linux-kernel - [PATCH] initramfs: Panic with memory information

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Date:   Thu, 14 Jan 2021 15:15:16 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     opendmb@...il.com, Florian Fainelli <f.fainelli@...il.com>,
        Barret Rhoden <brho@...gle.com>, Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] initramfs: Panic with memory information

On systems with large amounts of reserved memory we may fail to
successfully complete unpack_to_rootfs() and be left with:

 Kernel panic - not syncing: write error

this is not too helpful to understand what happened, so let's wrap the
panic() calls with a surrounding show_mem() such that we have a chance
of understanding the memory conditions leading to these allocation
failures.

Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
 init/initramfs.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index 55b74d7e5260..9dafda6a401b 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -11,6 +11,7 @@
 #include <linux/utime.h>
 #include <linux/file.h>
 #include <linux/memblock.h>
+#include <linux/mm.h>
 #include <linux/namei.h>
 #include <linux/init_syscalls.h>
 
@@ -45,6 +46,11 @@ static void __init error(char *x)
 		message = x;
 }
 
+#define panic_show_mem(...) {	\
+	show_mem(0, NULL);	\
+	panic(__VA_ARGS__);	\
+}
+
 /* link hash */
 
 #define N_ALIGN(len) ((((len) + 1) & ~3) + 2)
@@ -80,7 +86,7 @@ static char __init *find_link(int major, int minor, int ino,
 	}
 	q = kmalloc(sizeof(struct hash), GFP_KERNEL);
 	if (!q)
-		panic("can't allocate link hash entry");
+		panic_show_mem("can't allocate link hash entry");
 	q->major = major;
 	q->minor = minor;
 	q->ino = ino;
@@ -125,7 +131,7 @@ static void __init dir_add(const char *name, time64_t mtime)
 {
 	struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
 	if (!de)
-		panic("can't allocate dir_entry buffer");
+		panic_show_mem("can't allocate dir_entry buffer");
 	INIT_LIST_HEAD(&de->list);
 	de->name = kstrdup(name, GFP_KERNEL);
 	de->mtime = mtime;
@@ -460,7 +466,7 @@ static char * __init unpack_to_rootfs(char *buf, unsigned long len)
 	name_buf = kmalloc(N_ALIGN(PATH_MAX), GFP_KERNEL);
 
 	if (!header_buf || !symlink_buf || !name_buf)
-		panic("can't allocate buffers");
+		panic_show_mem("can't allocate buffers");
 
 	state = Start;
 	this_header = 0;
@@ -607,7 +613,7 @@ static int __init populate_rootfs(void)
 	/* Load the built in initramfs */
 	char *err = unpack_to_rootfs(__initramfs_start, __initramfs_size);
 	if (err)
-		panic("%s", err); /* Failed to decompress INTERNAL initramfs */
+		panic_show_mem("%s", err); /* Failed to decompress INTERNAL initramfs */
 
 	if (!initrd_start || IS_ENABLED(CONFIG_INITRAMFS_FORCE))
 		goto done;
-- 
2.25.1