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>

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index c73425d..543a6d0 100644 (file)
--- 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 (file)
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;
+}