[PATCH v14 net-next 05/11] bpf: handle pseudo BPF_CALL insn
in native eBPF programs userspace is using pseudo BPF_CALL instructions
which encode one of 'enum bpf_func_id' inside insn->imm field.
Verifier checks that program using correct function arguments to given func_id.
If all checks passed, kernel needs to fixup BPF_CALL->imm fields by
replacing func_id with in-kernel function pointer.
eBPF interpreter just calls the function.
In-kernel eBPF users continue to use generic BPF_CALL.
Signed-off-by: Alexei Starovoitov
---
kernel/bpf/syscall.c | 37 +
1 file changed, 37 insertions(+)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0afb4eaa1887..b513659d120f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -357,6 +357,40 @@ void bpf_register_prog_type(struct bpf_prog_type_list *tl)
list_add(>list_node, _prog_types);
}
+/* fixup insn->imm field of bpf_call instructions:
+ * if (insn->imm == BPF_FUNC_map_lookup_elem)
+ * insn->imm = bpf_map_lookup_elem - __bpf_call_base;
+ * else if (insn->imm == BPF_FUNC_map_update_elem)
+ * insn->imm = bpf_map_update_elem - __bpf_call_base;
+ * else ...
+ *
+ * this function is called after eBPF program passed verification
+ */
+static void fixup_bpf_calls(struct bpf_prog *prog)
+{
+ const struct bpf_func_proto *fn;
+ int i;
+
+ for (i = 0; i < prog->len; i++) {
+ struct bpf_insn *insn = >insnsi[i];
+
+ if (insn->code == (BPF_JMP | BPF_CALL)) {
+ /* we reach here when program has bpf_call instructions
+* and it passed bpf_check(), means that
+* ops->get_func_proto must have been supplied, check it
+*/
+ BUG_ON(!prog->aux->ops->get_func_proto);
+
+ fn = prog->aux->ops->get_func_proto(insn->imm);
+ /* all functions that have prototype and verifier
allowed
+* programs to call them, must be real in-kernel
functions
+*/
+ BUG_ON(!fn->func);
+ insn->imm = fn->func - __bpf_call_base;
+ }
+ }
+}
+
/* drop refcnt on maps used by eBPF program and free auxilary data */
static void free_used_maps(struct bpf_prog_aux *aux)
{
@@ -478,6 +512,9 @@ static int bpf_prog_load(union bpf_attr *attr)
if (err < 0)
goto free_used_maps;
+ /* fixup BPF_CALL->imm field */
+ fixup_bpf_calls(prog);
+
/* eBPF program is ready to be JITed */
bpf_prog_select_runtime(prog);
--
1.7.9.5
--
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[PATCH v14 net-next 05/11] bpf: handle pseudo BPF_CALL insn
in native eBPF programs userspace is using pseudo BPF_CALL instructions
which encode one of 'enum bpf_func_id' inside insn-imm field.
Verifier checks that program using correct function arguments to given func_id.
If all checks passed, kernel needs to fixup BPF_CALL-imm fields by
replacing func_id with in-kernel function pointer.
eBPF interpreter just calls the function.
In-kernel eBPF users continue to use generic BPF_CALL.
Signed-off-by: Alexei Starovoitov a...@plumgrid.com
---
kernel/bpf/syscall.c | 37 +
1 file changed, 37 insertions(+)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0afb4eaa1887..b513659d120f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -357,6 +357,40 @@ void bpf_register_prog_type(struct bpf_prog_type_list *tl)
list_add(tl-list_node, bpf_prog_types);
}
+/* fixup insn-imm field of bpf_call instructions:
+ * if (insn-imm == BPF_FUNC_map_lookup_elem)
+ * insn-imm = bpf_map_lookup_elem - __bpf_call_base;
+ * else if (insn-imm == BPF_FUNC_map_update_elem)
+ * insn-imm = bpf_map_update_elem - __bpf_call_base;
+ * else ...
+ *
+ * this function is called after eBPF program passed verification
+ */
+static void fixup_bpf_calls(struct bpf_prog *prog)
+{
+ const struct bpf_func_proto *fn;
+ int i;
+
+ for (i = 0; i prog-len; i++) {
+ struct bpf_insn *insn = prog-insnsi[i];
+
+ if (insn-code == (BPF_JMP | BPF_CALL)) {
+ /* we reach here when program has bpf_call instructions
+* and it passed bpf_check(), means that
+* ops-get_func_proto must have been supplied, check it
+*/
+ BUG_ON(!prog-aux-ops-get_func_proto);
+
+ fn = prog-aux-ops-get_func_proto(insn-imm);
+ /* all functions that have prototype and verifier
allowed
+* programs to call them, must be real in-kernel
functions
+*/
+ BUG_ON(!fn-func);
+ insn-imm = fn-func - __bpf_call_base;
+ }
+ }
+}
+
/* drop refcnt on maps used by eBPF program and free auxilary data */
static void free_used_maps(struct bpf_prog_aux *aux)
{
@@ -478,6 +512,9 @@ static int bpf_prog_load(union bpf_attr *attr)
if (err 0)
goto free_used_maps;
+ /* fixup BPF_CALL-imm field */
+ fixup_bpf_calls(prog);
+
/* eBPF program is ready to be JITed */
bpf_prog_select_runtime(prog);
--
1.7.9.5
--
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the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
