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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Wed, 19 Oct 2022 09:27:37 +0200
Message-ID: <CAMj1kXFNhayBgXSaHxKpdnWbmQsoG5WpT9U6FhOXqJ0dsHHp4w@mail.gmail.com>
Subject: Re: [PATCH 12/16] x86/boot: Add EFI kernel extraction interface
To:     Evgeniy Baskov <baskov@ispras.ru>
Cc:     Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Alexey Khoroshilov <khoroshilov@ispras.ru>,
        lvc-project@linuxtesting.org, x86@kernel.org,
        linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org
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Precedence: bulk

On Tue, 6 Sept 2022 at 12:42, Evgeniy Baskov <baskov@ispras.ru> wrote:
>
> To enable extraction of kernel image from EFI stub code directly
> extraction code needs to have separate interface that avoid part
> of low level initialization logic, i.e. serial port setup.
>
> Add kernel extraction function callable from libstub as a part
> of preparation for extracting the kernel directly from EFI environment.
>
> Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
> ---
>  arch/x86/boot/compressed/head_32.S |  3 +-
>  arch/x86/boot/compressed/head_64.S |  2 +-
>  arch/x86/boot/compressed/misc.c    | 85 +++++++++++++++++++++---------
>  arch/x86/boot/compressed/misc.h    |  2 +
>  arch/x86/boot/compressed/putstr.c  |  9 ++++
>  5 files changed, 73 insertions(+), 28 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
> index 3b354eb9516d..b46a1c4109cf 100644
> --- a/arch/x86/boot/compressed/head_32.S
> +++ b/arch/x86/boot/compressed/head_32.S
> @@ -217,8 +217,7 @@ SYM_DATA(image_offset, .long 0)
>   */
>         .bss
>         .balign 4
> -boot_heap:
> -       .fill BOOT_HEAP_SIZE, 1, 0
> +SYM_DATA(boot_heap,    .fill BOOT_HEAP_SIZE, 1, 0)
>  boot_stack:
>         .fill BOOT_STACK_SIZE, 1, 0
>  boot_stack_end:
> diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
> index 889ca7176aa7..37ce094571b5 100644
> --- a/arch/x86/boot/compressed/head_64.S
> +++ b/arch/x86/boot/compressed/head_64.S
> @@ -1007,7 +1007,7 @@ SYM_FUNC_END(startup32_check_sev_cbit)
>   */
>         .bss
>         .balign 4
> -SYM_DATA_LOCAL(boot_heap,      .fill BOOT_HEAP_SIZE, 1, 0)
> +SYM_DATA(boot_heap,    .fill BOOT_HEAP_SIZE, 1, 0)
>
>  SYM_DATA_START_LOCAL(boot_stack)
>         .fill BOOT_STACK_SIZE, 1, 0
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> index e2c0d05ac293..8016cc5c300e 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -293,11 +293,11 @@ static void parse_elf(void *output, unsigned long output_len,
>   *             |-------uncompressed kernel image---------|
>   *
>   */
> -asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
> -                                 unsigned char *input_data,
> -                                 unsigned long input_len,
> -                                 unsigned char *output,
> -                                 unsigned long output_len)
> +static void *do_extract_kernel(void *rmode,
> +                              unsigned char *input_data,
> +                              unsigned long input_len,
> +                              unsigned char *output,
> +                              unsigned long output_len)
>  {
>         const unsigned long kernel_total_size = VO__end - VO__text;
>         unsigned long virt_addr = LOAD_PHYSICAL_ADDR;
> @@ -311,18 +311,6 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
>
>         sanitize_boot_params(boot_params);
>
> -       init_default_io_ops();
> -
> -       /*
> -        * Detect TDX guest environment.
> -        *
> -        * It has to be done before console_init() in order to use
> -        * paravirtualized port I/O operations if needed.
> -        */
> -       early_tdx_detect();
> -
> -       init_bare_console();
> -
>         /*
>          * Save RSDP address for later use. Have this after console_init()
>          * so that early debugging output from the RSDP parsing code can be
> @@ -330,11 +318,6 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
>          */
>         boot_params->acpi_rsdp_addr = get_rsdp_addr();
>
> -       debug_putstr("early console in extract_kernel\n");
> -
> -       free_mem_ptr     = heap;        /* Heap */
> -       free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
> -
