* [Qemu-devel] [PATCH v2] linux-user/mmap.c: Always zero MAP_ANONYMOUS memory in mmap_frag()
@ 2015-12-21 2:33 chengang
2015-12-21 9:43 ` Laurent Vivier
0 siblings, 1 reply; 2+ messages in thread
From: chengang @ 2015-12-21 2:33 UTC (permalink / raw)
To: riku.voipio, laurent; +Cc: peter.maydell, Chen Gang, Chen Gang, qemu-devel, rth
From: Chen Gang <chengang@emindsoft.com.cn>
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>
---
linux-user/mmap.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 7b459d5..29fe646 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -186,10 +186,12 @@ 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) && ((flags & MAP_PRIVATE) || (fd == -1))) {
+ memset(g2h(start), 0, end - start);
+ }
}
return 0;
}
--
1.7.3.4
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [Qemu-devel] [PATCH v2] linux-user/mmap.c: Always zero MAP_ANONYMOUS memory in mmap_frag()
2015-12-21 2:33 [Qemu-devel] [PATCH v2] linux-user/mmap.c: Always zero MAP_ANONYMOUS memory in mmap_frag() chengang
@ 2015-12-21 9:43 ` Laurent Vivier
0 siblings, 0 replies; 2+ messages in thread
From: Laurent Vivier @ 2015-12-21 9:43 UTC (permalink / raw)
To: Chen Gang; +Cc: peter.maydell, riku.voipio, qemu-devel, rth
Le 21/12/2015 03:33, chengang@emindsoft.com.cn a écrit :
> From: Chen Gang <chengang@emindsoft.com.cn>
>
> When mapping MAP_ANONYMOUS memory fragments, still need notice about to
> set it zero, or it will cause issues.
Perhaps you can explain in the commit message why this page is not
already filled by zeros ?
> Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
> ---
> linux-user/mmap.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/linux-user/mmap.c b/linux-user/mmap.c
> index 7b459d5..29fe646 100644
> --- a/linux-user/mmap.c
> +++ b/linux-user/mmap.c
> @@ -186,10 +186,12 @@ 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) && ((flags & MAP_PRIVATE) || (fd == -1))) {
According to manpage, for MAP_ANONYMOUS, fd can be ignored.
Why do you check if the page is MAP_PRIVATE or not ?
> + memset(g2h(start), 0, end - start);
> + }
> }
> return 0;
> }
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2015-12-21 2:33 [Qemu-devel] [PATCH v2] linux-user/mmap.c: Always zero MAP_ANONYMOUS memory in mmap_frag() chengang
2015-12-21 9:43 ` Laurent Vivier
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