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    Subject[PATCH v8 1/2] efi: Introduce efi_memdesc_ptr to get pointer to memmap descriptor
    Date
    The existing map iteration helper for_each_efi_memory_desc_in_map can
    only be used after OS initializes EFI to fill data of struct efi_memory_map.
    Before that we also need iterate map descriptors which are stored in several
    intermediate structures, like struct efi_boot_memmap for arch independent
    usage and struct efi_info for x86 ARCH only.

    Introduce efi_memdesc_ptr to get pointer to a map descriptor, and replace
    several places of open code with it.

    Suggested-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Baoquan He <bhe@redhat.com>
    ---
    arch/x86/boot/compressed/eboot.c | 2 +-
    drivers/firmware/efi/libstub/efi-stub-helper.c | 4 ++--
    include/linux/efi.h | 19 +++++++++++++++++++
    3 files changed, 22 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
    index c3e869eaef0c..31e12b43be77 100644
    --- a/arch/x86/boot/compressed/eboot.c
    +++ b/arch/x86/boot/compressed/eboot.c
    @@ -767,7 +767,7 @@ static efi_status_t setup_e820(struct boot_params *params,
    m |= (u64)efi->efi_memmap_hi << 32;
    #endif

    - d = (efi_memory_desc_t *)(m + (i * efi->efi_memdesc_size));
    + d = efi_memdesc_ptr(m, efi->efi_memdesc_size, i);
    switch (d->type) {
    case EFI_RESERVED_TYPE:
    case EFI_RUNTIME_SERVICES_CODE:
    diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
    index b0184360efc6..2db55c32e7ed 100644
    --- a/drivers/firmware/efi/libstub/efi-stub-helper.c
    +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
    @@ -205,7 +205,7 @@ efi_status_t efi_high_alloc(efi_system_table_t *sys_table_arg,
    unsigned long m = (unsigned long)map;
    u64 start, end;

    - desc = (efi_memory_desc_t *)(m + (i * desc_size));
    + desc = efi_memdesc_ptr(m, desc_size, i);
    if (desc->type != EFI_CONVENTIONAL_MEMORY)
    continue;

    @@ -298,7 +298,7 @@ efi_status_t efi_low_alloc(efi_system_table_t *sys_table_arg,
    unsigned long m = (unsigned long)map;
    u64 start, end;

    - desc = (efi_memory_desc_t *)(m + (i * desc_size));
    + desc = efi_memdesc_ptr(m, desc_size, i);

    if (desc->type != EFI_CONVENTIONAL_MEMORY)
    continue;
    diff --git a/include/linux/efi.h b/include/linux/efi.h
    index 8269bcb8ccf7..9a6ea328705f 100644
    --- a/include/linux/efi.h
    +++ b/include/linux/efi.h
    @@ -1020,6 +1020,25 @@ extern int efi_memattr_init(void);
    extern int efi_memattr_apply_permissions(struct mm_struct *mm,
    efi_memattr_perm_setter fn);

    +/*
    + * efi_memdesc_ptr - get the n-th efi memmap descriptor
    + * @map: the start of efi memmap
    + * @desc_size: the size of space for each efi memmap descriptor
    + * @n: the index of efi memmap descriptor
    + *
    + * EFI boot service provides function GetMemoryMap() to get a copy of the
    + * current memory map which is an array of memory descriptors, each of
    + * which describes a contiguous block of memory. And also get the size of
    + * map, and the size of each descriptor, etc. Note that per section 6.2 of
    + * UEFI Spec 2.6 Errata A, the returned size of each descriptor might not
    + * be equal to sizeof(efi_memory_memdesc_t) since efi_memory_memdesc_t may
    + * be extended in the future in response to hardware innovation. Thus OS
    + * MUST use the returned size of descriptor to find the start of each
    + * efi_memory_memdesc_t in the memory map array.
    + */
    +#define efi_memdesc_ptr(map, desc_size, n) \
    + (efi_memory_desc_t *)((void *)(map) + ((n) * (desc_size)))
    +
    /* Iterate through an efi_memory_map */
    #define for_each_efi_memory_desc_in_map(m, md) \
    for ((md) = (m)->map; \
    --
    2.5.5
    \
     
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