Re: [PATCH v5 04/12] fprobe: Use ftrace_regs in fprobe entry handler

Jiri Olsa
2023-09-25T10:42:15Z

On Sun, Sep 24, 2023 at 10:36:36PM +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>

I was getting bpf selftests failures with this patchset and when
bisecting I'm getting crash when running on top of this change

looks like it's missing some of the regs NULL checks added later?

jirka

---
[ 124.089449][ T677] BUG: kernel NULL pointer dereference, address: 0000000000000098
[ 124.090102][ T677] #PF: supervisor read access in kernel mode
[ 124.090568][ T677] #PF: error_code(0x0000) - not-present page
[ 124.091039][ T677] PGD 158fd8067 P4D 158fd8067 PUD 10896a067 PMD 0
[ 124.091482][ T677] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI
[ 124.091986][ T677] CPU: 1 PID: 677 Comm: test_progs Tainted: G OE 6.6.0-rc2+ #768 1c8a8990289f2615e36dadd01915b80e8da29bf5
[ 124.092898][ T677] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38 04/01/2014
[ 124.093613][ T677] RIP: 0010:arch_rethook_prepare+0x0/0x30
[ 124.094060][ T677] Code: 90 90 90 90 90 90 90 90 90 90 48 89 b7 a8 00 00 00 c3 cc cc cc cc 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <48> 8b 86 98 00 00 00 48 8b 10 48 89 57 20 48 8b 96 98 00 00 00 48
[ 124.096239][ T677] RSP: 0018:ffffc90003d3bc98 EFLAGS: 00010286
[ 124.096708][ T677] RAX: 0000000000000000 RBX: ffff88815d9fbe50 RCX: ffff88815d9fbe40
[ 124.097332][ T677] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff88815d9fbe40
[ 124.097946][ T677] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000004
[ 124.098554][ T677] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff81fbb7b0
[ 124.099108][ T677] R13: ffffffff81fbd47b R14: fffffffffffffff7 R15: ffff88815d9fbe40
[ 124.099720][ T677] FS: 00007f9c2063ed00(0000) GS:ffff88846d200000(0000) knlGS:0000000000000000
[ 124.100403][ T677] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 124.100908][ T677] CR2: 0000000000000098 CR3: 0000000108e02002 CR4: 0000000000770ee0
[ 124.101537][ T677] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 124.102096][ T677] DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
[ 124.102689][ T677] PKRU: 55555554
[ 124.102988][ T677] Call Trace:
[ 124.103303][ T677] <TASK>
[ 124.103580][ T677] ? __die+0x1f/0x70
[ 124.103928][ T677] ? page_fault_oops+0x176/0x4d0
[ 124.104348][ T677] ? __pte_offset_map_lock+0xa5/0x190
[ 124.104818][ T677] ? do_user_addr_fault+0x73/0x870
[ 124.105277][ T677] ? exc_page_fault+0x81/0x250
[ 124.105709][ T677] ? asm_exc_page_fault+0x22/0x30
[ 124.106171][ T677] ? bpf_prog_test_run_tracing+0x14b/0x2c0
[ 124.106675][ T677] ? __pfx_bpf_fentry_test1+0x10/0x10
[ 124.107135][ T677] ? __pfx_arch_rethook_prepare+0x10/0x10
[ 124.107598][ T677] rethook_hook+0x10/0x30
[ 124.107966][ T677] fprobe_handler+0x129/0x210
[ 124.108351][ T677] ? __pfx_bpf_fentry_test1+0x10/0x10
[ 124.108796][ T677] ? bpf_prog_test_run_tracing+0x14b/0x2c0
[ 124.109276][ T677] arch_ftrace_ops_list_func+0xf2/0x200
[ 124.109708][ T677] ftrace_call+0x5/0x44
[ 124.110060][ T677] ? bpf_fentry_test1+0x5/0x10
[ 124.110463][ T677] bpf_fentry_test1+0x5/0x10
[ 124.110881][ T677] bpf_prog_test_run_tracing+0x14b/0x2c0
[ 124.111337][ T677] __sys_bpf+0x305/0x2820
[ 124.111705][ T677] __x64_sys_bpf+0x1a/0x30
[ 124.112053][ T677] do_syscall_64+0x38/0x90
[ 124.116245][ T677] entry_SYSCALL_64_after_hwframe+0x6e/0xd8
[ 124.116688][ T677] RIP: 0033:0x7f9c20806b5d
[ 124.117078][ T677] 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 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 7b 92 0c 00 f7 d8 64 89 01 48
[ 124.118487][ T677] RSP: 002b:00007ffc615e5228 EFLAGS: 00000206 ORIG_RAX: 0000000000000141
[ 124.119090][ T677] RAX: ffffffffffffffda RBX: 00007f9c20918000 RCX: 00007f9c20806b5d
[ 124.119698][ T677] RDX: 0000000000000050 RSI: 00007ffc615e5260 RDI: 000000000000000a
[ 124.120298][ T677] RBP: 00007ffc615e5240 R08: 0000000000000000 R09: 00007ffc615e5260
[ 124.120893][ T677] R10: 0000000000000064 R11: 0000000000000206 R12: 0000000000000001
[ 124.121486][ T677] R13: 0000000000000000 R14: 00007f9c2094d000 R15: 00000000011a8db0
[ 124.122156][ T677] </TASK>
[ 124.122421][ T677] Modules linked in: bpf_testmod(OE) intel_rapl_msr intel_rapl_common crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel kvm_intel rapl iTCO_wdt iTCO_vendor_support i2c_i801 i2c_smbus lpc_ich drm loop drm_panel_orientation_quirks zram
[ 124.125064][ T677] CR2: 0000000000000098
[ 124.125431][ T677] ---[ end trace 0000000000000000 ]---
[ 124.125861][ T677] RIP: 0010:arch_rethook_prepare+0x0/0x30
[ 124.126316][ T677] Code: 90 90 90 90 90 90 90 90 90 90 48 89 b7 a8 00 00 00 c3 cc cc cc cc 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <48> 8b 86 98 00 00 00 48 8b 10 48 89 57 20 48 8b 96 98 00 00 00 48
[ 124.127761][ T677] RSP: 0018:ffffc90003d3bc98 EFLAGS: 00010286
[ 124.128238][ T677] RAX: 0000000000000000 RBX: ffff88815d9fbe50 RCX: ffff88815d9fbe40
[ 124.128856][ T677] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff88815d9fbe40
[ 124.129502][ T677] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000004
[ 124.130129][ T677] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff81fbb7b0
[ 124.130767][ T677] R13: ffffffff81fbd47b R14: fffffffffffffff7 R15: ffff88815d9fbe40
[ 124.131410][ T677] FS: 00007f9c2063ed00(0000) GS:ffff88846d200000(0000) knlGS:0000000000000000
[ 124.132084][ T677] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 124.132600][ T677] CR2: 0000000000000098 CR3: 0000000108e02002 CR4: 0000000000770ee0
[ 124.133128][ T677] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 124.133698][ T677] DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
[ 124.134302][ T677] PKRU: 55555554
[ 124.134584][ T677] note: test_progs[677] exited with irqs disabled
[ 124.135192][ T677] note: test_progs[677] exited with preempt_count 2