root/tools/testing/selftests/x86/test_syscall_vdso.c

DEFINITIONS

1. main
2. get_syscall
3. print_regs64
4. check_regs64
5. prep_args
6. print_flags
7. run_syscall
8. run_syscall_twice
9. ptrace_me
10. main

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * 32-bit syscall ABI conformance test.
   4  *
   5  * Copyright (c) 2015 Denys Vlasenko
   6  */
   7 /*
   8  * Can be built statically:
   9  * gcc -Os -Wall -static -m32 test_syscall_vdso.c thunks_32.S
  10  */
  11 #undef _GNU_SOURCE
  12 #define _GNU_SOURCE 1
  13 #undef __USE_GNU
  14 #define __USE_GNU 1
  15 #include <unistd.h>
  16 #include <stdlib.h>
  17 #include <string.h>
  18 #include <stdio.h>
  19 #include <signal.h>
  20 #include <sys/types.h>
  21 #include <sys/select.h>
  22 #include <sys/time.h>
  23 #include <elf.h>
  24 #include <sys/ptrace.h>
  25 #include <sys/wait.h>
  26 
  27 #if !defined(__i386__)
  28 int main(int argc, char **argv, char **envp)
  29 {
  30         printf("[SKIP]\tNot a 32-bit x86 userspace\n");
  31         return 0;
  32 }
  33 #else
  34 
  35 long syscall_addr;
  36 long get_syscall(char **envp)
  37 {
  38         Elf32_auxv_t *auxv;
  39         while (*envp++ != NULL)
  40                 continue;
  41         for (auxv = (void *)envp; auxv->a_type != AT_NULL; auxv++)
  42                 if (auxv->a_type == AT_SYSINFO)
  43                         return auxv->a_un.a_val;
  44         printf("[WARN]\tAT_SYSINFO not supplied\n");
  45         return 0;
  46 }
  47 
  48 asm (
  49         "       .pushsection .text\n"
  50         "       .global int80\n"
  51         "int80:\n"
  52         "       int     $0x80\n"
  53         "       ret\n"
  54         "       .popsection\n"
  55 );
  56 extern char int80;
  57 
  58 struct regs64 {
  59         uint64_t rax, rbx, rcx, rdx;
  60         uint64_t rsi, rdi, rbp, rsp;
  61         uint64_t r8,  r9,  r10, r11;
  62         uint64_t r12, r13, r14, r15;
  63 };
  64 struct regs64 regs64;
  65 int kernel_is_64bit;
  66 
  67 asm (
  68         "       .pushsection .text\n"
  69         "       .code64\n"
  70         "get_regs64:\n"
  71         "       push    %rax\n"
  72         "       mov     $regs64, %eax\n"
  73         "       pop     0*8(%rax)\n"
  74         "       movq    %rbx, 1*8(%rax)\n"
  75         "       movq    %rcx, 2*8(%rax)\n"
  76         "       movq    %rdx, 3*8(%rax)\n"
  77         "       movq    %rsi, 4*8(%rax)\n"
  78         "       movq    %rdi, 5*8(%rax)\n"
  79         "       movq    %rbp, 6*8(%rax)\n"
  80         "       movq    %rsp, 7*8(%rax)\n"
  81         "       movq    %r8,  8*8(%rax)\n"
  82         "       movq    %r9,  9*8(%rax)\n"
  83         "       movq    %r10, 10*8(%rax)\n"
  84         "       movq    %r11, 11*8(%rax)\n"
  85         "       movq    %r12, 12*8(%rax)\n"
  86         "       movq    %r13, 13*8(%rax)\n"
  87         "       movq    %r14, 14*8(%rax)\n"
  88         "       movq    %r15, 15*8(%rax)\n"
  89         "       ret\n"
  90         "poison_regs64:\n"
  91         "       movq    $0x7f7f7f7f, %r8\n"
  92         "       shl     $32, %r8\n"
  93         "       orq     $0x7f7f7f7f, %r8\n"
  94         "       movq    %r8, %r9\n"
  95         "       incq    %r9\n"
  96         "       movq    %r9, %r10\n"
  97         "       incq    %r10\n"
  98         "       movq    %r10, %r11\n"
  99         "       incq    %r11\n"
 100         "       movq    %r11, %r12\n"
 101         "       incq    %r12\n"
 102         "       movq    %r12, %r13\n"
 103         "       incq    %r13\n"
 104         "       movq    %r13, %r14\n"
 105         "       incq    %r14\n"
 106         "       movq    %r14, %r15\n"
 107         "       incq    %r15\n"
 108         "       ret\n"
 109         "       .code32\n"
 110         "       .popsection\n"
 111 );
 112 extern void get_regs64(void);
