[PATCH v5 1/2] kallsyms: move kallsyms_show_value() out of kallsyms.c

[PATCH v5 1/2] kallsyms: move kallsyms_show_value() out of kallsyms.c

[Maninder Singh]

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 ksyms_common.c.

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

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>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
---
earlier conversations:(then it has dependancy on other change, but that
was stashed from linux-next, now it can be pushed)
https://lore.kernel.org/lkml/202205111525.92B1C597@keescook/T/
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
v3 -> v4: patch order changed, file name changed form knosyms -> ksyms_common
and copyright header modified.
v4 -> v5: license changed to kallsyms.c file, and bpf changes are
dropped as confirmed from BPF side:
https://lore.kernel.org/lkml/CAEf4Bzb4B9FxMnf3t81D22FWkciLOvwDPLY0BbEPGGe7R5QPrg@mail.gmail.com/T/

 kernel/Makefile       |  2 +-
 kernel/kallsyms.c     | 35 ---------------------------------
 kernel/ksyms_common.c | 45 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 36 deletions(-)
 create mode 100644 kernel/ksyms_common.c

diff --git a/kernel/Makefile b/kernel/Makefile
index f9e3fd9195d9..3947122d618b 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 ksyms_common.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/ksyms_common.c b/kernel/ksyms_common.c
new file mode 100644
index 000000000000..3840fa1c9c86
--- /dev/null
+++ b/kernel/ksyms_common.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ksyms_common.c: A split of kernel/kallsyms.c
+ * Contains a 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

[PATCH v5 2/2] kallsyms: make kallsyms_show_value() as generic function

[Maninder Singh]

This change makes function kallsyms_show_value() as
generic function without dependency on CONFIG_KALLSYMS.

Now module address will be displayed with lsmod and /proc/modules.

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)

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>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 include/linux/kallsyms.h | 11 +++--------
 kernel/ksyms_common.c    |  2 --
 2 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index 1037f4957caa..c3f075e8f60c 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -65,6 +65,9 @@ static inline void *dereference_symbol_descriptor(void *ptr)
 	return ptr;
 }
 
+/* How and when do we show kallsyms values? */
+extern bool kallsyms_show_value(const struct cred *cred);
+
 #ifdef CONFIG_KALLSYMS
 unsigned long kallsyms_sym_address(int idx);
 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, unsigned long),
@@ -94,9 +97,6 @@ extern int sprint_backtrace_build_id(char *buffer, unsigned long address);
 
 int lookup_symbol_name(unsigned long addr, char *symname);
 
-/* 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)
@@ -154,11 +154,6 @@ static inline int lookup_symbol_name(unsigned long addr, char *symname)
 	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/ksyms_common.c b/kernel/ksyms_common.c
index 3840fa1c9c86..cf1a73cbf2f6 100644
--- a/kernel/ksyms_common.c
+++ b/kernel/ksyms_common.c
@@ -6,7 +6,6 @@
 #include <linux/kallsyms.h>
 #include <linux/security.h>
 
-#ifdef CONFIG_KALLSYMS
 static inline int kallsyms_for_perf(void)
 {
 #ifdef CONFIG_PERF_EVENTS
@@ -42,4 +41,3 @@ bool kallsyms_show_value(const struct cred *cred)
 		return false;
 	}
 }
-#endif
-- 
2.17.1

Re: [PATCH v5 2/2] kallsyms: make kallsyms_show_value() as generic function

[Luis Chamberlain]

On Thu, Jun 08, 2023 at 09:01:19AM +0530, Maninder Singh wrote:
> This change makes function kallsyms_show_value() as
> generic function without dependency on CONFIG_KALLSYMS.
> 
> Now module address will be displayed with lsmod and /proc/modules.
> 
> 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)
> 
> 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>
> Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>

Thanks! Pushed to modules-next.

  Luis