On 5/8/24 10:31 AM, Kees Cook wrote:
After commit 4d1cd3b2c5c1 ("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
aeb7923733d1 ("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]
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
Cc: Chris Kennelly <ckennelly@xxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Fangrui Song <maskray@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Yang Yingliang <yangyingliang@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kselftest@xxxxxxxxxxxxxxx
---
tools/testing/selftests/exec/Makefile | 19 +++---
tools/testing/selftests/exec/load_address.c | 67 +++++++++++++++++----
2 files changed, 66 insertions(+), 20 deletions(-)
diff --git a/tools/testing/selftests/exec/Makefile b/tools/testing/selftests/exec/Makefile
index fb4472ddffd8..619cff81d796 100644
--- a/tools/testing/selftests/exec/Makefile
+++ b/tools/testing/selftests/exec/Makefile
@@ -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 $@
Hi Kees,
Didn't we learn recently, though, that -static-pie is gcc 8.1+, while the
kernel's minimum gcc version is 5?
thanks,
--
John Hubbard
NVIDIA
diff --git a/tools/testing/selftests/exec/load_address.c b/tools/testing/selftests/exec/load_address.c
index 17e3207d34ae..8257fddba8c8 100644
--- a/tools/testing/selftests/exec/load_address.c
+++ b/tools/testing/selftests/exec/load_address.c
@@ -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();
}
