWjhL1+9AX189TsaTa8p4Cs5Kgs1WEXGxNbnTSouPth4tnDhIMJGqMy6PF4q6txRsNrOL8nq3AL6DiXkkb1reuWXh8jfy3KGDOsfkPsjgjJDQID3FppuOJ9Vdmw5wSS6KiTcqHxv8h2Wox739323oZUgeyuoeIHQz2I6ouyLRZy2alURGQzZQ71Dj/LFyNySN8tLYdmBr28fYjB8m/jh+CfgxC5IQY3sHgeCadTbogLcOnudWKm5rwp6YUBjbUruL9TTTOialeKoByBGzWF6RlpeOni/VxcUKa5uAWRQau//rXJ70imdwtw8LcaCNubEXFCLAmfXcg2aP4qfCZQkGZ3G8YBHbl+h7OdC4Qtg0EnjgrA/kDZAo2ql2BPD4TVl2rcQA5iqm6bsuIrVM+g/B+jiN9SM17RXTiC/v3BXzgbMUNpWpogdmIIBPrgAXMKSs4WtC57utGw7bq36zlTjB6tiRQVj955z2UQYeDIQIXe5r6N9nDasyiuU2JVjwcRz2oycZK8pdeDZ46jIdfG3EF5YKQzZwxZ5qlqQJCCylZ5zeNl6LjzZHlIB1OuviEzPV7cwGeqPQjwY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, 24 Aug 2025 16:07:59 +0300 Mike Rapoport wrote: > From: "Mike Rapoport (Microsoft)" > > 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] > [ 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] > [ 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) Thanks, > Fixes: 5d79c2be5081 ("x86/ftrace: enable EXECMEM_ROX_CACHE for ftrace allocations") > Signed-off-by: Mike Rapoport (Microsoft) > --- > 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)