Re: [PATCH 7/9] bsd-user: Don't try to mmap fd when it is -1 independently from MAP_ANONYMOUS flag

From: Warner Losh <imp@bsdimp.com>
To: QEMU Developers <qemu-devel@nongnu.org>
Cc: Kyle Evans <kevans@freebsd.org>, Guy Yur <guyyur@gmail.com>
Subject: Re: [PATCH 7/9] bsd-user: Don't try to mmap fd when it is -1 independently from MAP_ANONYMOUS flag
Date: Thu, 16 Sep 2021 20:58:51 -0600	[thread overview]
Message-ID: <CANCZdfr2W_7rOvmk9-TsN-iC893eu+7CB4TaN6f6P_+xXdZv9w@mail.gmail.com> (raw)
In-Reply-To: <20210917025635.32011-8-imp@bsdimp.com>

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On Thu, Sep 16, 2021 at 8:56 PM Warner Losh <imp@bsdimp.com> wrote:

> From: Guy Yur <guyyur@ngmail.com>
>

I need to fix this email address in the next round or for the pull request.
It's gmail.com, not ngmail.com.

Switch checks for !(flags & MAP_ANONYMOUS) with checks for fd != -1.
> MAP_STACK and MAP_GUARD also force fd == -1 and they don't require
> mapping the fd either.
>
> Signed-off-by: Guy Yur <guyyur@gmail.com>
> [ partially merged before, finishing the job and documenting origin]
> Signed-off-by: Warner Losh <imp@bsdimp.com>
> ---
>  bsd-user/mmap.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/bsd-user/mmap.c b/bsd-user/mmap.c
> index 8b763fffc3..347d314aa9 100644
> --- a/bsd-user/mmap.c
> +++ b/bsd-user/mmap.c
> @@ -154,7 +154,7 @@ static int mmap_frag(abi_ulong real_start,
>      if (prot1 == 0) {
>          /* no page was there, so we allocate one */
>          void *p = mmap(host_start, qemu_host_page_size, prot,
> -                       flags | MAP_ANON, -1, 0);
> +                       flags | ((fd != -1) ? MAP_ANON : 0), -1, 0);
>          if (p == MAP_FAILED)
>              return -1;
>          prot1 = prot;
> @@ -162,7 +162,7 @@ static int mmap_frag(abi_ulong real_start,
>      prot1 &= PAGE_BITS;
>
>      prot_new = prot | prot1;
> -    if (!(flags & MAP_ANON)) {
> +    if (fd != -1) {
>          /* msync() won't work here, so we return an error if write is
>             possible while it is a shared mapping */
>          if ((flags & TARGET_BSD_MAP_FLAGMASK) == MAP_SHARED &&
> @@ -571,7 +571,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len,
> int prot,
>           * worst case: we cannot map the file because the offset is not
>           * aligned, so we read it
>           */
> -        if (!(flags & MAP_ANON) &&
> +        if (fd != -1 &&
>              (offset & ~qemu_host_page_mask) != (start &
> ~qemu_host_page_mask)) {
>              /*
>               * msync() won't work here, so we return an error if write is
> --
> 2.32.0
>
>

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