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Date: Fri, 21 Dec 2012 12:16:31 +0100
From: Anton Arapov <anton@...hat.com>
To: Oleg Nesterov <oleg@...hat.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Josh Stone <jistone@...hat.com>,
Frank Eigler <fche@...hat.com>,
Anton Arapov <anton@...hat.com>,
Anithra P Janakiraman <anithra@...ux.vnet.ibm.com>
Subject: [RFC PATCH 1/6] uretprobes/x86: hijack return address
Function to hijack the return address, replace it with a "trampoline"
and functio to predict the stack pointer address value at return.
Signed-off-by: Anton Arapov <anton@...hat.com>
Signed-off-by: Anithra P Janakiraman <anithra@...ux.vnet.ibm.com>
---
arch/x86/include/asm/uprobes.h | 6 +++++
arch/x86/kernel/uprobes.c | 57 ++++++++++++++++++++++++++++++++++++++++++
include/linux/uprobes.h | 11 +++++++-
kernel/events/uprobes.c | 5 +++-
4 files changed, 77 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index 8ff8be7..9517c55 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -18,9 +18,11 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2008-2011
+ * Copyright (C) Red Hat, Inc. 2011-2012
* Authors:
* Srikar Dronamraju
* Jim Keniston
+ * Anton Arapov (uretprobes)
*/
#include <linux/notifier.h>
@@ -55,4 +57,7 @@ extern int arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs);
extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
extern int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
+
+extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long rp_trampoline_vaddr, struct pt_regs *regs);
+extern unsigned long arch_uretprobe_predict_sp_at_return(struct pt_regs *regs, struct task_struct *tsk);
#endif /* _ASM_UPROBES_H */
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index c71025b..1a30607 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -16,9 +16,11 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2008-2011
+ * Copyright (C) Red Hat, Inc. 2011-2012
* Authors:
* Srikar Dronamraju
* Jim Keniston
+ * Anton Arapov (uretprobes)
*/
#include <linux/kernel.h>
#include <linux/sched.h>
@@ -695,3 +697,57 @@ bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
send_sig(SIGTRAP, current, 0);
return ret;
}
+
+extern unsigned long
+arch_uretprobe_hijack_return_addr(unsigned long rp_trampoline_vaddr, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+ int rasize, ncopied;
+ unsigned long orig_return_vaddr = 0; /* clear high bits for 32-bit apps */
+
+ if (is_ia32_task())
+ rasize = 4;
+ else
+ rasize = 8;
+
+ ncopied = copy_from_user(&orig_return_vaddr, (void __user *)regs->sp, rasize);
+ if (unlikely(ncopied))
+ return -EFAULT;
+
+ /* check whether address has been already hijacked */
+ if (orig_return_vaddr == rp_trampoline_vaddr)
+ return orig_return_vaddr;
+
+ ncopied = copy_to_user((void __user *)regs->sp, &rp_trampoline_vaddr, rasize);
+ if (unlikely(ncopied)) {
+ if (ncopied != rasize) {
+ printk(KERN_ERR "uretprobe: return address clobbered: "
+ "pid=%d, %%sp=%#lx, %%ip=%#lx\n",
+ current->pid, regs->sp, regs->ip);
+ utask->doomed = true;
+ }
+ return -EFAULT;
+ }
+
+ return orig_return_vaddr;
+}
+
+/*
+ * On x86_32, if a function returns a struct or union, the return
+ * value is copied into an area created by the caller. The address
+ * of this area is passed on the stack as a "hidden" first argument.
+ * When such a function returns, it uses a "ret $4" instruction to pop
+ * not only the return address but also the hidden arg. To accommodate
+ * such functions, we add 4 bytes of slop when predicting the return
+ * address. See PR #10078.
+ */
+#define STRUCT_RETURN_SLOP 4
+
+extern unsigned long
+arch_uretprobe_predict_sp_at_return(struct pt_regs *regs, struct task_struct *tsk)
+{
+ if (test_tsk_thread_flag(tsk, TIF_IA32))
+ return (unsigned long) (regs->sp + 4 + STRUCT_RETURN_SLOP);
+ else
+ return (unsigned long) (regs->sp + 8);
+}
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 83742b9..a5db480 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -18,10 +18,13 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2008-2012
+ * Copyright (C) Red Hat, Inc. 2011-2012
* Authors:
* Srikar Dronamraju
* Jim Keniston
- * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra <pzijlstr@...hat.com>
+ * Oleg Nesterov
+ * Peter Zijlstra <pzijlstr@...hat.com>
+ * Anton Arapov (uretprobes)
*/
#include <linux/errno.h>
@@ -60,6 +63,12 @@ struct uprobe_task {
unsigned long xol_vaddr;
unsigned long vaddr;
+
+ /*
+ * Unexpected error in probe point handling has left task's
+ * text or stack corrupted. Kill task ASAP.
+ */
+ bool doomed;
};
/*
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c3b65d1..30f2ebc 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -16,10 +16,12 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2008-2012
+ * Copyright (C) Red Hat, Inc. 2011-2012
* Authors:
* Srikar Dronamraju
* Jim Keniston
- * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra <pzijlstr@...hat.com>
+ * Peter Zijlstra <pzijlstr@...hat.com>
+ * Anton Arapov (uretprobes)
*/
#include <linux/kernel.h>
@@ -1298,6 +1300,7 @@ static struct uprobe_task *add_utask(void)
if (unlikely(!utask))
return NULL;
+ utask->doomed = false;
current->utask = utask;
return utask;
}
--
1.8.0.2
--
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