Commit b57a2907 authored by Kees Cook's avatar Kees Cook
Browse files

selftests/exec: Build both static and non-static load_address tests 

After commit 4d1cd3b2 ("tools/testing/selftests/exec: fix link
error"), the load address alignment tests tried to build statically.
This was silently ignored in some cases. However, after attempting to
further fix the build by switching to "-static-pie", the test started
failing. This appears to be due to non-PT_INTERP ET_DYN execs ("static
PIE") not doing alignment correctly, which remains unfixed[1]. See commit
aeb79237 ("revert "fs/binfmt_elf: use PT_LOAD p_align values for
static PIE"") for more details.

Provide rules to build both static and non-static PIE binaries, improve
debug reporting, and perform several test steps instead of a single
all-or-nothing test. However, do not actually enable static-pie tests;
alignment specification is only supported for ET_DYN with PT_INTERP
("regular PIE").

Link: https://bugzilla.kernel.org/show_bug.cgi?id=215275 [1]
Link: https://lore.kernel.org/r/20240508173149.677910-1-keescook@chromium.org


Signed-off-by: default avatarKees Cook <kees@kernel.org>
parent c3f38fa6

tools/testing/selftests/exec/Makefile

+12 −7
Original line number Diff line number Diff line
@@ -3,8 +3,13 @@ CFLAGS = -Wall 
CFLAGS += -Wno-nonnull

CFLAGS += -D_GNU_SOURCE



ALIGNS := 0x1000 0x200000 0x1000000

ALIGN_PIES        := $(patsubst %,load_address.%,$(ALIGNS))

ALIGN_STATIC_PIES := $(patsubst %,load_address.static.%,$(ALIGNS))

ALIGNMENT_TESTS   := $(ALIGN_PIES)



TEST_PROGS := binfmt_script.py

TEST_GEN_PROGS := execveat load_address_4096 load_address_2097152 load_address_16777216 non-regular

TEST_GEN_PROGS := execveat non-regular $(ALIGNMENT_TESTS)

TEST_GEN_FILES := execveat.symlink execveat.denatured script subdir

# Makefile is a run-time dependency, since it's accessed by the execveat test

TEST_FILES := Makefile
@@ -28,9 +33,9 @@ $(OUTPUT)/execveat.symlink: $(OUTPUT)/execveat 
$(OUTPUT)/execveat.denatured: $(OUTPUT)/execveat

	cp $< $@

	chmod -x $@

$(OUTPUT)/load_address_4096: load_address.c

	$(CC) $(CFLAGS) $(LDFLAGS) -Wl,-z,max-page-size=0x1000 -pie -static $< -o $@

$(OUTPUT)/load_address_2097152: load_address.c

	$(CC) $(CFLAGS) $(LDFLAGS) -Wl,-z,max-page-size=0x200000 -pie -static $< -o $@

$(OUTPUT)/load_address_16777216: load_address.c

	$(CC) $(CFLAGS) $(LDFLAGS) -Wl,-z,max-page-size=0x1000000 -pie -static $< -o $@
 
$(OUTPUT)/load_address.0x%: load_address.c

	$(CC) $(CFLAGS) $(LDFLAGS) -Wl,-z,max-page-size=$(lastword $(subst ., ,$@)) \

		-fPIE -pie $< -o $@

$(OUTPUT)/load_address.static.0x%: load_address.c

	$(CC) $(CFLAGS) $(LDFLAGS) -Wl,-z,max-page-size=$(lastword $(subst ., ,$@)) \

		-fPIE -static-pie $< -o $@

tools/testing/selftests/exec/load_address.c

+54 −13
Original line number Diff line number Diff line
@@ -5,11 +5,13 @@ 
#include <link.h>

#include <stdio.h>

#include <stdlib.h>

#include <stdbool.h>

#include "../kselftest.h"



struct Statistics {

	unsigned long long load_address;

	unsigned long long alignment;

	bool interp;

};



int ExtractStatistics(struct dl_phdr_info *info, size_t size, void *data)
@@ -26,11 +28,20 @@ int ExtractStatistics(struct dl_phdr_info *info, size_t size, void *data) 
	stats->alignment = 0;



	for (i = 0; i < info->dlpi_phnum; i++) {

		unsigned long long align;



		if (info->dlpi_phdr[i].p_type == PT_INTERP) {

			stats->interp = true;

			continue;

		}



		if (info->dlpi_phdr[i].p_type != PT_LOAD)

			continue;



		if (info->dlpi_phdr[i].p_align > stats->alignment)

			stats->alignment = info->dlpi_phdr[i].p_align;

		align = info->dlpi_phdr[i].p_align;



		if (align > stats->alignment)

			stats->alignment = align;

	}



	return 1;  // Terminate dl_iterate_phdr.
@@ -38,27 +49,57 @@ int ExtractStatistics(struct dl_phdr_info *info, size_t size, void *data) 


int main(int argc, char **argv)

{

	struct Statistics extracted;

	unsigned long long misalign;

	struct Statistics extracted = { };

	unsigned long long misalign, pow2;

	bool interp_needed;

	char buf[1024];

	FILE *maps;

	int ret;



	ksft_print_header();

	ksft_set_plan(1);

	ksft_set_plan(4);



	/* Dump maps file for debugging reference. */

	maps = fopen("/proc/self/maps", "r");

	if (!maps)

		ksft_exit_fail_msg("FAILED: /proc/self/maps: %s\n", strerror(errno));

	while (fgets(buf, sizeof(buf), maps)) {

		ksft_print_msg("%s", buf);

	}

	fclose(maps);



	/* Walk the program headers. */

	ret = dl_iterate_phdr(ExtractStatistics, &extracted);

	if (ret != 1)

		ksft_exit_fail_msg("FAILED: dl_iterate_phdr\n");



	if (extracted.alignment == 0)

		ksft_exit_fail_msg("FAILED: No alignment found\n");

	else if (extracted.alignment & (extracted.alignment - 1))

		ksft_exit_fail_msg("FAILED: Alignment is not a power of 2\n");

	/* Report our findings. */

	ksft_print_msg("load_address=%#llx alignment=%#llx\n",

		       extracted.load_address, extracted.alignment);



	/* If we're named with ".static." we expect no INTERP. */

	interp_needed = strstr(argv[0], ".static.") == NULL;



	/* Were we built as expected? */

	ksft_test_result(interp_needed == extracted.interp,

			 "%s INTERP program header %s\n",

			 interp_needed ? "Wanted" : "Unwanted",

			 extracted.interp ? "seen" : "missing");



	/* Did we find an alignment? */

	ksft_test_result(extracted.alignment != 0,

			 "Alignment%s found\n", extracted.alignment ? "" : " NOT");



	/* Is the alignment sane? */

	pow2 = extracted.alignment & (extracted.alignment - 1);

	ksft_test_result(pow2 == 0,

			 "Alignment is%s a power of 2: %#llx\n",

			 pow2 == 0 ? "" : " NOT", extracted.alignment);



	/* Is the load address aligned? */

	misalign = extracted.load_address & (extracted.alignment - 1);

	if (misalign)

		ksft_exit_fail_msg("FAILED: alignment = %llu, load_address = %llu\n",

				   extracted.alignment, extracted.load_address);

	ksft_test_result(misalign == 0, "Load Address is %saligned (%#llx)\n",

			 misalign ? "MIS" : "", misalign);



	ksft_test_result_pass("Completed\n");

	ksft_finished();

}