loader: Handle ELF files with overlapping zero-init data

[Qemu-devel] [PATCH 2/2] loader: Ignore zero-sized ELF segments

Posted by Peter Maydell 8 years, 6 months ago

Some ELF files have program headers that specify segments that
are of zero size. Ignore them, rather than trying to create
zero-length ROM blobs for them, because the zero-length blob
can falsely trigger the overlapping-ROM-blobs check.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 include/hw/elf_ops.h | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h
index 2e526d3..d192e7e 100644
--- a/include/hw/elf_ops.h
+++ b/include/hw/elf_ops.h
@@ -451,14 +451,24 @@ static int glue(load_elf, SZ)(const char *name, int fd,
                 *pentry = ehdr.e_entry - ph->p_vaddr + ph->p_paddr;
             }
 
-            if (load_rom) {
-                snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
-
-                /* rom_add_elf_program() seize the ownership of 'data' */
-                rom_add_elf_program(label, data, file_size, mem_size, addr, as);
-            } else {
-                cpu_physical_memory_write(addr, data, file_size);
+            if (mem_size == 0) {
+                /* Some ELF files really do have segments of zero size;
+                 * just ignore them rather than trying to create empty
+                 * ROM blobs, because the zero-length blob can falsely
+                 * trigger the overlapping-ROM-blobs check.
+                 */
                 g_free(data);
+            } else {
+                if (load_rom) {
+                    snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
+
+                    /* rom_add_elf_program() seize the ownership of 'data' */
+                    rom_add_elf_program(label, data, file_size, mem_size,
+                                        addr, as);
+                } else {
+                    cpu_physical_memory_write(addr, data, file_size);
+                    g_free(data);
+                }
             }
 
             total_size += mem_size;
-- 
2.7.4

Re: [Qemu-devel] [Qemu-arm] [PATCH 2/2] loader: Ignore zero-sized ELF segments

Posted by Philippe Mathieu-Daudé 8 years, 6 months ago

On 08/07/2017 11:39 AM, Peter Maydell wrote:
> Some ELF files have program headers that specify segments that
> are of zero size. Ignore them, rather than trying to create
> zero-length ROM blobs for them, because the zero-length blob
> can falsely trigger the overlapping-ROM-blobs check.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> ---
>   include/hw/elf_ops.h | 24 +++++++++++++++++-------
>   1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h
> index 2e526d3..d192e7e 100644
> --- a/include/hw/elf_ops.h
> +++ b/include/hw/elf_ops.h
> @@ -451,14 +451,24 @@ static int glue(load_elf, SZ)(const char *name, int fd,
>                   *pentry = ehdr.e_entry - ph->p_vaddr + ph->p_paddr;
>               }
>   
> -            if (load_rom) {
> -                snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
> -
> -                /* rom_add_elf_program() seize the ownership of 'data' */
> -                rom_add_elf_program(label, data, file_size, mem_size, addr, as);
> -            } else {
> -                cpu_physical_memory_write(addr, data, file_size);
> +            if (mem_size == 0) {
> +                /* Some ELF files really do have segments of zero size;
> +                 * just ignore them rather than trying to create empty
> +                 * ROM blobs, because the zero-length blob can falsely
> +                 * trigger the overlapping-ROM-blobs check.
> +                 */
>                   g_free(data);
> +            } else {
> +                if (load_rom) {
> +                    snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
> +
> +                    /* rom_add_elf_program() seize the ownership of 'data' */
> +                    rom_add_elf_program(label, data, file_size, mem_size,
> +                                        addr, as);
> +                } else {
> +                    cpu_physical_memory_write(addr, data, file_size);
> +                    g_free(data);
> +                }
>               }
>   
>               total_size += mem_size;
>

Re: [Qemu-devel] [PATCH 2/2] loader: Ignore zero-sized ELF segments

Posted by Hua Yanghao 8 years, 6 months ago

Tested-by: Hua Yanghao <huayanghao@gmail.com>

On Mon, Aug 7, 2017 at 4:39 PM, Peter Maydell <peter.maydell@linaro.org> wrote:
> Some ELF files have program headers that specify segments that
> are of zero size. Ignore them, rather than trying to create
> zero-length ROM blobs for them, because the zero-length blob
> can falsely trigger the overlapping-ROM-blobs check.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  include/hw/elf_ops.h | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h
> index 2e526d3..d192e7e 100644
> --- a/include/hw/elf_ops.h
> +++ b/include/hw/elf_ops.h
> @@ -451,14 +451,24 @@ static int glue(load_elf, SZ)(const char *name, int fd,
>                  *pentry = ehdr.e_entry - ph->p_vaddr + ph->p_paddr;
>              }
>
> -            if (load_rom) {
> -                snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
> -
> -                /* rom_add_elf_program() seize the ownership of 'data' */
> -                rom_add_elf_program(label, data, file_size, mem_size, addr, as);
> -            } else {
> -                cpu_physical_memory_write(addr, data, file_size);
> +            if (mem_size == 0) {
> +                /* Some ELF files really do have segments of zero size;
> +                 * just ignore them rather than trying to create empty
> +                 * ROM blobs, because the zero-length blob can falsely
> +                 * trigger the overlapping-ROM-blobs check.
> +                 */
>                  g_free(data);
> +            } else {
> +                if (load_rom) {
> +                    snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
> +
> +                    /* rom_add_elf_program() seize the ownership of 'data' */
> +                    rom_add_elf_program(label, data, file_size, mem_size,
> +                                        addr, as);
> +                } else {
> +                    cpu_physical_memory_write(addr, data, file_size);
> +                    g_free(data);
> +                }
>              }
>
>              total_size += mem_size;
> --
> 2.7.4
>

Re: [Qemu-devel] [PATCH 2/2] loader: Ignore zero-sized ELF segments

Posted by Richard Henderson 8 years, 6 months ago

On 08/07/2017 07:39 AM, Peter Maydell wrote:
> Some ELF files have program headers that specify segments that
> are of zero size. Ignore them, rather than trying to create
> zero-length ROM blobs for them, because the zero-length blob
> can falsely trigger the overlapping-ROM-blobs check.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  include/hw/elf_ops.h | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~