linux-kernel - [PATCH 1/1] kallsyms: print module name in %ps/S case when KALLSYMS is disabled

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Date:   Tue,  1 Feb 2022 09:30:44 +0530
From:   Maninder Singh <maninder1.s@...sung.com>
To:     pmladek@...e.com, rostedt@...dmis.org, senozhatsky@...omium.org,
        andriy.shevchenko@...ux.intel.com, linux@...musvillemoes.dk
Cc:     akpm@...ux-foundation.org, wangkefeng.wang@...wei.com,
        mbenes@...e.cz, swboyd@...omium.org, ojeda@...nel.org,
        linux-kernel@...r.kernel.org, will@...nel.org,
        catalin.marinas@....com, Maninder Singh <maninder1.s@...sung.com>,
        Vaneet Narang <v.narang@...sung.com>
Subject: [PATCH 1/1] kallsyms: print module name in %ps/S case when KALLSYMS
 is disabled

original:
With KALLSYMS
                   %pS                               %ps
[16.4200]  hello_init+0x0/0x24 [crash]        hello_init [crash]

Without KALLSYMS:
[16.2200]      0xbe200040                         0xbe200040

With Patch (Without KALLSYMS:) load address + current offset [Module Name]

[13.5993]  0xbe200000+0x40 [crash]           0xbe200000+0x40 [crash]

It will help in better debugging and checking when KALLSYMS is disabled,
user will get information about module name and load address of module.

verified for arm64:
/ # insmod /crash.ko

[   19.263556] 0xffff800000ec0000+0x38 [crash]

..

[   19.276023] Call trace:
[   19.276277]  0xffff800000ec0000+0x28 [crash]
[   19.276567]  0xffff800000ec0000+0x58 [crash]
[   19.276727]  0xffff800000ec0000+0x74 [crash]
[   19.276866]  0xffff8000080127d0
[   19.276978]  0xffff80000812d95c
[   19.277085]  0xffff80000812f554

Signed-off-by: Vaneet Narang <v.narang@...sung.com>
Signed-off-by: Maninder Singh <maninder1.s@...sung.com>
---
 include/linux/kallsyms.h | 27 +++++++++++++++++++++++++++
 lib/vsprintf.c           |  5 +++--
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index 5fb17dd4b6fa..ebfeb6099c28 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -163,6 +163,33 @@ 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/lib/vsprintf.c b/lib/vsprintf.c
index 61528094ec87..41c74abb1726 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -985,9 +985,7 @@ char *symbol_string(char *buf, char *end, void *ptr,
 		    struct printf_spec spec, const char *fmt)
 {
 	unsigned long value;
-#ifdef CONFIG_KALLSYMS
 	char sym[KSYM_SYMBOL_LEN];
-#endif
 
 	if (fmt[1] == 'R')
 		ptr = __builtin_extract_return_addr(ptr);
@@ -1007,6 +1005,9 @@ 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))
+		return string_nocheck(buf, end, sym, spec);
+
 	return special_hex_number(buf, end, value, sizeof(void *));
 #endif
 }
-- 
2.17.1