From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andriin@fb.com>,
"Steven Rostedt (VMware)" <rostedt@goodmis.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>, Daniel Xu <dxu@dxuuu.xyz>,
Viktor Malik <vmalik@redhat.com>
Subject: Re: [PATCH 10/19] bpf: Allow to store caller's ip as argument
Date: Tue, 8 Jun 2021 11:49:31 -0700 [thread overview]
Message-ID: <CAEf4BzZH5ck1Do7oRxP9D5U2v659tFXNW2RfCYAQXV_d2dYc4g@mail.gmail.com> (raw)
In-Reply-To: <20210605111034.1810858-11-jolsa@kernel.org>
On Sat, Jun 5, 2021 at 4:12 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> When we will have multiple functions attached to trampoline
> we need to propagate the function's address to the bpf program.
>
> Adding new BPF_TRAMP_F_IP_ARG flag to arch_prepare_bpf_trampoline
> function that will store origin caller's address before function's
> arguments.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> arch/x86/net/bpf_jit_comp.c | 18 ++++++++++++++----
> include/linux/bpf.h | 5 +++++
> 2 files changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index b77e6bd78354..d2425c18272a 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -1951,7 +1951,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> void *orig_call)
> {
> int ret, i, cnt = 0, nr_args = m->nr_args;
> - int stack_size = nr_args * 8;
> + int stack_size = nr_args * 8, ip_arg = 0;
> struct bpf_tramp_progs *fentry = &tprogs[BPF_TRAMP_FENTRY];
> struct bpf_tramp_progs *fexit = &tprogs[BPF_TRAMP_FEXIT];
> struct bpf_tramp_progs *fmod_ret = &tprogs[BPF_TRAMP_MODIFY_RETURN];
> @@ -1975,6 +1975,9 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> */
> orig_call += X86_PATCH_SIZE;
>
> + if (flags & BPF_TRAMP_F_IP_ARG)
> + stack_size += 8;
> +
nit: move it a bit up where we adjust stack_size for BPF_TRAMP_F_CALL_ORIG flag?
> prog = image;
>
> EMIT1(0x55); /* push rbp */
> @@ -1982,7 +1985,14 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> EMIT4(0x48, 0x83, 0xEC, stack_size); /* sub rsp, stack_size */
> EMIT1(0x53); /* push rbx */
>
> - save_regs(m, &prog, nr_args, stack_size);
> + if (flags & BPF_TRAMP_F_IP_ARG) {
> + emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8);
> + EMIT4(0x48, 0x83, 0xe8, X86_PATCH_SIZE); /* sub $X86_PATCH_SIZE,%rax*/
> + emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -stack_size);
> + ip_arg = 8;
> + }
why not pass flags into save_regs and let it handle this case without
this extra ip_arg adjustment?
> +
> + save_regs(m, &prog, nr_args, stack_size - ip_arg);
>
> if (flags & BPF_TRAMP_F_CALL_ORIG) {
> /* arg1: mov rdi, im */
> @@ -2011,7 +2021,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> }
>
> if (flags & BPF_TRAMP_F_CALL_ORIG) {
> - restore_regs(m, &prog, nr_args, stack_size);
> + restore_regs(m, &prog, nr_args, stack_size - ip_arg);
>
similarly (and symmetrically), pass flags into restore_regs() to
handle that ip_arg transparently?
> if (flags & BPF_TRAMP_F_ORIG_STACK) {
> emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8);
> @@ -2052,7 +2062,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> }
>
> if (flags & BPF_TRAMP_F_RESTORE_REGS)
> - restore_regs(m, &prog, nr_args, stack_size);
> + restore_regs(m, &prog, nr_args, stack_size - ip_arg);
>
> /* This needs to be done regardless. If there were fmod_ret programs,
> * the return value is only updated on the stack and still needs to be
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 16fc600503fb..6cbf3c81c650 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -559,6 +559,11 @@ struct btf_func_model {
> */
> #define BPF_TRAMP_F_ORIG_STACK BIT(3)
>
> +/* First argument is IP address of the caller. Makes sense for fentry/fexit
> + * programs only.
