From: Anton Blanchard <anton@samba.org>
Date: Mon, 21 Sep 2009 16:57:40 +0000 (+0000)
Subject: powerpc/perf_counter: Fix vdso detection
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=f2053f1a7bf6005b4e81826b1ac8d0b4117c4cf0;p=openwrt%2Fstaging%2Fblogic.git

powerpc/perf_counter: Fix vdso detection

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 <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 3faaf29bdb29..94e2df3cae07 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -240,6 +240,13 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 		goto fail_mmapsem;
 	}
 
+	/*
+	 * 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.
@@ -260,11 +267,10 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 				     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;