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From:   Maninder Singh <maninder1.s@samsung.com>
To:     mcgrof@kernel.org, avimalin@gmail.com, ast@kernel.org,
        daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com,
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        mhiramat@kernel.org, anil.s.keshavamurthy@intel.com,
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        keescook@chromium.org
Cc:     linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        v.narang@samsung.com, Maninder Singh <maninder1.s@samsung.com>,
        Onkarnath <onkarnath.1@samsung.com>
Subject: [PATCH 1/2] kallsyms: add kallsyms_show_value definition in all
 cases
Date:   Wed, 11 May 2022 13:36:56 +0530
Message-Id: <20220511080657.3996053-1-maninder1.s@samsung.com>
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References: <CGME20220511080722epcas5p459493d02ff662a7c75590e44a11e34a6@epcas5p4.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:

/ # 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)
/ #

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.
https://lkml.org/lkml/2022/4/13/326

 include/linux/filter.h   |  7 ++++++
 include/linux/kallsyms.h | 10 +++-----
 kernel/Makefile          |  2 +-
 kernel/kallsyms.c        | 35 ---------------------------
 kernel/kallsyms_tiny.c   | 51 ++++++++++++++++++++++++++++++++++++++++
 5 files changed, 62 insertions(+), 43 deletions(-)
 create mode 100644 kernel/kallsyms_tiny.c

diff --git a/include/linux/filter.h b/include/linux/filter.h
index ed0c0ff42ad5..98c4365e726d 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -951,6 +951,7 @@ bool bpf_jit_needs_zext(void);
 bool bpf_jit_supports_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,
@@ -958,6 +959,12 @@ 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 c24fa627ab6e..c5e63a217404 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_kallsym_common(char *buffer, unsigned long address, int build_
 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;
-}
-
 #endif /*CONFIG_KALLSYMS*/
 
 static inline void print_ip_sym(const char *loglvl, unsigned long ip)
diff --git a/kernel/Makefile b/kernel/Makefile
index 318789c728d3..844ed3df95f6 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 kallsyms_tiny.o
 
 obj-$(CONFIG_USERMODE_DRIVER) += usermode_driver.o
 obj-$(CONFIG_MODULES) += kmod.o
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 9a0d6cfca619..d818048cb9f7 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -819,41 +819,6 @@ 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/kernel/kallsyms_tiny.c b/kernel/kallsyms_tiny.c
new file mode 100644
index 000000000000..96ad06836126
--- /dev/null
+++ b/kernel/kallsyms_tiny.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Samsung Electronics Co., Ltd
+ *
+ * Author:
+ *	Maninder singh <maninder1.s@samsung.com>
+ *	Onkarnath <onkarnath.1@samsung.com>
+ *
+ * A split of kernel/kallsyms.c
+ * Contains few generic definitions independent of CONFIG_KALLSYMS
+ * or defined under !CONFIG_KALLSYMS.
+ */
+
+#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