bpf trampoline support "jmp" mode #6353
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For now, the "nop" will be replaced with a "call" instruction when a function is hooked by the ftrace. However, sometimes the "call" can break the RSB and introduce extra overhead. Therefore, introduce the flag FTRACE_OPS_FL_JMP, which indicate that the ftrace_ops should be called with a "jmp" instead of "call". For now, it is only used by the direct call case. When a direct ftrace_ops is marked with FTRACE_OPS_FL_JMP, the last bit of the ops->direct_call will be set to 1. Therefore, we can tell if we should use "jmp" for the callback in ftrace_call_replace(). Signed-off-by: Menglong Dong <[email protected]>
Implement the DYNAMIC_FTRACE_WITH_JMP for x86_64. In ftrace_call_replace, we will use JMP32_INSN_OPCODE instead of CALL_INSN_OPCODE if the address should use "jmp". Meanwhile, adjust the direct call in the ftrace_regs_caller. Signed-off-by: Menglong Dong <[email protected]>
Some places calculate the origin_call by checking if BPF_TRAMP_F_SKIP_FRAME is set. However, it should use BPF_TRAMP_F_ORIG_STACK for this propose. Just fix them. Signed-off-by: Menglong Dong <[email protected]>
In the origin call case, if BPF_TRAMP_F_SKIP_FRAME is not set, it means that the trampoline is not called, but "jmp". Introduce the function bpf_trampoline_need_jmp() to check if the trampoline is in "jmp" mode. Do some adjustment on the "jmp" mode for the x86_64. The main adjustment that we make is for the stack parameter passing case, as the stack alignment logic changes in the "jmp" mode without the "rip". What's more, the location of the parameters on the stack also changes. Signed-off-by: Menglong Dong <[email protected]>
Introduce the function bpf_arch_text_poke_type(), which is able to specify both the current and new opcode. If it is not implemented by the arch, bpf_arch_text_poke() will be called directly if the current opcode is the same as the new one. Otherwise, -EOPNOTSUPP will be returned. Signed-off-by: Menglong Dong <[email protected]>
Implement the bpf_arch_text_poke_type() for x86_64. Signed-off-by: Menglong Dong <[email protected]>
Implement the "jmp" mode for the bpf trampoline. For the ftrace_managed case, we need only to set the FTRACE_OPS_FL_JMP on the tr->fops if "jmp" is needed. For the bpf poke case, the new flag BPF_TRAMP_F_JMPED is introduced to store and check if the trampoline is in the "jmp" mode. Signed-off-by: Menglong Dong <[email protected]>
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Upstream branch: 93ce3be |
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=1023419 expired. Closing PR. |
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Pull request for series with
subject: bpf trampoline support "jmp" mode
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1023419