From 7cfa935df23105fec704e7311ebdba410798c3d5 Mon Sep 17 00:00:00 2001
From: Al Stone <ahs3@redhat.com>
Date: Fri, 30 Nov 2012 16:08:01 -0700
Subject: first commit of the patch tool

Signed-off-by: Al Stone <ahs3@redhat.com>
---
 Makefile |  21 +++++++++++
 paxf.c   | 129 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 150 insertions(+)
 create mode 100644 Makefile
 create mode 100644 paxf.c

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..0ed0c94
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,21 @@
+#
+#	patch a binary .axf file with a new set of kernel parameters
+#
+
+CC ?= gcc
+CFLAGS ?= -g
+
+OBJ = paxf.o
+
+
+all: paxf
+
+paxf: paxf.o
+	$(CC) $(CFLAGS) -o paxf $(OBJ)
+
+clean:
+	rm -f paxf $(OBJ)
+
+.c.o:
+	$(CC) $(CFLAGS) -c $<
+
diff --git a/paxf.c b/paxf.c
new file mode 100644
index 0000000..3e167e6
--- /dev/null
+++ b/paxf.c
@@ -0,0 +1,129 @@
+/**********************************************************************
+ *  Given a linux-system.axf file built in a certain way, replace
+ *  the kernel parameters used with whatever I'd like to put in
+ *  there instead.
+ *
+ *  This is a quick and dirty hack; if it works for *anything* other
+ *  than this, I think I'll laugh hysterically.
+ *
+ * 
+ *  Copyright (c) 2012, Al Stone <ahs3@ahs3.net>
+ * 
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of version 2 (only) of the GNU General
+ *  Public License as published by the Free Software Foundation.
+ *
+ **********************************************************************/
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#define ARG_OFFSET      0x4000e4
+#define AXF_FILE        "./linux-system-useless.axf"
+#define BUFFER_LENGTH   400
+
+void
+usage() {
+    fprintf(stderr, "usage: paxf <output-axf> <kernel-parameters>\n\n");
+    fprintf(stderr, "where:\n");
+    fprintf(stderr, 
+            "   <output-axf>        => name to use for patched axf file\n");
+    fprintf(stderr,
+            "   <kernel-parameters> => the kernel parameters wanted as a\n");
+    fprintf(stderr,
+            "                          single string (assume there are NO\n");
+    fprintf(stderr,
+            "                          parameters provided by default)\n");
+}
+
+int
+main(int argv, char *argc[]) {
+
+    int infd, outfd;
+    char *fname;
+    char *kargs;
+
+    /* crude argument handling */
+    if (argv < 3) {
+        usage();
+        exit(1);
+    }
+    fname = argc[1];
+    kargs = argc[2];
+
+    outfd = open(fname, O_RDWR | O_CREAT | O_TRUNC,
+                 S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
+    if (! (outfd > 0)) {
+        fprintf(stderr, "? cannot open %s as output\n", fname);
+        exit(1);
+    }
+
+    if (strlen(kargs) > BUFFER_LENGTH) {
+        fprintf(stderr, "? not enough space for the kernel args (%d)\n",
+                strlen(kargs));
+        exit(1);
+    }
+
+    /*
+     * map in the entire axf file to use as a template, then copy
+     * it all to the new location, except for the bits we need to
+     * change
+     */
+    unsigned char *axf = NULL;
+    struct stat stat_buf;
+    off_t axf_size;
+    int count;
+    unsigned char *buf;
+
+    if (stat(AXF_FILE, &stat_buf) == 0) {
+        axf_size = stat_buf.st_size;
+    }
+    else {
+        fprintf(stderr, "? cannot stat %s (%d)\n", AXF_FILE, errno);
+        exit(1);
+    }
+
+    infd = open(AXF_FILE, O_RDONLY);
+    if (infd) {
+        axf = mmap(NULL, axf_size, PROT_READ, MAP_PRIVATE, infd, 0);
+        if (axf <= 0) {
+            fprintf(stderr, "? memory map failed (%d)\n", errno);
+            exit(1);
+        }
+
+        /* copy everything before the kernel args */
+        lseek(infd, 0, SEEK_SET);
+        lseek(outfd, 0, SEEK_SET);
+        write(outfd, axf, ARG_OFFSET);
+
+        /*
+         * replace the BUFFER_LENGTH space in the input axf file
+         * with the arguments we really want
+         */
+        buf = malloc(BUFFER_LENGTH + 1);
+        memset(buf, ' ', BUFFER_LENGTH);
+        memcpy(buf, kargs, strlen(kargs));
+        write(outfd, buf, BUFFER_LENGTH);
+
+        /* copy everything after the kernel args */
+        write(outfd, axf + ARG_OFFSET + BUFFER_LENGTH,
+              axf_size - (ARG_OFFSET + BUFFER_LENGTH));
+
+        close(outfd);
+        free(buf);
+        munmap(axf, axf_size);
+        close(infd);
+    }
+    else {
+        fprintf(stderr, "? cannot open %s as input\n", AXF_FILE);
+        exit(1);
+    }
+}
+
-- 
cgit