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Message-Id: <65ba0315001b0a2e71d4c708148835a39f10906f.1441146105.git.luto@kernel.org>
Date: Tue, 1 Sep 2015 15:41:02 -0700
From: Andy Lutomirski <luto@...nel.org>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Brian Gerst <brgerst@...il.com>,
Denys Vlasenko <dvlasenk@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...nel.org>
Subject: [RFC 02/30] selftests/x86: Add a test for syscall restart and arg modification
This tests assumptions about how fast syscall works wrt pt_regs and,
in particular, what happens if IP is decremented by 2 during a syscall.
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
tools/testing/selftests/x86/Makefile | 3 +-
tools/testing/selftests/x86/ptrace_syscall.c | 294 +++++++++++++++++++++
.../testing/selftests/x86/raw_syscall_helper_32.S | 46 ++++
3 files changed, 342 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/x86/ptrace_syscall.c
create mode 100644 tools/testing/selftests/x86/raw_syscall_helper_32.S
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 751d3e040dff..d4a1fa755fc5 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 ldt_gdt syscall_nt
+TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs ldt_gdt syscall_nt ptrace_syscall
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault sigreturn unwind_vdso
TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
@@ -60,3 +60,4 @@ endif
# Some tests have additional dependencies.
sysret_ss_attrs_64: thunks.S
+ptrace_syscall_32: raw_syscall_helper_32.S
diff --git a/tools/testing/selftests/x86/ptrace_syscall.c b/tools/testing/selftests/x86/ptrace_syscall.c
new file mode 100644
index 000000000000..5105b49cd8aa
--- /dev/null
+++ b/tools/testing/selftests/x86/ptrace_syscall.c
@@ -0,0 +1,294 @@
+#define _GNU_SOURCE
+
+#include <sys/ptrace.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/syscall.h>
+#include <sys/user.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <err.h>
+#include <string.h>
+#include <asm/ptrace-abi.h>
+#include <sys/auxv.h>
+
+/* Bitness-agnostic defines for user_regs_struct fields. */
+#ifdef __x86_64__
+# define user_syscall_nr orig_rax
+# define user_arg0 rdi
+# define user_arg1 rsi
+# define user_arg2 rdx
+# define user_arg3 r10
+# define user_arg4 r8
+# define user_arg5 r9
+# define user_ip rip
+# define user_ax rax
+#else
+# define user_syscall_nr orig_eax
+# define user_arg0 ebx
+# define user_arg1 ecx
+# define user_arg2 edx
+# define user_arg3 esi
+# define user_arg4 edi
+# define user_arg5 ebp
+# define user_ip eip
+# define user_ax eax
+#endif
+
+static int nerrs = 0;
+
+struct syscall_args32 {
+ uint32_t nr, arg0, arg1, arg2, arg3, arg4, arg5;
+};
+
+#ifdef __i386__
+extern void sys32_helper(struct syscall_args32 *, void *);
+extern void int80_and_ret(void);
+#endif
+
+/*
+ * Helper to invoke int80 with controlled regs and capture the final regs.
