Messages in this thread | | | Date | Thu, 24 Sep 2009 22:59:00 +0300 | Subject | Re: [PATCH] NOMMU: Fix MAP_PRIVATE mmap() of objects where the data can be mapped directly | From | Pekka Enberg <> |
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Hi David,
On Thu, Sep 24, 2009 at 5:13 PM, David Howells <dhowells@redhat.com> wrote: > Fix MAP_PRIVATE mmap() of files and devices where the data in the backing store > might be mapped directly. Use the BDI_CAP_MAP_DIRECT capability flag to govern > whether or not we should be trying to map a file directly. This can be used to > determine whether or not a region has been filled in at the point where we call > do_mmap_shared() or do_mmap_private(). > > The BDI_CAP_MAP_DIRECT capability flag is cleared by validate_mmap_request() if > there's any reason we can't use it. It's also cleared in do_mmap_pgoff() if > f_op->get_unmapped_area() fails. > > > Without this fix, attempting to run a program from a RomFS image on a > non-mappable MTD partition results in a BUG as the kernel attempts XIP, and > this can be caught in gdb: > > Program received signal SIGABRT, Aborted. > 0xc005dce8 in add_nommu_region (region=<value optimized out>) at mm/nommu.c:547 > (gdb) bt > #0 0xc005dce8 in add_nommu_region (region=<value optimized out>) at mm/nommu.c:547 > #1 0xc005f168 in do_mmap_pgoff (file=0xc31a6620, addr=<value optimized out>, len=3808, prot=3, flags=6146, pgoff=0) at mm/nommu.c:1373 > #2 0xc00a96b8 in elf_fdpic_map_file (params=0xc33fbbec, file=0xc31a6620, mm=0xc31bef60, what=0xc0213144 "executable") at mm.h:1145 > #3 0xc00aa8b4 in load_elf_fdpic_binary (bprm=0xc316cb00, regs=<value optimized out>) at fs/binfmt_elf_fdpic.c:343 > #4 0xc006b588 in search_binary_handler (bprm=0x6, regs=0xc33fbce0) at fs/exec.c:1234 > #5 0xc006c648 in do_execve (filename=<value optimized out>, argv=0xc3ad14cc, envp=0xc3ad1460, regs=0xc33fbce0) at fs/exec.c:1356 > #6 0xc0008cf0 in sys_execve (name=<value optimized out>, argv=0xc3ad14cc, envp=0xc3ad1460) at arch/frv/kernel/process.c:263 > #7 0xc00075dc in __syscall_call () at arch/frv/kernel/entry.S:897
I have no idea about the BDI_CAP_MAP_DIRECT bits but...
> Note that this fix does the following commit differently: > > commit a190887b58c32d19c2eee007c5eb8faa970a69ba > Author: David Howells <dhowells@redhat.com> > Date: Sat Sep 5 11:17:07 2009 -0700 > nommu: fix error handling in do_mmap_pgoff()
...changes to this part of the code look like nice cleanup to me.
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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