Libpayload

libpayload is a small BSD-licensed static library (a lightweight implementation of common and useful functions) intended to be used as a basis for coreboot payloads.

The benefits of linking a coreboot payload against libpayload are:

• Payloads do not have to implement and maintain low-level code for I/O, common functions, etc.
• Payloads can be recompiled and deployed for CPU architectures supported by coreboot in the future.
• The libpayload functions can be tested and scrutinized outside payload development.
• Payloads themselves may be partly host-tested, e.g. against an emulation libpayload.

Just give us a main() and a pocket full of dreams and we'll do the rest.

Features

• Provides a subset of libc functions (e.g. malloc, printf, strcmp, etc).
• Provides an optional tiny (n)curses implementation.
• Provides various small drivers for
  • keyboard
  • PC speaker
  • NVRAM/CMOS access
  • serial console
  • VGA
  • Geode framebuffer
• Reads and parses the coreboot table.http://qa.coreboot.org/docs/libpayload/

Design

• Discussion of the API for passing parameters to the payload

Payloads using libpayload

• FILO is a bootloader which loads boot images from a local filesystem, without help from legacy BIOS services.
• coreinfo is a small payload which can display system information such as PCI info, an NVRAM dump, or the coreboot v3 printk buffer.
• GRUB invaders has been ported successfully to libpayload (patch pending).
• tint (a console tetris clone) has been successfully ported to libpayload.
• lxdialog from the Linux kconfig utility has been ported to be usable when linked with libpayload (patch pending).

Downloading and building libpayload

$ svn co svn://coreboot.org/repos/trunk/payloads/libpayload
$ cd libpayload
$ make menuconfig
$ make

Documentation

See the autogenerated documentation for libpayload here.

Libc coverage

Status Function/Macro/Variable assert.h no assert() ctype.h yes int isalnum(int character) yes int isalpha(int character) yes int isascii(int character) yes int isblanc(int character) yes int iscntrl(int character) yes int isdigit(int character) yes int isgraph(int character) yes int islower(int character) yes int isprint(int character) yes int ispunct(int character) yes int isspace(int character) yes int isupper(int character) yes int isxdigit(int character) yes int tolower(int character) yes int toupper(int character) errno.h no errno (global) float.h limits.h locale.h no char *setlocale(int category, const char *locale) no struct lconv *localeconv(void) math.h no double exp(double x) no double log(double x) no double log10(double x) no double pow(double x, double y) no double sqrt(double x) no double ceil(double x) no double floor(double x) no double fabs(double x) no double ldexp(double x, int n) no double frexp(double x, int* exp) no double modf(double x, double* ip) no double fmod(double x, double y) no double sin(double x) no double cos(double x) no double tan(double x) no double asin(double x) no double acos(double x) no double atan(double x) no double atan2(double y, double x) no double sinh(double x) no double cosh(double x) no double tanh(double x) setjmp.h no int setjmp(jmp_buf env) no void longjmp(jmp_buf env, int val) signal.h no void (*signal(int sig, void (*handler)(int)))(int) no int raise(int sig) stdarg.h no void va_start(va_list ap, lastarg) no type va_arg(va_list ap, type) no void va_end(va_list ap) stddef.h TODO stdio.h no FILE* fopen(const char* filename, const char* mode) no FILE* freopen(const char* filename, const char* mode, FILE* stream) no int fflush(FILE* stream) no int fclose(FILE* stream) no int remove(const char* filename) no int rename(const char* oldname, const char* newname) no FILE* tmpfile() no char* tmpnam(char s[L_tmpnam]) no int setvbuf(FILE* stream, char* buf, int mode, size_t size) no void setbuf(FILE* stream, char* buf) no int fprintf(FILE* stream, const char* format, ...) yes int printf(const char* format, ...) yes int sprintf(char* s, const char* format, ...) yes int snprintf(char* s, size_t size, const char* format, ...) no int vfprintf(FILE* stream, const char* format, va_list arg) yes int vprintf(const char* format, va_list arg) yes int vsprintf(char* s, const char* format, va_list arg) yes int vsnprintf(char* s, size_t size, const char* format, va_list arg) no int fscanf(FILE* stream, const char* format, ...) no int scanf(const char* format, ...) no int sscanf(char* s, const char* format, ...) no int fgetc(FILE* stream) no char* fgets(char* s, int n, FILE* stream) no int fputc(int c, FILE* stream) no char* fputs(const char* s, FILE* stream) no int getc(FILE* stream) yes int getchar(void) no char* gets(char* s) no int putc(int c, FILE* stream) yes int putchar(int c) yes int puts(const char* s) no int ungetc(int c, FILE* stream) no size_t fread(void* ptr, size_t size, size_t nobj, FILE* stream) no size_t fwrite(const void* ptr, size_t size, size_t nobj, FILE* stream) no int fseek(FILE* stream, long offset, int origin) no long ftell(FILE* stream) no void rewind(FILE* stream) no int fgetpos(FILE* stream, fpos_t* ptr) no int fsetpos(FILE* stream, const fpos_t* ptr) no void clearerr(FILE* stream) no int feof(FILE* stream) no int ferror(FILE* stream) no void perror(const char* s)

