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-rw-r--r--tools/testing/selftests/x86/Makefile2
-rw-r--r--tools/testing/selftests/x86/syscall_arg_fault.c130
2 files changed, 131 insertions, 1 deletions
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index caa60d5..e8df47e 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -5,7 +5,7 @@ include ../lib.mk
.PHONY: all all_32 all_64 warn_32bit_failure clean
TARGETS_C_BOTHBITS := sigreturn single_step_syscall sysret_ss_attrs
-TARGETS_C_32BIT_ONLY := entry_from_vm86
+TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault
TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
BINARIES_32 := $(TARGETS_C_32BIT_ALL:%=%_32)
diff --git a/tools/testing/selftests/x86/syscall_arg_fault.c b/tools/testing/selftests/x86/syscall_arg_fault.c
new file mode 100644
index 0000000..7db4fc9
--- /dev/null
+++ b/tools/testing/selftests/x86/syscall_arg_fault.c
@@ -0,0 +1,130 @@
+/*
+ * syscall_arg_fault.c - tests faults 32-bit fast syscall stack args
+ * Copyright (c) 2015 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.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/signal.h>
+#include <sys/ucontext.h>
+#include <err.h>
+#include <setjmp.h>
+#include <errno.h>
+
+/* Our sigaltstack scratch space. */
+static unsigned char altstack_data[SIGSTKSZ];
+
+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 volatile sig_atomic_t sig_traps;
+static sigjmp_buf jmpbuf;
+
+static volatile sig_atomic_t n_errs;
+
+static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
+{
+ ucontext_t *ctx = (ucontext_t*)ctx_void;
+
+ if (ctx->uc_mcontext.gregs[REG_EAX] != -EFAULT) {
+ printf("[FAIL]\tAX had the wrong value: 0x%x\n",
+ ctx->uc_mcontext.gregs[REG_EAX]);
+ n_errs++;
+ } else {
+ printf("[OK]\tSeems okay\n");
+ }
+
+ siglongjmp(jmpbuf, 1);
+}
+
+static void sigill(int sig, siginfo_t *info, void *ctx_void)
+{
+ printf("[SKIP]\tIllegal instruction\n");
+ siglongjmp(jmpbuf, 1);
+}
+
+int main()
+{
+ stack_t stack = {
+ .ss_sp = altstack_data,
+ .ss_size = SIGSTKSZ,
+ };
+ if (sigaltstack(&stack, NULL) != 0)
+ err(1, "sigaltstack");
+
+ sethandler(SIGSEGV, sigsegv, SA_ONSTACK);
+ sethandler(SIGILL, sigill, SA_ONSTACK);
+
+ /*
+ * Exercise another nasty special case. The 32-bit SYSCALL
+ * and SYSENTER instructions (even in compat mode) each
+ * clobber one register. A Linux system call has a syscall
+ * number and six arguments, and the user stack pointer
+ * needs to live in some register on return. That means
+ * that we need eight registers, but SYSCALL and SYSENTER
+ * only preserve seven registers. As a result, one argument
+ * ends up on the stack. The stack is user memory, which
+ * means that the kernel can fail to read it.
+ *
+ * The 32-bit fast system calls don't have a defined ABI:
+ * we're supposed to invoke them through the vDSO. So we'll
+ * fudge it: we set all regs to invalid pointer values and
+ * invoke the entry instruction. The return will fail no
+ * matter what, and we completely lose our program state,
+ * but we can fix it up with a signal handler.
+ */
+
+ printf("[RUN]\tSYSENTER with invalid state\n");
+ if (sigsetjmp(jmpbuf, 1) == 0) {
+ asm volatile (
+ "movl $-1, %%eax\n\t"
+ "movl $-1, %%ebx\n\t"
+ "movl $-1, %%ecx\n\t"
+ "movl $-1, %%edx\n\t"
+ "movl $-1, %%esi\n\t"
+ "movl $-1, %%edi\n\t"
+ "movl $-1, %%ebp\n\t"
+ "movl $-1, %%esp\n\t"
+ "sysenter"
+ : : : "memory", "flags");
+ }
+
+ printf("[RUN]\tSYSCALL with invalid state\n");
+ if (sigsetjmp(jmpbuf, 1) == 0) {
+ asm volatile (
+ "movl $-1, %%eax\n\t"
+ "movl $-1, %%ebx\n\t"
+ "movl $-1, %%ecx\n\t"
+ "movl $-1, %%edx\n\t"
+ "movl $-1, %%esi\n\t"
+ "movl $-1, %%edi\n\t"
+ "movl $-1, %%ebp\n\t"
+ "movl $-1, %%esp\n\t"
+ "syscall\n\t"
+ "pushl $0" /* make sure we segfault cleanly */
+ : : : "memory", "flags");
+ }
+
+ return 0;
+}
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