+ */
+static void do_full_int80(struct syscall_args32 *args)
+{
+#ifdef __x86_64__
+ register unsigned long bp asm("bp") = args->arg5;
+ asm volatile ("int $0x80"
+ : "+a" (args->nr),
+ "+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2),
+ "+S" (args->arg3), "+D" (args->arg4), "+r" (bp));
+ args->arg5 = bp;
+#else
+ sys32_helper(args, int80_and_ret);
+#endif
+}
+
+#ifdef __i386__
+static void (*vsyscall32)(void);
+
+/*
+ * Nasty helper to invoke AT_SYSINFO (i.e. __kernel_vsyscall) with
+ * controlled regs and capture the final regs. This is so nasty that it
+ * crashes my copy of gdb :)
+ */
+static void do_full_vsyscall32(struct syscall_args32 *args)
+{
+ sys32_helper(args, vsyscall32);
+}
+#endif
+
+static siginfo_t wait_trap(pid_t chld)
+{
+ siginfo_t si;
+ if (waitid(P_PID, chld, &si, WEXITED|WSTOPPED) != 0)
+ err(1, "waitid");
+ if (si.si_pid != chld)
+ errx(1, "got unexpected pid in event\n");
+ if (si.si_code != CLD_TRAPPED)
+ errx(1, "got unexpected event type %d\n", si.si_code);
+ return si;
+}
+
+static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
+ int flags)
+{
+ struct sigaction sa;
+ memset(&sa, 0, sizeof(sa));
+ sa.sa_sigaction = handler;
+ sa.sa_flags = SA_SIGINFO | flags;
+ sigemptyset(&sa.sa_mask);
+ if (sigaction(sig, &sa, 0))
+ err(1, "sigaction");
+}
+
+static void clearhandler(int sig)
+{
+ struct sigaction sa;
+ memset(&sa, 0, sizeof(sa));
+ sa.sa_handler = SIG_DFL;
+ sigemptyset(&sa.sa_mask);
+ if (sigaction(sig, &sa, 0))
+ err(1, "sigaction");
+}
+
+#ifdef __x86_64__
+# define REG_BP REG_RBP
+#else
+# define REG_BP REG_EBP
+#endif
+
+static void empty_handler(int sig, siginfo_t *si, void *ctx_void)
+{
+}
+
+static void test_sys32_regs(void (*do_syscall)(struct syscall_args32 *))
+{
+ struct syscall_args32 args = {
+ .nr = 224, /* gettid */
+ .arg0 = 10, .arg1 = 11, .arg2 = 12,
+ .arg3 = 13, .arg4 = 14, .arg5 = 15,
+ };
+
+ do_syscall(&args);
+
+ if (args.nr != getpid() ||
+ args.arg0 != 10 || args.arg1 != 11 || args.arg2 != 12 ||
+ args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
+ printf("[FAIL]\tgetpid() failed to preseve regs\n");
+ nerrs++;
+ } else {
+ printf("[OK]\tgetpid() preserves regs\n");
+ }
+
+ sethandler(SIGUSR1, empty_handler, 0);
+
+ args.nr = 37; /* kill */
+ args.arg0 = getpid();
+ args.arg1 = SIGUSR1;
+ do_syscall(&args);
+ if (args.nr != 0 ||
+ args.arg0 != getpid() || args.arg1 != SIGUSR1 || args.arg2 != 12 ||
+ args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
+ printf("[FAIL]\tkill(getpid(), SIGUSR1) failed to preseve regs\n");
+ nerrs++;
+ } else {
+ printf("[OK]\tkill(getpid(), SIGUSR1) preserves regs\n");
+ }
+ clearhandler(SIGUSR1);
+}
+
+static void test_ptrace_syscall_restart(void)
+{
+ printf("[RUN]\tptrace-induced syscall restart\n");
+ pid_t chld = fork();
+ if (chld < 0)
+ err(1, "fork");
+
+ if (chld == 0) {
+ if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
+ err(1, "PTRACE_TRACEME");
+
+ printf("\tChild will make one syscall\n");
+ raise(SIGSTOP);
+
+ syscall(SYS_gettid, 10, 11, 12, 13, 14, 15);
+ _exit(0);
+ }
+
+ int status;
+
+ /* Wait for SIGSTOP. */
+ if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
+ err(1, "waitpid");
+
+ struct user_regs_struct regs;
+
+ printf("[RUN]\tSYSEMU\n");
+ if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
+ err(1, "PTRACE_SYSCALL");
+ wait_trap(chld);
+
+ if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0)
+ err(1, "PTRACE_GETREGS");
+
+ if (regs.user_syscall_nr != SYS_gettid ||
+ regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
+ regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
+ regs.user_arg4 != 14 || regs.user_arg5 != 15) {
+ printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
+ nerrs++;
+ } else {
+ printf("[OK]\tInitial nr and args are correct\n");
+ }
+
+ printf("[RUN]\tRestart the syscall (ip = 0x%lx)\n",
+ (unsigned long)regs.user_ip);
+
+ /*
+ * This does exactly what it appears to do if syscall is int80 or
+ * SYSCALL64. For SYSCALL32 or SYSENTER, though, this is highly
+ * magical. It needs to work so that ptrace and syscall restart
+ * work as expected.
