[tip:x86/mm] selftests/x86: Add vDSO mremap() test

tip-bot for Dmitry Safonov
2016-07-08T13:17:41Z

Commit-ID: f80fd3a5fff88a9ace7e8cd11d07cf874a63ea9f
Gitweb: http://git.kernel.org/tip/f80fd3a5fff88a9ace7e8cd11d07cf874a63ea9f
Author: Dmitry Safonov <dsafonov@virtuozzo.com>
AuthorDate: Tue, 28 Jun 2016 14:35:39 +0300
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 8 Jul 2016 14:17:51 +0200

selftests/x86: Add vDSO mremap() test

Should print this on vDSO remapping success (on new kernels):

[root@localhost ~]# ./test_mremap_vdso_32
AT_SYSINFO_EHDR is 0xf773f000
[NOTE] Moving vDSO: [f773f000, f7740000] -> [a000000, a001000]
[OK]

Or print that mremap() for vDSOs is unsupported:

[root@localhost ~]# ./test_mremap_vdso_32
AT_SYSINFO_EHDR is 0xf773c000
[NOTE] Moving vDSO: [0xf773c000, 0xf773d000] -> [0xf7737000, 0xf7738000]
[FAIL] mremap() of the vDSO does not work on this kernel!

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: 0x7f454c46@gmail.com
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kselftest@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160628113539.13606-3-dsafonov@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
tools/testing/selftests/x86/Makefile | 2 +-
tools/testing/selftests/x86/test_mremap_vdso.c | 111 +++++++++++++++++++++++++
2 files changed, 112 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index c73425d..543a6d0 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -4,7 +4,7 @@ include ../lib.mk

.PHONY: all all_32 all_64 warn_32bit_failure clean

-TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall \
+TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \
check_initial_reg_state sigreturn ldt_gdt iopl
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
new file mode 100644
index 0000000..bf0d687
--- /dev/null
+++ b/tools/testing/selftests/x86/test_mremap_vdso.c
@@ -0,0 +1,111 @@
+/*
+ * 32-bit test to check vDSO mremap.
+ *
+ * Copyright (c) 2016 Dmitry Safonov
+ * Suggested-by: Andrew Lutomirski
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+/*
+ * Can be built statically:
+ * gcc -Os -Wall -static -m32 test_mremap_vdso.c
+ */
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
+
+#include <sys/mman.h>
+#include <sys/auxv.h>
+#include <sys/syscall.h>
+#include <sys/wait.h>
+
+#define PAGE_SIZE 4096
+
+static int try_to_remap(void *vdso_addr, unsigned long size)
+{
+ void *dest_addr, *new_addr;
+
+ /* Searching for memory location where to remap */
+ dest_addr = mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+ if (dest_addr == MAP_FAILED) {
+ printf("[WARN]\tmmap failed (%d): %m\n", errno);
+ return 0;
+ }
+
+ printf("[NOTE]\tMoving vDSO: [%p, %#lx] -> [%p, %#lx]\n",
+ vdso_addr, (unsigned long)vdso_addr + size,
+ dest_addr, (unsigned long)dest_addr + size);
+ fflush(stdout);
+
+ new_addr = mremap(vdso_addr, size, size,
+ MREMAP_FIXED|MREMAP_MAYMOVE, dest_addr);
+ if ((unsigned long)new_addr == (unsigned long)-1) {
+ munmap(dest_addr, size);
+ if (errno == EINVAL) {
+ printf("[NOTE]\tvDSO partial move failed, will try with bigger size\n");
+ return -1; /* Retry with larger */
+ }
+ printf("[FAIL]\tmremap failed (%d): %m\n", errno);
+ return 1;
+ }
+
+ return 0;
+
+}
+
+int main(int argc, char **argv, char **envp)
+{
+ pid_t child;
+
+ child = fork();
+ if (child == -1) {
+ printf("[WARN]\tfailed to fork (%d): %m\n", errno);
+ return 1;
+ }
+
+ if (child == 0) {
+ unsigned long vdso_size = PAGE_SIZE;
+ unsigned long auxval;
+ int ret = -1;
+
+ auxval = getauxval(AT_SYSINFO_EHDR);
+ printf("\tAT_SYSINFO_EHDR is %#lx\n", auxval);
+ if (!auxval || auxval == -ENOENT) {
+ printf("[WARN]\tgetauxval failed\n");
+ return 0;
+ }
+
+ /* Simpler than parsing ELF header */
+ while (ret < 0) {
+ ret = try_to_remap((void *)auxval, vdso_size);
+ vdso_size += PAGE_SIZE;
+ }
+
+ /* Glibc is likely to explode now - exit with raw syscall */
+ asm volatile ("int $0x80" : : "a" (__NR_exit), "b" (!!ret));
+ } else {
+ int status;
+
+ if (waitpid(child, &status, 0) != child ||
+ !WIFEXITED(status)) {
+ printf("[FAIL]\tmremap() of the vDSO does not work on this kernel!\n");
+ return 1;
+ } else if (WEXITSTATUS(status) != 0) {
+ printf("[FAIL]\tChild failed with %d\n",
+ WEXITSTATUS(status));
+ return 1;
+ }
+ printf("[OK]\n");
+ }
+
+ return 0;
+}