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From: Jiri Olsa <olsajiri@gmail.com>
Date: Tue, 19 Dec 2023 14:23:23 +0100
To: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Florent Revest <revest@chromium.org>,
	linux-trace-kernel@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>, bpf <bpf@vger.kernel.org>,
	Sven Schnelle <svens@linux.ibm.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Alan Maguire <alan.maguire@oracle.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>, Guo Ren <guoren@kernel.org>
Subject: Re: [PATCH v5 24/34] fprobe: Use ftrace_regs in fprobe entry handler
Message-ID: <ZYGZS190qqH-zUAB@krava>
References: <170290509018.220107.1347127510564358608.stgit@devnote2>
 <170290538307.220107.14964448383069008953.stgit@devnote2>
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In-Reply-To: <170290538307.220107.14964448383069008953.stgit@devnote2>

On Mon, Dec 18, 2023 at 10:16:23PM +0900, Masami Hiramatsu (Google) wrote:
> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> This allows fprobes to be available with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
> instead of CONFIG_DYNAMIC_FTRACE_WITH_REGS, then we can enable fprobe
> on arm64.
> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> Acked-by: Florent Revest <revest@chromium.org>

this change breaks kprobe multi bpf tests (crash below), which are
partially fixed by [1] later on, but I think we have to keep
bisecting crash free

it looks like the rethook will get wrong pointer.. I'm still trying
to digest the whole thing, so I might have some updates later ;-)

