From 9212eab21f2bd6b69def9e5b0b445395a814ef6e Mon Sep 17 00:00:00 2001 From: Erik van der Kouwe Date: Fri, 23 Jul 2010 14:22:49 +0000 Subject: [PATCH] Add padtext utility (needed for Multiboot) --- commands/Makefile | 2 +- commands/padtext/Makefile | 4 + commands/padtext/padtext.c | 248 +++++++++++++++++++++++++++++++++++++ 3 files changed, 253 insertions(+), 1 deletion(-) create mode 100644 commands/padtext/Makefile create mode 100644 commands/padtext/padtext.c diff --git a/commands/Makefile b/commands/Makefile index 357adf352..f8dcf6614 100644 --- a/commands/Makefile +++ b/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 diff --git a/commands/padtext/Makefile b/commands/padtext/Makefile new file mode 100644 index 000000000..e2ca2e61b --- /dev/null +++ b/commands/padtext/Makefile @@ -0,0 +1,4 @@ +PROG= padtext +MAN= + +.include diff --git a/commands/padtext/padtext.c b/commands/padtext/padtext.c new file mode 100644 index 000000000..761c3c3e1 --- /dev/null +++ b/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 +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* 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; +} -- 2.44.0