loader: Map all of RAM in the loader

.github/workflows/pr.yml

@@ -27,13 +27,17 @@ jobs:
       - name: Run Clippy
         # Make sure CI fails on all warnings, including Clippy lints
         run: nix develop --ignore-environment -c bash -c "cd tool/microkit && cargo-clippy --all-targets --all-features -- -D warnings -Wclippy::get_unwrap"
+      - name: Run Clippy (loader)
+        run: nix develop --ignore-environment -c bash -c 'make -C loader clippy CLIPPY_FLAGS="-D warnings -Wclippy::get_unwrap" BUILD_DIR=$(mktemp -d) RUST_ONLY=True'
 
   rustfmt_check:
     runs-on: [self-hosted, macos, ARM64]
     steps:
       - uses: actions/checkout@v4
       - name: Run rustfmt
         run: nix develop --ignore-environment -c bash -c "cd tool/microkit && cargo-fmt --check"
+      - name: Run rustfmt (loader)
+        run: nix develop --ignore-environment -c bash -c 'make -C loader rustfmt-check BUILD_DIR=$(mktemp -d) RUST_ONLY=True'
 
   code:
     name: Freeze Code

build_sdk.py

@@ -796,6 +796,26 @@ def build_sel4(
             json_dst.chmod(0o744)
 
 
+def test_loader(build_dir: Path) -> None:
+    build_dir = build_dir / "loader"
+    build_dir.mkdir(exist_ok=True, parents=True)
+
+    make_args = f"BUILD_DIR={build_dir.absolute()} RUST_ONLY=True"
+
+    r = system(
+        f"make -C loader tests {make_args}"
+    )
+    if r != 0:
+        raise Exception(f"Tests failed: loader")
+
+    # We don't pass CLIPPYARGS, so this is warning-only
+    r = system(
+        f"make -C loader clippy {make_args}"
+    )
+    if r != 0:
+        raise Exception(f"Clippy failed: loader")
+
+
 def build_elf_component(
     component_name: str,
     sdk_dir: Path,
@@ -1094,6 +1114,8 @@ def main() -> None:
 
     if not args.skip_run_time:
         build_dir = Path("build")
+        test_loader(build_dir)
+
         for (board, configs) in build_goals:
             for config in configs:
                 if not args.skip_sel4:

example/hello/Makefile

@@ -27,7 +27,7 @@ ifeq ($(ARCH),aarch64)
   TARGET_TRIPLE := aarch64-none-elf
   CFLAGS_ARCH := -mstrict-align
 else ifeq ($(ARCH),riscv64)
-  TARGET_TRIPLE := riscv64-unknown-elf
+  TARGET_TRIPLE := riscv64-none-elf
   CFLAGS_ARCH := -march=rv64imafdc_zicsr_zifencei -mabi=lp64d
 else ifeq ($(ARCH),x86_64)
 	TARGET_TRIPLE := x86_64-linux-gnu

example/hello/hello.c

@@ -6,6 +6,8 @@
 #include <stdint.h>
 #include <microkit.h>
 
+char xxxxxxxxxxx[100000000] = { 1 };
+
 void init(void)
 {
     microkit_dbg_puts("hello, world\n");

loader/Makefile

@@ -3,6 +3,15 @@
 #
 # SPDX-License-Identifier: BSD-2-Clause
 #
+
+ifneq ($(strip $(RUST_ONLY)),)
+	ARCH := dummy
+	BOARD := dummy
+	LINK_ADDRESS := dummy
+	TARGET_TRIPLE := dummy
+	SEL4_SDK := dummy
+endif
+
 ifeq ($(strip $(BUILD_DIR)),)
 $(error BUILD_DIR must be specified)
 endif
@@ -35,34 +44,46 @@ else
   LD = $(TARGET_TRIPLE)-ld
 endif
 
+RUSTC := rustc
+CLIPPY := clippy-driver
+RUSTFMT := rustfmt
+
 ifeq ($(ARCH),aarch64)
 	CFLAGS_AARCH64 := -mcpu=$(GCC_CPU) -mgeneral-regs-only -mstrict-align -mno-outline-atomics
 	CFLAGS_ARCH := $(CFLAGS_AARCH64) -DARCH_aarch64
 	ASM_FLAGS_ARCH := -mcpu=$(GCC_CPU)
 	ARCH_DIR := aarch64
+	RUST_TARGET_TRIPLE := aarch64-unknown-none
 else ifeq ($(ARCH),riscv64)
-	CFLAGS_RISCV64 := -mcmodel=medany -march=rv64imac_zicsr_zifencei -mabi=lp64
+	CFLAGS_RISCV64 := -mcmodel=medany -march=rv64gc -mabi=lp64d
 	CFLAGS_ARCH := $(CFLAGS_RISCV64) -DARCH_riscv64
-	ASM_FLAGS_ARCH := -march=rv64imac_zicsr_zifencei -mabi=lp64
+	ASM_FLAGS_ARCH := -march=rv64gc -mabi=lp64d
+	RUST_TARGET_TRIPLE := riscv64gc-unknown-none-elf
 	ARCH_DIR := riscv
 endif
 
