}
static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
- struct bpf_prog *p, int stack_size, bool mod_ret)
+ struct bpf_prog *p, int stack_size, bool save_ret)
{
u8 *prog = *pprog;
u8 *jmp_insn;
if (emit_call(&prog, p->bpf_func, prog))
return -EINVAL;
- /* BPF_TRAMP_MODIFY_RETURN trampolines can modify the return
+ /*
+ * BPF_TRAMP_MODIFY_RETURN trampolines can modify the return
* of the previous call which is then passed on the stack to
* the next BPF program.
+ *
+ * BPF_TRAMP_FENTRY trampoline may need to return the return
+ * value of BPF_PROG_TYPE_STRUCT_OPS prog.
*/
- if (mod_ret)
+ if (save_ret)
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
/* replace 2 nops with JE insn, since jmp target is known */
}
static int invoke_bpf(const struct btf_func_model *m, u8 **pprog,
- struct bpf_tramp_progs *tp, int stack_size)
+ struct bpf_tramp_progs *tp, int stack_size,
+ bool save_ret)
{
int i;
u8 *prog = *pprog;
for (i = 0; i < tp->nr_progs; i++) {
- if (invoke_bpf_prog(m, &prog, tp->progs[i], stack_size, false))
+ if (invoke_bpf_prog(m, &prog, tp->progs[i], stack_size,
+ save_ret))
return -EINVAL;
}
*pprog = prog;
return 0;
}
+static bool is_valid_bpf_tramp_flags(unsigned int flags)
+{
+ if ((flags & BPF_TRAMP_F_RESTORE_REGS) &&
+ (flags & BPF_TRAMP_F_SKIP_FRAME))
+ return false;
+
+ /*
+ * BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops,
+ * and it must be used alone.
+ */
+ if ((flags & BPF_TRAMP_F_RET_FENTRY_RET) &&
+ (flags & ~BPF_TRAMP_F_RET_FENTRY_RET))
+ return false;
+
+ return true;
+}
+
/* Example:
* __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev);
* its 'struct btf_func_model' will be nr_args=2
struct bpf_tramp_progs *fmod_ret = &tprogs[BPF_TRAMP_MODIFY_RETURN];
u8 **branches = NULL;
u8 *prog;
+ bool save_ret;
/* x86-64 supports up to 6 arguments. 7+ can be added in the future */
if (nr_args > 6)
return -ENOTSUPP;
- if ((flags & BPF_TRAMP_F_RESTORE_REGS) &&
- (flags & BPF_TRAMP_F_SKIP_FRAME))
+ if (!is_valid_bpf_tramp_flags(flags))
return -EINVAL;
- if (flags & BPF_TRAMP_F_CALL_ORIG)
- stack_size += 8; /* room for return value of orig_call */
+ /* room for return value of orig_call or fentry prog */
+ save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET);
+ if (save_ret)
+ stack_size += 8;
if (flags & BPF_TRAMP_F_IP_ARG)
stack_size += 8; /* room for IP address argument */
}
if (fentry->nr_progs)
- if (invoke_bpf(m, &prog, fentry, stack_size))
+ if (invoke_bpf(m, &prog, fentry, stack_size,
+ flags & BPF_TRAMP_F_RET_FENTRY_RET))
return -EINVAL;
if (fmod_ret->nr_progs) {
}
if (fexit->nr_progs)
- if (invoke_bpf(m, &prog, fexit, stack_size)) {
+ if (invoke_bpf(m, &prog, fexit, stack_size, false)) {
ret = -EINVAL;
goto cleanup;
}
ret = -EINVAL;
goto cleanup;
}
- /* restore original return value back into RAX */
- emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8);
}
+ /* restore return value of orig_call or fentry prog back into RAX */
+ if (save_ret)
+ emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8);
EMIT1(0x5B); /* pop rbx */
EMIT1(0xC9); /* leave */
const struct btf_type *mtype, *ptype;
struct bpf_prog *prog;
u32 moff;
+ u32 flags;
moff = btf_member_bit_offset(t, member) / 8;
ptype = btf_type_resolve_ptr(btf_vmlinux, member->type, NULL);
tprogs[BPF_TRAMP_FENTRY].progs[0] = prog;
tprogs[BPF_TRAMP_FENTRY].nr_progs = 1;
+ flags = st_ops->func_models[i].ret_size > 0 ?
+ BPF_TRAMP_F_RET_FENTRY_RET : 0;
err = arch_prepare_bpf_trampoline(NULL, image,
st_map->image + PAGE_SIZE,
- &st_ops->func_models[i], 0,
- tprogs, NULL);
+ &st_ops->func_models[i],
+ flags, tprogs, NULL);
if (err < 0)
goto reset_unlock;