On 2025/10/20 16:19, Jiri Olsa wrote:
> On Sat, Oct 18, 2025 at 10:21:22PM +0800, Menglong Dong wrote:
>
> SNIP
>
> > /* mov rax, qword ptr [rbp - rounded_stack_depth - 8] */
> > #define LOAD_TRAMP_TAIL_CALL_CNT_PTR(stack) \
> > __LOAD_TCC_PTR(-round_up(stack, 8) - 8)
> > @@ -3179,8 +3270,10 @@ static int __arch_prepare_bpf_trampoline(struct
> > bpf_tramp_image *im, void *rw_im
> > void *func_addr)
> > {
> > int i, ret, nr_regs = m->nr_args, stack_size = 0;
> > - int regs_off, nregs_off, ip_off, run_ctx_off, arg_stack_off, rbx_off;
> > + int regs_off, nregs_off, session_off, ip_off, run_ctx_off,
> > + arg_stack_off, rbx_off;
> > struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
> > + struct bpf_tramp_links *session = &tlinks[BPF_TRAMP_SESSION];
> > struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
> > struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
> > void *orig_call = func_addr;
> > @@ -3222,6 +3315,8 @@ static int __arch_prepare_bpf_trampoline(struct
> > bpf_tramp_image *im, void *rw_im
> > *
> > * RBP - nregs_off [ regs count ] always
> > *
> > + * RBP - session_off [ session flags ] tracing session
> > + *
> > * RBP - ip_off [ traced function ] BPF_TRAMP_F_IP_ARG flag
> > *
> > * RBP - rbx_off [ rbx value ] always
> > @@ -3246,6 +3341,8 @@ static int __arch_prepare_bpf_trampoline(struct
> > bpf_tramp_image *im, void *rw_im
> > /* regs count */
> > stack_size += 8;
> > nregs_off = stack_size;
> > + stack_size += 8;
> > + session_off = stack_size;
>
> should this depend on session->nr_links ?
Hmm...my mistake, it should. And this also break the bpf_get_func_ip(),
which I'll fix in the next version.
>
> jirka
>
> >
> > if (flags & BPF_TRAMP_F_IP_ARG)
> > stack_size += 8; /* room for IP address argument */
> > @@ -3345,6 +3442,13 @@ static int __arch_prepare_bpf_trampoline(struct
> > bpf_tramp_image *im, void *rw_im
> > return -EINVAL;
> > }
> >
> > + if (session->nr_links) {
> > + if (invoke_bpf_session_entry(m, &prog, session, regs_off,
> > + run_ctx_off, session_off,
> > + image, rw_image))
> > + return -EINVAL;
> > + }
> > +
> > if (fmod_ret->nr_links) {
> > branches = kcalloc(fmod_ret->nr_links, sizeof(u8 *),
> > GFP_KERNEL);
> > @@ -3409,6 +3513,15 @@ static int __arch_prepare_bpf_trampoline(struct
> > bpf_tramp_image *im, void *rw_im
> > }
> > }
> >
> > + if (session->nr_links) {
> > + if (invoke_bpf_session_exit(m, &prog, session, regs_off,
> > + run_ctx_off, session_off,
> > + image, rw_image)) {
> > + ret = -EINVAL;
> > + goto cleanup;
> > + }
> > + }
> > +
> > if (flags & BPF_TRAMP_F_RESTORE_REGS)
> > restore_regs(m, &prog, regs_off);
> >
>
>
