bpf: fsession support #10601
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bpf: fsession support #10601
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Upstream branch: a069190 |
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The fsession is something that similar to kprobe session. It allow to attach a single BPF program to both the entry and the exit of the target functions. Introduce the struct bpf_fsession_link, which allows to add the link to both the fentry and fexit progs_hlist of the trampoline. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn> Co-developed-by: Leon Hwang <leon.hwang@linux.dev> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
For now, ctx[-1] is used to store the nr_args in the trampoline. However, 1-byte is enough to store such information. Therefore, we use only the last byte of ctx[-1] to store the nr_args, and reserve the rest for other usages. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
If fsession exists, we will use the bit (1 << BPF_TRAMP_M_IS_RETURN) in ctx[-1] to store the "is_return" flag. Introduce the kfunc bpf_fsession_is_return(), which is used to tell if it is fexit currently. Meanwhile, inline it in the verifier. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn> Co-developed-by: Leon Hwang <leon.hwang@linux.dev> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Implement session cookie for fsession. In order to limit the stack usage, we make 4 as the maximum of the cookie count. The offset of the current cookie is stored in the "(ctx[-1] >> BPF_TRAMP_M_COOKIE) & 0xFF". Therefore, we can get the session cookie with ctx[-offset]. The stack will look like this: return value -> 8 bytes argN -> 8 bytes ... arg1 -> 8 bytes nr_args -> 8 bytes ip (optional) -> 8 bytes cookie2 -> 8 bytes cookie1 -> 8 bytes Inline the bpf_fsession_cookie() in the verifier too. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Introduce the helper emit_st_r0_imm64(), which is used to store a imm64 to the stack with the help of r0. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Add BPF_TRACE_FSESSION supporting to x86_64, including: 1. clear the return value in the stack before fentry to make the fentry of the fsession can only get 0 with bpf_get_func_ret(). 2. clear all the session cookies' value in the stack. 2. store the index of the cookie to ctx[-1] before the calling to fsession 3. store the "is_return" flag to ctx[-1] before the calling to fexit of the fsession. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn> Co-developed-by: Leon Hwang <leon.hwang@linux.dev> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Add BPF_TRACE_FSESSION to libbpf and bpftool. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Add testcases for BPF_TRACE_FSESSION. The function arguments and return value are tested both in the entry and exit. And the kfunc bpf_fsession_is_ret() is also tested. As the layout of the stack changed for fsession, so we also test bpf_get_func_ip() for it. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
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Upstream branch: ea180ff |
Test session cookie for fsession. Multiple fsession BPF progs is attached to bpf_fentry_test1() and session cookie is read and write in the testcase. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Test the fsession when it is used together with fentry, fexit. Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=1038207 expired. Closing PR. |
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Pull request for series with
subject: bpf: fsession support
version: 6
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1038207