Re: [v4 PATCH 3/3] RISC-V: Add EFI stub support.
From: Palmer Dabbelt
Date: Tue Apr 21 2020 - 16:08:34 EST
On Mon, 20 Apr 2020 20:33:36 PDT (-0700), Atish Patra wrote:
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@xxxxxxx>
---
arch/riscv/Kconfig | 20 ++++
arch/riscv/Makefile | 1 +
arch/riscv/configs/defconfig | 1 +
arch/riscv/include/asm/efi.h | 44 +++++++++
drivers/firmware/efi/Kconfig | 2 +-
drivers/firmware/efi/libstub/Makefile | 10 ++
drivers/firmware/efi/libstub/riscv-stub.c | 106 ++++++++++++++++++++++
7 files changed, 183 insertions(+), 1 deletion(-)
create mode 100644 arch/riscv/include/asm/efi.h
create mode 100644 drivers/firmware/efi/libstub/riscv-stub.c
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index f39e326a7a42..eb4f41c8f3ce 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -379,10 +379,30 @@ 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_STUB
So I guess just "select RISCV_ISA_C" would be sufficient to make this work, but
I still feel flike an explicit "c.li" is saner.
+ 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 fb6e37db836d..079435804d6d 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -80,6 +80,7 @@ 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 4da4886246a4..ae69e12d306a 100644
--- a/arch/riscv/configs/defconfig
+++ b/arch/riscv/configs/defconfig
@@ -129,3 +129,4 @@ CONFIG_DEBUG_BLOCK_EXT_DEVT=y
# CONFIG_RUNTIME_TESTING_MENU is not set
CONFIG_MEMTEST=y
# CONFIG_SYSFS_SYSCALL is not set
+CONFIG_EFI=y
diff --git a/arch/riscv/include/asm/efi.h b/arch/riscv/include/asm/efi.h
new file mode 100644
index 000000000000..62d7d5eafed8
--- /dev/null
+++ b/arch/riscv/include/asm/efi.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ * Based on arch/arm64/include/asm/efi.h
+ */
+#ifndef _ASM_EFI_H
+#define _ASM_EFI_H
+
+#include <asm/io.h>
+#include <asm/mmu_context.h>
+#include <asm/ptrace.h>
+#include <asm/tlbflush.h>
+
+#define VA_BITS_MIN 39
I don't see this actually being used, but if it's releant to some macro that
I'm missing then EFI support should depend on rv64.
+
+/* on RISC-V, the FDT may be located anywhere in system RAM */
+static inline unsigned long efi_get_max_fdt_addr(unsigned long dram_base)
+{
+ return ULONG_MAX;
+}
+
+/* Load initrd at enough distance from DRAM start */
+static inline unsigned long efi_get_max_initrd_addr(unsigned long dram_base,
+ unsigned long image_addr)
+{
+ return dram_base + SZ_256M;
+}
+
+#define efi_bs_call(func, ...) efi_system_table()->boottime->func(__VA_ARGS__)
+#define efi_rt_call(func, ...) efi_system_table()->runtime->func(__VA_ARGS__)
+#define efi_is_native() (true)
+
+#define efi_table_attr(inst, attr) (inst->attr)
+
+#define efi_call_proto(inst, func, ...) inst->func(inst, ##__VA_ARGS__)
+
+#define alloc_screen_info(x...) (&screen_info)
+extern char stext_offset[];
+
+static inline void free_screen_info(struct screen_info *si)
+{
+}
+
+#endif /* _ASM_EFI_H */
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 2a2b2b96a1dc..fcdc789d3f87 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -111,7 +111,7 @@ config EFI_GENERIC_STUB
config EFI_ARMSTUB_DTB_LOADER
bool "Enable the DTB loader"
- depends on EFI_GENERIC_STUB
+ depends on EFI_GENERIC_STUB && !RISCV
default y
help
Select this config option to add support for the dtb= command
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 0f57293d777e..eb365c55c0fe 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -22,6 +22,8 @@ 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-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt
@@ -57,6 +59,7 @@ lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o fdt.o string.o \
lib-$(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=$(TEXT_OFFSET)
@@ -100,6 +103,13 @@ STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc
STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
+# For RISC-V, we don't need anything special other than arm64. Keep all the
+# symbols in .init section and make sure that no absolute symbols references
+# doesn't exist.
+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..bd1d6fed8754
--- /dev/null
+++ b/drivers/firmware/efi/libstub/riscv-stub.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2013, 2014 Linaro Ltd; <roy.franz@xxxxxxxxxx>
+ * 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"
+/*
+ * RISC-V requires the kernel image to placed 2 MB aligned base for 64 bit and
+ * 4MB for 32 bit.
+ */
+#ifdef CONFIG_64BIT
+#define MIN_KIMG_ALIGN SZ_2M
+#else
+#define MIN_KIMG_ALIGN SZ_4M
+#endif
+
+typedef __attribute__((noreturn)) void (*jump_kernel_func)(unsigned int,
+ unsigned long);
+efi_status_t check_platform_features(void)
+{
+ return EFI_SUCCESS;
+}
+
+static u32 get_boot_hartid_from_fdt(unsigned long fdt)
+{
+ int chosen_node, len;
+ const fdt32_t *prop;
+
+ chosen_node = fdt_path_offset((void *)fdt, "/chosen");
+ if (chosen_node < 0)
+ return U32_MAX;
+ prop = fdt_getprop((void *)fdt, chosen_node, "boot-hartid", &len);
+ if (!prop || len != sizeof(u32))
+ return U32_MAX;
+
+ return fdt32_to_cpu(*prop);
+}
+
+/*
+ * 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 fdt_size)
+{
+ unsigned long kernel_entry = entrypoint + (unsigned long)stext_offset;
+ jump_kernel_func jump_kernel = (jump_kernel_func) kernel_entry;
+ u32 hartid = get_boot_hartid_from_fdt(fdt);
+
+ if (hartid == U32_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 = 0;
+ unsigned long preferred_addr;
+
+ kernel_size = _edata - _start;
+ *reserve_size = kernel_size + (_end - _edata);
+ *image_addr = (unsigned long)_start;
+
+ /*
+ * RISC-V kernel maps PAGE_OFFSET virtual address to the same physical
+ * address where kernel is booted. That's why kernel should boot from
+ * as low as possible to avoid wastage of memory. Currently, dram_base
+ * is occupied by the firmware. So the preferred address for kernel to
+ * boot is next aligned address. If preferred address is not available,
+ * relocate_kernel will fall back to efi_low_alloc_above to allocate
+ * lowest possible memory region as long as the address and size meets
+ * the alignment constraints.
+ */
+ preferred_addr = round_up(dram_base, MIN_KIMG_ALIGN) + MIN_KIMG_ALIGN;
+ status = efi_relocate_kernel(image_addr, kernel_size, *reserve_size,
+ preferred_addr, MIN_KIMG_ALIGN, dram_base);
+
+ if (status != EFI_SUCCESS) {
+ pr_efi_err("Failed to relocate kernel\n");
+ *reserve_size = 0;
+ return status;
+ }
+
+ return EFI_SUCCESS;
+}