[PATCH v11 13/15] unwind_user/sframe: Show file name in debug output

[Jens Remus <jremus@linux.ibm.com>]

From: Josh Poimboeuf <jpoimboe@kernel.org>

When debugging sframe issues, the error messages aren't all that helpful
without knowing what file a corresponding .sframe section belongs to.
Prefix debug output strings with the file name.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Indu Bhagat <indu.bhagat@oracle.com>
Cc: "Jose E. Marchesi" <jemarch@gnu.org>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Jens Remus <jremus@linux.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Sam James <sam@gentoo.org>
Cc: Kees Cook <kees@kernel.org>
Cc: "Carlos O'Donell" <codonell@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 include/linux/sframe.h       |  4 +++-
 kernel/unwind/sframe.c       | 23 ++++++++++--------
 kernel/unwind/sframe_debug.h | 45 +++++++++++++++++++++++++++++++-----
 3 files changed, 56 insertions(+), 16 deletions(-)

diff --git a/include/linux/sframe.h b/include/linux/sframe.h
index 9a72209696f9..b79c5ec09229 100644
--- a/include/linux/sframe.h
+++ b/include/linux/sframe.h
@@ -10,7 +10,9 @@
 
 struct sframe_section {
 	struct rcu_head	rcu;
-
+#ifdef CONFIG_DYNAMIC_DEBUG
+	const char	*filename;
+#endif
 	unsigned long	sframe_start;
 	unsigned long	sframe_end;
 	unsigned long	text_start;
diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
index 77ef1f0bb9c5..82eaf3c5d6b0 100644
--- a/kernel/unwind/sframe.c
+++ b/kernel/unwind/sframe.c
@@ -331,14 +331,17 @@ int sframe_find(unsigned long ip, struct unwind_user_frame *frame)
 end:
 	user_read_access_end();
 
-	if (ret == -EFAULT)
+	if (ret == -EFAULT) {
+		dbg_sec("removing bad .sframe section\n");
 		WARN_ON_ONCE(sframe_remove_section(sec->sframe_start));
+	}
 
 	return ret;
 }
 
 static void free_section(struct sframe_section *sec)
 {
+	dbg_free(sec);
 	kfree(sec);
 }
 
@@ -349,7 +352,7 @@ static int sframe_read_header(struct sframe_section *sec)
 	unsigned int num_fdes;
 
 	if (copy_from_user(&shdr, (void __user *)sec->sframe_start, sizeof(shdr))) {
-		dbg("header usercopy failed\n");
+		dbg_sec("header usercopy failed\n");
 		return -EFAULT;
 	}
 
@@ -358,18 +361,18 @@ static int sframe_read_header(struct sframe_section *sec)
 	    !(shdr.preamble.flags & SFRAME_F_FDE_SORTED) ||
 	    !(shdr.preamble.flags & SFRAME_F_FDE_FUNC_START_PCREL) ||
 	    shdr.auxhdr_len) {
-		dbg("bad/unsupported sframe header\n");
+		dbg_sec("bad/unsupported sframe header\n");
 		return -EINVAL;
 	}
 
 	if (!shdr.num_fdes || !shdr.num_fres) {
-		dbg("no fde/fre entries\n");
+		dbg_sec("no fde/fre entries\n");
 		return -EINVAL;
 	}
 
 	header_end = sec->sframe_start + SFRAME_HEADER_SIZE(shdr);
 	if (header_end >= sec->sframe_end) {
-		dbg("header doesn't fit in section\n");
+		dbg_sec("header doesn't fit in section\n");
 		return -EINVAL;
 	}
 
@@ -381,7 +384,7 @@ static int sframe_read_header(struct sframe_section *sec)
 	fres_end   = fres_start + shdr.fre_len;
 
 	if (fres_start < fdes_end || fres_end > sec->sframe_end) {
-		dbg("inconsistent fde/fre offsets\n");
+		dbg_sec("inconsistent fde/fre offsets\n");
 		return -EINVAL;
 	}
 
@@ -437,6 +440,8 @@ int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end,
 	sec->text_start		= text_start;
 	sec->text_end		= text_end;
 