 113 extern void poison_regs64(void);
 114 extern unsigned long call64_from_32(void (*function)(void));
 115 void print_regs64(void)
 116 {
 117         if (!kernel_is_64bit)
 118                 return;
 119         printf("ax:%016llx bx:%016llx cx:%016llx dx:%016llx\n", regs64.rax,  regs64.rbx,  regs64.rcx,  regs64.rdx);
 120         printf("si:%016llx di:%016llx bp:%016llx sp:%016llx\n", regs64.rsi,  regs64.rdi,  regs64.rbp,  regs64.rsp);
 121         printf(" 8:%016llx  9:%016llx 10:%016llx 11:%016llx\n", regs64.r8 ,  regs64.r9 ,  regs64.r10,  regs64.r11);
 122         printf("12:%016llx 13:%016llx 14:%016llx 15:%016llx\n", regs64.r12,  regs64.r13,  regs64.r14,  regs64.r15);
 123 }
 124 
 125 int check_regs64(void)
 126 {
 127         int err = 0;
 128         int num = 8;
 129         uint64_t *r64 = &regs64.r8;
 130         uint64_t expected = 0x7f7f7f7f7f7f7f7fULL;
 131 
 132         if (!kernel_is_64bit)
 133                 return 0;
 134 
 135         do {
 136                 if (*r64 == expected++)
 137                         continue; /* register did not change */
 138                 if (syscall_addr != (long)&int80) {
 139                         /*
 140                          * Non-INT80 syscall entrypoints are allowed to clobber R8+ regs:
 141                          * either clear them to 0, or for R11, load EFLAGS.
 142                          */
 143                         if (*r64 == 0)
 144                                 continue;
 145                         if (num == 11) {
 146                                 printf("[NOTE]\tR11 has changed:%016llx - assuming clobbered by SYSRET insn\n", *r64);
 147                                 continue;
 148                         }
 149                 } else {
 150                         /*
 151                          * INT80 syscall entrypoint can be used by
 152                          * 64-bit programs too, unlike SYSCALL/SYSENTER.
 153                          * Therefore it must preserve R12+
 154                          * (they are callee-saved registers in 64-bit C ABI).
 155                          *
 156                          * Starting in Linux 4.17 (and any kernel that
 157                          * backports the change), R8..11 are preserved.
 158                          * Historically (and probably unintentionally), they
 159                          * were clobbered or zeroed.
 160                          */
 161                 }
 162                 printf("[FAIL]\tR%d has changed:%016llx\n", num, *r64);
 163                 err++;
 164         } while (r64++, ++num < 16);
 165 
 166         if (!err)
 167                 printf("[OK]\tR8..R15 did not leak kernel data\n");
 168         return err;
 169 }
 170 
 171 int nfds;
 172 fd_set rfds;
 173 fd_set wfds;
 174 fd_set efds;
 175 struct timespec timeout;
 176 sigset_t sigmask;
 177 struct {
 178         sigset_t *sp;
 179         int sz;
 180 } sigmask_desc;
 181 
 182 void prep_args()
 183 {
 184         nfds = 42;
 185         FD_ZERO(&rfds);
 186         FD_ZERO(&wfds);
 187         FD_ZERO(&efds);
 188         FD_SET(0, &rfds);
 189         FD_SET(1, &wfds);
 190         FD_SET(2, &efds);
 191         timeout.tv_sec = 0;
 192         timeout.tv_nsec = 123;
 193         sigemptyset(&sigmask);
 194         sigaddset(&sigmask, SIGINT);
 195         sigaddset(&sigmask, SIGUSR2);
 196         sigaddset(&sigmask, SIGRTMAX);
 197         sigmask_desc.sp = &sigmask;
 198         sigmask_desc.sz = 8; /* bytes */
 199 }
 200 
 201 static void print_flags(const char *name, unsigned long r)
 202 {
 203         static const char *bitarray[] = {
 204         "\n" ,"c\n" ,/* Carry Flag */
 205         "0 " ,"1 "  ,/* Bit 1 - always on */
 206         ""   ,"p "  ,/* Parity Flag */
 207         "0 " ,"3? " ,
 208         ""   ,"a "  ,/* Auxiliary carry Flag */
 209         "0 " ,"5? " ,
 210         ""   ,"z "  ,/* Zero Flag */
 211         ""   ,"s "  ,/* Sign Flag */
 212         ""   ,"t "  ,/* Trap Flag */
 213         ""   ,"i "  ,/* Interrupt Flag */
 214         ""   ,"d "  ,/* Direction Flag */
 215         ""   ,"o "  ,/* Overflow Flag */
 216         "0 " ,"1 "  ,/* I/O Privilege Level (2 bits) */
 217         "0"  ,"1"   ,/* I/O Privilege Level (2 bits) */
 218         ""   ,"n "  ,/* Nested Task */
 219         "0 " ,"15? ",
 220         ""   ,"r "  ,/* Resume Flag */
 221         ""   ,"v "  ,/* Virtual Mode */
 222         ""   ,"ac " ,/* Alignment Check/Access Control */
 223         ""   ,"vif ",/* Virtual Interrupt Flag */
 224         ""   ,"vip ",/* Virtual Interrupt Pending */
 225         ""   ,"id " ,/* CPUID detection */
 226         NULL
 227         };
 228         const char **bitstr;
 229         int bit;
 230 
 231         printf("%s=%016lx ", name, r);
 232         bitstr = bitarray + 42;
 233         bit = 21;
 234         if ((r >> 22) != 0)
 235                 printf("(extra bits are set) ");
 236         do {
 237                 if (bitstr[(r >> bit) & 1][0])
 238                         fputs(bitstr[(r >> bit) & 1], stdout);
 239                 bitstr -= 2;
 240                 bit--;
 241         } while (bit >= 0);
 242 }
 243 
 244 int run_syscall(void)
 245 {
 246         long flags, bad_arg;
 247 
 248         prep_args();
 249 
 250         if (kernel_is_64bit)
 251                 call64_from_32(poison_regs64);
 252         /*print_regs64();*/
 253 
 254         asm("\n"
 255         /* Try 6-arg syscall: pselect. It should return quickly */
 256         "       push    %%ebp\n"
 257         "       mov     $308, %%eax\n"     /* PSELECT */
 258         "       mov     nfds, %%ebx\n"     /* ebx  arg1 */
 259         "       mov     $rfds, %%ecx\n"    /* ecx  arg2 */
 260         "       mov     $wfds, %%edx\n"    /* edx  arg3 */
 261         "       mov     $efds, %%esi\n"    /* esi  arg4 */
 262         "       mov     $timeout, %%edi\n" /* edi  arg5 */
 263         "       mov     $sigmask_desc, %%ebp\n" /* %ebp arg6 */
 264         "       push    $0x200ed7\n"      /* set almost all flags */
 265         "       popf\n"         /* except TF, IOPL, NT, RF, VM, AC, VIF, VIP */
 266         "       call    *syscall_addr\n"
 267         /* Check that registers are not clobbered */
 268         "       pushf\n"
 269         "       pop     %%eax\n"
 270         "       cld\n"
 271         "       cmp     nfds, %%ebx\n"     /* ebx  arg1 */
 272         "       mov     $1, %%ebx\n"
 273         "       jne     1f\n"
 274         "       cmp     $rfds, %%ecx\n"    /* ecx  arg2 */
 275         "       mov     $2, %%ebx\n"
 276         "       jne     1f\n"
 277         "       cmp     $wfds, %%edx\n"    /* edx  arg3 */
 278         "       mov     $3, %%ebx\n"
 279         "       jne     1f\n"
 280         "       cmp     $efds, %%esi\n"    /* esi  arg4 */
 281         "       mov     $4, %%ebx\n"
 282         "       jne     1f\n"
 283         "       cmp     $timeout, %%edi\n" /* edi  arg5 */
 284         "       mov     $5, %%ebx\n"
 285         "       jne     1f\n"
 286         "       cmpl    $sigmask_desc, %%ebp\n" /* %ebp arg6 */
 287         "       mov     $6, %%ebx\n"
 288         "       jne     1f\n"
 289         "       mov     $0, %%ebx\n"
 290         "1:\n"
 291         "       pop     %%ebp\n"
 292         : "=a" (flags), "=b" (bad_arg)
 293         :
 294         : "cx", "dx", "si", "di"
 295         );
 296 
 297         if (kernel_is_64bit) {
 298                 memset(&regs64, 0x77, sizeof(regs64));
 299                 call64_from_32(get_regs64);
 300                 /*print_regs64();*/
 301         }
 302 
 303         /*
 304          * On paravirt kernels, flags are not preserved across syscalls.
