[PATCH] kexec.c: workaround getline and fscanf to make it *libc agnostic. Tested against klibc and dietlibc.

[Simon Horman]

On Thu, Nov 26, 2009 at 12:37:08AM +0100, Bernhard Walle wrote:
> Simon Horman schrieb:
> >  
> > +
> > +	if ( NULL == p)
> > +		return -1;
> 
> Wouldn't that be better 'p == NULL'?

Agreed

> > +	ret = strtol(line, &p, 10);
> > +
> > +	/* Too long */
> > +	if (ret > INT_MAX)
> > +		return -1;
> 
> An integer that can be represented in 2 (strlen("__\0")==3) cannot be
> larger than INT_MAX on any platform I can imagine. ;-)

True, though it doesn't seem outrageous to check anyway.
Perhaps the string format will change in future.

----------------------------------------------------------------------

From: Andrea Adami <andrea.adami at gmail.com>
To: kexec at lists.infradead.org
Subject: [PATCH] kexec.c: workaround getline and fscanf to make it *libc
	agnostic. Tested against klibc and dietlibc.

Based on a patch by Andrea Adami and Yuri Bushmelev
I have:

* Cleaned up indentation
* Rearranged the logic in get_command_line()
* Increased the buffer for reading the command line
  from 1024 to 2048 bytes as this is now possible on x86

Only compile tested against glibc.

Cc: Andrea Adami <andrea.adami at gmail.com>
Cc: Yuri Bushmelev <jay4mail at gmail.com>
Cc: Bernhard Walle <bernhard at bwalle.de>
Signed-off-by: Simon Horman <horms at verge.net.au>

Index: kexec-tools/kexec/kexec.c
===================================================================
--- kexec-tools.orig/kexec/kexec.c	2009-11-26 10:10:01.000000000 +1100
+++ kexec-tools/kexec/kexec.c	2009-11-26 11:13:46.000000000 +1100
@@ -933,15 +933,32 @@ void usage(void)
 
 static int kexec_loaded(void)
 {
-	int ret;
+	long ret = -1;
 	FILE *fp;
+	char *p;
+	char line[3];
 
 	fp = fopen("/sys/kernel/kexec_loaded", "r");
 	if (fp == NULL)
 		return -1;
-	fscanf(fp, "%d", &ret);
+
+	p = fgets(line, sizeof(line), fp);
 	fclose(fp);
-	return ret;
+
+	if (p == NULL)
+		return -1;
+
+	ret = strtol(line, &p, 10);
+
+	/* Too long */
+	if (ret > INT_MAX)
+		return -1;
+
+	/* No digits were found */
+	if (p == line)
+		return -1;
+
+	return (int)ret;
 }
 
 /*
@@ -989,24 +1006,28 @@ static void remove_parameter(char *line,
 char *get_command_line(void)
 {
 	FILE *fp;
-	size_t len;
-	char *line = NULL;
+	char *line;
+	const int sizeof_line = 2048;
+
+	line = malloc(sizeof_line);
+	if (line == NULL)
+		die("Could not allocate memory to read /proc/cmdline.");
 
 	fp = fopen("/proc/cmdline", "r");
 	if (!fp)
-		die("Could not read /proc/cmdline.");
-	getline(&line, &len, fp);
+		die("Could not open /proc/cmdline.");
+
+	if (fgets(line, sizeof_line, fp) == NULL)
+		die("Can't read /proc/cmdline.");
+
 	fclose(fp);
 
-	if (line) {
-		/* strip newline */
-		*(line + strlen(line) - 1) = 0;
-
-		remove_parameter(line, "BOOT_IMAGE");
-		if (kexec_flags & KEXEC_ON_CRASH)
-			remove_parameter(line, "crashkernel");
-	} else
-		line = strdup("");
+	/* strip newline */
+	line[strlen(line) - 1] = '\0';
+
+	remove_parameter(line, "BOOT_IMAGE");
+	if (kexec_flags & KEXEC_ON_CRASH)
+		remove_parameter(line, "crashkernel");
 
 	return line;
 }