Re: [PATCH 1/9] bsd-user: Apply e6deac9cf99 from linux-user (zero anonymous memory)

[Philippe Mathieu-Daudé]

On 9/17/21 4:56 AM, Warner Losh wrote:
> From: Mikaël Urankar <mikael.urankar@gmail.com>
> 
> linux-user/mmap.c: Always zero MAP_ANONYMOUS memory in mmap_frag()

Please use it as subject, "bsd-user/mmap: Always zero MAP_ANONYMOUS
memory in mmap_frag()"

Then describe:

Similar to the equivalent linux-user commit e6deac9cf99, ...

> 
> When mapping MAP_ANONYMOUS memory fragments, still need notice about to
> set it zero, or it will cause issues.
> 
> Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
> Reviewed-by: Laurent Vivier <laurent@vivier.eu>
> Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

^ These tags were for another file, not this one, please
remove them.

> [ bsd-user merge by Mikaël Urankar, updated for untagged by Warner Losh ]
> Signed-off-by: Mikaël Urankar <mikael.urankar@gmail.com>
> Signed-off-by: Warner Losh <imp@bsdimp.com>
> ---
>  bsd-user/mmap.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/bsd-user/mmap.c b/bsd-user/mmap.c
> index b40ab9045f..fc3c1480f5 100644
> --- a/bsd-user/mmap.c
> +++ b/bsd-user/mmap.c
> @@ -180,10 +180,12 @@ static int mmap_frag(abi_ulong real_start,
>          if (prot_new != (prot1 | PROT_WRITE))
>              mprotect(host_start, qemu_host_page_size, prot_new);
>      } else {
> -        /* just update the protection */
>          if (prot_new != prot1) {
>              mprotect(host_start, qemu_host_page_size, prot_new);
>          }
> +        if (prot_new & PROT_WRITE) {
> +            memset(g2h_untagged(start), 0, end - start);
> +        }
>      }
>      return 0;
>  }
>