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ARM: 8148/1: flush TLS and thumbee register state during exec

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The TPIDRURO and TPIDRURW registers need to be flushed during exec;
otherwise TLS information is potentially leaked.  TPIDRURO in
particular needs careful treatment.  Since flush_thread basically
needs the same code used to set the TLS in arm_syscall, pull that into
a common set_tls helper in tls.h and use it in both places.

Similarly, TEEHBR needs to be cleared during exec as well.  Clearing
its save slot in thread_info isn't right as there is no guarantee
that a thread switch will occur before the new program runs.  Just
setting the register directly is sufficient.

Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Nathan Lynch 2014-09-11 02:49:08 +01:00 committed by Russell King
parent 7a0bd49713
commit fbfb872f5f
4 changed files with 66 additions and 17 deletions
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62
arch/arm/include/asm/tls.h
View file

@ -1,6 +1,9 @@
#ifndef __ASMARM_TLS_H
#define __ASMARM_TLS_H
#include <linux/compiler.h>
#include <asm/thread_info.h>
#ifdef __ASSEMBLY__
#include <asm/asm-offsets.h>
.macro switch_tls_none, base, tp, tpuser, tmp1, tmp2
@ -50,6 +53,47 @@
#endif
#ifndef __ASSEMBLY__
static inline void set_tls(unsigned long val)
{
struct thread_info *thread;
thread = current_thread_info();
thread->tp_value[0] = val;
/*
* This code runs with preemption enabled and therefore must
* be reentrant with respect to switch_tls.
*
* We need to ensure ordering between the shadow state and the
* hardware state, so that we don't corrupt the hardware state
* with a stale shadow state during context switch.
*
* If we're preempted here, switch_tls will load TPIDRURO from
* thread_info upon resuming execution and the following mcr
* is merely redundant.
*/
barrier();
if (!tls_emu) {
if (has_tls_reg) {
asm("mcr p15, 0, %0, c13, c0, 3"
: : "r" (val));
} else {
/*
* User space must never try to access this
* directly. Expect your app to break
* eventually if you do so. The user helper
* at 0xffff0fe0 must be used instead. (see
* entry-armv.S for details)
*/
*((unsigned int *)0xffff0ff0) = val;
}
}
}
static inline unsigned long get_tpuser(void)
{
unsigned long reg = 0;
@ -59,5 +103,23 @@ static inline unsigned long get_tpuser(void)
return reg;
}
static inline void set_tpuser(unsigned long val)
{
/* Since TPIDRURW is fully context-switched (unlike TPIDRURO),
* we need not update thread_info.
*/
if (has_tls_reg && !tls_emu) {
asm("mcr p15, 0, %0, c13, c0, 2"
: : "r" (val));
}
}
static inline void flush_tls(void)
{
set_tls(0);
set_tpuser(0);
}
#endif
#endif /* __ASMARM_TLS_H */

2
arch/arm/kernel/process.c
View file

@ -334,6 +334,8 @@ void flush_thread(void)
memset(&tsk->thread.debug, 0, sizeof(struct debug_info));
memset(&thread->fpstate, 0, sizeof(union fp_state));
flush_tls();
thread_notify(THREAD_NOTIFY_FLUSH, thread);
}

2
arch/arm/kernel/thumbee.c
View file

@ -45,7 +45,7 @@ static int thumbee_notifier(struct notifier_block *self, unsigned long cmd, void
switch (cmd) {
case THREAD_NOTIFY_FLUSH:
thread->thumbee_state = 0;
teehbr_write(0);
break;
case THREAD_NOTIFY_SWITCH:
current_thread_info()->thumbee_state = teehbr_read();

17
arch/arm/kernel/traps.c
View file

@ -581,7 +581,6 @@ do_cache_op(unsigned long start, unsigned long end, int flags)
#define NR(x) ((__ARM_NR_##x) - __ARM_NR_BASE)
asmlinkage int arm_syscall(int no, struct pt_regs *regs)
{
struct thread_info *thread = current_thread_info();
siginfo_t info;
if ((no >> 16) != (__ARM_NR_BASE>> 16))
@ -632,21 +631,7 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
return regs->ARM_r0;
case NR(set_tls):
thread->tp_value[0] = regs->ARM_r0;
if (tls_emu)
return 0;
if (has_tls_reg) {
asm ("mcr p15, 0, %0, c13, c0, 3"
: : "r" (regs->ARM_r0));
} else {
/*
* User space must never try to access this directly.
* Expect your app to break eventually if you do so.
* The user helper at 0xffff0fe0 must be used instead.
* (see entry-armv.S for details)
*/
*((unsigned int *)0xffff0ff0) = regs->ARM_r0;
}
set_tls(regs->ARM_r0);
return 0;
#ifdef CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG