Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Maninder Singh <maninder1.s@samsung.com>
To:     ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com,
        andrii@kernel.org, martin.lau@linux.dev, song@kernel.org,
        yhs@fb.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com,
        jolsa@kernel.org, thunder.leizhen@huawei.com, mcgrof@kernel.org,
        boqun.feng@gmail.com, vincenzopalazzodev@gmail.com,
        ojeda@kernel.org, jgross@suse.com, brauner@kernel.org,
        michael.christie@oracle.com, samitolvanen@google.com,
        glider@google.com, peterz@infradead.org, keescook@chromium.org,
        stephen.s.brennan@oracle.com, alan.maguire@oracle.com
Cc:     linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
        Maninder Singh <maninder1.s@samsung.com>,
        Onkarnath <onkarnath.1@samsung.com>
Subject: [PATCH 1/1] kallsyms: add kallsyms_show_value defination in all
 cases
Date:   Wed, 31 May 2023 09:56:00 +0530
Message-Id: <20230531042600.819453-1-maninder1.s@samsung.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain; charset="utf-8"
CMS-TYPE: 105P
References: <CGME20230531042611epcas5p1f46c41ccec93ce04eef4fe861242ac19@epcas5p1.samsung.com>
Precedence: bulk

kallsyms_show_value return false if KALLSYMS is disabled,
but its usage is done by module.c also.
Thus when KALLSYMS is disabled, system will not print module
load address:

Earlier:
=======
/ # insmod  test.ko
/ # lsmod
test 12288 0 - Live 0x0000000000000000 (O)  // No Module Load address
/ #

With change:
==========
/ # insmod test.ko
/ # lsmod
test 12288 0 - Live 0xffff800000fc0000 (O)  // Module address
/ # cat /proc/modules
test 12288 0 - Live 0xffff800000fc0000 (O)

New file knosyms.c is added (name suggested by Kees Cook),
which includes common defination irrespective of CONFIG_KALLSYMS.

BPF code has high dependency on kallsyms,
so bpf_dump_raw_ok check is not changed.

Co-developed-by: Onkarnath <onkarnath.1@samsung.com>
Signed-off-by: Onkarnath <onkarnath.1@samsung.com>
Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
---
BPF logic is not changed and seems kprobe will work, rest kprobe
maintainer can comment if it can cause issue. Tested for modules data.

earlier conversations:(then it has dependancy on other change, but that
was stashed from linux-next, now it can be pushed)
https://lkml.org/lkml/2022/5/11/212
https://lkml.org/lkml/2022/4/13/47

 include/linux/filter.h   |  7 ++++++
 include/linux/kallsyms.h | 10 +++-----
 kernel/Makefile          |  2 +-
 kernel/kallsyms.c        | 35 ---------------------------
 kernel/knosyms.c         | 52 ++++++++++++++++++++++++++++++++++++++++
 5 files changed, 63 insertions(+), 43 deletions(-)
 create mode 100644 kernel/knosyms.c

diff --git a/include/linux/filter.h b/include/linux/filter.h
index bbce89937fde..f67010e7c6fe 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -923,6 +923,7 @@ bool bpf_jit_supports_kfunc_call(void);
 bool bpf_jit_supports_far_kfunc_call(void);
 bool bpf_helper_changes_pkt_data(void *func);
 
+#ifdef CONFIG_KALLSYMS
 static inline bool bpf_dump_raw_ok(const struct cred *cred)
 {
 	/* Reconstruction of call-sites is dependent on kallsyms,
@@ -930,6 +931,12 @@ static inline bool bpf_dump_raw_ok(const struct cred *cred)
 	 */
 	return kallsyms_show_value(cred);
 }
+#else
+static inline bool bpf_dump_raw_ok(const struct cred *cred)
+{
+	return false;
+}
+#endif
 
 struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
 				       const struct bpf_insn *patch, u32 len);
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index fe3c9993b5bf..3f3559ba0c56 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -24,6 +24,9 @@
 struct cred;
 struct module;
 
+/* How and when do we show kallsyms values? */
+extern bool kallsyms_show_value(const struct cred *cred);
+
 static inline int is_kernel_text(unsigned long addr)
 {
 	if (__is_kernel_text(addr))
@@ -95,8 +98,6 @@ extern int sprint_backtrace_build_id(char *buffer, unsigned long address);
 int lookup_symbol_name(unsigned long addr, char *symname);
 int lookup_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name);
 
