[PATCH v3 2/2] Add self-test for verifying load alignment.

Chris Kennelly
2020-08-20T17:09:52Z

This produces a PIE binary with a variety of p_align requirements,
suitable for verifying that the load address meets that alignment
requirement.

Signed-off-by: Chris Kennelly <ckennelly@google.com>
---
tools/testing/selftests/exec/.gitignore | 1 +
tools/testing/selftests/exec/Makefile | 9 ++-
tools/testing/selftests/exec/load_address.c | 68 +++++++++++++++++++++
3 files changed, 76 insertions(+), 2 deletions(-)
create mode 100644 tools/testing/selftests/exec/load_address.c

diff --git a/tools/testing/selftests/exec/.gitignore b/tools/testing/selftests/exec/.gitignore
index 344a99c6da1b7..9e2f00343f15f 100644
--- a/tools/testing/selftests/exec/.gitignore
+++ b/tools/testing/selftests/exec/.gitignore
@@ -7,6 +7,7 @@ execveat.moved
execveat.path.ephemeral
execveat.ephemeral
execveat.denatured
+/load_address_*
/recursion-depth
xxxxxxxx*
pipe
diff --git a/tools/testing/selftests/exec/Makefile b/tools/testing/selftests/exec/Makefile
index 0a13b110c1e66..cf69b2fcce59e 100644
--- a/tools/testing/selftests/exec/Makefile
+++ b/tools/testing/selftests/exec/Makefile
@@ -4,7 +4,7 @@ CFLAGS += -Wno-nonnull
CFLAGS += -D_GNU_SOURCE

TEST_PROGS := binfmt_script non-regular
-TEST_GEN_PROGS := execveat
+TEST_GEN_PROGS := execveat load_address_4096 load_address_2097152 load_address_16777216
TEST_GEN_FILES := execveat.symlink execveat.denatured script subdir pipe
# Makefile is a run-time dependency, since it's accessed by the execveat test
TEST_FILES := Makefile
@@ -27,4 +27,9 @@ $(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 $< -o $@
+$(OUTPUT)/load_address_2097152: load_address.c
+ $(CC) $(CFLAGS) $(LDFLAGS) -Wl,-z,max-page-size=0x200000 -pie $< -o $@
+$(OUTPUT)/load_address_16777216: load_address.c
+ $(CC) $(CFLAGS) $(LDFLAGS) -Wl,-z,max-page-size=0x1000000 -pie $< -o $@
diff --git a/tools/testing/selftests/exec/load_address.c b/tools/testing/selftests/exec/load_address.c
new file mode 100644
index 0000000000000..d487c2f6a6150
--- /dev/null
+++ b/tools/testing/selftests/exec/load_address.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <link.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+struct Statistics {
+ unsigned long long load_address;
+ unsigned long long alignment;
+};
+
+int ExtractStatistics(struct dl_phdr_info *info, size_t size, void *data)
+{
+ struct Statistics *stats = (struct Statistics *) data;
+ int i;
+
+ if (info->dlpi_name != NULL && info->dlpi_name[0] != '\0') {
+ // Ignore headers from other than the executable.
+ return 2;
+ }
+
+ stats->load_address = (unsigned long long) info->dlpi_addr;
+ stats->alignment = 0;
+
+ for (i = 0; i < info->dlpi_phnum; i++) {
+ 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;
+ }
+
+ return 1; // Terminate dl_iterate_phdr.
+}
+
+int main(int argc, char **argv)
+{
+ struct Statistics extracted;
+ unsigned long long misalign;
+ int ret;
+
+ ret = dl_iterate_phdr(ExtractStatistics, &extracted);
+ if (ret != 1) {
+ fprintf(stderr, "FAILED\n");
+ return 1;
+ }
+
+ if (extracted.alignment == 0) {
+ fprintf(stderr, "No alignment found\n");
+ return 1;
+ } else if (extracted.alignment & (extracted.alignment - 1)) {
+ fprintf(stderr, "Alignment is not a power of 2\n");
+ return 1;
+ }
+
+ misalign = extracted.load_address & (extracted.alignment - 1);
+ if (misalign) {
+ printf("alignment = %llu, load_address = %llu\n",
+ extracted.alignment, extracted.load_address);
+ fprintf(stderr, "FAILED\n");
+ return 1;
+ }
+
+ fprintf(stderr, "PASS\n");
+ return 0;
+}
--
2.28.0.297.g1956fa8f8d-goog