tests/libs/elftls_skew_align_test_helper.cpp

/*
 * Copyright (C) 2024 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
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 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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// LLD tries not to generate a PT_TLS segment where (p_vaddr % p_align) is
// non-zero. It can still do so if the p_align values are greater than a page.

#include <stdint.h>
#include <unistd.h>

#include "CHECK.h"

struct SmallVar {
  int field;
  char buffer[0x100 - sizeof(int)];
};

struct AlignedVar {
  int field;
  char buffer[0x20000 - sizeof(int)];
} __attribute__((aligned(0x20000)));

__thread struct SmallVar var1 = {13};
__thread struct SmallVar var2 = {17};
__thread struct AlignedVar var3;
__thread struct AlignedVar var4;

static uintptr_t var_addr(void* value) {
  // Maybe the optimizer would assume that the variable has the alignment it is
  // declared with.
  asm volatile("" : "+r,m"(value) : : "memory");
  return reinterpret_cast<uintptr_t>(value);
}

int main() {
  // Bionic only allocates ELF TLS blocks with up to page alignment.
  CHECK((var_addr(&var3) & (getpagesize() - 1)) == 0);
  CHECK((var_addr(&var4) & (getpagesize() - 1)) == 0);

  // TODO: These TLS accesses are broken with the current version of LLD. See
  // https://github.com/llvm/llvm-project/issues/84743.
#if !defined(__riscv)
  CHECK(var1.field == 13);
  CHECK(var2.field == 17);
#endif

  CHECK(var3.field == 0);
  CHECK(var4.field == 0);
  return 0;
}