From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: "Song Liu" <songliubraving@fb.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Martin KaFai Lau" <kafai@fb.com>, "Yonghong Song" <yhs@fb.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
netdev@vger.kernel.org
Subject: [PATCH bpf-next v4 1/8] bpf: Add bpf_kallsyms_lookup_name helper
Date: Thu, 21 Oct 2021 00:45:19 +0530 [thread overview]
Message-ID: <20211020191526.2306852-2-memxor@gmail.com> (raw)
In-Reply-To: <20211020191526.2306852-1-memxor@gmail.com>
This helper allows us to get the address of a kernel symbol from inside
a BPF_PROG_TYPE_SYSCALL prog (used by gen_loader), so that we can
relocate typeless ksym vars.
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 16 ++++++++++++++++
kernel/bpf/syscall.c | 27 +++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 16 ++++++++++++++++
4 files changed, 60 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d604c8251d88..17206aae329d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2107,6 +2107,7 @@ extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
+extern const struct bpf_func_proto bpf_kallsyms_lookup_name_proto;
const struct bpf_func_proto *tracing_prog_func_proto(
enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 6fc59d61937a..03da5511e3bf 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4909,6 +4909,21 @@ union bpf_attr {
* Return
* The number of bytes written to the buffer, or a negative error
* in case of failure.
+ *
+ * long bpf_kallsyms_lookup_name(const char *name, int name_sz, int flags, u64 *res)
+ * Description
+ * Get the address of a kernel symbol, returned in *res*. *res* is
+ * set to 0 if the symbol is not found.
+ * Return
+ * On success, zero. On error, a negative value.
+ *
+ * **-EINVAL** if *flags* is not zero.
+ *
+ * **-EINVAL** if string *name* is not the same size as *name_sz*.
+ *
+ * **-ENOENT** if symbol is not found.
+ *
+ * **-EPERM** if caller does not have permission to obtain kernel address.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5089,6 +5104,7 @@ union bpf_attr {
FN(task_pt_regs), \
FN(get_branch_snapshot), \
FN(trace_vprintk), \
+ FN(kallsyms_lookup_name), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e50c0bfdb7d..95214e536db6 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4753,6 +4753,31 @@ static const struct bpf_func_proto bpf_sys_close_proto = {
.arg1_type = ARG_ANYTHING,
};
+BPF_CALL_4(bpf_kallsyms_lookup_name, const char *, name, int, name_sz, int, flags, u64 *, res)
+{
+ if (flags)
+ return -EINVAL;
+
+ if (name_sz <= 1 || name[name_sz - 1])
+ return -EINVAL;
+
+ if (!bpf_dump_raw_ok(current_cred()))
+ return -EPERM;
+
+ *res = kallsyms_lookup_name(name);
+ return *res ? 0 : -ENOENT;
+}
+
+const struct bpf_func_proto bpf_kallsyms_lookup_name_proto = {
+ .func = bpf_kallsyms_lookup_name,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_CONST_SIZE,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_PTR_TO_LONG,
+};
+
static const struct bpf_func_proto *
syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
@@ -4763,6 +4788,8 @@ syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_btf_find_by_name_kind_proto;
case BPF_FUNC_sys_close:
return &bpf_sys_close_proto;
+ case BPF_FUNC_kallsyms_lookup_name:
+ return &bpf_kallsyms_lookup_name_proto;
default:
return tracing_prog_func_proto(func_id, prog);
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 6fc59d61937a..03da5511e3bf 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4909,6 +4909,21 @@ union bpf_attr {
* Return
* The number of bytes written to the buffer, or a negative error
* in case of failure.
+ *
+ * long bpf_kallsyms_lookup_name(const char *name, int name_sz, int flags, u64 *res)
+ * Description
+ * Get the address of a kernel symbol, returned in *res*. *res* is
+ * set to 0 if the symbol is not found.
+ * Return
+ * On success, zero. On error, a negative value.
+ *
+ * **-EINVAL** if *flags* is not zero.
+ *
+ * **-EINVAL** if string *name* is not the same size as *name_sz*.
+ *
+ * **-ENOENT** if symbol is not found.
+ *
+ * **-EPERM** if caller does not have permission to obtain kernel address.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5089,6 +5104,7 @@ union bpf_attr {
FN(task_pt_regs), \
FN(get_branch_snapshot), \
FN(trace_vprintk), \
+ FN(kallsyms_lookup_name), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.33.1
next prev parent reply other threads:[~2021-10-20 19:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-20 19:15 [PATCH bpf-next v4 0/8] Typeless/weak ksym for gen_loader + misc fixups Kumar Kartikeya Dwivedi
2021-10-20 19:15 ` Kumar Kartikeya Dwivedi [this message]
2021-10-20 19:15 ` [PATCH bpf-next v4 2/8] libbpf: Add typeless ksym support to gen_loader Kumar Kartikeya Dwivedi
2021-10-20 19:15 ` [PATCH bpf-next v4 3/8] libbpf: Add weak " Kumar Kartikeya Dwivedi
2021-10-20 19:15 ` [PATCH bpf-next v4 4/8] libbpf: Ensure that BPF syscall fds are never 0, 1, or 2 Kumar Kartikeya Dwivedi
2021-10-20 22:09 ` Andrii Nakryiko
2021-10-20 22:33 ` Kumar Kartikeya Dwivedi
2021-10-20 23:02 ` Andrii Nakryiko
2021-10-20 19:15 ` [PATCH bpf-next v4 5/8] libbpf: Use O_CLOEXEC uniformly when opening fds Kumar Kartikeya Dwivedi
2021-10-20 19:15 ` [PATCH bpf-next v4 6/8] selftests/bpf: Add weak/typeless ksym test for light skeleton Kumar Kartikeya Dwivedi
2021-10-20 22:17 ` Andrii Nakryiko
2021-10-20 22:37 ` Kumar Kartikeya Dwivedi
2021-10-20 22:43 ` Andrii Nakryiko
2021-10-20 19:15 ` [PATCH bpf-next v4 7/8] selftests/bpf: Fix fd cleanup in sk_lookup test Kumar Kartikeya Dwivedi
2021-10-20 22:19 ` Andrii Nakryiko
2021-10-20 19:15 ` [PATCH bpf-next v4 8/8] selftests/bpf: Fix memory leak in test_ima Kumar Kartikeya Dwivedi
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