lib/efi_selftest/efi_selftest_unaligned.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * efi_selftest_unaligned
   4  *
   5  * Copyright (c) 2018 Heinrich Schuchardt <xypron.glpk@gmx.de>
   6  *
   7  * Test unaligned memory access on ARMv7.
   8  */
   9
  10 #include <efi_selftest.h>
  11
  12 struct aligned_buffer {
  13         char a[8] __aligned(8);
  14 };
  15
  16 /*
  17  * Return an u32 at a given address.
  18  * If the address is not four byte aligned, an unaligned memory access
  19  * occurs.
  20  *
  21  * @addr:       address to read
  22  * Return:      value at the address
  23  */
  24 static inline u32 deref(void *addr)
  25 {
  26         int ret;
  27
  28         asm(
  29                 "ldr %[out], [%[in]]\n\t"
  30                 : [out] "=r" (ret)
  31                 : [in] "r" (addr)
  32         );
  33         return ret;
  34 }
  35
  36 /*
  37  * Execute unit test.
  38  * An unaligned memory access is executed. The result is checked.
  39  *
  40  * Return:      EFI_ST_SUCCESS for success
  41  */
  42 static int execute(void)
  43 {
  44         struct aligned_buffer buf = {
  45                 {0, 1, 2, 3, 4, 5, 6, 7},
  46         };
  47         u32 r = 0;
  48
  49         /* Read an unaligned address */
  50         r = deref(&buf.a[1]);
  51
  52         /* UEFI only supports low endian systems */
  53         if (r != 0x04030201) {
  54                 efi_st_error("Unaligned access failed");
  55                 return EFI_ST_FAILURE;
  56         }
  57
  58         return EFI_ST_SUCCESS;
  59 }
  60
  61 EFI_UNIT_TEST(unaligned) = {
  62         .name = "unaligned memory access",
  63         .phase = EFI_EXECUTE_BEFORE_BOOTTIME_EXIT,
  64         .execute = execute,
  65 };