arch: add support for configurable page size on ARM64

This commit is based on earlier work from Łukasz Stelmach
<l.stelmach@samsung.com> to add support for different page sizes on
ARM64.

In his initial submission, Łukasz took an approach similar to this
one, i.e make it ARM64-specific. Following the feedback on the mailing
list, his second version [1] tried to generalize the logic to
configure the page size between architectures. But the general
consensus during the review process was that there wasn't much to
generalize in the end.

So, this new iteration is back to a simpler approach:

 * We have new options in Config.in.arm to configure the page
   size. Only 4 KB and 64 KB are supported, because our testing in
   Qemu and real hardware has not allowed to get a successful setup
   for 16 KB pages. We can always re-add support for 16 KB later if
   that is resolved.

 * The logic to define the ARCH_TOOLCHAIN_WRAPPER_OPTS options is
   moved from the ARC-specific file to arch/arch.mk, and extended to
   cover ARM64.

 * The appropriate logic in uclibc.mk and linux.mk is added to tweak
   the relevant configuration options.

 * A test case is added in the runtime test infrastructure to test
   building and booting under Qemu a 64 KB configuration, with all 3 C
   libraries.

For the regular configuration of 4 KB pages, this commit makes one
functional change: on ARM64, -Wl,-z,max-page-size=4096 is now passed in
the compiler flags of the wrapper.

[1] https://patchwork.ozlabs.org/project/buildroot/list/?series=275452

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

arch/Config.in.arm

@@ -770,6 +770,31 @@ config BR2_ARM_INSTRUCTIONS_THUMB2
 
 endchoice
 
+choice
+	prompt "MMU Page Size"
+	default BR2_ARM64_PAGE_SIZE_4K
+	depends on BR2_aarch64 || BR2_aarch64_be
+	help
+	  The default is 4KB, and you should probably keep this unless
+	  you know what you are doing. In particular, the kernel
+	  configuration must match this choice. If your kernel is
+	  built by Buildroot, the kernel configuration is
+	  automatically adjusted, but not if you built your kernel
+	  outside of Buildroot.
+
+config BR2_ARM64_PAGE_SIZE_4K
+	bool "4KB"
+
+config BR2_ARM64_PAGE_SIZE_64K
+	bool "64KB"
+
+endchoice
+
+config BR2_ARM64_PAGE_SIZE
+	string
+	default "4K" if BR2_ARM64_PAGE_SIZE_4K
+	default "64K" if BR2_ARM64_PAGE_SIZE_64K
+
 config BR2_ARCH
 	default "arm"		if BR2_arm
 	default "armeb"		if BR2_armeb

arch/arch.mk

@@ -18,5 +18,16 @@ GCC_TARGET_FPU := $(call qstrip,$(BR2_GCC_TARGET_FPU))
 GCC_TARGET_FLOAT_ABI := $(call qstrip,$(BR2_GCC_TARGET_FLOAT_ABI))
 GCC_TARGET_MODE := $(call qstrip,$(BR2_GCC_TARGET_MODE))
 
+# Explicitly set LD's "max-page-size" instead of relying on some defaults
+ifeq ($(BR2_ARC_PAGE_SIZE_4K)$(BR2_ARM64_PAGE_SIZE_4K),y)
+ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=4096
+else ifeq ($(BR2_ARC_PAGE_SIZE_8K),y)
+ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=8192
+else ifeq ($(BR2_ARC_PAGE_SIZE_16K),y)
+ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=16384
+else ifeq ($(BR2_ARM64_PAGE_SIZE_64K),y)
+ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=65536
+endif
+
 # Include any architecture specific makefiles.
 -include $(sort $(wildcard arch/arch.mk.*))

arch/arch.mk.arc

@@ -5,13 +5,4 @@ ifeq ($(BR2_ARC_ATOMIC_EXT),y)
 ARCH_TOOLCHAIN_WRAPPER_OPTS = -matomic
 endif
 
-# Explicitly set LD's "max-page-size" instead of relying on some defaults
-ifeq ($(BR2_ARC_PAGE_SIZE_4K),y)
-ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=4096
-else ifeq ($(BR2_ARC_PAGE_SIZE_8K),y)
-ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=8192
-else ifeq ($(BR2_ARC_PAGE_SIZE_16K),y)
-ARCH_TOOLCHAIN_WRAPPER_OPTS += -Wl,-z,max-page-size=16384
-endif
-
 endif

