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Subject[RFC PATCH 5/5] RISC-V: Add EFI stub support.
Date
Add a RISC-V architecture specific stub code that actually copies the
actual kernel image to a valid address and jump to it after boot services
are terminated. Enable UEFI related kernel configs as well for RISC-V.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
arch/riscv/Kconfig | 20 ++++
arch/riscv/Makefile | 1 +
arch/riscv/configs/defconfig | 1 +
drivers/firmware/efi/libstub/Makefile | 8 ++
drivers/firmware/efi/libstub/riscv-stub.c | 135 ++++++++++++++++++++++
5 files changed, 165 insertions(+)
create mode 100644 drivers/firmware/efi/libstub/riscv-stub.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 42c122170cfd..68b1d565e51d 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -372,10 +372,30 @@ config CMDLINE_FORCE

endchoice

+config EFI_STUB
+ bool
+
+config EFI
+ bool "UEFI runtime support"
+ depends on OF
+ select LIBFDT
+ select UCS2_STRING
+ select EFI_PARAMS_FROM_FDT
+ select EFI_STUB
+ select EFI_GENERIC_ARCH_STUB
+ default y
+ help
+ This option provides support for runtime services provided
+ by UEFI firmware (such as non-volatile variables, realtime
+ clock, and platform reset). A UEFI stub is also provided to
+ allow the kernel to be booted as an EFI application. This
+ is only useful on systems that have UEFI firmware.
+
endmenu

menu "Power management options"

source "kernel/power/Kconfig"
+source "drivers/firmware/Kconfig"

endmenu
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index b9009a2fbaf5..0afaa89ba9ad 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -78,6 +78,7 @@ head-y := arch/riscv/kernel/head.o
core-y += arch/riscv/

libs-y += arch/riscv/lib/
+core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a

PHONY += vdso_install
vdso_install:
diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
index e2ff95cb3390..0a5d3578f51e 100644
--- a/arch/riscv/configs/defconfig
+++ b/arch/riscv/configs/defconfig
@@ -125,3 +125,4 @@ CONFIG_DEBUG_BLOCK_EXT_DEVT=y
# CONFIG_FTRACE is not set
# CONFIG_RUNTIME_TESTING_MENU is not set
CONFIG_MEMTEST=y
+CONFIG_EFI=y
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 2c5b76787126..38facb61745b 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -21,6 +21,8 @@ cflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
-fno-builtin -fpic \
$(call cc-option,-mno-single-pic-base)
+cflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
+ -fpic

cflags-$(CONFIG_EFI_GENERIC_ARCH_STUB) += -I$(srctree)/scripts/dtc/libfdt

@@ -55,6 +57,7 @@ lib-$(CONFIG_EFI_GENERIC_ARCH_STUB) += efi-stub.o fdt.o string.o \
lib-$(CONFIG_ARM) += arm32-stub.o
lib-$(CONFIG_ARM64) += arm64-stub.o
lib-$(CONFIG_X86) += x86-stub.o
+lib-$(CONFIG_RISCV) += riscv-stub.o
CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)

@@ -79,6 +82,11 @@ STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
--prefix-symbols=__efistub_
STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS

+STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \
+ --prefix-symbols=__efistub_
+STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20
+
+
$(obj)/%.stub.o: $(obj)/%.o FORCE
$(call if_changed,stubcopy)

