linux-kernel - [PATCH v3 1/3] kallsyms: move kallsyms_show

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Message-Id: <20230605040731.13828-1-maninder1.s@samsung.com>
Date:   Mon,  5 Jun 2023 09:37:29 +0530
From:   Maninder Singh <maninder1.s@...sung.com>
To:     ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com,
        jolsa@...nel.org, thunder.leizhen@...wei.com, mcgrof@...nel.org,
        boqun.feng@...il.com, vincenzopalazzodev@...il.com,
        ojeda@...nel.org, jgross@...e.com, brauner@...nel.org,
        michael.christie@...cle.com, samitolvanen@...gle.com,
        glider@...gle.com, peterz@...radead.org, keescook@...omium.org,
        stephen.s.brennan@...cle.com, alan.maguire@...cle.com,
        pmladek@...e.com
Cc:     linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        Maninder Singh <maninder1.s@...sung.com>,
        Onkarnath <onkarnath.1@...sung.com>
Subject: [PATCH v3 1/3] kallsyms: move kallsyms_show_value() out of
 kallsyms.c

function kallsyms_show_value() is used by other parts
like modules_open(), kprobes_read() etc. which can work in case of
!KALLSYMS also.

e.g. as of now lsmod do not show module address if KALLSYMS is disabled.
since kallsyms_show_value() defination is not present, it returns false
in !KALLSYMS.

/ # lsmod
test 12288 0 - Live 0x0000000000000000 (O)

So kallsyms_show_value() can be made generic
without dependency on KALLSYMS.

Thus moving out function to a new file knosyms.c.

With this patch code is just moved to new file
and no functional change.

Next patch will enable defination of function for all cases.

Co-developed-by: Onkarnath <onkarnath.1@...sung.com>
Signed-off-by: Onkarnath <onkarnath.1@...sung.com>
Signed-off-by: Maninder Singh <maninder1.s@...sung.com>
---
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
v1 -> v2: separate out bpf and kallsyms change
v2 -> v3: make kallsym changes in2 patches, non functional and
functional change

 kernel/Makefile   |  2 +-
 kernel/kallsyms.c | 35 ----------------------------------
 kernel/knosyms.c  | 48 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 36 deletions(-)
 create mode 100644 kernel/knosyms.c

diff --git a/kernel/Makefile b/kernel/Makefile
index f9e3fd9195d9..918d3e9b14bc 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 8193e947aa10..0f82c3d5a57d 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -907,41 +907,6 @@ 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..9e2c72a89ea5
--- /dev/null
+++ b/kernel/knosyms.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023 Samsung Electronics Co., Ltd
+ *
+ * A split of kernel/kallsyms.c
+ * It will contain few generic function definations independent of config KALLSYMS.
+ */
+
+#include <linux/kallsyms.h>
+#include <linux/security.h>
+
+#ifdef CONFIG_KALLSYMS
+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;
+	}
+}
+#endif
-- 
2.17.1