On Mon, 2020-02-17 at 13:49 +0100, Ard Biesheuvel wrote:
> Expose efi_entry() as the PE/COFF entrypoint directly, instead of
> jumping into a wrapper that fiddles with stack buffers and other
> stuff that the compiler is much better at. The only reason this
> code exists is to obtain a pointer to the base of the image, but
> we can get the same value from the loaded_image protocol, which
> we already need for other reasons anyway.
>
> Update the return type as well, to make it consistent with what
> is required for a PE/COFF executable entrypoint.
>
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
> Apologies to Atish for making him track a moving target, but this is
> another
> bit of cleanup work that I would like to merge before taking the
> RISC-V
> changes on top.
>
And I thought I am done rebasing my patches ;). Jokes apart, this is
actually much cleaner approach in retrieving image base and parsing DT
compared to what I currently have for RISC-V.
> On RISC-V, I would expect efi_enter_kernel() to be implemented as a C
> routine
> that finds the hart id in the DT (which is passed as an argument),
> and pass
> it to the startup code of the kernel proper.
>
Yes. I probably won't need efi-entry.S for RISC-V at all which
simplifies the RISC-V implementation. Yay!!
Is there a tree with this patch ? I tried to find it in your kernel.org
repo but couldn't find it. As there are 3 efi related patch set in
flight, I am not sure about the order in which they should be applied.
> arch/arm/boot/compressed/efi-header.S | 2 +-
> arch/arm/boot/compressed/head.S | 44 +++-----------
> arch/arm64/kernel/efi-entry.S | 64 +++-----------------
> arch/arm64/kernel/efi-header.S | 2 +-
> drivers/firmware/efi/libstub/arm-stub.c | 37 +++++------
> drivers/firmware/efi/libstub/arm32-stub.c | 1 +
> drivers/firmware/efi/libstub/arm64-stub.c | 3 +-
> 7 files changed, 42 insertions(+), 111 deletions(-)
>
> diff --git a/arch/arm/boot/compressed/efi-header.S
> b/arch/arm/boot/compressed/efi-header.S
> index a5983588f96b..e38fbda02b93 100644
> --- a/arch/arm/boot/compressed/efi-header.S
> +++ b/arch/arm/boot/compressed/efi-header.S
> @@ -60,7 +60,7 @@ optional_header:
> .long __pecoff_code_size @ SizeOfCode
> .long __pecoff_data_size @
> SizeOfInitializedData
> .long 0 @
> SizeOfUninitializedData
> - .long efi_stub_entry - start @
> AddressOfEntryPoint
> + .long efi_entry - start @
> AddressOfEntryPoint
> .long start_offset @ BaseOfCode
> .long __pecoff_data_start - start @ BaseOfData
>
> diff --git a/arch/arm/boot/compressed/head.S
> b/arch/arm/boot/compressed/head.S
> index 088b0a060876..941cd28a13c3 100644
> --- a/arch/arm/boot/compressed/head.S
> +++ b/arch/arm/boot/compressed/head.S
> @@ -1437,50 +1437,22 @@ __enter_kernel:
> reloc_code_end:
>
> #ifdef CONFIG_EFI_STUB
> - .align 2
> -_start: .long start - .
> -
> -ENTRY(efi_stub_entry)
> - @ allocate space on stack for passing current zImage
> address
> - @ and for the EFI stub to return of new entry point of
> - @ zImage, as EFI stub may copy the kernel. Pointer
> address
> - @ is passed in r2. r0 and r1 are passed through from
> the
> - @ EFI firmware to efi_entry
> - adr ip, _start
> - ldr r3, [ip]
> - add r3, r3, ip
> - stmfd sp!, {r3, lr}
> - mov r2, sp @ pass zImage address
> in r2
> - bl efi_entry
> -
> - @ Check for error return from EFI stub. r0 has FDT
> address
> - @ or error code.