 CFLAGS := -std=gnu11 -g -O3 -nostdlib -ffreestanding \
 					-MP -MD $(CFLAGS_ARCH) -DBOARD_$(BOARD) -I$(SEL4_SDK)/include \
 					-Wall -Werror -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations \
-					-Wundef -Wno-nonnull -Wnested-externs
+					-Wundef -Wno-nonnull -Wnested-externs -ffunction-sections -fdata-sections
 
 ASM_FLAGS := $(ASM_FLAGS_ARCH) -g -MP -MD -I$(SEL4_SDK)/include
 
+RUST_EDITION := 2024
+RUSTFLAGS := --edition $(RUST_EDITION) -g -C opt-level=2
+CLIPPY_FLAGS ?=
+
 PROGS := loader.elf
-OBJECTS := loader.o crt0.o uart.o cutil.o
+OBJECTS := loader.o crt0.o uart.o cutil.o libpage_tables.a
 
 ifeq ($(ARCH),aarch64)
 	OBJECTS += util64.o el.o exceptions.o init.o mmu.o cpus.o
 else ifeq ($(ARCH),riscv64)
 	OBJECTS += exceptions.o init.o mmu.o cpus.o sbi.o
 endif
 
+RUST_CRATES := page_tables
+
 LINKSCRIPT_INPUT := $(ARCH).ld
 LINKSCRIPT := $(BUILD_DIR)/link.ld
 
@@ -80,6 +101,18 @@ $(BUILD_DIR)/%.o : src/$(ARCH_DIR)/%.c
 $(BUILD_DIR)/%.o : src/%.c
 	$(CC) -c $(CFLAGS) $< -o $@
 
+# Note: having multiple libs with staticlib will give duplicate linker symbol
+# issues. Use "--crate-type rlib" instead, but then we need to link a single
+# copy of the rust corelibs. For now this is fine.
+$(BUILD_DIR)/lib%.a : src/%.rs
+	$(RUSTC) $(RUSTFLAGS) \
+		--emit dep-info,metadata,link \
+		--out-dir $(BUILD_DIR) -L dependency=$(BUILD_DIR) \
+		--target $(RUST_TARGET_TRIPLE) \
+		--crate-type staticlib \
+		--crate-name $(patsubst lib%.a,%,$(notdir $@)) \
+		$<
+
 -include $(BUILD_DIR)/*.d
 
 OBJPROG = $(addprefix $(BUILD_DIR)/, $(PROGS))
@@ -89,5 +122,41 @@ all: $(OBJPROG)
 $(LINKSCRIPT): $(LINKSCRIPT_INPUT)
 	$(CPP) -DLINK_ADDRESS=$(LINK_ADDRESS) $< | grep -v "^#" > $@
 
+LDFLAGS := -T$(LINKSCRIPT)
+
 $(OBJPROG): $(addprefix $(BUILD_DIR)/, $(OBJECTS)) $(LINKSCRIPT)
-	$(LD) -T$(LINKSCRIPT) $(addprefix $(BUILD_DIR)/, $(OBJECTS)) -o $@
+	$(LD) $(LDFLAGS) --start-group $(addprefix $(BUILD_DIR)/, $(OBJECTS)) --end-group -o $@
+
+rusttest_%: src/%.rs
+	$(RUSTC) $(RUSTFLAGS) \
+		--emit dep-info,metadata,link \
+		--out-dir $(BUILD_DIR) -L dependency=$(BUILD_DIR) \
+		-Awarnings \
+		--test \
+		--crate-name "$@" \
+		$<
+
+tests: $(addprefix rusttest_, $(RUST_CRATES))
+	$(BUILD_DIR)/rusttest_page_tables
+
+rustclippy_%: src/%.rs
+	$(CLIPPY) $(RUSTFLAGS) \
+		--emit dep-info,metadata,link \
+		--out-dir $(BUILD_DIR) -L dependency=$(BUILD_DIR) \
+		$(CLIPPYFLAGS) \
+		-Cpanic=abort \
+		--crate-type staticlib \
+		--crate-name "$@" \
+		$<
+
+clippy: $(addprefix rustclippy_, $(RUST_CRATES))
+
+rustfmt_%: src/%.rs
+	$(RUSTFMT) $(RUSTFMT_FLAGS) \
+		--edition $(RUST_EDITION) \
+		$<
+
+rustfmt: $(addprefix rustfmt_, $(RUST_CRATES))
+
+rustfmt-check: RUSTFMT_FLAGS += --check
+rustfmt-check: rustfmt

