From 925d1c401fa6cfd0df5d2e37da8981494ccdec07 Mon Sep 17 00:00:00 2001 From: Matt Helsley Date: Tue, 29 Apr 2008 01:01:36 -0700 Subject: procfs task exe symlink 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. [akpm@linux-foundation.org: improve comments] [yamamoto@valinux.co.jp: fix dup_mmap] Signed-off-by: Matt Helsley Cc: Oleg Nesterov Cc: David Howells Cc:"Eric W. Biederman" Cc: Christoph Hellwig Cc: Al Viro Cc: Hugh Dickins Signed-off-by: YAMAMOTO Takashi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/fork.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'kernel') diff --git a/kernel/fork.c b/kernel/fork.c index de5c16c6b6ec..068ffe007529 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -431,6 +431,7 @@ void mmput(struct mm_struct *mm) if (atomic_dec_and_test(&mm->mm_users)) { exit_aio(mm); exit_mmap(mm); + set_mm_exe_file(mm, NULL); if (!list_empty(&mm->mmlist)) { spin_lock(&mmlist_lock); list_del(&mm->mmlist); @@ -543,6 +544,8 @@ struct mm_struct *dup_mm(struct task_struct *tsk) if (init_new_context(tsk, mm)) goto fail_nocontext; + dup_mm_exe_file(oldmm, mm); + err = dup_mmap(mm, oldmm); if (err) goto free_pt; -- cgit v1.2.3