Re: [PATCH 1/1] util/memfd: allow allocating 0 bytes

["Marc-André Lureau" <marcandre.lureau@gmail.com>]

Hi

On Wed, Mar 26, 2025 at 8:21 PM donno2048 <just4now666666@gmail.com> wrote:
>
> This silently fixes issues resulting from trying to allocate 0 bytes.
>
> Fixes error, for example, for writing byte 0x20 to port 0x3c0, then word 0xf09 to port 0x3b4 when CPU is initiated, which shouldn't break.
>

This is worth a test.

> Signed-off-by: donno2048 <just4now666666@gmail.com>
> ---
>  util/memfd.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/util/memfd.c b/util/memfd.c
> index 07beab174d..4f2c4ea1dd 100644
> --- a/util/memfd.c
> +++ b/util/memfd.c
> @@ -131,9 +131,13 @@ void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
>          }
>      }
>
> -    ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
> -    if (ptr == MAP_FAILED) {
> -        goto err;
> +    if (size != 0) {
> +        ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
> +        if (ptr == MAP_FAILED) {
> +            goto err;
> +        }
> +    } else {
> +        ptr = fdopen(mfd, "rw");

I don't understand fdopen() here, it returns a FILE*

>      }
>
>      *fd = mfd;
> --
> 2.30.2
>
>


-- 
Marc-André Lureau