On Thu, Aug 11, 2022 at 10:24:35PM -0700, Yonghong Song wrote:
SNIP
> }
>
> static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
> @@ -2020,6 +2081,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
> struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
> struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
> + int struct_val_off, extra_nregs = 0;
> u8 **branches = NULL;
> u8 *prog;
> bool save_ret;
> @@ -2028,6 +2090,20 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> if (nr_args > 6)
> return -ENOTSUPP;
>
> + for (i = 0; i < MAX_BPF_FUNC_ARGS; i++) {
> + if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) {
> + /* Only support up to 16 bytes struct which should keep
> + * values in registers.
> + */
it seems that if the struct contains 'double' field, it's passed in
SSE register, which we don't support is save/restore
we should probably check struct's BTF in btf_distill_func_proto and
fail if we found anything else than regular regs types?
> + if (m->arg_size[i] > 16)
> + return -ENOTSUPP;
> +
> + extra_nregs += (m->arg_size[i] + 7) / 8 - 1;
> + }
> + }
> + if (nr_args + extra_nregs > 6)
should this value be minus the number of actually found struct arguments?
> + return -ENOTSUPP;
> +
> /* Generated trampoline stack layout:
> *
> * RBP + 8 [ return address ]
> @@ -2066,6 +2142,13 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> stack_size += (sizeof(struct bpf_tramp_run_ctx) + 7) & ~0x7;
> run_ctx_off = stack_size;
>
> + /* For structure argument */
> + for (i = 0; i < MAX_BPF_FUNC_ARGS; i++) {
> + if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG)
> + stack_size += (m->arg_size[i] + 7) & ~0x7;
> + }
> + struct_val_off = stack_size;
could you please update the 'Generated trampoline stack layout' table
above with this offset
thanks,
jirka
> +
> if (flags & BPF_TRAMP_F_SKIP_FRAME) {
> /* skip patched call instruction and point orig_call to actual
> * body of the kernel function.
> @@ -2101,7 +2184,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -ip_off);
> }
>
> - save_regs(m, &prog, nr_args, regs_off);
> + save_regs(m, &prog, nr_args, regs_off, struct_val_off);
>
> if (flags & BPF_TRAMP_F_CALL_ORIG) {
> /* arg1: mov rdi, im */
> @@ -2131,7 +2214,7 @@ 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, regs_off);
> + restore_regs(m, &prog, nr_args, regs_off, struct_val_off);
>
> if (flags & BPF_TRAMP_F_ORIG_STACK) {
> emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8);
> @@ -2172,7 +2255,7 @@ 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, regs_off);
> + restore_regs(m, &prog, nr_args, regs_off, struct_val_off);
>
> /* 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
> --
> 2.30.2
>
