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From: Chris Kennelly <ckennelly@google.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Song Liu <songliubraving@fb.com>
Cc: David Rientjes <rientjes@google.com>,
	Ian Rogers <irogers@google.com>, Hugh Dickens <hughd@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Sandeep Patil <sspatil@google.com>,
	Fangrui Song <maskray@google.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux@googlegroups.com,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Chris Kennelly <ckennelly@google.com>
Subject: [PATCH v4 2/2] Add self-test for verifying load alignment.
Date: Fri, 21 Aug 2020 19:38:48 -0400	[thread overview]
Message-ID: <20200821233848.3904680-3-ckennelly@google.com> (raw)
In-Reply-To: <20200821233848.3904680-1-ckennelly@google.com>

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


      parent reply	other threads:[~2020-08-21 23:39 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21 23:38 [PATCH v4 0/2] Selecting Load Addresses According to p_align Chris Kennelly
2020-08-21 23:38 ` [PATCH v4 1/2] fs/binfmt_elf: Use PT_LOAD p_align values for suitable start address Chris Kennelly
2020-08-21 23:38 ` Chris Kennelly [this message]

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