Created
January 12, 2020 12:07
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Read binary data from a file into a C struct using mmap(2)
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| /* | |
| * Load raw binary data from a mmap(2)'ed file | |
| * Mind your endianness and alignment. | |
| * | |
| * Sun, 12 Jan 2020 12:00:00 +0000 | |
| * By Gydo194 | |
| * | |
| * This code is in the public domain, you may use and redistribute this | |
| * file as you wish, however I shall not be responsible for any damage caused | |
| * by you doing so. | |
| */ | |
| #include <stdio.h> | |
| #include <fcntl.h> | |
| #include <sys/types.h> | |
| #include <sys/stat.h> | |
| #include <unistd.h> | |
| #include <sys/io.h> | |
| #include <sys/mman.h> | |
| #define COLOR_RED "\e[31m" | |
| #define COLOR_GREEN "\e[32m" | |
| #define COLOR_RESET "\e[0m" | |
| typedef unsigned char u8_t; | |
| typedef unsigned short u16_t; | |
| struct mtef | |
| { | |
| u8_t value1; | |
| u8_t value2; | |
| }; | |
| /* file as unsigned char for now */ | |
| unsigned char *file; | |
| int size, status, fd; | |
| struct stat s; | |
| void mmap_file(const char * const filename) | |
| { | |
| /* open file */ | |
| fd = open (filename, O_RDONLY); | |
| /* Get the size of the file. */ | |
| status = fstat (fd, & s); | |
| size = s.st_size; | |
| file = (char *) mmap (0, size, PROT_READ, MAP_PRIVATE, fd, 0); | |
| } | |
| void interpret_memory_region(const void * const address) | |
| { | |
| const struct mtef * mtef_region; | |
| u8_t parsed_value1, parsed_value2; | |
| /* zero just to be sure */ | |
| parsed_value1 = 0x00; | |
| parsed_value2 = 0x00; | |
| /* cast raw memory region to struct */ | |
| mtef_region = (const struct mtef *) address; | |
| printf(COLOR_GREEN "Loaded address '0x%X' as MTEF struct" COLOR_RESET "\n", mtef_region); | |
| /* copy values from mapped address onto the stack */ | |
| puts("Loading values..."); | |
| parsed_value1 = mtef_region->value1; | |
| parsed_value2 = mtef_region->value2; | |
| puts(COLOR_GREEN "Success!" COLOR_RESET); | |
| /* if all goes well.. */ | |
| printf(COLOR_GREEN "VALUE 1: '%d'\nVALUE 2: '%d'" COLOR_RESET "\n", parsed_value1, parsed_value2); | |
| } | |
| int main(int argc, char const *argv[]) | |
| { | |
| if(argc < 2) | |
| { | |
| /* i do want a file path from you */ | |
| printf(COLOR_RED "Usage: %s <file>" COLOR_RESET "\n", argv[0]); | |
| return 1; | |
| } | |
| printf("Loading file '%s' ...\n", argv[1]); | |
| mmap_file(argv[1]); | |
| puts(COLOR_GREEN "Success!" COLOR_RESET); | |
| interpret_memory_region(file); | |
| return 0; | |
| } |
You are not unmapping the memory and closing the file. That is a big uff
Left as an excersise to the reader.
This was just a proof of concept to show how this works to my friend. Error handling and proper cleanup has been neglected a bit. Maybe i should have stated that sonewhere.
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You are not unmapping the memory and closing the file. That is a big uff