Message-Id: <20200421033336.9663-4-atish.patra@wdc.com>
Date:   Mon, 20 Apr 2020 20:33:36 -0700
From:   Atish Patra <atish.patra@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Atish Patra <atish.patra@....com>,
        Ard Biesheuvel <ardb@...nel.org>, linux-efi@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Heinrich Schuchardt <xypron.glpk@....de>
Subject: [v4 PATCH 3/3] RISC-V: Add EFI stub support.

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@....com>
---
 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
+	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
+
+/* 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@...aro.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"
+/*
+ * 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;
+}
-- 
2.24.0

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