+ */
+ regs.user_ax = regs.user_syscall_nr;
+ regs.user_ip -= 2;
+ if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0)
+ err(1, "PTRACE_SETREGS");
+
+ if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
+ err(1, "PTRACE_SYSCALL");
+ wait_trap(chld);
+
+ if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0)
+ err(1, "PTRACE_GETREGS");
+
+ if (regs.user_syscall_nr != SYS_gettid ||
+ regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
+ regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
+ regs.user_arg4 != 14 || regs.user_arg5 != 15) {
+ printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
+ nerrs++;
+ } else {
+ printf("[OK]\tRestarted nr and args are correct\n");
+ }
+
+ printf("[RUN]\tChange nr and args and restart the syscall (ip = 0x%lx)\n",
+ (unsigned long)regs.user_ip);
+
+ regs.user_ax = SYS_getpid;
+ regs.user_arg0 = 20;
+ regs.user_arg1 = 21;
+ regs.user_arg2 = 22;
+ regs.user_arg3 = 23;
+ regs.user_arg4 = 24;
+ regs.user_arg5 = 25;
+ regs.user_ip -= 2;
+
+ if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0)
+ err(1, "PTRACE_SETREGS");
+
+ if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
+ err(1, "PTRACE_SYSCALL");
+ wait_trap(chld);
+
+ if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0)
+ err(1, "PTRACE_GETREGS");
+
+ if (regs.user_syscall_nr != SYS_getpid ||
+ regs.user_arg0 != 20 || regs.user_arg1 != 21 || regs.user_arg2 != 22 ||
+ regs.user_arg3 != 23 || regs.user_arg4 != 24 || regs.user_arg5 != 25) {
+ printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
+ nerrs++;
+ } else {
+ printf("[OK]\tReplacement nr and args are correct\n");
+ }
+
+ if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
+ err(1, "PTRACE_CONT");
+ if (waitpid(chld, &status, 0) != chld)
+ err(1, "waitpid");
+ if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+ printf("[FAIL]\tChild failed\n");
+ nerrs++;
+ } else {
+ printf("[OK]\tChild exited cleanly\n");
+ }
+}
+
+int main()
+{
+ printf("[RUN]\tCheck int80 return regs\n");
+ test_sys32_regs(do_full_int80);
+
+#if defined(__i386__) && (!defined(__GLIBC__) || __GLIBC__ > 2 || __GLIBC_MINOR__ >= 16)
+ vsyscall32 = (void *)getauxval(AT_SYSINFO);
+ printf("[RUN]\tCheck AT_SYSINFO return regs\n");
+ test_sys32_regs(do_full_vsyscall32);
+#endif
+
+ test_ptrace_syscall_restart();
+
+ return 0;
+}
diff --git a/tools/testing/selftests/x86/raw_syscall_helper_32.S b/tools/testing/selftests/x86/raw_syscall_helper_32.S
new file mode 100644
index 000000000000..d01a13aafc8c
--- /dev/null
+++ b/tools/testing/selftests/x86/raw_syscall_helper_32.S
@@ -0,0 +1,46 @@
+.global sys32_helper
+sys32_helper:
+ /* Args: syscall_args_32*, function pointer */
+ pushl %ebp
+ pushl %ebx
+ pushl %esi
+ pushl %edi
+ movl 5*4(%esp), %eax /* pointer to args struct */
+
+ movl 1*4(%eax), %ebx
+ movl 2*4(%eax), %ecx
+ movl 3*4(%eax), %edx
+ movl 4*4(%eax), %esi
+ movl 5*4(%eax), %edi
+ movl 6*4(%eax), %ebp
+ movl 0*4(%eax), %eax
+
+ call *(6*4)(%esp) /* Do the syscall */
+
+ /* Now we need to recover without losing any reg values */
+ pushl %eax
+ movl 6*4(%esp), %eax
+ popl 0*4(%eax)
+ movl %ebx, 1*4(%eax)
+ movl %ecx, 2*4(%eax)
+ movl %edx, 3*4(%eax)
+ movl %esi, 4*4(%eax)
+ movl %edi, 5*4(%eax)
+ movl %ebp, 6*4(%eax)
+
+ popl %edi
+ popl %esi
+ popl %ebx
+ popl %ebp
+ ret
+
+ .type sys32_helper, @function
+ .size sys32_helper, .-sys32_helper
+
+.global int80_and_ret
+int80_and_ret:
+ int $0x80
+ ret
+
+ .type int80_and_ret, @function
+ .size int80_and_ret, .-int80_and_ret
--
2.4.3
--
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