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From:   Maninder Singh <maninder1.s@samsung.com>
To:     mcgrof@kernel.org, pmladek@suse.com, rostedt@goodmis.org,
        senozhatsky@chromium.org, andriy.shevchenko@linux.intel.com,
        linux@rasmusvillemoes.dk, akpm@linux-foundation.org,
        wangkefeng.wang@huawei.com
Cc:     v.narang@samsung.com, swboyd@chromium.org, ojeda@kernel.or,
        linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org,
        avimalin@gmail.com, atomlin@redhat.com,
        Maninder Singh <maninder1.s@samsung.com>
Subject: [PATCH 1/1] kallsyms: enhance %pS/s/b printing when KALLSYSMS is
 disabled
Date:   Mon, 28 Feb 2022 11:04:47 +0530
Message-Id: <20220228053447.1584704-1-maninder1.s@samsung.com>
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References: <CGME20220228053457epcas5p1dac3fced39d1594f8fdfc5e64e23ac73@epcas5p1.samsung.com>
Precedence: bulk

with commit '82b37e632513 ("kallsyms: print module name in %ps/S
case when KALLSYMS is disabled"), module name printing was enhanced.

As per suggestion from Petr Mladek <pmladek@suse.com>, covering
other flavours also to print build id also.

for %pB no change as it needs to know symbol name to adjust address
value which can't be done without KALLSYMS.

original output with KALLSYMS:
[8.842129] ps function_1 [crash]
[8.842735] pS function_1+0x4/0x2c [crash]
[8.842890] pSb function_1+0x4/0x2c [crash b367e79021b9f3b0172f9a36d4261c1f528ca1b3]
[8.843175] pB function_1+0x4/0x2c [crash]
[8.843362] pBb function_1+0x4/0x2c [crash b367e79021b9f3b0172f9a36d4261c1f528ca1b3]

original output without KALLSYMS:
[12.487424] ps 0xffff800000eb008c
[12.487598] pS 0xffff800000eb008c
[12.487723] pSb 0xffff800000eb008c
[12.487850] pB 0xffff800000eb008c
[12.487967] pBb 0xffff800000eb008c

With patched kernel without KALLSYMS:
[9.205207] ps 0xffff800000eb008c [crash]
[9.205564] pS 0xffff800000eb0000+0x8c [crash]
[9.205757] pSb 0xffff800000eb0000+0x8c [crash b367e79021b9f3b0172f9a36d4261c1f528ca1b3]
[9.206066] pB 0xffff800000eb0000+0x8c [crash]
[9.206257] pBb 0xffff800000eb0000+0x8c [crash b367e79021b9f3b0172f9a36d4261c1f528ca1b3]

Suggested-by: Petr Mladek <pmladek@suse.com>
Co-developed-by: Vaneet Narang <v.narang@samsung.com>
Signed-off-by: Vaneet Narang <v.narang@samsung.com>
Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
---
earlier discussion: https://lkml.org/lkml/2022/2/10/185

 include/linux/kallsyms.h | 27 --------------
 kernel/module.c          |  4 +--
 lib/vsprintf.c           | 76 +++++++++++++++++++++++++++++++++++++++-
 3 files changed, 76 insertions(+), 31 deletions(-)

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index ebfeb6099c28..5fb17dd4b6fa 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -163,33 +163,6 @@ static inline bool kallsyms_show_value(const struct cred *cred)
 	return false;
 }
 
-#ifdef CONFIG_MODULES
-static inline int fill_minimal_module_info(char *sym, int size, unsigned long value)
-{
-	struct module *mod;
-	unsigned long offset;
-	int ret = 0;
-
-	preempt_disable();
-	mod = __module_address(value);
-	if (mod) {
-		offset = value - (unsigned long)mod->core_layout.base;
-		snprintf(sym, size - 1, "0x%lx+0x%lx [%s]",
-				(unsigned long)mod->core_layout.base, offset, mod->name);
-
-		sym[size - 1] = '\0';
-		ret = 1;
-	}
-
-	preempt_enable();
-	return ret;
-}
-#else
-static inline int fill_minimal_module_info(char *sym, int size, unsigned long value)
-{
-	return 0;
-}
-#endif /*CONFIG_MODULES*/
 #endif /*CONFIG_KALLSYMS*/
 
 static inline void print_ip_sym(const char *loglvl, unsigned long ip)
diff --git a/kernel/module.c b/kernel/module.c
index 46a5c2ed1928..ccccb135c7fe 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1465,12 +1465,10 @@ resolve_symbol_wait(struct module *mod,
 	return ksym;
 }
 
