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SubjectRe: recent change to exit_mmap
Anton Blanchard <anton@samba.org> wrote:
>
>
> > On seconds thoughts...
> >
> > Are the first two SET_PERSONALITY() calls in there actually doing anything?
> > Perhaps you're right, and we only need the one at line 615, whcih is in the
> > right place?
>
> Sounds good. The following patch tests out OK.
>
> Anton
>
> ===== fs/binfmt_elf.c 1.34 vs edited =====
> --- 1.34/fs/binfmt_elf.c Mon Nov 25 19:59:02 2002
> +++ edited/fs/binfmt_elf.c Sat Jan 18 18:16:52 2003
> @@ -536,8 +536,6 @@
> strcmp(elf_interpreter,"/usr/lib/ld.so.1") == 0)
> ibcs2_interpreter = 1;
>
> - SET_PERSONALITY(elf_ex, ibcs2_interpreter);
> -
> interpreter = open_exec(elf_interpreter);
> retval = PTR_ERR(interpreter);
> if (IS_ERR(interpreter))
> @@ -578,9 +576,6 @@
> // printk(KERN_WARNING "ELF: Ambiguous type, using ELF\n");
> interpreter_type = INTERPRETER_ELF;
> }
> - } else {
> - /* Executables without an interpreter also need a personality */
> - SET_PERSONALITY(elf_ex, ibcs2_interpreter);
> }

Unfortunately it isn't right. See, we set the peronality prior to looking up
the elf interpreter because different types of executables can have different
filesystem namespaces. open_exec() needs it. The IBCS stuff needs this, as
well as (thanks davem):

"When we have a personality like "SunOS" or whatever, we allow the usage
of an alternate '/' for file lookups, it trumps whatever would be found in
the normal /, so we could put the SunOS ld.so under /emul/SunOS/lib for
example using an emulation alternative-root of /emul/SunOS"

And we can't dump the currect exec image until we've determined that the
interpreter is available.

So it's all a bit of a stew. We're back to the original patch. Could you
please test it? (This includes the ia64 bit)


diff -puN mm/mmap.c~exit_mmap-fix mm/mmap.c
--- 25/mm/mmap.c~exit_mmap-fix 2003-01-17 22:35:13.000000000 -0800
+++ 25-akpm/mm/mmap.c 2003-01-17 22:41:10.000000000 -0800
@@ -1379,6 +1379,22 @@ void build_mmap_rb(struct mm_struct * mm
}
}

+/*
+ * During exit_mmap, TASK_SIZE is not a reliable indication of the virtual
+ * size of the mm which is being torn down. Because on the exec() path, this
+ * process may have switched its personality from 64-bit to 32-bit prior to
+ * calling exit_mmap(). So TASK_SIZE returns a value suitable for a 32-bit
+ * process, and not the 64-bit process whose mm we need to empty.
+ *
+ * So what we do is to always unmap the largest virtual address space which
+ * the architecture supports. unmap_vmas() will then unmap every VMA in the
+ * mm, which is what we want to happen here.
+ */
+
+#ifndef TASK_SIZE_MAX
+#define TASK_SIZE_MAX TASK_SIZE
+#endif
+
/* Release all mmaps. */
void exit_mmap(struct mm_struct *mm)
{
@@ -1395,7 +1411,7 @@ void exit_mmap(struct mm_struct *mm)
tlb = tlb_gather_mmu(mm, 1);
flush_cache_mm(mm);
mm->map_count -= unmap_vmas(&tlb, mm, mm->mmap, 0,
- TASK_SIZE, &nr_accounted);
+ TASK_SIZE_MAX, &nr_accounted);
vm_unacct_memory(nr_accounted);
BUG_ON(mm->map_count); /* This is just debugging */
clear_page_tables(tlb, FIRST_USER_PGD_NR, USER_PTRS_PER_PGD);
diff -puN include/asm-ppc64/processor.h~exit_mmap-fix include/asm-ppc64/processor.h
--- 25/include/asm-ppc64/processor.h~exit_mmap-fix 2003-01-17 22:41:32.000000000 -0800
+++ 25-akpm/include/asm-ppc64/processor.h 2003-01-17 22:42:03.000000000 -0800
@@ -630,6 +630,7 @@ extern struct task_struct *last_task_use

#define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \
TASK_SIZE_USER32 : TASK_SIZE_USER64)
+#define TASK_SIZE_MAX TASK_SIZE_USER64
#endif /* __KERNEL__ */


diff -puN include/asm-ia64/processor.h~exit_mmap-fix include/asm-ia64/processor.h
--- 25/include/asm-ia64/processor.h~exit_mmap-fix 2003-01-17 22:46:08.000000000 -0800
+++ 25-akpm/include/asm-ia64/processor.h 2003-01-17 22:47:19.000000000 -0800
@@ -39,6 +39,12 @@
#define TASK_SIZE (current->thread.task_size)

/*
+ * This determines the virtual address space which must be torn down
+ * during exec.
+ *
+#define TASK_SIZE_MAX DEFAULT_TASK_SIZE
+
+/*
* This decides where the kernel will search for a free chunk of vm
* space during mmap's.
*/
_

-
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