From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Thu, 28 Oct 2021 12:04:54 +0530
Subject: bpf: Add bpf_kallsyms_lookup_name helper
Patch-mainline: v5.16-rc1
Git-commit: d6aef08a872b9e23eecc92d0e92393473b13c497
References: jsc#PED-1377
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.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211028063501.2239335-2-memxor@gmail.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.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(+)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2114,6 +2114,7 @@ extern const struct bpf_func_proto bpf_f
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);
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4923,6 +4923,21 @@ union bpf_attr {
* Dynamically cast a *sk* pointer to a *unix_sock* pointer.
* Return
* *sk* if casting is valid, or **NULL** otherwise.
+ *
+ * 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), \
@@ -5104,6 +5119,7 @@ union bpf_attr {
FN(get_branch_snapshot), \
FN(trace_vprintk), \
FN(skc_to_unix_sock), \
+ FN(kallsyms_lookup_name), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4784,6 +4784,31 @@ static const struct bpf_func_proto bpf_s
.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)
{
@@ -4794,6 +4819,8 @@ syscall_prog_func_proto(enum bpf_func_id
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);
}
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4926,6 +4926,21 @@ union bpf_attr {
* Dynamically cast a *sk* pointer to a *unix_sock* pointer.
* Return
* *sk* if casting is valid, or **NULL** otherwise.
+ *
+ * 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), \
@@ -5107,6 +5122,7 @@ union bpf_attr {
FN(get_branch_snapshot), \
FN(trace_vprintk), \
FN(skc_to_unix_sock), \
+ FN(kallsyms_lookup_name), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper