compiler-rt/test/shadowcallstack/libc_support.h

   1 // This header provides replacements for certain libc functions. It is necessary
   2 // in order to safely run the tests on aarch64, because the system libc might
   3 // not have been compiled with -ffixed-x18.
   4
   5 #pragma once
   6
   7 #include <stddef.h>
   8 #include <stdint.h>
   9 #include <stdio.h>
  10
  11 #ifdef __aarch64__
  12
  13 size_t scs_strlen(const char *p) {
  14   size_t retval = 0;
  15   while (*p++)
  16     retval++;
  17   return retval;
  18 }
  19
  20 // We mark this function as noinline to make sure that its callers do not
  21 // become leaf functions as a result of inlining. This is because we want to
  22 // make sure that we generate the correct code for non-leaf functions.
  23
  24 __attribute__((noinline)) void scs_fputs_stdout(const char *p) {
  25   __asm__ __volatile__(
  26       "mov x0, #1\n"  // stdout
  27       "mov x1, %0\n"
  28       "mov x2, %1\n"
  29       "mov x8, #64\n"  // write
  30       "svc #0\n" ::"r"(p),
  31       "r"(scs_strlen(p))
  32       : "x0", "x1", "x2", "x8");
  33 }
  34
  35 #else
  36 #error Unsupported platform
  37 #endif