> - cmn r0, #1
> - beq efi_load_fail
> -
> - @ Preserve return value of efi_entry() in r4
> - mov r4, r0
> +ENTRY(efi_enter_kernel)
> + mov r4, r0 @ preserve entrypoint
> + mov r5, r1 @ preserve DT pointer
> bl cache_clean_flush
> bl cache_off
>
> @ Set parameters for booting zImage according to boot
> protocol
> - @ put FDT address in r2, it was returned by efi_entry()
> - @ r1 is the machine type, and r0 needs to be 0
> mov r0, #0
> mov r1, #0xFFFFFFFF
> - mov r2, r4
> + mov r2, r5
>
> - @ Branch to (possibly) relocated zImage that is in [sp]
> - ldr lr, [sp]
> + @ Branch to (possibly) relocated zImage @ [r4]
> ldr ip, =start_offset
> - add lr, lr, ip
> - mov pc, lr @ no mode
> switch
> -
> -efi_load_fail:
> - @ Return EFI_LOAD_ERROR to EFI firmware on error.
> - ldr r0, =0x80000001
> - ldmfd sp!, {ip, pc}
> -ENDPROC(efi_stub_entry)
> + add r4, r4, ip
> + mov pc, r4 @ no mode switch
> +ENDPROC(efi_enter_kernel)
> #endif
>
> .align
> diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-
> entry.S
> index 304d5b02ca67..49e3b1ad1b36 100644
> --- a/arch/arm64/kernel/efi-entry.S
> +++ b/arch/arm64/kernel/efi-entry.S
> @@ -10,55 +10,18 @@
>
> #include <asm/assembler.h>
>
> -#define EFI_LOAD_ERROR 0x8000000000000001
> -
> __INIT
>
> - /*
> - * We arrive here from the EFI boot manager with:
> - *
> - * * CPU in little-endian mode
> - * * MMU on with identity-mapped RAM
> - * * Icache and Dcache on
> - *
> - * We will most likely be running from some place other than
> where
> - * we want to be. The kernel image wants to be placed at
> TEXT_OFFSET
> - * from start of RAM.
> - */
> -ENTRY(entry)
> - /*
> - * Create a stack frame to save FP/LR with extra space
> - * for image_addr variable passed to efi_entry().
> - */
> - stp x29, x30, [sp, #-32]!
> - mov x29, sp
> -
> - /*
> - * Call efi_entry to do the real work.
> - * x0 and x1 are already set up by firmware. Current runtime
> - * address of image is calculated and passed via *image_addr.
> - *
> - * unsigned long efi_entry(void *handle,
> - * efi_system_table_t *sys_table,
> - * unsigned long *image_addr) ;
> - */
> - adr_l x8, _text
> - add x2, sp, 16
> - str x8, [x2]
> - bl efi_entry
> - cmn x0, #1
> - b.eq efi_load_fail
> -
> +ENTRY(efi_enter_kernel)
> /*
> * efi_entry() will have copied the kernel image if necessary
> and we
> - * return here with device tree address in x0 and the kernel
> entry
> - * point stored at *image_addr. Save those values in registers
> which
> - * are callee preserved.
> + * end up here with device tree address in x1 and the kernel
> entry
> + * point stored in x0. Save those values in registers which are
> + * callee preserved.
> */
> - mov x20, x0 // DTB address
> - ldr x0, [sp, #16] // relocated _text address
> + mov x20, x1 // DTB address
> ldr w21, =stext_offset
> - add x21, x0, x21
> + add x21, x0, x21 // relocated Image address
>
> /*
> * Calculate size of the kernel Image (same for original and
> copy).
> @@ -80,9 +43,8 @@ ENTRY(entry)
> * entries for the VA range of the current image, so no
> maintenance is
> * necessary.
