WIP: Emulate the vsyscall page in userspace in the x86_64 Docker image

.travis.yml

@@ -23,6 +23,7 @@ matrix:
     - env: PLATFORM="x86_64"
 
 script:
+  - make -C docker/vsyscall_emu
   - docker build --rm -t quay.io/pypa/manylinux1_$PLATFORM:$TRAVIS_COMMIT -f docker/Dockerfile-$PLATFORM docker/
 
 

docker/Dockerfile-x86_64

@@ -8,6 +8,9 @@ ENV PATH /opt/rh/devtoolset-2/root/usr/bin:$PATH
 ENV LD_LIBRARY_PATH /opt/rh/devtoolset-2/root/usr/lib64:/opt/rh/devtoolset-2/root/usr/lib:/usr/local/lib64:/usr/local/lib
 ENV PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
 
+COPY vsyscall_emu/vsyscall_emu.so /usr/local/lib/vsyscall_emu.so
+COPY vsyscall_emu/ld.so.preload /etc/ld.so.preload
+
 COPY build_scripts /build_scripts
 RUN bash build_scripts/build.sh && rm -r build_scripts
 

docker/vsyscall_emu/.gitignore

@@ -0,0 +1 @@
+vsyscall_emu.so

docker/vsyscall_emu/Makefile

@@ -0,0 +1,13 @@
+ifeq ($(PLATFORM),x86_64)
+  all: vsyscall_emu.so
+else
+  all:
+endif
+
+vsyscall_emu.so: vsyscall_emu.c
+	$(CC) -fPIC -shared -o $@ $< -ldl
+
+clean:
+	$(RM) -f vsyscall_emu.so
+
+.PHONY: clean

docker/vsyscall_emu/ld.so.preload

@@ -0,0 +1 @@
+/usr/local/lib/vsyscall_emu.so

docker/vsyscall_emu/vsyscall_emu.c

@@ -0,0 +1,138 @@
+#define _GNU_SOURCE
+#include <sys/syscall.h>
+#include <dlfcn.h>
+#include <signal.h>
+#include <ucontext.h>
+#include <unistd.h>
+
+static struct sigaction next_handler = {
+	.sa_handler = SIG_DFL,
+};
+
+static int (*real_sigaction)(int, const struct sigaction *, struct sigaction *);
+
+static sigset_t visible_oldset;
+
+static int (*real_sigprocmask)(int, const sigset_t *, sigset_t *);
+
+int
+sigaction(int signum,
+          const struct sigaction *act,
+          struct sigaction *old_act)
+{
+	if (signum != SIGSEGV) {
+		return real_sigaction(signum, act, old_act);
+	}
+
+	if (old_act) {
+		*old_act = next_handler;
+	}
+	if (act) {
+		next_handler = *act;
+	}
+	return 0;
+}
+
+sighandler_t
+signal(int signum, sighandler_t handler)
+{
+	struct sigaction sa = {
+		.sa_handler = handler,
+		.sa_flags = SA_RESETHAND | SA_NODEFER,
+	}, oldsa;
+	if (sigaction(signum, &sa, &oldsa) == 0) {
+		return oldsa.sa_handler;
+	} else {
+		return SIG_ERR;
+	}
+}
+
+int
+sigprocmask (int how, const sigset_t *newset, sigset_t *oldset)
+{
+	sigset_t newset_without_sigsegv;
+	const sigset_t *to_install;
+	int result;
+
+	if (newset && how == SIG_BLOCK && sigismember(newset, SIGSEGV)) {
+		newset_without_sigsegv = *newset;
+		sigdelset(&newset_without_sigsegv, SIGSEGV);
+		to_install = &newset_without_sigsegv;
+	} else {
+		to_install = newset;
+	}
+
+	result = real_sigprocmask(how, to_install, oldset);
+	if (oldset) {
+		*oldset = visible_oldset;
+	}
+	if (newset) {
+		visible_oldset = *newset;
+	}
+	return result;
+}
+
+static greg_t VSYS_gettimeofday = 0xffffffffff600000;
+static long
+syscall_gettimeofday(long arg1, long arg2) {
+	return syscall(SYS_gettimeofday, arg1, arg2);
+}
+
+static greg_t VSYS_time = 0xffffffffff600400;
+static long
+syscall_time(long arg1) {
+	return syscall(SYS_time, arg1);
+}
+
+static greg_t VSYS_getcpu = 0xffffffffff600800;
+static long
+syscall_getcpu(long arg1, long arg2, long arg3) {
+	return syscall(SYS_getcpu, arg1, arg2, arg3);
+}
+
+static void
+handler(int sig, siginfo_t *si, void *ctx)
+{
+	greg_t *regs = ((ucontext_t *)ctx)->uc_mcontext.gregs;
+	if (regs[REG_RIP] == VSYS_gettimeofday) {
+		regs[REG_RIP] = (greg_t)(void *)syscall_gettimeofday;
+	} else if (regs[REG_RIP] == VSYS_time) {
+		regs[REG_RIP] = (greg_t)(void *)syscall_time;
+	} else if (regs[REG_RIP] == VSYS_getcpu) {
+		regs[REG_RIP] = (greg_t)(void *)syscall_getcpu;
+	} else if (next_handler.sa_flags & SA_SIGINFO) {
+		next_handler.sa_sigaction(sig, si, ctx);
+	} else if (next_handler.sa_handler != SIG_DFL && next_handler.sa_handler != SIG_IGN) {
+		next_handler.sa_handler(sig);
+	} else {
+		// SIG_IGN is treated as SIG_DFL
+		struct sigaction sa = {
+			.sa_handler = SIG_DFL,
+		};
+		real_sigaction(sig, &sa, NULL);
+	}
+}
+
+__attribute__((constructor))
+static void
+init(void)
+{
+	real_sigaction = dlsym(RTLD_NEXT, "sigaction");
+	if (!real_sigaction) {
+		return;
+	}
+
+	real_sigprocmask = dlsym(RTLD_NEXT, "sigprocmask");
+	if (!real_sigprocmask) {
+		return;
+	}
+	if (real_sigprocmask(SIG_BLOCK, NULL, &visible_oldset) == -1) {
+		return;
+	}
+
+	struct sigaction sa = {
+		.sa_sigaction = handler,
+		.sa_flags = SA_RESTART | SA_SIGINFO,
+	};
+	real_sigaction(SIGSEGV, &sa, NULL);
+}