-#ifdef CONFIG_KALLSYMS
 static inline bool sect_empty(const Elf_Shdr *sect)
 {
 	return !(sect->sh_flags & SHF_ALLOC) || sect->sh_size == 0;
 }
-#endif
 
 /*
  * /sys/module/foo/sections stuff
@@ -2799,7 +2797,7 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
 }
 #endif /* CONFIG_KALLSYMS */
 
-#if IS_ENABLED(CONFIG_KALLSYMS) && IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
+#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
 static void init_build_id(struct module *mod, const struct load_info *info)
 {
 	const Elf_Shdr *sechdr;
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index cb7345ff57f3..d4a24fd29494 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -980,6 +980,80 @@ char *bdev_name(char *buf, char *end, struct block_device *bdev,
 }
 #endif
 
+#if !defined(CONFIG_KALLSYMS) && defined(CONFIG_MODULES)
+static int sprint_module_info(char *buf, char *end, unsigned long value,
+			     const char *fmt)
+{
+	struct module *mod;
+	unsigned long offset = 1;
+	unsigned long base;
+	int ret = 0;
+	const char *modname;
+	int modbuildid = 0;
+	int len;
+#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
+	const unsigned char *buildid = NULL;
+#endif
+
+	if (is_ksym_addr(value))
+		return 0;
+
+	if (*fmt == 'B' && fmt[1] == 'b')
+		modbuildid = 1;
+	else if (*fmt == 'S' && (fmt[1] == 'b' || (fmt[1] == 'R' && fmt[2] == 'b')))
+		modbuildid = 1;
+	else if (*fmt != 's') {
+		/*
+		 * do nothing.
+		 */
+	} else
+		offset = 0;
+
+	preempt_disable();
+	mod = __module_address(value);
+	if (mod) {
+		ret = 1;
+		modname = mod->name;
+#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
+		if (modbuildid)
+			buildid = mod->build_id;
+#endif
+		if (offset) {
+			base = (unsigned long)mod->core_layout.base;
+			offset = value - base;
+		}
+	}
+
+	preempt_enable();
+	if (!ret)
+		return 0;
+
+	/* address belongs to module */
+	if (offset)
+		len = sprintf(buf, "0x%lx+0x%lx", base, offset);
+	else
+		len = sprintf(buf, "0x%lx", value);
+
+	len += sprintf(buf + len, " [%s", modname);
+#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
+	if (modbuildid && buildid) {
+		/* build ID should match length of sprintf */
+		static_assert(sizeof(typeof_member(struct module, build_id)) == 20);
+		len += sprintf(buf + len, " %20phN", buildid);
+	}
+#endif
+	len += sprintf(buf + len, "]");
+
+	return len;
+}
+#else
+static inline int sprint_module_info(char *buf, char *end, unsigned long value,
+			     const char *fmt)
+{
+	return 0;
+}
+#endif
+
 static noinline_for_stack
 char *symbol_string(char *buf, char *end, void *ptr,
 		    struct printf_spec spec, const char *fmt)
@@ -1005,7 +1079,7 @@ char *symbol_string(char *buf, char *end, void *ptr,
 
 	return string_nocheck(buf, end, sym, spec);
 #else
-	if (fill_minimal_module_info(sym, KSYM_SYMBOL_LEN, value))
+	if (sprint_module_info(sym, end, value, fmt))
 		return string_nocheck(buf, end, sym, spec);
 
 	return special_hex_number(buf, end, value, sizeof(void *));
-- 
2.17.1