> */
> - adr x0, entry
> - adr x1, entry_end
> - sub x1, x1, x0
> + adr x0, efi_enter_kernel
> + mov x1, efi_enter_kernel_size
> bl __flush_dcache_area
>
> /* Turn off Dcache and MMU */
> @@ -110,11 +72,5 @@ ENTRY(entry)
> mov x2, xzr
> mov x3, xzr
> br x21
> -
> -efi_load_fail:
> - mov x0, #EFI_LOAD_ERROR
> - ldp x29, x30, [sp], #32
> - ret
> -
> -entry_end:
> -ENDPROC(entry)
> +ENDPROC(efi_enter_kernel)
> + .set efi_enter_kernel_size, . - efi_enter_kernel
> diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-
> header.S
> index a7cfacce3e15..40c704c5d3a5 100644
> --- a/arch/arm64/kernel/efi-header.S
> +++ b/arch/arm64/kernel/efi-header.S
> @@ -27,7 +27,7 @@ optional_header:
> .long __initdata_begin - efi_header_end // SizeOfCode
> .long __pecoff_data_size //
> SizeOfInitializedData
> .long 0 //
> SizeOfUninitializedData
> - .long __efistub_entry - _head //
> AddressOfEntryPoint
> + .long __efistub_efi_entry - _head //
> AddressOfEntryPoint
> .long efi_header_end - _head // BaseOfCode
>
> extra_header_fields:
> diff --git a/drivers/firmware/efi/libstub/arm-stub.c
> b/drivers/firmware/efi/libstub/arm-stub.c
> index 56e475c1aa55..439c094f7bf2 100644
> --- a/drivers/firmware/efi/libstub/arm-stub.c
> +++ b/drivers/firmware/efi/libstub/arm-stub.c
> @@ -133,17 +133,20 @@ efi_status_t handle_kernel_image(unsigned long
> *image_addr,
> unsigned long *reserve_size,
> unsigned long dram_base,
> efi_loaded_image_t *image);
> +
> +void __noreturn efi_enter_kernel(unsigned long entrypoint, unsigned
> long fdt);
> +
> /*
> * EFI entry point for the arm/arm64 EFI stubs. This is the
> entrypoint
> * that is described in the PE/COFF header. Most of the code is the
> same
> * for both archictectures, with the arch-specific code provided in
> the
> * handle_kernel_image() function.
> */
> -unsigned long efi_entry(void *handle, efi_system_table_t
> *sys_table_arg,
> - unsigned long *image_addr)
> +efi_status_t efi_entry(efi_handle_t handle, efi_system_table_t
> *sys_table_arg)
> {
> efi_loaded_image_t *image;
> efi_status_t status;
> + unsigned long image_addr;
> unsigned long image_size = 0;
> unsigned long dram_base;
> /* addr/point and size pairs for memory management*/
> @@ -153,7 +156,6 @@ unsigned long efi_entry(void *handle,
> efi_system_table_t *sys_table_arg,
> unsigned long fdt_size = 0;
> char *cmdline_ptr = NULL;
> int cmdline_size = 0;
> - unsigned long new_fdt_addr;
> efi_guid_t loaded_image_proto = LOADED_IMAGE_PROTOCOL_GUID;
> unsigned long reserve_addr = 0;
> unsigned long reserve_size = 0;
> @@ -165,8 +167,10 @@ unsigned long efi_entry(void *handle,
> efi_system_table_t *sys_table_arg,
> sys_table = sys_table_arg;
>
> /* Check if we were booted by the EFI firmware */
> - if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
> + if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE) {
> + status = EFI_INVALID_PARAMETER;
> goto fail;
> + }
>
> status = check_platform_features();
> if (status != EFI_SUCCESS)
> @@ -187,6 +191,7 @@ unsigned long efi_entry(void *handle,
> efi_system_table_t *sys_table_arg,
> dram_base = get_dram_base();
> if (dram_base == EFI_ERROR) {
> pr_efi_err("Failed to find DRAM base\n");
> + status = EFI_LOAD_ERROR;
> goto fail;
> }
>
> @@ -198,6 +203,7 @@ unsigned long efi_entry(void *handle,
> efi_system_table_t *sys_table_arg,
> cmdline_ptr = efi_convert_cmdline(image, &cmdline_size,
> ULONG_MAX);
> if (!cmdline_ptr) {