> + */
> +#define BPF_TRAMP_F_IP_ARG BIT(4)
> +
> /* Each call __bpf_prog_enter + call bpf_func + call __bpf_prog_exit is ~50
> * bytes on x86. Pick a number to fit into BPF_IMAGE_SIZE / 2
> */
> --
> 2.31.1
>
next prev parent reply other threads:[~2021-06-08 18:54 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-05 11:10 [RFCv3 00/19] x86/ftrace/bpf: Add batch support for direct/tracing attach Jiri Olsa
2021-06-05 11:10 ` [PATCH 01/19] x86/ftrace: Remove extra orig rax move Jiri Olsa
2021-06-05 11:10 ` [PATCH 02/19] x86/ftrace: Remove fault protection code in prepare_ftrace_return Jiri Olsa
2021-06-05 11:10 ` [PATCH 03/19] x86/ftrace: Make function graph use ftrace directly Jiri Olsa
2021-06-08 18:35 ` Andrii Nakryiko
2021-06-08 18:51 ` Jiri Olsa
2021-06-08 19:11 ` Steven Rostedt
2021-06-05 11:10 ` [PATCH 04/19] tracing: Add trampoline/graph selftest Jiri Olsa
2021-06-05 11:10 ` [PATCH 05/19] ftrace: Add ftrace_add_rec_direct function Jiri Olsa
2021-06-05 11:10 ` [PATCH 06/19] ftrace: Add multi direct register/unregister interface Jiri Olsa
2021-06-05 11:10 ` [PATCH 07/19] ftrace: Add multi direct modify interface Jiri Olsa
2021-06-05 11:10 ` [PATCH 08/19] ftrace/samples: Add multi direct interface test module Jiri Olsa
2021-06-05 11:10 ` [PATCH 09/19] bpf, x64: Allow to use caller address from stack Jiri Olsa
2021-06-07 3:07 ` Yonghong Song
2021-06-07 18:13 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 10/19] bpf: Allow to store caller's ip as argument Jiri Olsa
2021-06-07 3:21 ` Yonghong Song
2021-06-07 18:15 ` Jiri Olsa
2021-06-08 18:49 ` Andrii Nakryiko [this message]
2021-06-08 20:58 ` Jiri Olsa
2021-06-08 21:02 ` Andrii Nakryiko
2021-06-08 21:11 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 11/19] bpf: Add support to load multi func tracing program Jiri Olsa
2021-06-07 3:56 ` Yonghong Song
2021-06-07 18:18 ` Jiri Olsa
2021-06-07 19:35 ` Yonghong Song
2021-06-05 11:10 ` [PATCH 12/19] bpf: Add bpf_trampoline_alloc function Jiri Olsa
2021-06-05 11:10 ` [PATCH 13/19] bpf: Add support to link multi func tracing program Jiri Olsa
2021-06-07 5:36 ` Yonghong Song
2021-06-07 18:25 ` Jiri Olsa
2021-06-07 19:39 ` Yonghong Song
2021-06-08 15:42 ` Alexei Starovoitov
2021-06-08 18:17 ` Jiri Olsa
2021-06-08 18:49 ` Alexei Starovoitov
2021-06-08 21:07 ` Jiri Olsa
2021-06-08 23:05 ` Alexei Starovoitov
2021-06-09 5:08 ` Andrii Nakryiko
2021-06-09 13:42 ` Jiri Olsa
2021-06-09 13:33 ` Jiri Olsa
2021-06-09 5:18 ` Andrii Nakryiko
2021-06-09 13:53 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 14/19] libbpf: Add btf__find_by_pattern_kind function Jiri Olsa
2021-06-09 5:29 ` Andrii Nakryiko
2021-06-09 13:59 ` Jiri Olsa
2021-06-09 14:19 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 15/19] libbpf: Add support to link multi func tracing program Jiri Olsa
2021-06-07 5:49 ` Yonghong Song
2021-06-07 18:28 ` Jiri Olsa
2021-06-07 19:42 ` Yonghong Song
2021-06-07 20:11 ` Jiri Olsa
2021-06-09 5:34 ` Andrii Nakryiko
2021-06-09 14:17 ` Jiri Olsa
2021-06-10 17:05 ` Andrii Nakryiko
2021-06-10 20:35 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 16/19] selftests/bpf: Add fentry multi func test Jiri Olsa
2021-06-07 6:06 ` Yonghong Song
2021-06-07 18:42 ` Jiri Olsa
2021-06-09 5:40 ` Andrii Nakryiko
2021-06-09 14:29 ` Jiri Olsa
2021-06-10 17:00 ` Andrii Nakryiko
2021-06-10 20:28 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 17/19] selftests/bpf: Add fexit " Jiri Olsa
2021-06-05 11:10 ` [PATCH 18/19] selftests/bpf: Add fentry/fexit " Jiri Olsa
2021-06-09 5:41 ` Andrii Nakryiko
2021-06-09 14:29 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 19/19] selftests/bpf: Temporary fix for fentry_fexit_multi_test Jiri Olsa
2021-06-17 20:29 ` [RFCv3 00/19] x86/ftrace/bpf: Add batch support for direct/tracing attach Andrii Nakryiko
2021-06-19 8:33 ` Jiri Olsa
2021-06-19 16:19 ` Yonghong Song
2021-06-19 17:09 ` Jiri Olsa
2021-06-20 16:56 ` Yonghong Song
2021-06-20 17:47 ` Alexei Starovoitov
2021-06-21 6:46 ` Andrii Nakryiko
2021-06-21 6:50 ` Andrii Nakryiko
2021-07-06 20:26 ` Andrii Nakryiko
2021-07-07 15:19 ` Jiri Olsa
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