+	dbg_init(sec);
+
 	ret = sframe_read_header(sec);
 	if (ret) {
 		dbg_print_header(sec);
@@ -445,8 +450,8 @@ int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end,
 
 	ret = mtree_insert_range(sframe_mt, sec->text_start, sec->text_end, sec, GFP_KERNEL);
 	if (ret) {
-		dbg("mtree_insert_range failed: text=%lx-%lx\n",
-		    sec->text_start, sec->text_end);
+		dbg_sec("mtree_insert_range failed: text=%lx-%lx\n",
+			sec->text_start, sec->text_end);
 		goto err_free;
 	}
 
@@ -468,7 +473,7 @@ static int __sframe_remove_section(struct mm_struct *mm,
 				   struct sframe_section *sec)
 {
 	if (!mtree_erase(&mm->sframe_mt, sec->text_start)) {
-		dbg("mtree_erase failed: text=%lx\n", sec->text_start);
+		dbg_sec("mtree_erase failed: text=%lx\n", sec->text_start);
 		return -EINVAL;
 	}
 
diff --git a/kernel/unwind/sframe_debug.h b/kernel/unwind/sframe_debug.h
index 055c8c8fae24..7794bf0bd78c 100644
--- a/kernel/unwind/sframe_debug.h
+++ b/kernel/unwind/sframe_debug.h
@@ -10,26 +10,59 @@
 #define dbg(fmt, ...)							\
 	pr_debug("%s (%d): " fmt, current->comm, current->pid, ##__VA_ARGS__)
 
+#define dbg_sec(fmt, ...)						\
+	dbg("%s: " fmt, sec->filename, ##__VA_ARGS__)
+
 static __always_inline void dbg_print_header(struct sframe_section *sec)
 {
 	unsigned long fdes_end;
 
 	fdes_end = sec->fdes_start + (sec->num_fdes * sizeof(struct sframe_fde));
 
-	dbg("SEC: sframe:0x%lx-0x%lx text:0x%lx-0x%lx "
-	    "fdes:0x%lx-0x%lx fres:0x%lx-0x%lx "
-	    "ra_off:%d fp_off:%d\n",
-	    sec->sframe_start, sec->sframe_end, sec->text_start, sec->text_end,
-	    sec->fdes_start, fdes_end, sec->fres_start, sec->fres_end,
-	    sec->ra_off, sec->fp_off);
+	dbg_sec("SEC: sframe:0x%lx-0x%lx text:0x%lx-0x%lx "
+		"fdes:0x%lx-0x%lx fres:0x%lx-0x%lx "
+		"ra_off:%d fp_off:%d\n",
+		sec->sframe_start, sec->sframe_end, sec->text_start, sec->text_end,
+		sec->fdes_start, fdes_end, sec->fres_start, sec->fres_end,
+		sec->ra_off, sec->fp_off);
+}
+
+static inline void dbg_init(struct sframe_section *sec)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+
+	guard(mmap_read_lock)(mm);
+	vma = vma_lookup(mm, sec->sframe_start);
+	if (!vma)
+		sec->filename = kstrdup("(vma gone???)", GFP_KERNEL);
+	else if (vma->vm_file)
+		sec->filename = kstrdup_quotable_file(vma->vm_file, GFP_KERNEL);
+	else if (vma->vm_ops && vma->vm_ops->name)
+		sec->filename = kstrdup(vma->vm_ops->name(vma), GFP_KERNEL);
+	else if (arch_vma_name(vma))
+		sec->filename = kstrdup(arch_vma_name(vma), GFP_KERNEL);
+	else if (!vma->vm_mm)
+		sec->filename = kstrdup("(vdso)", GFP_KERNEL);
+	else
+		sec->filename = kstrdup("(anonymous)", GFP_KERNEL);
+}
+
+static inline void dbg_free(struct sframe_section *sec)
+{
+	kfree(sec->filename);
 }
 
 #else /* !CONFIG_DYNAMIC_DEBUG */
 
 #define dbg(args...)			no_printk(args)
+#define dbg_sec(args...	)		no_printk(args)
 
 static inline void dbg_print_header(struct sframe_section *sec) {}
 
+static inline void dbg_init(struct sframe_section *sec) {}
+static inline void dbg_free(struct sframe_section *sec) {}
+
 #endif /* !CONFIG_DYNAMIC_DEBUG */
 
 #endif /* _SFRAME_DEBUG_H */
-- 
2.48.1