Re: [Qemu-devel] [PATCH] linux-user: Support gdb 'qOffsets' query for ELF

[Laurent Vivier <laurent@vivier.eu>]

Le 17/08/2019 à 01:34, Josh Kunz via Qemu-devel a écrit :
> This is needed to support debugging PIE ELF binaries running under QEMU
> user mode. Currently, `code_offset` and `data_offset` remain unset for
> all ELF binaries, so GDB is unable to correctly locate the position of
> the binary's text and data.
> 
> The fields `code_offset`, and `data_offset` were originally added way
> back in 2006 to support debugging of bFMT executables (978efd6aac6),
> and support was just never added for ELF. Since non-PIE binaries are
> loaded at exactly the address specified in the binary, GDB does not need
> to relocate any symbols, so the buggy behavior is not normally observed.
> 
> Buglink: https://bugs.launchpad.net/qemu/+bug/1528239
> Signed-off-by: Josh Kunz <jkz@google.com>
> ---
>  linux-user/elfload.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 3365e192eb..ceac035208 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2380,6 +2380,8 @@ static void load_elf_image(const char *image_name, int image_fd,
>      }
>  
>      info->load_bias = load_bias;
> +    info->code_offset = load_bias;
> +    info->data_offset = load_bias;
>      info->load_addr = load_addr;
>      info->entry = ehdr->e_entry + load_bias;
>      info->start_code = -1;
> 

Applied to my linux-user branch.

Thanks,
Laurent