auxv: dump elf auxillary vector information on freebsd

auxv.c

#include <stdio.h>                                                              
#include <elf.h>                                                                
                                                                                
/* /usr/include/x86/elf.h AT_* defs */                                          
                                                                                
typedef struct {                                                                
        const char *str_val;                                                    
        int type;                                                               
} Elf_AuxStr;                                                                   
                                                                                
Elf_AuxStr aux_map[AT_COUNT][2] = {                                                
        {"AT_NLL",      0},                                                     
        {"AT_IGNORE",   1},                                                     
        {"AT_EXECFD",   2},                                                     
        {"AT_PHDR",     3},                                                     
        {"AT_PHENT",    4},                                                     
        {"AT_PHNUM",    5},                                                     
        {"AT_PAGESZ",   6},                                                     
        {"AT_BASE",     7},                                                     
        {"AT_FLAGS",    8},                                                     
        {"AT_ENTRY",    9},                                                     
        {"AT_NOTELF",   10},                                                    
        {"AT_UID",      11},                                                    
        {"AT_EUID",     12},                                                    
        {"AT_GID",      13},                                                    
        {"AT_EGID",     14},                                                    
        {"AT_EXECPATH", 15},                                                    
        {"AT_CANARY",   16},                                                    
        {"AT_CANARYLEN", 17},                                                   
        {"AT_OSRELDATE", 18},                                                   
        {"AT_NCPUS",    19},                                                    
        {"AT_PAGESIZES", 20},                                                   
        {"AT_PAGESIZESLEN", 21},                                                
        {"AT_TIMEKEEP", 22},                                                    
        {"AT_STACKPROT", 23},                                                   
                                                                                
};                                                                              
                                                                                
int                                                                             
main(int argc, char* argv[], char* envp[])                                      
{                                                                               
        Elf_Auxinfo *aux_info;                                                  
        Elf_Auxinfo *auxp;                                                      
        Elf_AuxStr *aux_str;                                                    
        while(*envp++ != NULL);                                                 
                                                                                
        for (auxp = (Elf_Auxinfo *)envp; auxp->a_type != AT_NULL; auxp++)       
        {                                                                       
                aux_str = aux_map[auxp->a_type];                                   
                printf("val: %s int: %02d ptr: 0x%lx\n", aux_str->str_val, aux_str->type, auxp->a_un.a_val);
        }                                                                       
}

• Build:

(sbz@ogoshi:/tmp/) % cc -o auxv auxv.c

• Run:

(sbz@ogoshi:/tmp) % ./auxv            
val: AT_PHDR int: 03 ptr: 0x400040
val: AT_PHENT int: 04 ptr: 0x38
val: AT_PHNUM int: 05 ptr: 0x8
val: AT_PAGESZ int: 06 ptr: 0x1000
val: AT_FLAGS int: 08 ptr: 0x0
val: AT_ENTRY int: 09 ptr: 0x4004e0
val: AT_BASE int: 07 ptr: 0x600000
val: AT_EXECPATH int: 15 ptr: 0xffffefd6
val: AT_OSRELDATE int: 18 ptr: 0xf4270
val: AT_CANARY int: 16 ptr: 0xffffef96
val: AT_CANARYLEN int: 17 ptr: 0x40
val: AT_NCPUS int: 19 ptr: 0x4
val: AT_PAGESIZES int: 20 ptr: 0xffffef7e
val: AT_PAGESIZESLEN int: 21 ptr: 0x18
val: AT_TIMEKEEP int: 22 ptr: 0xfffff020
val: AT_STACKPROT int: 23 ptr: 0x3