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authorChris Metcalf <cmetcalf@tilera.com>2012-04-28 18:51:43 -0400
committerChris Metcalf <cmetcalf@tilera.com>2012-05-16 16:01:16 -0400
commitfc327e268fbef08e129ad51aa3a7113ee9bc6ba5 (patch)
treeba75f2ac9509090c6896a4fbc6be7c3aaba1aaf6 /arch/tile/kernel/intvec_64.S
parent36be50515fe2aef61533b516fa2576a2c7fe7664 (diff)
arch/tile: fix up some issues in calling do_work_pending()
First, we were at risk of handling thread-info flags, in particular do_signal(), when returning from kernel space. This could happen after a failed kernel_execve(), or when forking a kernel thread. The fix is to test in do_work_pending() for user_mode() and return immediately if so; we already had this test for one of the flags, so I just hoisted it to the top of the function. Second, if a ptraced process updated the callee-saved registers in the ptregs struct and then processed another thread-info flag, we would overwrite the modifications with the original callee-saved registers. To fix this, we add a register to note if we've already saved the registers once, and skip doing it on additional passes through the loop. To avoid a performance hit from the couple of extra instructions involved, I modified the GET_THREAD_INFO() macro to be guaranteed to be one instruction, then bundled it with adjacent instructions, yielding an overall net savings. Reported-By: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Diffstat (limited to 'arch/tile/kernel/intvec_64.S')
-rw-r--r--arch/tile/kernel/intvec_64.S38
1 files changed, 28 insertions, 10 deletions
diff --git a/arch/tile/kernel/intvec_64.S b/arch/tile/kernel/intvec_64.S
index 49d9d6621682..30ae76e50c44 100644
--- a/arch/tile/kernel/intvec_64.S
+++ b/arch/tile/kernel/intvec_64.S
@@ -647,6 +647,20 @@ STD_ENTRY(interrupt_return)
FEEDBACK_REENTER(interrupt_return)
/*
+ * Use r33 to hold whether we have already loaded the callee-saves
+ * into ptregs. We don't want to do it twice in this loop, since
+ * then we'd clobber whatever changes are made by ptrace, etc.
+ */
+ {
+ movei r33, 0
+ move r32, sp
+ }
+
+ /* Get base of stack in r32. */
+ EXTRACT_THREAD_INFO(r32)
+
+.Lretry_work_pending:
+ /*
* Disable interrupts so as to make sure we don't
* miss an interrupt that sets any of the thread flags (like
* need_resched or sigpending) between sampling and the iret.
@@ -656,9 +670,6 @@ STD_ENTRY(interrupt_return)
IRQ_DISABLE(r20, r21)
TRACE_IRQS_OFF /* Note: clobbers registers r0-r29 */
- /* Get base of stack in r32; note r30/31 are used as arguments here. */
- GET_THREAD_INFO(r32)
-
/* Check to see if there is any work to do before returning to user. */
{
@@ -674,16 +685,18 @@ STD_ENTRY(interrupt_return)
/*
* Make sure we have all the registers saved for signal
- * handling or single-step. Call out to C code to figure out
+ * handling or notify-resume. Call out to C code to figure out
* exactly what we need to do for each flag bit, then if
* necessary, reload the flags and recheck.
*/
- push_extra_callee_saves r0
{
PTREGS_PTR(r0, PTREGS_OFFSET_BASE)
- jal do_work_pending
+ bnez r33, 1f
}
- bnez r0, .Lresume_userspace
+ push_extra_callee_saves r0
+ movei r33, 1
+1: jal do_work_pending
+ bnez r0, .Lretry_work_pending
/*
* In the NMI case we
@@ -968,11 +981,16 @@ handle_syscall:
shl16insli r20, r20, hw0(irq_stat + IRQ_CPUSTAT_SYSCALL_COUNT_OFFSET)
add r20, r20, tp
ld4s r21, r20
- addi r21, r21, 1
- st4 r20, r21
+ {
+ addi r21, r21, 1
+ move r31, sp
+ }
+ {
+ st4 r20, r21
+ EXTRACT_THREAD_INFO(r31)
+ }
/* Trace syscalls, if requested. */
- GET_THREAD_INFO(r31)
addi r31, r31, THREAD_INFO_FLAGS_OFFSET
ld r30, r31
andi r30, r30, _TIF_SYSCALL_TRACE