loader/aarch64.ld

@@ -8,6 +8,12 @@ PHDRS
     all PT_LOAD AT (LINK_ADDRESS);
 }
 
+
+//    text PT_LOAD FLAGS(5); /* RX */
+//    rodata PT_LOAD FLAGS(4); /* RO */
+//    data PT_LOAD FLAGS(6); /* RW */
+//    bss PT_LOAD FLAGS(6); /* RW */
+
 SECTIONS
 {
     . = LINK_ADDRESS;
@@ -17,23 +23,34 @@ SECTIONS
     .text :
     {
         _text = .;
-        *(.text.start)
-        *(.text*)
-        *(.rodata)
+
+        KEEP(*(.text.start))
+        *(.text .text.*)
+
         _text_end = .;
     } :all
 
+    .rodata :
+    {
+        *(.rodata .rodata.* .rodata..Lanon.*)
+    } :all
+
     .data :
     {
         _data = .;
-        *(.data)
+        *(.data .data.*)
+        *(.data.*)
+
+        KEEP(*(.data.uart_addr))
+
         _data_end = .;
     } :all
 
     .bss :
     {
         _bss = .;
         *(.bss)
+        *(.bss.*)
         *(COMMON)
         . = ALIGN(4);
         _bss_end = .;

loader/riscv64.ld

@@ -15,27 +15,37 @@ SECTIONS
     .text :
     {
         _text = .;
-        *(.text.start)
-        *(.text*)
-        *(.rodata)
+
+        KEEP(*(.text.start))
+        *(.text .text.*)
+
         _text_end = .;
     } :all
 
+    .rodata :
+    {
+        *(.rodata .rodata.* .rodata..Lanon.*)
+    } :all
+
     .data :
     {
         _data = .;
-        *(.data)
+        *(.data .data.*)
+        *(.data.*)
         __global_pointer$ = . + 0x800;
-    *(.srodata)
-    *(.sdata)
-       _data_end = .;
+        *(.srodata .srodata.*)
+        *(.sdata .sdata.*)
+
+        KEEP(*(.data.uart_addr))
+
+        _data_end = .;
     } :all
 
     .bss :
     {
         _bss = .;
-    *(.sbss)
-        *(.bss)
+        *(.sbss .sbss.*)
+        *(.bss .bss.*)
         *(COMMON)
         . = ALIGN(4);
         _bss_end = .;

loader/src/aarch64/cpus.c

@@ -8,6 +8,7 @@
 #include <stdint.h>
 
 #include "smc.h"
+#include "../arch.h"
 #include "../cpus.h"
 #include "../cutil.h"
 #include "../loader.h"
@@ -101,6 +102,14 @@ void arm_secondary_cpu_entry(int logical_cpu, uint64_t mpidr_el1)
     puthex64(mpidr_el1);
     puts("\n");
 
+    int r = arch_mmu_enable(logical_cpu);
+    if (r != 0) {
+        LDR_PRINT("ERROR", logical_cpu, "failed to enable MMU: ");
+        puthex32(r);
+        puts("\n");
+        for (;;) {}
+    }
+
     if (logical_cpu == 0) {
         LDR_PRINT("ERROR", logical_cpu, "secondary CPU should not have logical id 0!!!\n");
         goto fail;

loader/src/aarch64/init.c

@@ -80,36 +80,6 @@ void arch_init(void)
     configure_gicv2();
 #endif
 
-    /* Drop to correct EL before disabling MMU */
-    int r = ensure_correct_el(0);
-    if (r != 0) {
-        puts("LDR|ERROR: failed to ensure correct EL\n");
-        fail();
-    }
-
-    /* Disable the MMU, as U-Boot will start in virtual memory on some platforms
-     * (https://docs.u-boot.org/en/latest/arch/arm64.html), which means that
-     * certain physical memory addresses contain page table information which
-     * the loader doesn't know about and would need to be careful not to
-     * overwrite.
-     *
-     * This also means that we would need to worry about caching.
-     * TODO: should we do that instead?
-     * note the issues where it forces us to flush any shared addresses all the
-     * way to cache as we might have mixed non-cached/cached access.
-     */
-    puts("LDR|INFO: disabling MMU (if it was enabled)\n");
-    enum el el = current_el();
-
-    if (el == EL1) {
-        el1_mmu_disable();
-    } else if (el == EL2) {
-        el2_mmu_disable();
-    } else {
-        puts("LDR|ERROR: unknown EL level for MMU disable\n");
-        fail();
-    }
-
 #if !defined(ARM_PSCI_UNAVAILABLE)
     uint32_t ret = arm_smc32_call(PSCI_FUNCTION_VERSION, /* unused */ 0, 0, 0);
     /* the return value has no error codes, but if we get it wrong this is what we will get */