Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1560995 > unrolled thread

Re: [PATCHv2 4/5] x86/mm: for MAP_32BIT check in_compat_syscall() instead TIF_ADDR32

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: [PATCHv2 4/5] x86/mm: for MAP_32BIT check in_compat_syscall()  instead TIF_ADDR32 Andy Lutomirski <luto@amacapital.net> - 2017-01-17 21:40 +0100

#1560995 — Re: [PATCHv2 4/5] x86/mm: for MAP_32BIT check in_compat_syscall() instead TIF_ADDR32

On Mon, Jan 16, 2017 at 4:33 AM, Dmitry Safonov <dsafonov@virtuozzo.com> wrote:
> At this momet, logic in arch_get_unmapped_area{,_topdown} for mmaps with
> MAP_32BIT flag checks TIF_ADDR32 which means:
> o if 32-bit ELF changes mode to 64-bit on x86_64 and then tries to
>   mmap() with MAP_32BIT it'll result in addr over 4Gb (as default is
>   top-down allocation)
> o if 64-bit ELF changes mode to 32-bit and tries mmap() with MAP_32BIT,
>   it'll allocate only memory in 1GB space: [0x40000000, 0x80000000).
>
> Fix it by handeling MAP_32BIT in 64-bit syscalls only.
> As a little bonus it'll make thread flag a little less used.

Seems like an improvement.  Also, jeez, the mmap code is complicated.

[toc] | [standalone]

Back to top | Article view | linux.kernel

csiph-web