[PATCH v8 3/5] lib: efi_loader: efi_memory.c: add efi_realloc() for realloc memory

[Ilias Apalodimas]

Hi Paul


On Thu, 3 Jul 2025 at 09:28, Ying-Chun Liu (PaulLiu) <paulliu at debian.org> wrote:
>
> From: "Ying-Chun Liu (PaulLiu)" <paul.liu at linaro.org>
>
> Add efi_realloc() for realloc memory that previously alloc by efi_alloc().
>
> Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu at linaro.org>
> Cc: Heinrich Schuchardt <xypron.glpk at gmx.de>
> Cc: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> Cc: Peter Robinson <pbrobinson at gmail.com>
> Cc: Simon Glass <sjg at chromium.org>
> ---
> V4: Fix efi_realloc return failure code.
> V6: Return error status when efi_alloc failed.
> ---
>  include/efi_loader.h        | 10 +++++++
>  lib/efi_loader/efi_memory.c | 58 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 68 insertions(+)
>
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index d0c72d0bc58..13ca2ec9a4e 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -878,6 +878,16 @@ efi_status_t efi_next_variable_name(efi_uintn_t *size, u16 **buf,
>  #define efi_size_in_pages(size) (((size) + EFI_PAGE_MASK) >> EFI_PAGE_SHIFT)
>  /* Allocate boot service data pool memory */
>  void *efi_alloc(size_t len);
> +/**
> + * efi_realloc() - reallocate boot services data pool memory
> + *
> + * Reallocate memory from pool for a new size and copy the data from old one.
> + *
> + * @ptr:       pointer to the buffer
> + * @size:      number of bytes to allocate
> + * Return:     EFI status to indicate success or not
> + */
> +efi_status_t efi_realloc(void **ptr, size_t len);
>  /* Allocate pages on the specified alignment */
>  void *efi_alloc_aligned_pages(u64 len, int memory_type, size_t align);
>  /* More specific EFI memory allocator, called by EFI payloads */
> diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
> index 0abb1f6159a..1570e300570 100644
> --- a/lib/efi_loader/efi_memory.c
> +++ b/lib/efi_loader/efi_memory.c
> @@ -666,6 +666,64 @@ void *efi_alloc(size_t size)
>         return buf;
>  }
>
> +/**
> + * efi_realloc() - reallocate boot services data pool memory
> + *
> + * Reallocate memory from pool for a new size and copy the data from old one.
> + *
> + * @ptr:       pointer to old buffer
> + * @size:      number of bytes to allocate
> + * Return:     EFI status to indicate success or not
> + */
> +efi_status_t efi_realloc(void **ptr, size_t size)
> +{
> +       efi_status_t ret;
> +       void *new_ptr;
> +       struct efi_pool_allocation *alloc;
> +       u64 num_pages = efi_size_in_pages(size +
> +                                         sizeof(struct efi_pool_allocation));
> +       size_t old_size;
> +
> +       if (!*ptr) {
> +               *ptr = efi_alloc(size);
> +               if (*ptr)
> +                       return EFI_SUCCESS;
> +               return EFI_OUT_OF_RESOURCES;
> +       }
> +
> +       ret = efi_check_allocated((uintptr_t)*ptr, true);
> +       if (ret != EFI_SUCCESS)
> +               return ret;
> +

Don't we also need a check here that the memory type you are trying to
reallocate is Boot Services Data?
If someone uses this currently to reallocate memory, it will change
whatever type he has to BDS.

You either add a check or better don't use efi_alloc(). Use
efi_allocate_pool() and preserve the type.

> +       alloc = container_of(*ptr, struct efi_pool_allocation, data);
> +
> +       /* Check that this memory was allocated by efi_allocate_pool() */
> +       if (((uintptr_t)alloc & EFI_PAGE_MASK) ||
> +           alloc->checksum != checksum(alloc)) {
> +               printf("%s: illegal realloc 0x%p\n", __func__, *ptr);
> +               return EFI_INVALID_PARAMETER;
> +       }
> +
> +       /* Don't realloc. The actual size in pages is the same. */
> +       if (alloc->num_pages == num_pages)
> +               return EFI_SUCCESS;

What if the size is smaller? Can't we just free the extra pages
instead of reallocing?

> +
> +       old_size = alloc->num_pages * EFI_PAGE_SIZE -
> +               sizeof(struct efi_pool_allocation);
> +
> +       new_ptr = efi_alloc(size);
> +
> +       /* copy old data to new alloced buffer */
> +       memcpy(new_ptr, *ptr, min(size, old_size));
> +
> +       /* free the old buffer */
> +       efi_free_pool(*ptr);
> +
> +       *ptr = new_ptr;
> +
> +       return EFI_SUCCESS;
> +}
> +
>  /**
>   * efi_free_pool() - free memory from pool
>   *
> --
> 2.39.5
>

Thanks
/Ilias