>         /*
>          * The memory hole needed for the kernel is the larger of either
>          * the entire decompressed kernel plus relocation table, or the
> @@ -387,12 +370,12 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
>         if (virt_addr & (MIN_KERNEL_ALIGN - 1))
>                 error("Destination virtual address inappropriately aligned");
>  #ifdef CONFIG_X86_64
> -       if (heap > 0x3fffffffffffUL)
> +       if (phys_addr > 0x3fffffffffffUL)
>                 error("Destination address too large");
>         if (virt_addr + max(output_len, kernel_total_size) > KERNEL_IMAGE_SIZE)
>                 error("Destination virtual address is beyond the kernel mapping area");
>  #else
> -       if (heap > ((-__PAGE_OFFSET-(128<<20)-1) & 0x7fffffff))
> +       if (phys_addr > ((-__PAGE_OFFSET-(128<<20)-1) & 0x7fffffff))
>                 error("Destination address too large");
>  #endif
>  #ifndef CONFIG_RELOCATABLE
> @@ -406,12 +389,64 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
>         parse_elf(output, output_len, virt_addr);
>         debug_putstr("done.\nBooting the kernel.\n");
>
> +       return output;
> +}
> +
> +asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
> +                                 unsigned char *input_data,
> +                                 unsigned long input_len,
> +                                 unsigned char *output,
> +                                 unsigned long output_len)
> +{
> +       void *entry;
> +
> +       init_default_io_ops();
> +
> +       /*
> +        * Detect TDX guest environment.
> +        *
> +        * It has to be done before console_init() in order to use
> +        * paravirtualized port I/O operations if needed.
> +        */
> +       early_tdx_detect();
> +
> +       init_bare_console();
> +
> +       debug_putstr("early console in extract_kernel\n");
> +
> +       free_mem_ptr     = heap;        /* Heap */
> +       free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
> +
> +       entry = do_extract_kernel(rmode, input_data,
> +                                 input_len, output, output_len);
> +
>         /* Disable exception handling before booting the kernel */
>         cleanup_exception_handling();
>
> -       return output;
> +       return entry;
>  }
>
> +void *efi_extract_kernel(struct boot_params *rmode,
> +                        struct efi_iofunc *iofunc,
> +                        unsigned char *input_data,
> +                        unsigned long input_len,
> +                        unsigned char *output,
> +                        unsigned long output_len)
> +{
> +       extern char boot_heap[BOOT_HEAP_SIZE];
> +
> +       free_mem_ptr     = (unsigned long)boot_heap;    /* Heap */
> +       free_mem_end_ptr = (unsigned long)boot_heap + BOOT_HEAP_SIZE;
> +
> +       init_efi_console(iofunc);
> +
> +       return do_extract_kernel(rmode, input_data,
> +                                input_len, output, output_len);
> +}
> +
> +
> +
> +
>  void fortify_panic(const char *name)
>  {
>         error("detected buffer overflow");
> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
> index 39dc3de50268..b5aa0af6c59e 100644
> --- a/arch/x86/boot/compressed/misc.h
> +++ b/arch/x86/boot/compressed/misc.h
> @@ -26,6 +26,7 @@
>  #include <asm/boot.h>
>  #include <asm/bootparam.h>
>  #include <asm/desc_defs.h>
> +#include <asm/shared/extract.h>
>
>  #include "tdx.h"
>
> @@ -126,6 +127,7 @@ static inline void console_init(void)
>
>  /* putstr.c */
>  void init_bare_console(void);
> +void init_efi_console(struct efi_iofunc *iofunc);
>
>  #ifdef CONFIG_AMD_MEM_ENCRYPT
>  void sev_enable(struct boot_params *bp);
> diff --git a/arch/x86/boot/compressed/putstr.c b/arch/x86/boot/compressed/putstr.c
> index accba0de8be9..238d9677df61 100644
> --- a/arch/x86/boot/compressed/putstr.c
> +++ b/arch/x86/boot/compressed/putstr.c
> @@ -32,6 +32,15 @@ void init_bare_console(void)
>         console_init();
>  }
>
> +void init_efi_console(struct efi_iofunc *iofunc)

struct efi_iofunc does not exist yet

> +{
> +       __putstr = iofunc->putstr;
> +       __puthex = iofunc->puthex;
> +#ifdef CONFIG_X86_64
> +       kernel_add_identity_map = iofunc->map_range;
> +#endif
> +}
> +
>  static void scroll(void)
>  {
>         int i;
> --
> 2.35.1
>