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Message-ID: <mhng-eeb13dd6-b358-491a-909c-30b1725f95c7@palmerdabbelt-glaptop1>
Date: Tue, 21 Apr 2020 13:08:30 -0700 (PDT)
From: Palmer Dabbelt <palmer@...belt.com>
To: Atish Patra <Atish.Patra@....com>
CC: linux-kernel@...r.kernel.org, Atish Patra <Atish.Patra@....com>,
ardb@...nel.org, linux-efi@...r.kernel.org,
linux-riscv@...ts.infradead.org, masahiroy@...nel.org,
xypron.glpk@....de
Subject: Re: [v4 PATCH 3/3] RISC-V: Add EFI stub support.
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@....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
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@...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;
> +}
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