Status Function/Macro/Variable stdlib.h yes int abs(int n) yes long labs(long n) yes long long llabs(long long n) no div_t div(int num, int denom) no ldiv_t ldiv(long num, long denom) no double atof(const char* s) no int atoi(const char* s) no long atol(const char* s) no double strtod(const char* s, char** endp) no long strtol(const char* s, char** endp, int base) yes unsigned long strtoul(const char* s, char** endp, int base) yes void* calloc(size_t nobj, size_t size) yes void* malloc(size_t size) yes void* realloc(void* p, size_t size) yes void free(void* p) yes void * memalign (size_t align, size_t size) yes void abort() no void exit(int status) no int atexit(void (*fcm)(void)) no int system(const char* s) no char* getenv(const char* name) no void* bsearch(const void* key, const void* base, size_t n, size_t size, int (*cmp)(const void* keyval, const void* datum)) no void qsort(void* base, size_t n, size_t size, int (*cmp)(const void*, const void*)) yes int rand(void) yes void srand(unsigned int seed) string.h yes char* strcpy(char* s, const char* ct) yes char* strncpy(char* s, const char* ct, size_t n) no char* strcat(char* s, const char* ct) yes char* strncat(char* s, const char* ct, size_t n) yes int strcmp(const char* cs, const char* ct) yes int strncmp(const char* cs, const char* ct, size_t n) no int strcoll(const char* cs, const char* ct) yes char* strchr(const char* cs, int c) no char* strrchr(const char* cs, int c) no size_t strspn(const char* cs, const char* ct) no size_t strcspn(const char* cs, const char* ct) no char* strpbrk(const char* cs, const char* ct) yes char* strstr(const char* cs, const char* ct) yes size_t strlen(const char* cs) yes size_t strnlen(const char* cs, size_t maxlen) yes char * strdup (const char *s) no char* strerror(int n) no char* strtok(char* s, const char* t) no size_t strxfrm(char* s, const char* ct, size_t n) yes void* memcpy(void* s, const void* ct, size_t n) yes void* memmove(void* s, const void* ct, size_t n) yes int memcmp(const void* cs, const void* ct, size_t n) no void* memchr(const void* cs, int c, size_t n) yes void* memset(void* s, int c, size_t n) time.h no clock_t clock(void) yes int gettimeofday (struct timeval *tv, void *tz) no time_t time(time_t* tp) no double difftime(time_t time2, time_t time1) no time_t mktime(struct tm* tp) no char* asctime(const struct tm* tp) no char* ctime(const time_t* tp) no struct tm* gmtime(const time_t* tp) no struct tm* localtime(const time_t* tp) no size_t strftime(char* s, size_t smax, const char* fmt, const struct tm* tp) unistd.h yes int exec (long addr, int argc, char **argv)

Usage example

Here's an example of a very simple payload (hello.c) and how to build it:

#include <libpayload.h>

int main(void)
{
    printf("Hello, world!\n");
    halt();
    return 0;
}

Building the payload:

lpgcc -o hello.elf hello.c

I, the copyright holder of this work, hereby release it into the public domain. This applies worldwide. In case this is not legally possible: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.