wireguard: selftests: use maximum cpu features and allow rng seeding

By forcing the maximum CPU that QEMU has available, we expose additional
capabilities, such as the RNDR instruction, which increases test
coverage. This then allows the CI to skip the fake seeding step in some
cases. Also enable STRICT_KERNEL_RWX to catch issues related to early
jump labels when the RNG is initialized at boot.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

tools/testing/selftests/wireguard/qemu/Makefile

@@ -64,8 +64,8 @@ QEMU_VPORT_RESULT := virtio-serial-device
 ifeq ($(HOST_ARCH),$(ARCH))
 QEMU_MACHINE := -cpu host -machine virt,gic_version=host,accel=kvm
 else
-QEMU_MACHINE := -cpu cortex-a53 -machine virt
-CFLAGS += -march=armv8-a -mtune=cortex-a53
+QEMU_MACHINE := -cpu max -machine virt
+CFLAGS += -march=armv8-a
 endif
 else ifeq ($(ARCH),aarch64_be)
 CHOST := aarch64_be-linux-musl
@@ -76,8 +76,8 @@ QEMU_VPORT_RESULT := virtio-serial-device
 ifeq ($(HOST_ARCH),$(ARCH))
 QEMU_MACHINE := -cpu host -machine virt,gic_version=host,accel=kvm
 else
-QEMU_MACHINE := -cpu cortex-a53 -machine virt
-CFLAGS += -march=armv8-a -mtune=cortex-a53
+QEMU_MACHINE := -cpu max -machine virt
+CFLAGS += -march=armv8-a
 endif
 else ifeq ($(ARCH),arm)
 CHOST := arm-linux-musleabi
@@ -88,8 +88,8 @@ QEMU_VPORT_RESULT := virtio-serial-device
 ifeq ($(HOST_ARCH),$(ARCH))
 QEMU_MACHINE := -cpu host -machine virt,gic_version=host,accel=kvm
 else
-QEMU_MACHINE := -cpu cortex-a15 -machine virt
-CFLAGS += -march=armv7-a -mtune=cortex-a15 -mabi=aapcs-linux
+QEMU_MACHINE := -cpu max -machine virt
+CFLAGS += -march=armv7-a -mabi=aapcs-linux
 endif
 else ifeq ($(ARCH),armeb)
 CHOST := armeb-linux-musleabi
@@ -100,8 +100,8 @@ QEMU_VPORT_RESULT := virtio-serial-device
 ifeq ($(HOST_ARCH),$(ARCH))
 QEMU_MACHINE := -cpu host -machine virt,gic_version=host,accel=kvm
 else
-QEMU_MACHINE := -cpu cortex-a15 -machine virt
-CFLAGS += -march=armv7-a -mabi=aapcs-linux # We don't pass -mtune=cortex-a15 due to a compiler bug on big endian.
+QEMU_MACHINE := -cpu max -machine virt
+CFLAGS += -march=armv7-a -mabi=aapcs-linux
 LDFLAGS += -Wl,--be8
 endif
 else ifeq ($(ARCH),x86_64)
@@ -112,8 +112,7 @@ KERNEL_BZIMAGE := $(KERNEL_BUILD_PATH)/arch/x86/boot/bzImage
 ifeq ($(HOST_ARCH),$(ARCH))
 QEMU_MACHINE := -cpu host -machine q35,accel=kvm
 else
-QEMU_MACHINE := -cpu Skylake-Server -machine q35
-CFLAGS += -march=skylake-avx512
+QEMU_MACHINE := -cpu max -machine q35
 endif
 else ifeq ($(ARCH),i686)
 CHOST := i686-linux-musl
@@ -123,8 +122,7 @@ KERNEL_BZIMAGE := $(KERNEL_BUILD_PATH)/arch/x86/boot/bzImage
 ifeq ($(subst x86_64,i686,$(HOST_ARCH)),$(ARCH))
 QEMU_MACHINE := -cpu host -machine q35,accel=kvm
 else
-QEMU_MACHINE := -cpu coreduo -machine q35
-CFLAGS += -march=prescott
+QEMU_MACHINE := -cpu max -machine q35
 endif
 else ifeq ($(ARCH),mips64)
 CHOST := mips64-linux-musl
@@ -182,7 +180,7 @@ KERNEL_BZIMAGE := $(KERNEL_BUILD_PATH)/vmlinux
 ifeq ($(HOST_ARCH),$(ARCH))
 QEMU_MACHINE := -cpu host,accel=kvm -machine pseries
 else
-QEMU_MACHINE := -machine pseries
+QEMU_MACHINE := -machine pseries -device spapr-rng,rng=rng -object rng-random,id=rng
 endif
 else ifeq ($(ARCH),powerpc64le)
 CHOST := powerpc64le-linux-musl
@@ -192,7 +190,7 @@ KERNEL_BZIMAGE := $(KERNEL_BUILD_PATH)/vmlinux
 ifeq ($(HOST_ARCH),$(ARCH))
 QEMU_MACHINE := -cpu host,accel=kvm -machine pseries
 else
-QEMU_MACHINE := -machine pseries
+QEMU_MACHINE := -machine pseries -device spapr-rng,rng=rng -object rng-random,id=rng
 endif
 else ifeq ($(ARCH),powerpc)
 CHOST := powerpc-linux-musl
@@ -247,7 +245,7 @@ QEMU_VPORT_RESULT := virtio-serial-ccw
 ifeq ($(HOST_ARCH),$(ARCH))
 QEMU_MACHINE := -cpu host,accel=kvm -machine s390-ccw-virtio -append $(KERNEL_CMDLINE)
 else
-QEMU_MACHINE := -machine s390-ccw-virtio -append $(KERNEL_CMDLINE)
+QEMU_MACHINE := -cpu max -machine s390-ccw-virtio -append $(KERNEL_CMDLINE)
 endif
 else
 $(error I only build: x86_64, i686, arm, armeb, aarch64, aarch64_be, mips, mipsel, mips64, mips64el, powerpc64, powerpc64le, powerpc, m68k, riscv64, riscv32, s390x)

