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#include <linux/elf.h> // for Elf64_Sym, (anonymous struct)::(anonymous)
#include <string.h> // for NULL, strcmp
struct timespec;
int (*__vdso_clock_gettime)(int, struct timespec *) = NULL;
int (*__vdso_getcpu)(unsigned *, unsigned *, void *) = NULL;
int (*__vdso_time)(long *) = NULL;
static __inline __attribute__((used)) void vdso_setup(Elf64_Ehdr *vdso_addr)
{
Elf64_Phdr *phdr =
(Elf64_Phdr *)((char *)vdso_addr + vdso_addr->e_phoff);
for (int i = 0; i < vdso_addr->e_phnum; i++) {
if (phdr[i].p_type == PT_DYNAMIC) {
Elf64_Dyn *dyn = (Elf64_Dyn *)((char *)vdso_addr +
phdr[i].p_offset);
const char *strtab = NULL;
Elf64_Sym *symtab = NULL;
for (; dyn->d_tag != DT_NULL; dyn++) {
if (dyn->d_tag == DT_STRTAB) {
strtab = (const char *)vdso_addr +
dyn->d_un.d_ptr;
} else if (dyn->d_tag == DT_SYMTAB) {
symtab =
(Elf64_Sym *)((char *)vdso_addr +
dyn->d_un.d_ptr);
}
}
if (strtab == NULL || symtab == NULL) {
return;
}
Elf64_Sym *sym = symtab;
while ((char *)sym < (char *)strtab) {
if (sym->st_name != 0 && sym->st_value != 0) {
const char *name =
strtab + sym->st_name;
if (strcmp(name,
"__vdso_clock_gettime") == 0)
__vdso_clock_gettime =
(void *)(vdso_addr +
sym->st_value);
else if (strcmp(name,
"__vdso_getcpu") == 0)
__vdso_getcpu =
(void *)(vdso_addr +
sym->st_value);
else if (strcmp(name, "__vdso_time") ==
0)
__vdso_time =
(void *)(vdso_addr +
sym->st_value);
}
sym = (Elf64_Sym *)((char *)sym +
sizeof(Elf64_Sym));
}
}
}
}
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