jirka


[1] fprobe: Rewrite fprobe on function-graph tracer
---
Dec 19 13:50:04 qemu kernel: BUG: kernel NULL pointer dereference, address: 0000000000000098
Dec 19 13:50:04 qemu kernel: #PF: supervisor read access in kernel mode
Dec 19 13:50:04 qemu kernel: #PF: error_code(0x0000) - not-present page
Dec 19 13:50:04 qemu kernel: PGD 10955f067 P4D 10955f067 PUD 103113067 PMD 0 
Dec 19 13:50:04 qemu kernel: Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN NOPTI
Dec 19 13:50:04 qemu kernel: CPU: 1 PID: 747 Comm: test_progs Tainted: G    B      OE      6.7.0-rc3+ #194 85bc8297edbc7f21acfc743dabbd52cac073a6bf
Dec 19 13:50:04 qemu kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38 04/01/2014
Dec 19 13:50:04 qemu kernel: RIP: 0010:arch_rethook_prepare+0x18/0x60
Dec 19 13:50:04 qemu kernel: Code: 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 41 55 41 54 55 48 89 f5 53 48 89 fb 48 8d be 98 00 00 00 e8 68 8f 59 >
Dec 19 13:50:04 qemu kernel: RSP: 0018:ffff888125f97a88 EFLAGS: 00010286
Dec 19 13:50:04 qemu kernel: RAX: 0000000000000001 RBX: ffff88818a231410 RCX: ffffffff812190b6
Dec 19 13:50:04 qemu kernel: RDX: fffffbfff0c42e95 RSI: 0000000000000008 RDI: ffffffff862174a0
Dec 19 13:50:04 qemu kernel: RBP: 0000000000000000 R08: 0000000000000001 R09: fffffbfff0c42e94
Dec 19 13:50:04 qemu kernel: R10: ffffffff862174a7 R11: 0000000000000000 R12: ffff88818a231420
Dec 19 13:50:04 qemu kernel: R13: ffffffff8283ee8e R14: ffff88818a231410 R15: fffffffffffffff7
Dec 19 13:50:04 qemu kernel: FS:  00007ff8a16cfd00(0000) GS:ffff88842c600000(0000) knlGS:0000000000000000
Dec 19 13:50:05 qemu kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Dec 19 13:50:05 qemu kernel: CR2: 0000000000000098 CR3: 000000010633c005 CR4: 0000000000770ef0
Dec 19 13:50:05 qemu kernel: PKRU: 55555554
Dec 19 13:50:05 qemu kernel: Call Trace:
Dec 19 13:50:05 qemu kernel:  <TASK>
Dec 19 13:50:05 qemu kernel:  ? __die+0x1f/0x70
Dec 19 13:50:05 qemu kernel:  ? page_fault_oops+0x215/0x620
Dec 19 13:50:05 qemu kernel:  ? rcu_is_watching+0x34/0x60
Dec 19 13:50:05 qemu kernel:  ? __pfx_page_fault_oops+0x10/0x10
Dec 19 13:50:05 qemu kernel:  ? asm_sysvec_apic_timer_interrupt+0x16/0x20
Dec 19 13:50:05 qemu kernel:  ? do_user_addr_fault+0x4b3/0x910
Dec 19 13:50:05 qemu kernel:  ? exc_page_fault+0x77/0x130
Dec 19 13:50:05 qemu kernel:  ? asm_exc_page_fault+0x22/0x30
Dec 19 13:50:05 qemu kernel:  ? bpf_prog_test_run_tracing+0x1ce/0x2d0
Dec 19 13:50:05 qemu kernel:  ? add_taint+0x26/0x90
Dec 19 13:50:05 qemu kernel:  ? arch_rethook_prepare+0x18/0x60
Dec 19 13:50:05 qemu kernel:  ? arch_rethook_prepare+0x18/0x60
Dec 19 13:50:05 qemu kernel:  ? bpf_prog_test_run_tracing+0x1ce/0x2d0
Dec 19 13:50:05 qemu kernel:  rethook_hook+0x1e/0x50
Dec 19 13:50:05 qemu kernel:  ? __pfx_bpf_fentry_test1+0x10/0x10
Dec 19 13:50:05 qemu kernel:  ? bpf_prog_test_run_tracing+0x1ce/0x2d0
Dec 19 13:50:05 qemu kernel:  fprobe_handler+0x1ca/0x350
Dec 19 13:50:05 qemu kernel:  ? __pfx_bpf_fentry_test1+0x10/0x10
Dec 19 13:50:05 qemu kernel:  arch_ftrace_ops_list_func+0x143/0x2e0
Dec 19 13:50:05 qemu kernel:  ? bpf_prog_test_run_tracing+0x1ce/0x2d0
Dec 19 13:50:05 qemu kernel:  ftrace_call+0x5/0x44
Dec 19 13:50:05 qemu kernel:  ? __pfx_lock_release+0x10/0x10
Dec 19 13:50:05 qemu kernel:  ? rcu_is_watching+0x34/0x60
Dec 19 13:50:05 qemu kernel:  ? bpf_prog_test_run_tracing+0xcd/0x2d0
Dec 19 13:50:05 qemu kernel:  ? bpf_fentry_test1+0x5/0x10
Dec 19 13:50:05 qemu kernel:  ? rcu_is_watching+0x34/0x60
Dec 19 13:50:05 qemu kernel:  bpf_fentry_test1+0x5/0x10
Dec 19 13:50:05 qemu kernel:  bpf_prog_test_run_tracing+0x1ce/0x2d0
Dec 19 13:50:05 qemu kernel:  ? __pfx_lock_release+0x10/0x10
Dec 19 13:50:05 qemu kernel:  ? __pfx_bpf_prog_test_run_tracing+0x10/0x10
Dec 19 13:50:05 qemu kernel:  ? __pfx_lock_release+0x10/0x10
Dec 19 13:50:05 qemu kernel:  ? __fget_light+0xdf/0x100
Dec 19 13:50:05 qemu kernel:  ? __bpf_prog_get+0x107/0x150
Dec 19 13:50:05 qemu kernel:  __sys_bpf+0x552/0x2ef0
Dec 19 13:50:05 qemu kernel:  ? rcu_is_watching+0x34/0x60
Dec 19 13:50:05 qemu kernel:  ? __pfx___sys_bpf+0x10/0x10
Dec 19 13:50:05 qemu kernel:  ? __pfx_lock_release+0x10/0x10
Dec 19 13:50:05 qemu kernel:  ? vfs_write+0x1fa/0x740
Dec 19 13:50:05 qemu kernel:  ? rcu_is_watching+0x34/0x60
Dec 19 13:50:05 qemu kernel:  ? rcu_is_watching+0x34/0x60
Dec 19 13:50:05 qemu kernel:  ? lockdep_hardirqs_on_prepare+0xe/0x250
Dec 19 13:50:05 qemu kernel:  ? seqcount_lockdep_reader_access.constprop.0+0x105/0x120
Dec 19 13:50:05 qemu kernel:  ? seqcount_lockdep_reader_access.constprop.0+0xb2/0x120
Dec 19 13:50:05 qemu kernel:  __x64_sys_bpf+0x44/0x60
Dec 19 13:50:05 qemu kernel:  do_syscall_64+0x3f/0xf0
Dec 19 13:50:05 qemu kernel:  entry_SYSCALL_64_after_hwframe+0x6e/0x76
Dec 19 13:50:05 qemu kernel: RIP: 0033:0x7ff8a1897b4d
Dec 19 13:50:05 qemu kernel: Code: c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f >
Dec 19 13:50:05 qemu kernel: RSP: 002b:00007fff34f7d158 EFLAGS: 00000206 ORIG_RAX: 0000000000000141
Dec 19 13:50:05 qemu kernel: RAX: ffffffffffffffda RBX: 00007ff8a19aa000 RCX: 00007ff8a1897b4d
Dec 19 13:50:05 qemu kernel: RDX: 0000000000000050 RSI: 00007fff34f7d190 RDI: 000000000000000a
Dec 19 13:50:05 qemu kernel: RBP: 00007fff34f7d170 R08: 0000000000000000 R09: 00007fff34f7d190
Dec 19 13:50:05 qemu kernel: R10: 0000000000000064 R11: 0000000000000206 R12: 0000000000000004
Dec 19 13:50:05 qemu kernel: R13: 0000000000000000 R14: 00007ff8a19df000 R15: 0000000000e56db0
Dec 19 13:50:05 qemu kernel:  </TASK>
Dec 19 13:50:05 qemu kernel: Modules linked in: bpf_testmod(OE) intel_rapl_msr intel_rapl_common crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_inte>
Dec 19 13:50:05 qemu kernel: CR2: 0000000000000098
Dec 19 13:50:05 qemu kernel: ---[ end trace 0000000000000000 ]---