bpf: btf: Add BTF_FMODEL_SIGNED_ARG flag

s390x eBPF JIT needs to know whether a function return value is signed
and which function arguments are signed, in order to generate code
compliant with the s390x ABI.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230128000650.1516334-26-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 34551e4..c411c6b 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -899,8 +899,12 @@ enum bpf_cgroup_storage_type {
 /* The argument is a structure. */
 #define BTF_FMODEL_STRUCT_ARG          BIT(0)
 
+/* The argument is signed. */
+#define BTF_FMODEL_SIGNED_ARG          BIT(1)
+
 struct btf_func_model {
        u8 ret_size;
+       u8 ret_flags;
        u8 nr_args;
        u8 arg_size[MAX_BPF_FUNC_ARGS];
        u8 arg_flags[MAX_BPF_FUNC_ARGS];

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 5f628f3..e9b90d9 100644 (file)
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -236,6 +236,16 @@ static inline bool btf_type_is_small_int(const struct btf_type *t)
        return btf_type_is_int(t) && t->size <= sizeof(u64);
 }
 
+static inline u8 btf_int_encoding(const struct btf_type *t)
+{
+       return BTF_INT_ENCODING(*(u32 *)(t + 1));
+}
+
+static inline bool btf_type_is_signed_int(const struct btf_type *t)
+{
+       return btf_type_is_int(t) && (btf_int_encoding(t) & BTF_INT_SIGNED);
+}
+
 static inline bool btf_type_is_enum(const struct btf_type *t)
 {
        return BTF_INFO_KIND(t->info) == BTF_KIND_ENUM;
@@ -306,11 +316,6 @@ static inline u8 btf_int_offset(const struct btf_type *t)
        return BTF_INT_OFFSET(*(u32 *)(t + 1));
 }
 
-static inline u8 btf_int_encoding(const struct btf_type *t)
-{
-       return BTF_INT_ENCODING(*(u32 *)(t + 1));
-}
-
 static inline bool btf_type_is_scalar(const struct btf_type *t)
 {
        return btf_type_is_int(t) || btf_type_is_enum(t);

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 47b8cb9..1622a3b 100644 (file)
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6453,6 +6453,18 @@ static int __get_type_size(struct btf *btf, u32 btf_id,
        return -EINVAL;
 }
 
+static u8 __get_type_fmodel_flags(const struct btf_type *t)
+{
+       u8 flags = 0;
+
+       if (__btf_type_is_struct(t))
+               flags |= BTF_FMODEL_STRUCT_ARG;
+       if (btf_type_is_signed_int(t))
+               flags |= BTF_FMODEL_SIGNED_ARG;
+
+       return flags;
+}
+
 int btf_distill_func_proto(struct bpf_verifier_log *log,
                           struct btf *btf,
                           const struct btf_type *func,
@@ -6473,6 +6485,7 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
                        m->arg_flags[i] = 0;
                }
                m->ret_size = 8;
+               m->ret_flags = 0;
                m->nr_args = MAX_BPF_FUNC_REG_ARGS;
                return 0;
        }
@@ -6492,6 +6505,7 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
                return -EINVAL;
        }
        m->ret_size = ret;
+       m->ret_flags = __get_type_fmodel_flags(t);
 
        for (i = 0; i < nargs; i++) {
                if (i == nargs - 1 && args[i].type == 0) {
@@ -6516,7 +6530,7 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
                        return -EINVAL;
                }
                m->arg_size[i] = ret;
-               m->arg_flags[i] = __btf_type_is_struct(t) ? BTF_FMODEL_STRUCT_ARG : 0;
+               m->arg_flags[i] = __get_type_fmodel_flags(t);
        }
        m->nr_args = nargs;
        return 0;