[PATCH 3.14 48/73] ARM: 8226/1: cacheflush: get rid of restarting block

Greg Kroah-Hartman
2014-12-05T22:58:10Z

From: Vladimir Murzin <vladimir.murzin@arm.com>

commit 3f4aa45ceea5789a4aade536acc27f2e0d3da5e1 upstream.

We cannot restart cacheflush safely if a process provides user-defined
signal handler and signal is pending. In this case -EINTR is returned
and it is expected that process re-invokes syscall. However, there are
a few problems with that:
* looks like nobody bothers checking return value from cacheflush
* but if it did, we don't provide the restart address for that, so the
process has to use the same range again
* ...and again, what might lead to looping forever

So, remove cacheflush restarting code and terminate cache flushing
as early as fatal signal is pending.

Reported-by: Chanho Min <chanho.min@lge.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm/include/asm/thread_info.h | 11 -----------
arch/arm/kernel/traps.c | 31 ++-----------------------------
2 files changed, 2 insertions(+), 40 deletions(-)

--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -43,16 +43,6 @@ struct cpu_context_save {
__u32 extra[2]; /* Xscale 'acc' register, etc */
};

-struct arm_restart_block {
- union {
- /* For user cache flushing */
- struct {
- unsigned long start;
- unsigned long end;
- } cache;
- };
-};
-
/*
* low level task data that entry.S needs immediate access to.
* __switch_to() assumes cpu_context follows immediately after cpu_domain.
@@ -78,7 +68,6 @@ struct thread_info {
unsigned long thumbee_state; /* ThumbEE Handler Base register */
#endif
struct restart_block restart_block;
- struct arm_restart_block arm_restart_block;
};

#define INIT_THREAD_INFO(tsk) \
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -510,8 +510,6 @@ static int bad_syscall(int n, struct pt_
return regs->ARM_r0;
}

-static long do_cache_op_restart(struct restart_block *);
-
static inline int
__do_cache_op(unsigned long start, unsigned long end)
{
@@ -520,24 +518,8 @@ __do_cache_op(unsigned long start, unsig
do {
unsigned long chunk = min(PAGE_SIZE, end - start);

- if (signal_pending(current)) {
- struct thread_info *ti = current_thread_info();
-
- ti->restart_block = (struct restart_block) {
- .fn = do_cache_op_restart,
- };
-
- ti->arm_restart_block = (struct arm_restart_block) {
- {
- .cache = {
- .start = start,
- .end = end,
- },
- },
- };
-
- return -ERESTART_RESTARTBLOCK;
- }
+ if (fatal_signal_pending(current))
+ return 0;

ret = flush_cache_user_range(start, start + chunk);
if (ret)
@@ -550,15 +532,6 @@ __do_cache_op(unsigned long start, unsig
return 0;
}

-static long do_cache_op_restart(struct restart_block *unused)
-{
- struct arm_restart_block *restart_block;
-
- restart_block = &current_thread_info()->arm_restart_block;
- return __do_cache_op(restart_block->cache.start,
- restart_block->cache.end);
-}
-
static inline int
do_cache_op(unsigned long start, unsigned long end, int flags)
{