From: Oleg Nesterov <oleg@redhat.com>
To: Deepak Gupta <debug@rivosinc.com>
Cc: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
"olsajiri@gmail.com" <olsajiri@gmail.com>,
"songliubraving@fb.com" <songliubraving@fb.com>,
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"john.fastabend@gmail.com" <john.fastabend@gmail.com>,
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Subject: Re: [PATCHv5 bpf-next 6/8] x86/shstk: Add return uprobe support
Date: Wed, 15 May 2024 13:19:20 +0200 [thread overview]
Message-ID: <20240515111919.GA6821@redhat.com> (raw)
In-Reply-To: <ZkQTgQ3aKU4MAjPu@debug.ba.rivosinc.com>
Sorry for the late reply, I was on PTO.
On 05/14, Deepak Gupta wrote:
>
> Question,
>
> Is it kernel who is maintaining all return probes, meaning original return addresses
> are saved in kernel data structures on per task basis.
Yes. task_struct->utask->return_instances
See prepare_uretprobe() which inserts the new return_instance with
->orig_ret_vaddr = original return addresses
when the tracee enters the ret-probed function.
> Once uretprobe did its job then
> its kernel who is ensuring return to original return address ?
Yes. See instruction_pointer_set(regs, ri->orig_ret_vaddr) in
handle_trampoline().
I know absolutely nothing about the shadow stacks, trying to read
Documentation/arch/x86/shstk.rst but it doesn't tell me too much...
Where can I find more documentation? I didn't try to google yet.
Upon function return, the processor pops the shadow stack copy
and compares it to the normal stack copy. If the two differ, the
processor raises a control-protection fault.
grep-grep-grep... exc_control_protection I guess.
Let me ask a couple of really stupid questions. What if the shadow stack
is "shorter" than the normal stack? I mean,
enable_shstk()
{
prctl(ARCH_SHSTK_SHSTK);
}
what happens when enable_shstk() returns?
And what is the purpose of fpregs_lock_and_load() ? Why do we need to
fpregs_restore_userregs() in shstk_setup() and other places?
Oleg.
next prev parent reply other threads:[~2024-05-15 11:21 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 10:53 [PATCHv5 bpf-next 0/8] uprobe: uretprobe speed up Jiri Olsa
2024-05-07 10:53 ` [PATCHv5 bpf-next 1/8] uprobe: Wire up uretprobe system call Jiri Olsa
2024-05-07 10:53 ` [PATCHv5 bpf-next 2/8] uprobe: Add uretprobe syscall to speed up return probe Jiri Olsa
2024-05-07 10:53 ` [PATCHv5 bpf-next 3/8] selftests/bpf: Add uretprobe syscall test for regs integrity Jiri Olsa
2024-05-07 10:53 ` [PATCHv5 bpf-next 4/8] selftests/bpf: Add uretprobe syscall test for regs changes Jiri Olsa
2024-05-07 10:53 ` [PATCHv5 bpf-next 5/8] selftests/bpf: Add uretprobe syscall call from user space test Jiri Olsa
2024-05-07 16:57 ` Andrii Nakryiko
2024-05-07 10:53 ` [PATCHv5 bpf-next 6/8] x86/shstk: Add return uprobe support Jiri Olsa
2024-05-07 17:35 ` Edgecombe, Rick P
2024-05-09 8:30 ` Jiri Olsa
2024-05-09 16:24 ` Edgecombe, Rick P
2024-05-11 21:09 ` Jiri Olsa
2024-05-13 9:50 ` Masami Hiramatsu
2024-05-13 17:12 ` Edgecombe, Rick P
2024-05-13 21:23 ` Jiri Olsa
2024-05-15 1:10 ` Edgecombe, Rick P
2024-05-15 1:44 ` Deepak Gupta
2024-05-15 11:19 ` Oleg Nesterov [this message]
2024-05-15 14:36 ` Jiri Olsa
2024-05-15 15:18 ` Edgecombe, Rick P
2024-05-15 15:26 ` Oleg Nesterov
2024-05-15 15:31 ` Edgecombe, Rick P
2024-05-15 11:35 ` Oleg Nesterov
2024-05-15 15:13 ` Edgecombe, Rick P
2024-05-15 15:42 ` Oleg Nesterov
2024-05-19 22:18 ` Jiri Olsa
2024-05-21 1:31 ` Edgecombe, Rick P
2024-05-21 10:11 ` Jiri Olsa
2024-05-07 10:53 ` [PATCHv5 bpf-next 7/8] selftests/x86: Add return uprobe shadow stack test Jiri Olsa
2024-05-13 9:45 ` Masami Hiramatsu
2024-05-13 21:28 ` Jiri Olsa
2024-05-07 10:53 ` [PATCHv5 8/8] man2: Add uretprobe syscall page Jiri Olsa
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