Add padtext utility (needed for Multiboot)

commands/Makefile

@@ -37,7 +37,7 @@ SUBDIR=	aal add_route adduser advent arp ash at autil awk \
 .if ${ARCH} == "i386"
 SUBDIR+=	atnormalize dosread fdisk loadfont \
 	mixer autopart part partition playwave postmort \
-	recwave repartition screendump
+	recwave repartition screendump padtext
 SUBDIR+=	acd asmconv gas2ack
 .endif
 

commands/padtext/Makefile

@@ -0,0 +1,4 @@
+PROG=	padtext
+MAN=
+
+.include <bsd.prog.mk>

commands/padtext/padtext.c

@@ -0,0 +1,248 @@
+/* padtext: pad out the text segment of a separate I&D a.out binary to a 
+ * multiple of CLICK_SIZE, used for mult-boot
+ *
+ * author: Erik van der Kouwe, vdkouwe@cs.vu.nl, June 9th 2010
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <minix/a.out.h>
+#include <minix/config.h>
+#include <minix/const.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/* padding: x86 opcode int 3 (breakpoint) to ensure a trap if the padding area 
+ * accidentally gets executed
+ */
+#define PADDING_CHAR ((unsigned char) 0xcc)
+
+static const char *argv0, *pathin, *pathout;
+static int fdin, fdout;
+
+static int readfixed(void *buffer, size_t count)
+{
+	ssize_t r;
+
+	while (count > 0) {
+		/* read as many bytes as possible */
+		r = read(fdin, buffer, count);
+		if (r <= 0) {
+			if (r < 0) {
+				fprintf(stderr, 
+					"%s: %s: error while reading: %s\n", 
+					argv0, pathin, strerror(errno));
+			} else {
+				fprintf(stderr, 
+					"%s: %s: premature end of file, "
+					"expected %u more bytes\n", 
+					argv0, pathin, count);
+			}
+			return -1;
+		}
+
+		/* maybe we need to read another block */
+		buffer = (char *) buffer + r;
+		count -= r;
+	}
+
+	return 0;
+}
+
+static int writefixed(const void *buffer, size_t count)
+{
+	ssize_t r;
+
+	while (count > 0) {
+		/* read as many bytes as possible */
+		r = write(fdout, buffer, count);
+		if (r <= 0) {
+			if (r < 0) {
+				fprintf(stderr, 
+					"%s: %s: error while writing: %s\n", 
+					argv0, pathout, strerror(errno));
+			} else {
+				fprintf(stderr, 
+					"%s: %s: premature end of file\n", 
+					argv0, pathout);
+			}
+			return -1;
+		}
+
+		/* maybe we need to read another block */
+		buffer = (const char *) buffer + r;
+		count -= r;
+	}
+
+	return 0;
+}
+
+static int writepadding(size_t padsize)
+{
+	char buffer[CLICK_SIZE];
+
+	/* we never write more than a single click */
+	assert(padsize <= sizeof(buffer));
+	memset(buffer, PADDING_CHAR, padsize);
+	return writefixed(buffer, padsize);
+}
+
+static int copyfixed(size_t count)
+{
+	char buffer[4096];
+	size_t countnow;
+
+	while (count > 0) {
+		/* copying a fixed number of bytes, we expect everything to 
+		 * succeed 
+		 */ 
+		countnow = (count < sizeof(buffer)) ? count : sizeof(buffer);
+		if (readfixed(buffer, countnow) < 0 ||
+			writefixed(buffer, countnow) < 0) {
+			return -1;
+		}
+		count -= countnow;
+	}
+
+	return 0;
+}
+
+static int copyall(void)
+{
+	char buffer[4096];
+	ssize_t r;
+
+	for (; ; ) {
+		/* copy everything until EOF */ 
+		r = read(fdin, buffer, sizeof(buffer));
+		if (r <= 0) {
+			if (r < 0) {
+				fprintf(stderr,
+					"%s: %s: error while reading: %s\n", 
+					argv0, pathin, strerror(errno));
+				return -1;
+			} else {
+				/* EOF, stop copying */
+				break;
+			}
+		}
+
+		if (writefixed(buffer, r) < 0) {
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+static int padtext(void)
+{
+	struct exec headerin, headerout;
+	long padsize;
+
+	/* read header */
+	assert(A_MINHDR <= sizeof(headerin));
+	if (readfixed(&headerin, A_MINHDR) < 0) {
+		return -1;
+	}
+
+	/* check header sanity */
+	if (BADMAG(headerin) ||
+		headerin.a_hdrlen < A_MINHDR ||
+		(headerin.a_flags & ~(A_NSYM | A_EXEC | A_SEP)) != 0 ||
+		headerin.a_text < 0 ||
+		headerin.a_data < 0 ||
+		headerin.a_bss < 0 ||
+		headerin.a_entry != 0 ||
+		headerin.a_total < 0 ||
+		headerin.a_syms < 0) {
+		fprintf(stderr, "%s: %s: invalid a.out header\n", 
+			argv0, pathin);
+		return -1;
+	}
+
+	if (headerin.a_cpu != A_I80386) {
+		fprintf(stderr, "%s: %s: not an i386 executable\n", 
+			argv0, pathin);
+		return -1;
+	}
+
+	if ((headerin.a_flags & A_SEP) != A_SEP) {
+		fprintf(stderr, 
+			"%s: %s: combined I&D, padding text is impossible\n", 
+			argv0, pathin);
+		return -1;
+	}
+
+	/* adjust header */
+	headerout = headerin;
+	padsize = CLICK_SIZE - headerout.a_text % CLICK_SIZE;
+	if (padsize == CLICK_SIZE) padsize = 0;
+	printf("%s: %s: adding %ld bytes of padding\n", pathin, argv0, padsize);
+	headerout.a_text += padsize;
+
+	/* write header and copy text segment */
+	if (writefixed(&headerout, A_MINHDR) < 0 ||
+		copyfixed(headerin.a_hdrlen - A_MINHDR + headerin.a_text) < 0 ||
+		writepadding(padsize) < 0 ||
+		copyall() < 0) {
+		return -1;		
+	}
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	/* check parameters */
+	argv0 = argv[0];
+	if (argc > 3) {
+		printf("usage:\n");
+		printf("  %s [infile [outfile]]\n", argv0);
+		return 1;
+	}
+
+	if (argc >= 2) {
+		/* open specified input file */
+		pathin = argv[1];
+		fdin = open(pathin, O_RDONLY);
+		if (fdin < 0) {
+			fprintf(stderr, 
+				"%s: cannot open input file \"%s\" "
+				"for reading: %s\n",
+				argv0, pathin, strerror(errno));
+			return -1;
+		}
+	} else {
+		/* input from stdin */
+		pathin = "-";
+		fdin = STDIN_FILENO;
+	}
+		
+	if (argc >= 3) {
+		/* open specified output file */
+		pathout = argv[2];
+		fdout = creat(pathout, 0644);
+		if (fdout < 0) {
+			fprintf(stderr, 
+				"%s: cannot open output file \"%s\" "
+				"for writing: %s\n",
+				argv0, pathout, strerror(errno));
+			return -1;
+		}
+	} else {
+		/* output to stdout */
+		pathout = "-";
+		fdout = STDOUT_FILENO;
+	}
+
+	/* now do the job using the file handles */
+	if (padtext() < 0) {
+		return -1;
+	}
+
+	return 0;
+}