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
- USB stack
Reads and parses the coreboot table.

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, or an NVRAM dump.
GRUB invaders has been ported successfully to libpayload (patch pending).
tint (a "falling blocks" game) 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

It is now in main coreboot git tree (see Download_coreboot for additional reference)

$ git clone http://review.coreboot.org/p/coreboot
$ cd payloads/libpayload
$ make menuconfig
$ make install

Here gerrit you can find pending patches for libpayload

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	`char* strtok_r(char* s, const char* t, char **p)`
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;

} </source>

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.