diff --git a/drivers/firmware/efi/libstub/riscv-stub.c b/drivers/firmware/efi/libstub/riscv-stub.c
new file mode 100644
index 000000000000..3935b29ea93a
--- /dev/null
+++ b/drivers/firmware/efi/libstub/riscv-stub.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2013, 2014 Linaro Ltd; <roy.franz@linaro.org>
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ *
+ * This file implements the EFI boot stub for the RISC-V kernel.
+ * Adapted from ARM64 version at drivers/firmware/efi/libstub/arm64-stub.c.
+ */
+
+#include <linux/efi.h>
+#include <linux/libfdt.h>
+#include <linux/libfdt_env.h>
+#include <asm/efi.h>
+#include <asm/sections.h>
+
+#include "efistub.h"
+/*
+ * RISCV requires the kernel image to placed TEXT_OFFSET bytes beyond a 2 MB
+ * aligned base for 64 bit and 4MB for 32 bit.
+ */
+#if IS_ENABLED(CONFIG_64BIT)
+#define MIN_KIMG_ALIGN SZ_2M
+#else
+#define MIN_KIMG_ALIGN SZ_4M
+#endif
+/*
+ * TEXT_OFFSET ensures that we don't overwrite the firmware that probably sits
+ * at the beginning of the DRAM.
+ */
+#define TEXT_OFFSET MIN_KIMG_ALIGN
+
+typedef __attribute__((noreturn)) void (*jump_kernel_func)(unsigned int,
+ unsigned long);
+
+efi_status_t check_platform_features(void)
+{
+ return EFI_SUCCESS;
+}
+
+u64 get_boot_hartid_from_fdt(unsigned long fdt)
+{
+ int chosen_node, len;
+ const fdt64_t *prop;
+ uint64_t hartid = U64_MAX;
+
+ chosen_node = fdt_path_offset((void *)fdt, "/chosen");
+ if (chosen_node < 0)
+ return hartid;
+ prop = fdt_getprop((void *)fdt, chosen_node, "efi-boot-hartid", &len);
+ if (!prop || len != sizeof(u64))
+ return hartid;
+
+ hartid = fdt64_to_cpu(*prop);
+
+ return hartid;
+}
+
+/*
+ * Jump to real kernel here with following constraints.
+ * 1. MMU should be disabled.
+ * 2. a0 should contain hartid
+ * 3. a1 should DT address
+ */
+void __noreturn efi_enter_kernel(unsigned long entrypoint, unsigned long fdt)
+{
+ unsigned long kernel_entry = entrypoint + _start_kernel - _start;
+ jump_kernel_func jump_kernel = (void (*)(unsigned int, unsigned long))kernel_entry;
+ u64 hartid = get_boot_hartid_from_fdt(fdt);
+
+ if (hartid == U64_MAX)
+ /* We can not use panic or BUG at this point */
+ __asm__ __volatile__ ("ebreak");
+ /* Disable MMU */
+ csr_write(CSR_SATP, 0);
+ jump_kernel(hartid, fdt);
+}
+
+efi_status_t handle_kernel_image(unsigned long *image_addr,
+ unsigned long *image_size,
+ unsigned long *reserve_addr,
+ unsigned long *reserve_size,
+ unsigned long dram_base,
+ efi_loaded_image_t *image)
+{
+ efi_status_t status;
+ unsigned long kernel_size, kernel_memsize = 0;
+ unsigned long preferred_offset;
+
+ /*
+ * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond
+ * a KIMG_ALIGN aligned base.
+ */
+ preferred_offset = round_up(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET;
+
+ kernel_size = _edata - _start;
+ kernel_memsize = kernel_size + (_end - _edata);
+
+ /*
+ * Try a straight allocation at the preferred offset.
+ * This will work around the issue where, if dram_base == 0x0,
+ * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
+ * address of the allocation to be mistaken for a FAIL return
+ * value or a NULL pointer). It will also ensure that, on
+ * platforms where the [dram_base, dram_base + TEXT_OFFSET)
+ * interval is partially occupied by the firmware (like on APM
+ * Mustang), we can still place the kernel at the address
+ * 'dram_base + TEXT_OFFSET'.
+ */
+ if (*image_addr == preferred_offset)
+ return EFI_SUCCESS;
+
+ *image_addr = *reserve_addr = preferred_offset;
+ *reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN);
+
+ status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
+ EFI_LOADER_DATA,
+ *reserve_size / EFI_PAGE_SIZE,
+ (efi_physical_addr_t *)reserve_addr);
+
+ if (status != EFI_SUCCESS) {
+ *reserve_size = kernel_memsize + TEXT_OFFSET;
+ status = efi_low_alloc(*reserve_size, MIN_KIMG_ALIGN,
+ reserve_addr);
+
+ if (status != EFI_SUCCESS) {
+ pr_efi_err("Failed to relocate kernel\n");
+ *reserve_size = 0;
+ return status;
+ }
+ *image_addr = *reserve_addr + TEXT_OFFSET;
+ }
+ memcpy((void *)*image_addr, image->image_base, kernel_size);
+
+ return EFI_SUCCESS;
+}
--
2.24.0
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