 305          * Thus, we do not consider it a bug if some are changed.
 306          * We just show ones which do.
 307          */
 308         if ((0x200ed7 ^ flags) != 0) {
 309                 print_flags("[WARN]\tFlags before", 0x200ed7);
 310                 print_flags("[WARN]\tFlags  after", flags);
 311                 print_flags("[WARN]\tFlags change", (0x200ed7 ^ flags));
 312         }
 313 
 314         if (bad_arg) {
 315                 printf("[FAIL]\targ#%ld clobbered\n", bad_arg);
 316                 return 1;
 317         }
 318         printf("[OK]\tArguments are preserved across syscall\n");
 319 
 320         return check_regs64();
 321 }
 322 
 323 int run_syscall_twice()
 324 {
 325         int exitcode = 0;
 326         long sv;
 327 
 328         if (syscall_addr) {
 329                 printf("[RUN]\tExecuting 6-argument 32-bit syscall via VDSO\n");
 330                 exitcode = run_syscall();
 331         }
 332         sv = syscall_addr;
 333         syscall_addr = (long)&int80;
 334         printf("[RUN]\tExecuting 6-argument 32-bit syscall via INT 80\n");
 335         exitcode += run_syscall();
 336         syscall_addr = sv;
 337         return exitcode;
 338 }
 339 
 340 void ptrace_me()
 341 {
 342         pid_t pid;
 343 
 344         fflush(NULL);
 345         pid = fork();
 346         if (pid < 0)
 347                 exit(1);
 348         if (pid == 0) {
 349                 /* child */
 350                 if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) != 0)
 351                         exit(0);
 352                 raise(SIGSTOP);
 353                 return;
 354         }
 355         /* parent */
 356         printf("[RUN]\tRunning tests under ptrace\n");
 357         while (1) {
 358                 int status;
 359                 pid = waitpid(-1, &status, __WALL);
 360                 if (WIFEXITED(status))
 361                         exit(WEXITSTATUS(status));
 362                 if (WIFSIGNALED(status))
 363                         exit(WTERMSIG(status));
 364                 if (pid <= 0 || !WIFSTOPPED(status)) /* paranoia */
 365                         exit(255);
 366                 /*
 367                  * Note: we do not inject sig = WSTOPSIG(status).
 368                  * We probably should, but careful: do not inject SIGTRAP
 369                  * generated by syscall entry/exit stops.
 370                  * That kills the child.
 371                  */
 372                 ptrace(PTRACE_SYSCALL, pid, 0L, 0L /*sig*/);
 373         }
 374 }
 375 
 376 int main(int argc, char **argv, char **envp)
 377 {
 378         int exitcode = 0;
 379         int cs;
 380 
 381         asm("\n"
 382         "       movl    %%cs, %%eax\n"
 383         : "=a" (cs)
 384         );
 385         kernel_is_64bit = (cs == 0x23);
 386         if (!kernel_is_64bit)
 387                 printf("[NOTE]\tNot a 64-bit kernel, won't test R8..R15 leaks\n");
 388 
 389         /* This only works for non-static builds:
 390          * syscall_addr = dlsym(dlopen("linux-gate.so.1", RTLD_NOW), "__kernel_vsyscall");
 391          */
 392         syscall_addr = get_syscall(envp);
 393 
 394         exitcode += run_syscall_twice();
 395         ptrace_me();
 396         exitcode += run_syscall_twice();
 397 
 398         return exitcode;
 399 }
 400 #endif