> pr_efi_err("getting command line via
> LOADED_IMAGE_PROTOCOL\n");
> + status = EFI_OUT_OF_RESOURCES;
> goto fail;
> }
>
> @@ -213,7 +219,7 @@ unsigned long efi_entry(void *handle,
> efi_system_table_t *sys_table_arg,
>
> si = setup_graphics();
>
> - status = handle_kernel_image(image_addr, &image_size,
> + status = handle_kernel_image(&image_addr, &image_size,
> &reserve_addr,
> &reserve_size,
> dram_base, image);
> @@ -260,7 +266,7 @@ unsigned long efi_entry(void *handle,
> efi_system_table_t *sys_table_arg,
> pr_efi("Generating empty DTB\n");
>
> if (!noinitrd()) {
> - max_addr = efi_get_max_initrd_addr(dram_base,
> *image_addr);
> + max_addr = efi_get_max_initrd_addr(dram_base,
> image_addr);
> status = efi_load_initrd_dev_path(&initrd_addr,
> &initrd_size,
> max_addr);
> if (status == EFI_SUCCESS) {
> @@ -311,33 +317,30 @@ unsigned long efi_entry(void *handle,
> efi_system_table_t *sys_table_arg,
>
> install_memreserve_table();
>
> - new_fdt_addr = fdt_addr;
> status = allocate_new_fdt_and_exit_boot(handle,
> - &new_fdt_addr,
> efi_get_max_fdt_addr(dram_base),
> + &fdt_addr,
> efi_get_max_fdt_addr(dram_base),
> initrd_addr, initrd_size, cmdline_ptr,
> fdt_addr, fdt_size);
> + if (status != EFI_SUCCESS)
> + goto fail_free_initrd;
>
> - /*
> - * If all went well, we need to return the FDT address to the
> - * calling function so it can be passed to kernel as part of
> - * the kernel boot protocol.
> - */
> - if (status == EFI_SUCCESS)
> - return new_fdt_addr;
> + efi_enter_kernel(image_addr, fdt_addr);
> + /* not reached */
>
> +fail_free_initrd:
> pr_efi_err("Failed to update FDT and exit boot services\n");
>
> efi_free(initrd_size, initrd_addr);
> efi_free(fdt_size, fdt_addr);
>
> fail_free_image:
> - efi_free(image_size, *image_addr);
> + efi_free(image_size, image_addr);
> efi_free(reserve_size, reserve_addr);
> fail_free_cmdline:
> free_screen_info(si);
> efi_free(cmdline_size, (unsigned long)cmdline_ptr);
> fail:
> - return EFI_ERROR;
> + return status;
> }
>
> /*
> diff --git a/drivers/firmware/efi/libstub/arm32-stub.c
> b/drivers/firmware/efi/libstub/arm32-stub.c
> index 7b2a6382b647..113298b8ea65 100644
> --- a/drivers/firmware/efi/libstub/arm32-stub.c
> +++ b/drivers/firmware/efi/libstub/arm32-stub.c
> @@ -227,6 +227,7 @@ efi_status_t handle_kernel_image(unsigned long
> *image_addr,
> * Relocate the zImage, so that it appears in the lowest 128 MB
> * memory window.
> */
> + *image_addr = image->image_base;
> *image_size = image->image_size;
> status = efi_relocate_kernel(image_addr, *image_size,
> *image_size,
> kernel_base +
> MAX_UNCOMP_KERNEL_SIZE, 0, 0);
> diff --git a/drivers/firmware/efi/libstub/arm64-stub.c
> b/drivers/firmware/efi/libstub/arm64-stub.c
> index 719d03a64329..9254cd8ab2d3 100644
> --- a/drivers/firmware/efi/libstub/arm64-stub.c
> +++ b/drivers/firmware/efi/libstub/arm64-stub.c
> @@ -43,7 +43,6 @@ efi_status_t handle_kernel_image(unsigned long
> *image_addr,
> {
> efi_status_t status;
> unsigned long kernel_size, kernel_memsize = 0;
> - void *old_image_addr = (void *)*image_addr;
> unsigned long preferred_offset;
> u64 phys_seed = 0;
>
> @@ -141,7 +140,7 @@ efi_status_t handle_kernel_image(unsigned long
> *image_addr,
> }
> *image_addr = *reserve_addr + TEXT_OFFSET;
> }
> - memcpy((void *)*image_addr, old_image_addr, kernel_size);
> + memcpy((void *)*image_addr, image->image_base, kernel_size);
>
> return EFI_SUCCESS;
> }
--
Regards,
Atish
