Re: [PATCH] procfs task exe symlink

["Mike Frysinger" <vapier.adi@gmail.com>]

On Feb 6, 2008 8:44 PM, Matt Helsley <matthltc@us.ibm.com> wrote:
> The kernel implements readlink of /proc/pid/exe by getting the file from the
> first executable VMA. Then the path to the file is reconstructed and reported as
> the result.
>
> Because of the VMA walk the code is slightly different on nommu systems. This
> patch avoids separate /proc/pid/exe code on nommu systems. Instead of walking
> the VMAs to find the first executable file-backed VMA we store a reference to
> the exec'd file in the mm_struct.
>
> That reference would prevent the filesystem holding the executable file from
> being unmounted even after unmapping the VMAs. So we track the number of
> VM_EXECUTABLE VMAs and drop the new reference when the last one is unmapped.
> This avoids pinning the mounted filesystem.
>
> Andrew, these are the updates I promised. Please consider this patch for
> inclusion in -mm.

mm/nommu.c wasnt compiled tested, it's trivially broken:

> --- linux-2.6.24.orig/mm/nommu.c
> +++ linux-2.6.24/mm/nommu.c
> @@ -960,12 +960,15 @@ unsigned long do_mmap_pgoff(struct file
>         if (!vma)
>                 goto error_getting_vma;
>
>         INIT_LIST_HEAD(&vma->anon_vma_node);
>         atomic_set(&vma->vm_usage, 1);
> -       if (file)
> +       if (file) {
>                 get_file(file);
> +               if (vm_flags & VM_EXECUTABLE)
> +                       added_exe_file_vma(mm);
> +       }
>         vma->vm_file    = file;
>         vma->vm_flags   = vm_flags;
>         vma->vm_start   = addr;
>         vma->vm_end     = addr + len;
>         vma->vm_pgoff   = pgoff;

this function has no variable named "mm"

mm/nommu.c: In function 'do_mmap_pgoff':
mm/nommu.c:968: error: 'mm' undeclared (first use in this function)
mm/nommu.c:968: error: (Each undeclared identifier is reported only once
mm/nommu.c:968: error: for each function it appears in.)
make[1]: *** [mm/nommu.o] Error 1
-mike

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