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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Wed, 26 Feb 2020 08:28:28 +0100
Message-ID: <CAKv+Gu_iAzQ6et13aACarqns8-xzQ+YSqj+m3mVGGy=ny8GJBg@mail.gmail.com>
Subject: Re: [RFC PATCH 5/5] RISC-V: Add EFI stub support.
To:     Atish Patra <atish.patra@wdc.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Alexios Zavras <alexios.zavras@intel.com>,
        Allison Randal <allison@lohutok.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Anup Patel <Anup.Patel@wdc.com>, Arnd Bergmann <arnd@arndb.de>,
        Borislav Petkov <bp@suse.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Greentime Hu <greentime.hu@sifive.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        Kees Cook <keescook@chromium.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        linux-efi <linux-efi@vger.kernel.org>,
        linux-riscv@lists.infradead.org, Mao Han <han_mao@c-sky.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Michal Simek <michal.simek@xilinx.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
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        Paolo Bonzini <pbonzini@redhat.com>,
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        Thomas Gleixner <tglx@linutronix.de>,
        Will Deacon <will@kernel.org>,
        Alexander Graf <agraf@csgraf.de>,
        "leif@nuviainc.com" <leif@nuviainc.com>,
        "Chang, Abner (HPS SW/FW Technologist)" <abner.chang@hpe.com>,
        "Schaefer, Daniel (DualStudy)" <daniel.schaefer@hpe.com>
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On Wed, 26 Feb 2020 at 02:10, Atish Patra <atish.patra@wdc.com> 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@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)

You can use #ifdef here

> +#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.
> + */

Ugh. Really? On an EFI system, that memory should be reserved in some
way, we shouldn't be able to stomp on it like that.

> +#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)

static

> +{
> +       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;

Just return U64_MAX here

> +       prop = fdt_getprop((void *)fdt, chosen_node, "efi-boot-hartid", &len);

Please call this 'boot-hartid' not 'efi-boot-hartid' as the hartid
value is independent of whether you boot via EFI or not.

> +       if (!prop || len != sizeof(u64))
> +               return hartid;
> +

Return U64_MAX

> +       hartid = fdt64_to_cpu(*prop);
> +

and just return the swabbed value, so you can get rid of the local var.

> +       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)

This prototype has changed, and now includes the size of the fdt in param 3.

> +{
> +       unsigned long kernel_entry = entrypoint + _start_kernel - _start;

stext_offset ? It has a terrible name though, and I'll probably
propose to change it at some point, for all arches. But you can still
use it here.

> +       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'.

Better drop this entire last sentence (unless it is relevant, but then
rework it to drop the APM Mustang reference)

> +        */
> +       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
>