tools/testing/selftests/wireguard/qemu/init.c

@@ -21,6 +21,7 @@
 #include <sys/utsname.h>
 #include <sys/sendfile.h>
 #include <sys/sysmacros.h>
+#include <sys/random.h>
 #include <linux/random.h>
 #include <linux/version.h>
 
@@ -58,6 +59,8 @@ static void seed_rng(void)
 {
 	int bits = 256, fd;
 
+	if (!getrandom(NULL, 0, GRND_NONBLOCK))
+		return;
 	pretty_message("[+] Fake seeding RNG...");
 	fd = open("/dev/random", O_WRONLY);
 	if (fd < 0)

tools/testing/selftests/wireguard/qemu/kernel.config

@@ -31,6 +31,7 @@ CONFIG_TTY=y
 CONFIG_BINFMT_ELF=y
 CONFIG_BINFMT_SCRIPT=y
 CONFIG_VDSO=y
+CONFIG_STRICT_KERNEL_RWX=y
 CONFIG_VIRTUALIZATION=y
 CONFIG_HYPERVISOR_GUEST=y
 CONFIG_PARAVIRT=y
@@ -65,6 +66,8 @@ CONFIG_PROC_FS=y
 CONFIG_PROC_SYSCTL=y
 CONFIG_SYSFS=y
 CONFIG_TMPFS=y
+CONFIG_RANDOM_TRUST_CPU=y
+CONFIG_RANDOM_TRUST_BOOTLOADER=y
 CONFIG_CONSOLE_LOGLEVEL_DEFAULT=15
 CONFIG_LOG_BUF_SHIFT=18
 CONFIG_PRINTK_TIME=y