perf_counter uses arch_vma_name() to detect a vdso region which in turn uses
current->mm->context.vdso_base. We need to initialise this before doing
the mmap or else we fail to detect the vdso.
Signed-off-by: Anton Blanchard <an...@samba.org>
---
Index: linux.trees.git/arch/powerpc/kernel/vdso.c
===================================================================
--- linux.trees.git.orig/arch/powerpc/kernel/vdso.c 2009-07-15
10:00:41.000000000 +1000
+++ linux.trees.git/arch/powerpc/kernel/vdso.c 2009-07-15 10:01:40.000000000
+1000
@@ -240,6 +240,13 @@
}
/*
+ * Put vDSO base into mm struct. We need to do this before calling
+ * install_special_mapping or the perf counter mmap tracking code
+ * will fail to recognise it as a vDSO (since arch_vma_name fails).
+ */
+ current->mm->context.vdso_base = vdso_base;
+
+ /*
* our vma flags don't have VM_WRITE so by default, the process isn't
* allowed to write those pages.
* gdb can break that with ptrace interface, and thus trigger COW on
@@ -259,11 +266,10 @@
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
VM_ALWAYSDUMP,
vdso_pagelist);
- if (rc)
+ if (rc) {
+ current->mm->context.vdso_base = 0;
goto fail_mmapsem;
-
- /* Put vDSO base into mm struct */
- current->mm->context.vdso_base = vdso_base;
+ }
up_write(&mm->mmap_sem);
return 0;
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