-/* How and when do we show kallsyms values? */
-extern bool kallsyms_show_value(const struct cred *cred);
 
 #else /* !CONFIG_KALLSYMS */
 
@@ -160,11 +161,6 @@ static inline int lookup_symbol_attrs(unsigned long addr, unsigned long *size, u
 	return -ERANGE;
 }
 
-static inline bool kallsyms_show_value(const struct cred *cred)
-{
-	return false;
-}
-
 static inline int kallsyms_on_each_symbol(int (*fn)(void *, const char *, unsigned long),
 					  void *data)
 {
diff --git a/kernel/Makefile b/kernel/Makefile
index b69c95315480..76efc634b1a4 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -10,7 +10,7 @@ obj-y     = fork.o exec_domain.o panic.o \
 	    extable.o params.o \
 	    kthread.o sys_ni.o nsproxy.o \
 	    notifier.o ksysfs.o cred.o reboot.o \
-	    async.o range.o smpboot.o ucount.o regset.o
+	    async.o range.o smpboot.o ucount.o regset.o knosyms.o
 
 obj-$(CONFIG_USERMODE_DRIVER) += usermode_driver.o
 obj-$(CONFIG_MULTIUSER) += groups.o
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 77747391f49b..1dcb7051f852 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -961,41 +961,6 @@ late_initcall(bpf_ksym_iter_register);
 
 #endif /* CONFIG_BPF_SYSCALL */
 
-static inline int kallsyms_for_perf(void)
-{
-#ifdef CONFIG_PERF_EVENTS
-	extern int sysctl_perf_event_paranoid;
-	if (sysctl_perf_event_paranoid <= 1)
-		return 1;
-#endif
-	return 0;
-}
-
-/*
- * We show kallsyms information even to normal users if we've enabled
- * kernel profiling and are explicitly not paranoid (so kptr_restrict
- * is clear, and sysctl_perf_event_paranoid isn't set).
- *
- * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
- * block even that).
- */
-bool kallsyms_show_value(const struct cred *cred)
-{
-	switch (kptr_restrict) {
-	case 0:
-		if (kallsyms_for_perf())
-			return true;
-		fallthrough;
-	case 1:
-		if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
-				     CAP_OPT_NOAUDIT) == 0)
-			return true;
-		fallthrough;
-	default:
-		return false;
-	}
-}
-
 static int kallsyms_open(struct inode *inode, struct file *file)
 {
 	/*
diff --git a/kernel/knosyms.c b/kernel/knosyms.c
new file mode 100644
index 000000000000..f2c8755e22e7
--- /dev/null
+++ b/kernel/knosyms.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023 Samsung Electronics Co., Ltd
+ *
+ * Author:
+ *	Maninder singh <maninder1.s@samsung.com>
+ *	Onkarnath <onkarnath.1@samsung.com>
+ *
+ * A split of kernel/kallsyms.c
+ * to contain few generic function definations independent of config KALLSYMS
+ * or defined under KALLSYMS disabled.
+ */
+
+#include <linux/kallsyms.h>
+#include <linux/security.h>
+
+static inline int kallsyms_for_perf(void)
+{
+#ifdef CONFIG_PERF_EVENTS
+	extern int sysctl_perf_event_paranoid;
+
+	if (sysctl_perf_event_paranoid <= 1)
+		return 1;
+#endif
+	return 0;
+}
+
+/*
+ * We show kallsyms information even to normal users if we've enabled
+ * kernel profiling and are explicitly not paranoid (so kptr_restrict
+ * is clear, and sysctl_perf_event_paranoid isn't set).
+ *
+ * Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
+ * block even that).
+ */
+bool kallsyms_show_value(const struct cred *cred)
+{
+	switch (kptr_restrict) {
+	case 0:
+		if (kallsyms_for_perf())
+			return true;
+		fallthrough;
+	case 1:
+		if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
+				     CAP_OPT_NOAUDIT) == 0)
+			return true;
+		fallthrough;
+	default:
+		return false;
+	}
+}
+
-- 
2.17.1