On Sat, 2008-02-16 at 07:12 -0500, Mike Frysinger wrote:
> On Feb 6, 2008 8:44 PM, Matt Helsley <[EMAIL PROTECTED]> 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:
Thanks for the report. I've looked into this and the "obvious" fix,
using vma->vm_mm, isn't correct since it's never set. This means the
portions of the procfs task exe symlink patch using vma->vm_mm in
mm/nommu.c are incorrect.
The patch below attempts to fix this by using current->mm during mmap
and passing the current mm to put_vma() as well.
Mike, does this patch fix the compile problem(s)?
Signed-off-by: Matt Helsley <[EMAIL PROTECTED]>
---
Mike, I don't have a nommu compile or test environment. I have yet
to to generate a good CONFIG_MMU=n config on i386 (got one?). Since I
don't have any nommu hardware I'm also looking into using qemu. It looks
like I may need to build my own image from scratch. Do you have any
recommendations on testing nommu configs without hardware?
mm/nommu.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
Index: linux-2.6.24/mm/nommu.c
===================================================================
--- linux-2.6.24.orig/mm/nommu.c
+++ linux-2.6.24/mm/nommu.c
@@ -962,12 +962,14 @@ unsigned long do_mmap_pgoff(struct file
INIT_LIST_HEAD(&vma->anon_vma_node);
atomic_set(&vma->vm_usage, 1);
if (file) {
get_file(file);
- if (vm_flags & VM_EXECUTABLE)
- added_exe_file_vma(mm);
+ if (vm_flags & VM_EXECUTABLE) {
+ added_exe_file_vma(current->mm);
+ vma->vm_mm = current->mm;
+ }
}
vma->vm_file = file;
vma->vm_flags = vm_flags;
vma->vm_start = addr;
vma->vm_end = addr + len;
@@ -1053,11 +1055,11 @@ unsigned long do_mmap_pgoff(struct file
EXPORT_SYMBOL(do_mmap_pgoff);
/*
* handle mapping disposal for uClinux
*/
-static void put_vma(struct vm_area_struct *vma)
+static void put_vma(struct mm_struct *mm, struct vm_area_struct *vma)
{
if (vma) {
down_write(&nommu_vma_sem);
if (atomic_dec_and_test(&vma->vm_usage)) {
@@ -1078,11 +1080,11 @@ static void put_vma(struct vm_area_struc
askedalloc -= sizeof(*vma);
if (vma->vm_file) {
fput(vma->vm_file);
if (vma->vm_flags & VM_EXECUTABLE)
- removed_exe_file_vma(vma->vm_mm);
+ removed_exe_file_vma(mm);
}
kfree(vma);
}
up_write(&nommu_vma_sem);
@@ -1116,11 +1118,11 @@ int do_munmap(struct mm_struct *mm, unsi
return -EINVAL;
found:
vml = *parent;
- put_vma(vml->vma);
+ put_vma(mm, vml->vma);
*parent = vml->next;
realalloc -= kobjsize(vml);
askedalloc -= sizeof(*vml);
kfree(vml);
@@ -1161,11 +1163,11 @@ void exit_mmap(struct mm_struct * mm)
mm->total_vm = 0;
while ((tmp = mm->context.vmlist)) {
mm->context.vmlist = tmp->next;
- put_vma(tmp->vma);
+ put_vma(mm, tmp->vma);
realalloc -= kobjsize(tmp);
askedalloc -= sizeof(*tmp);
kfree(tmp);
}
--
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