linux/linux.mk

@@ -374,6 +374,14 @@ define LINUX_KCONFIG_FIXUP_CMDS
 		$(call KCONFIG_DISABLE_OPT,CONFIG_ARC_PAGE_SIZE_4K)
 		$(call KCONFIG_DISABLE_OPT,CONFIG_ARC_PAGE_SIZE_8K)
 		$(call KCONFIG_ENABLE_OPT,CONFIG_ARC_PAGE_SIZE_16K))
+	$(if $(BR2_ARM64_PAGE_SIZE_4K),
+		$(call KCONFIG_ENABLE_OPT,CONFIG_ARM64_4K_PAGES)
+		$(call KCONFIG_DISABLE_OPT,CONFIG_ARM64_16K_PAGES)
+		$(call KCONFIG_DISABLE_OPT,CONFIG_ARM64_64K_PAGES))
+	$(if $(BR2_ARM64_PAGE_SIZE_64K),
+		$(call KCONFIG_DISABLE_OPT,CONFIG_ARM64_4K_PAGES)
+		$(call KCONFIG_DISABLE_OPT,CONFIG_ARM64_16K_PAGES)
+		$(call KCONFIG_ENABLE_OPT,CONFIG_ARM64_64K_PAGES))
 	$(if $(BR2_TARGET_ROOTFS_CPIO),
 		$(call KCONFIG_ENABLE_OPT,CONFIG_BLK_DEV_INITRD))
 	# As the kernel gets compiled before root filesystems are

package/uclibc/uclibc.mk

@@ -73,6 +73,18 @@ define UCLIBC_BINFMT_CONFIG
 endef
 endif
 
+#
+# AArch64 definitions
+#
+
+ifeq ($(UCLIBC_TARGET_ARCH),aarch64)
+UCLIBC_ARM64_PAGE_SIZE = CONFIG_AARCH64_PAGE_SIZE_$(call qstrip,$(BR2_ARM64_PAGE_SIZE))
+define UCLIBC_AARCH64_PAGE_SIZE_CONFIG
+	$(SED) '/CONFIG_AARCH64_PAGE_SIZE_*/d' $(@D)/.config
+	$(call KCONFIG_ENABLE_OPT,$(UCLIBC_ARM64_PAGE_SIZE))
+endef
+endif # aarch64
+
 #
 # ARC definitions
 #
@@ -386,6 +398,7 @@ define UCLIBC_KCONFIG_FIXUP_CMDS
 	$(call KCONFIG_SET_OPT,SHARED_LIB_LOADER_PREFIX,"/lib")
 	$(UCLIBC_MMU_CONFIG)
 	$(UCLIBC_BINFMT_CONFIG)
+	$(UCLIBC_AARCH64_PAGE_SIZE_CONFIG)
 	$(UCLIBC_ARC_PAGE_SIZE_CONFIG)
 	$(UCLIBC_ARC_ATOMICS_CONFIG)
 	$(UCLIBC_ARM_ABI_CONFIG)

support/testing/tests/toolchain/test_aarch64_64k.py

@@ -0,0 +1,65 @@
+import os
+import re
+
+import infra.basetest
+
+
+class TestAarch64Pages64kBase(infra.basetest.BRTest):
+    __test__ = False
+    config = \
+        """
+        BR2_aarch64=y
+        BR2_ARM64_PAGE_SIZE_64K=y
+        BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_5_15=y
+        BR2_TARGET_GENERIC_GETTY_PORT="ttyAMA0"
+        BR2_LINUX_KERNEL=y
+        BR2_LINUX_KERNEL_CUSTOM_VERSION=y
+        BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.15.18"
+        BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
+        BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="board/qemu/aarch64-virt/linux.config"
+        BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL=y
+        BR2_TARGET_ROOTFS_CPIO=y
+        BR2_TARGET_ROOTFS_CPIO_GZIP=y
+        """
+
+    def login(self):
+        img = os.path.join(self.builddir, "images", "rootfs.cpio.gz")
+        kern = os.path.join(self.builddir, "images", "Image")
+        self.emulator.boot(arch="aarch64",
+                           kernel=kern,
+                           kernel_cmdline=["console=ttyAMA0"],
+                           options=["-M", "virt", "-cpu", "cortex-a57", "-m", "512M", "-initrd", img])
+        self.emulator.login()
+
+
+    def test_run(self):
+        self.login()
+
+        cmd = "dmesg | grep 'Dentry cache'"
+        output, exit_code = self.emulator.run(cmd, 120)
+        r = re.match(".*Dentry cache hash table entries: [0-9]* \(order: ([0-9]*), ([0-9]*) bytes.*", output[0])
+        order = int(r.group(1))
+        size = int(r.group(2))
+        self.assertEqual(2 ** order * 64 * 1024, size)
+
+class TestAarch64Pages64kGlibc(TestAarch64Pages64kBase):
+    __test__ = True
+    config = TestAarch64Pages64kBase.config + \
+        """
+        BR2_TOOLCHAIN_BUILDROOT_GLIBC=y
+        """
+
+class TestAarch64Pages64kuClibc(TestAarch64Pages64kBase):
+    __test__ = True
+    config = TestAarch64Pages64kBase.config + \
+        """
+        BR2_TOOLCHAIN_BUILDROOT_UCLIBC=y
+        """
+
+class TestAarch64Pages64kMusl(TestAarch64Pages64kBase):
+    __test__ = True
+    config = TestAarch64Pages64kBase.config + \
+        """
+        BR2_TOOLCHAIN_BUILDROOT_MUSL=y
+        """
+