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Groups > linux.kernel > #1560995
| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCHv2 4/5] x86/mm: for MAP_32BIT check in_compat_syscall() instead TIF_ADDR32 |
| Date | 2017-01-17 21:40 +0100 |
| Message-ID | <t0IHU-3fQ-7@gated-at.bofh.it> (permalink) |
| References | <t0Iye-3cj-5@gated-at.bofh.it> <t0IHU-3fQ-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
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.
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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
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