load_address.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2#ifndef _GNU_SOURCE
  3#define _GNU_SOURCE
  4#endif
  5#include <link.h>
  6#include <stdio.h>
  7#include <stdlib.h>
  8#include <stdbool.h>
  9#include "kselftest.h"
 10
 11struct Statistics {
 12	unsigned long long load_address;
 13	unsigned long long alignment;
 14	bool interp;
 15};
 16
 17int ExtractStatistics(struct dl_phdr_info *info, size_t size, void *data)
 18{
 19	struct Statistics *stats = (struct Statistics *) data;
 20	int i;
 21
 22	if (info->dlpi_name != NULL && info->dlpi_name[0] != '\0') {
 23		// Ignore headers from other than the executable.
 24		return 2;
 25	}
 26
 27	stats->load_address = (unsigned long long) info->dlpi_addr;
 28	stats->alignment = 0;
 29
 30	for (i = 0; i < info->dlpi_phnum; i++) {
 31		unsigned long long align;
 32
 33		if (info->dlpi_phdr[i].p_type == PT_INTERP) {
 34			stats->interp = true;
 35			continue;
 36		}
 37
 38		if (info->dlpi_phdr[i].p_type != PT_LOAD)
 39			continue;
 40
 41		align = info->dlpi_phdr[i].p_align;
 42
 43		if (align > stats->alignment)
 44			stats->alignment = align;
 45	}
 46
 47	return 1;  // Terminate dl_iterate_phdr.
 48}
 49
 50int main(int argc, char **argv)
 51{
 52	struct Statistics extracted = { };
 53	unsigned long long misalign, pow2;
 54	bool interp_needed;
 55	char buf[1024];
 56	FILE *maps;
 57	int ret;
 58
 59	ksft_print_header();
 60	ksft_set_plan(4);
 61
 62	/* Dump maps file for debugging reference. */
 63	maps = fopen("/proc/self/maps", "r");
 64	if (!maps)
 65		ksft_exit_fail_msg("FAILED: /proc/self/maps: %s\n", strerror(errno));
 66	while (fgets(buf, sizeof(buf), maps)) {
 67		ksft_print_msg("%s", buf);
 68	}
 69	fclose(maps);
 70
 71	/* Walk the program headers. */
 72	ret = dl_iterate_phdr(ExtractStatistics, &extracted);
 73	if (ret != 1)
 74		ksft_exit_fail_msg("FAILED: dl_iterate_phdr\n");
 75
 76	/* Report our findings. */
 77	ksft_print_msg("load_address=%#llx alignment=%#llx\n",
 78		       extracted.load_address, extracted.alignment);
 79
 80	/* If we're named with ".static." we expect no INTERP. */
 81	interp_needed = strstr(argv[0], ".static.") == NULL;
 82
 83	/* Were we built as expected? */
 84	ksft_test_result(interp_needed == extracted.interp,
 85			 "%s INTERP program header %s\n",
 86			 interp_needed ? "Wanted" : "Unwanted",
 87			 extracted.interp ? "seen" : "missing");
 88
 89	/* Did we find an alignment? */
 90	ksft_test_result(extracted.alignment != 0,
 91			 "Alignment%s found\n", extracted.alignment ? "" : " NOT");
 92
 93	/* Is the alignment sane? */
 94	pow2 = extracted.alignment & (extracted.alignment - 1);
 95	ksft_test_result(pow2 == 0,
 96			 "Alignment is%s a power of 2: %#llx\n",
 97			 pow2 == 0 ? "" : " NOT", extracted.alignment);
 98
 99	/* Is the load address aligned? */
100	misalign = extracted.load_address & (extracted.alignment - 1);
101	ksft_test_result(misalign == 0, "Load Address is %saligned (%#llx)\n",
102			 misalign ? "MIS" : "", misalign);
103
104	ksft_finished();
105}