/* * Copyright 2002-2019 Intel Corporation. * * This software is provided to you as Sample Source Code as defined in the accompanying * End User License Agreement for the Intel(R) Software Development Products ("Agreement") * section 1.L. * * This software and the related documents are provided as is, with no express or implied * warranties, other than those that are expressly stated in the License. */ #include #include #include #include #include #include #include #include #include #include #ifndef __NR_set_thread_area # define __NR_set_thread_area 243 #endif #ifndef __NR_get_thread_area # define __NR_get_thread_area 244 #endif #ifndef SYS_set_thread_area # define SYS_set_thread_area __NR_set_thread_area #endif #ifndef SYS_get_thread_area # define SYS_get_thread_area __NR_get_thread_area #endif typedef struct { unsigned int entry_number; unsigned int base_addr; unsigned int limit; unsigned int seg_32bit:1; unsigned int contents:2; unsigned int read_exec_only:1; unsigned int limit_in_pages:1; unsigned int seg_not_present:1; unsigned int useable:1; }UserDesc; # define TLS_GET_GS_REG() \ ({ int __seg; __asm ("movw %%gs, %w0" : "=q" (__seg)); __seg & 0xffff; }) # define TLS_SET_GS_REG(val) \ __asm ("movw %w0, %%gs" :: "q" (val)) # define TLS_GET_FS_REG() \ ({ int __seg; __asm ("movw %%fs, %w0" : "=q" (__seg)); __seg & 0xffff; }) # define TLS_SET_FS_REG(val) \ __asm ("movw %w0, %%fs" :: "q" (val)) typedef struct { unsigned int d1; unsigned int d2; }UserInfo; #define GDT_NUM_OF_ENTRIES 3 #define GDT_ENTRIES 16 unsigned int GdtFirstEntry() { static int first = 0; if (first) return first; UserDesc thrDescr; for (int i=0; i< GDT_ENTRIES; i++) { thrDescr.entry_number = i; int res = syscall(SYS_get_thread_area, &thrDescr); if ((res == 0) || (errno != EINVAL)) { first = i; return first; } } fprintf(stderr, "First GDT entry is not found\n"); exit(-1); } int main (int argc, char *argv[]) { int rc; int i; UserDesc tr; UserDesc set_tr; int res; tr.entry_number = GdtFirstEntry(); res = syscall(SYS_get_thread_area, &tr); if (res != 0) { printf("SYS_get_thread_area failed with error: %s\n", strerror(errno)); return 0; } tr.entry_number = (unsigned)-1; tr.base_addr = 0xabcd; res = syscall(SYS_set_thread_area, &tr); if (res != 0) { printf("SYS_set_thread_area failed with error: %s\n", strerror(errno)); return 0; } printf("Allocated entry is %d\n", tr.entry_number); memset(&set_tr, 0, sizeof(UserDesc)); set_tr.entry_number = tr.entry_number; set_tr.read_exec_only = 1; set_tr.seg_not_present = 1; set_tr.useable = 0; printf("Free entry %d\n", set_tr.entry_number); res = syscall(SYS_set_thread_area, &set_tr); if (res != 0) { printf("SYS_set_thread_area failed with error: %s\n", strerror(errno)); return 0; } tr.entry_number = (unsigned)-1; tr.base_addr = 0xcdef; res = syscall(SYS_set_thread_area, &tr); if (res != 0) { printf("SYS_set_thread_area failed with error: %s\n", strerror(errno)); return 0; } printf("Allocated entry is %d\n", tr.entry_number); tr.base_addr = 0; res = syscall(SYS_get_thread_area, &tr); if (res != 0) { printf("SYS_get_thread_area failed with error: %s\n", strerror(errno)); return 0; } printf("Base address for entry %d is 0x%x\n", tr.entry_number, tr.base_addr); tr.entry_number = GdtFirstEntry()+2; res = syscall(SYS_get_thread_area, &tr); if (res != 0) { printf("SYS_get_thread_area failed with error: %s\n", strerror(errno)); return 0; } printf("Base address for entry %d is 0x%x\n", tr.entry_number, tr.base_addr); return 0; }