single_step_syscall: New test

2 files changed, 134 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 2353f8c..f602715 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@ SIMPLE_C_TARGETS := dump-vsyscall context_switch_latency kernel_pf user_visible_
 
 SIMPLE_CC_TARGETS := evil-clock-test
 
-SPLIT_C_TARGETS := dump-vdso dump-vvar syscall_exit_regs sigreturn dump_all_pmcs
+SPLIT_C_TARGETS := dump-vdso dump-vvar syscall_exit_regs sigreturn dump_all_pmcs single_step_syscall
 SPLIT_CC_TARGETS := timing_test test_vsyscall test_vdso_parser
 
 ALL_TARGETS := $(SIMPLE_C_TARGETS) $(SIMPLE_CC_TARGETS) $(SPLIT_C_TARGETS:%=%_64) $(SPLIT_CC_TARGETS:%=%_64) $(SPLIT_C_TARGETS:%=%_32) $(SPLIT_CC_TARGETS:%=%_32) syscall32_from_64 segregs
diff --git a/single_step_syscall.c b/single_step_syscall.c
new file mode 100644
index 0000000..6c42bd0
--- /dev/null
+++ b/single_step_syscall.c
@@ -0,0 +1,133 @@
+#define _GNU_SOURCE
+
+#include <sys/time.h>
+#include <time.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <inttypes.h>
+#include <sys/mman.h>
+#include <sys/signal.h>
+#include <sys/ucontext.h>
+#include <asm/ldt.h>
+#include <err.h>
+#include <setjmp.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <sys/ptrace.h>
+#include <sys/user.h>
+
+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;
+
+#ifdef __x86_64__
+# define REG_IP REG_RIP
+# define WIDTH "q"
+#else
+# define REG_IP REG_EIP
+# define WIDTH "l"
+#endif
+
+static unsigned long get_eflags(void)
+{
+	unsigned long eflags;
+	asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags));
+	return eflags;
+}
+
+static void set_eflags(unsigned long eflags)
+{
+	asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH
+		      : : "rm" (eflags) : "flags");
+}
+
+#define X86_EFLAGS_TF (1UL << 8)
+
+static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
+{
+	ucontext_t *ctx = (ucontext_t*)ctx_void;
+
+	if (get_eflags() & X86_EFLAGS_TF) {
+		set_eflags(get_eflags() & ~X86_EFLAGS_TF);
+		printf("[WARN]\tSIGTRAP handler had TF set\n");
+		_exit(1);
+	}
+
+	sig_traps++;
+
+	if (sig_traps == 10000 || sig_traps == 10001) {
+		printf("[WARN]\tHit %d SIGTRAPs with si_addr 0x%lx, ip 0x%lx\n",
+		       (int)sig_traps,
+		       (unsigned long)info->si_addr,
+		       (unsigned long)ctx->uc_mcontext.gregs[REG_IP]);
+	}
+}
+
+static void check_result(void)
+{
+	unsigned long new_eflags = get_eflags();
+	set_eflags(new_eflags & ~X86_EFLAGS_TF);
+
+	if (!sig_traps) {
+		printf("[FAIL]\tNo SIGTRAP\n");
+		exit(1);
+	}
+
+	if (!(new_eflags & X86_EFLAGS_TF)) {
+		printf("[FAIL]\tTF was cleared\n");
+		exit(1);
+	}
+
+	printf("[OK]\tSurvived with TF set and %d traps\n", (int)sig_traps);
+	sig_traps = 0;
+}
+
+int main()
+{
+	int tmp;
+
+	sethandler(SIGTRAP, sigtrap, 0);
+
+	printf("[RUN]\tSet TF and check nop\n");
+	set_eflags(get_eflags() | X86_EFLAGS_TF);
+	asm volatile ("nop");
+	check_result();
+
+#ifdef __x86_64__
+	printf("[RUN]\tSet TF and check syscall-less opportunistic sysret\n");
+	set_eflags(get_eflags() | X86_EFLAGS_TF);
+	extern unsigned char post_nop[];
+	asm volatile ("pushf" WIDTH "\n\t"
+		      "pop" WIDTH " %%r11\n\t"
+		      "nop\n\t"
+		      "post_nop:"
+		      : : "c" (post_nop) : "r11");
+	check_result();
+#endif
+
+	printf("[RUN]\tSet TF and check int80\n");
+	set_eflags(get_eflags() | X86_EFLAGS_TF);
+	asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid));
+	check_result();
+
+	syscall(SYS_getpid);  /* Force symbol binding without TF set. */
+	printf("[RUN]\tSet TF and check a fast syscall\n");
+	set_eflags(get_eflags() | X86_EFLAGS_TF);
+	syscall(SYS_getpid);
+	check_result();
+
+	return 0;
+}