linux-kernel - [PATCH 1/1] kallsyms: add kallsyms_show

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Date:   Wed, 13 Apr 2022 11:23:05 +0530
From:   Maninder Singh <maninder1.s@...sung.com>
To:     mcgrof@...nel.org, pmladek@...e.com, rostedt@...dmis.org,
        senozhatsky@...omium.org, andriy.shevchenko@...ux.intel.com,
        akpm@...ux-foundation.org, wangkefeng.wang@...wei.com,
        wedsonaf@...gle.com, boqun.feng@...il.com,
        christophe.leroy@...roup.eu
Cc:     swboyd@...omium.org, ojeda@...nel.org, ast@...nel.org,
        gary@...yguo.net, mbenes@...e.cz, ndesaulniers@...gle.com,
        void@...ifault.com, jolsa@...nel.org, linux-kernel@...r.kernel.org,
        v.narang@...sung.com, Maninder Singh <maninder1.s@...sung.com>,
        Onkarnath <onkarnath.1@...sung.com>
Subject: [PATCH 1/1] kallsyms: add kallsyms_show_value definition in all
 cases

kallsyms_show_value return false if KALLSYMS is disabled,
but it's used in module.c also.
Thus when KALLSYMS is disabled, system will not print module
load address:

/ # insmod crash.ko
/ # lsmod
crash 12288 0 - Live 0x0000000000000000 (O)

After change (making definition generic)
============
/ # lsmod
crash 12288 0 - Live 0xffff800000ec0000 (O)
/ # cat /proc/modules
crash 12288 0 - Live 0xffff800000ec0000 (O)
/ #

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>
---
 include/linux/kallsyms.h | 11 +++--------
 kernel/kallsyms.c        | 35 -----------------------------------
 lib/vsprintf.c           | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 43 deletions(-)

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index e5ad6e31697d..efabb8c18492 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))
@@ -93,9 +96,6 @@ 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 */
 
 static inline unsigned long kallsyms_lookup_name(const char *name)
@@ -158,11 +158,6 @@ 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;
-}
-
 #endif /*CONFIG_KALLSYMS*/
 
 static inline void print_ip_sym(const char *loglvl, unsigned long ip)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index e8d2262ef2d2..71ef15ba20c7 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -818,41 +818,6 @@ static const struct seq_operations kallsyms_op = {
 	.show = s_show
 };
 
-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/lib/vsprintf.c b/lib/vsprintf.c
index 49ef55ffabd7..4bc96a4f3a00 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -870,6 +870,42 @@ static char *default_pointer(char *buf, char *end, const void *ptr,
 
 int kptr_restrict __read_mostly;
 
+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 noinline_for_stack
 char *restricted_pointer(char *buf, char *end, const void *ptr,
 			 struct printf_spec spec)
-- 
2.17.1