[SeaBIOS] [PATCH v5 3/5] QEMU fw_cfg: Add command to write back address of file

[Laszlo Ersek]

On 02/18/17 07:21, ben at skyportsystems.com wrote:
> From: Ben Warren <ben at skyportsystems.com>
> 
> This command is similar to ADD_POINTER, but instead of patching
> memory, it writes the pointer back to QEMU over the DMA interface.
> 
> Signed-off-by: Ben Warren <ben at skyportsystems.com>
> ---
>  src/fw/romfile_loader.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  src/fw/romfile_loader.h | 23 ++++++++++++++++++++---
>  2 files changed, 65 insertions(+), 3 deletions(-)

Reviewed-by: Laszlo Ersek <lersek at redhat.com>

Thanks
Laszlo

> diff --git a/src/fw/romfile_loader.c b/src/fw/romfile_loader.c
> index 7737453..30e7b58 100644
> --- a/src/fw/romfile_loader.c
> +++ b/src/fw/romfile_loader.c
> @@ -5,6 +5,7 @@
>  #include "romfile.h" // struct romfile_s
>  #include "malloc.h" // Zone*, _malloc
>  #include "output.h" // warn_*
> +#include "paravirt.h" // qemu_cfg_write_file
>  
>  struct romfile_loader_file {
>      struct romfile_s *file;
> @@ -127,6 +128,46 @@ err:
>      warn_internalerror();
>  }
>  
> +static void romfile_loader_write_pointer(struct romfile_loader_entry_s *entry,
> +                                         struct romfile_loader_files *files)
> +{
> +    struct romfile_s *dest_file;
> +    struct romfile_loader_file *src_file;
> +    unsigned dst_offset = le32_to_cpu(entry->wr_pointer.dst_offset);
> +    unsigned src_offset = le32_to_cpu(entry->wr_pointer.src_offset);
> +    u64 pointer = 0;
> +
> +    /* Writing back to a file that may not be loaded in RAM */
> +    dest_file = romfile_find(entry->wr_pointer.dest_file);
> +    src_file = romfile_loader_find(entry->wr_pointer.src_file, files);
> +
> +    if (!dest_file || !src_file || !src_file->data ||
> +        dst_offset + entry->wr_pointer.size < dst_offset ||
> +        dst_offset + entry->wr_pointer.size > dest_file->size ||
> +        src_offset >= src_file->file->size ||
> +        entry->wr_pointer.size < 1 || entry->wr_pointer.size > 8 ||
> +        entry->wr_pointer.size & (entry->wr_pointer.size - 1)) {
> +        goto err;
> +    }
> +
> +    pointer = (unsigned long)src_file->data + src_offset;
> +    /* Make sure the pointer fits within wr_pointer.size */
> +    if ((entry->wr_pointer.size != sizeof(u64)) &&
> +        ((pointer >> (entry->wr_pointer.size * 8)) > 0)) {
> +        goto err;
> +    }
> +    pointer = cpu_to_le64(pointer);
> +
> +    /* Only supported on QEMU */
> +    if (qemu_cfg_write_file(&pointer, dest_file, dst_offset,
> +                            entry->wr_pointer.size) != entry->wr_pointer.size) {
> +        goto err;
> +    }
> +    return;
> + err:
> +    warn_internalerror();
> +}
> +
>  int romfile_loader_execute(const char *name)
>  {
>      struct romfile_loader_entry_s *entry;
> @@ -161,6 +202,10 @@ int romfile_loader_execute(const char *name)
>                          break;
>                  case ROMFILE_LOADER_COMMAND_ADD_CHECKSUM:
>                          romfile_loader_add_checksum(entry, files);
> +                        break;
> +                case ROMFILE_LOADER_COMMAND_WRITE_POINTER:
> +                        romfile_loader_write_pointer(entry, files);
> +                        break;
>                  default:
>                          /* Skip commands that we don't recognize. */
>                          break;
> diff --git a/src/fw/romfile_loader.h b/src/fw/romfile_loader.h
> index bce3719..4dc50ab 100644
> --- a/src/fw/romfile_loader.h
> +++ b/src/fw/romfile_loader.h
> @@ -51,15 +51,32 @@ struct romfile_loader_entry_s {
>              u32 length;
>          } cksum;
>  
> +        /*
> +         * COMMAND_WRITE_POINTER - Write back to a host file via DMA,
> +         * @wr_pointer.dest_file at offset @wr_pointer.dst_offset, a pointer
> +         * to the table originating from @wr_pointer.src_file at offset
> +         * @wr_pointer.src_offset.
> +         * 1,2,4 or 8 byte unsigned addition is used depending on
> +         * @wr_pointer.size.
> +         */
> +        struct {
> +            char dest_file[ROMFILE_LOADER_FILESZ];
> +            char src_file[ROMFILE_LOADER_FILESZ];
> +            u32 dst_offset;
> +            u32 src_offset;
> +            u8 size;
> +        } wr_pointer;
> +
>          /* padding */
>          char pad[124];
>      };
>  };
>  
>  enum {
> -    ROMFILE_LOADER_COMMAND_ALLOCATE     = 0x1,
> -    ROMFILE_LOADER_COMMAND_ADD_POINTER  = 0x2,
> -    ROMFILE_LOADER_COMMAND_ADD_CHECKSUM = 0x3,
> +    ROMFILE_LOADER_COMMAND_ALLOCATE      = 0x1,
> +    ROMFILE_LOADER_COMMAND_ADD_POINTER   = 0x2,
> +    ROMFILE_LOADER_COMMAND_ADD_CHECKSUM  = 0x3,
> +    ROMFILE_LOADER_COMMAND_WRITE_POINTER = 0x4,
>  };
>  
>  enum {
>