Messages in this thread | | | Date | Fri, 3 Oct 2008 12:25:52 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH] x86_64: Implement personality ADDR_LIMIT_32BIT |
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On Fri, Oct 03, 2008 at 10:02:44AM +0200, Ingo Molnar wrote: > > * Kirill A. Shutemov <kirill@shutemov.name> wrote: > > > - /* for MAP_32BIT mappings we force the legact mmap base */ > > - if (!test_thread_flag(TIF_IA32) && (flags & MAP_32BIT)) > > + /* for MAP_32BIT mappings and ADDR_LIMIT_32BIT personality we force the > > + * legact mmap base > > + */ > > please use the customary multi-line comment style: > > /* > * Comment ..... > * ...... goes here: > */ > > and you might use the opportunity to fix the s/legact/legacy typo as > well.
Ok, I'll fix it.
> > but more generally, we already have ADDR_LIMIT_3GB support on x86.
Does ADDR_LIMIT_3GB really work?
$ cat 1.c #include <stdio.h> #include <sys/personality.h> #include <sys/ipc.h> #include <sys/shm.h>
#define ADDR_LIMIT_3GB 0x8000000
int main(void) { int id; void *shm;
personality(ADDR_LIMIT_3GB);
id = shmget(0x123456, 1, IPC_CREAT | 0600); shm = shmat(id, NULL, 0); printf("shm: %p\n", shm); shmdt(shm);
return 0; } $ gcc -Wall 1.c $ sudo ./a.out shm: 0x7f4fca755000
> Why > should support for ADDR_LIMIT_32BIT be added?
It's useful for user mode qemu when you try emulate 32-bit target on x86_64. For example, if shmat(2) return addres above 32-bit, target will get SIGSEGV on access to it.
-- Regards, Kirill A. Shutemov + Belarus, Minsk + ALT Linux Team, http://www.altlinux.com/ [unhandled content-type:application/pgp-signature] | |