xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

arch/tile: adopt prepare_exit_to_usermode() model from x86

Browse Source 
This change is a prerequisite change for TASK_ISOLATION but also
stands on its own for readability and maintainability.  The existing
tile do_work_pending() was called in a loop from assembly on
the slow path; this change moves the loop into C code as well.
For the x86 version see commit c5c46f59e4 ("x86/entry: Add new,
comprehensible entry and exit handlers written in C").

This change exposes a pre-existing bug on the older tilepro platform;
the singlestep processing is done last, but on tilepro (unlike tilegx)
we enable interrupts while doing that processing, so we could in
theory miss a signal or other asynchronous event.  A future change
could fix this by breaking the singlestep work into a "prepare"
step done in the main loop, and a "trigger" step done after exiting
the loop.  Since this change is intended as purely a restructuring
change, we call out the bug explicitly now, but don't yet fix it.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
This commit is contained in:
Chris Metcalf
2015-09-22 14:49:41 -04:00
parent 65a792e84f
commit 583b24a210
5 changed files with 81 additions and 111 deletions
Download Patch File Download Diff File Expand all files Collapse all files

53
arch/tile/kernel/intvec_64.S
View File

@@ -878,20 +878,6 @@ STD_ENTRY(interrupt_return)
.Lresume_userspace:
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
@@ -902,33 +888,28 @@ STD_ENTRY(interrupt_return)
IRQ_DISABLE(r20, r21)
TRACE_IRQS_OFF /* Note: clobbers registers r0-r29 */
/* Check to see if there is any work to do before returning to user. */
{
addi r29, r32, THREAD_INFO_FLAGS_OFFSET
moveli r1, hw1_last(_TIF_ALLWORK_MASK)
}
{
ld r29, r29
shl16insli r1, r1, hw0(_TIF_ALLWORK_MASK)
}
and r1, r29, r1
beqzt r1, .Lrestore_all
/*
* Make sure we have all the registers saved for signal
* 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.
* See if there are any work items (including single-shot items)
* to do. If so, save the callee-save registers to pt_regs
* and then dispatch to C code.
*/
move r21, sp
EXTRACT_THREAD_INFO(r21)
{
addi r22, r21, THREAD_INFO_FLAGS_OFFSET
moveli r20, hw1_last(_TIF_ALLWORK_MASK)
}
{
ld r22, r22
shl16insli r20, r20, hw0(_TIF_ALLWORK_MASK)
}
and r1, r22, r20
{
PTREGS_PTR(r0, PTREGS_OFFSET_BASE)
bnez r33, 1f
beqzt r1, .Lrestore_all
}
push_extra_callee_saves r0
movei r33, 1
1: jal do_work_pending
bnez r0, .Lretry_work_pending
jal prepare_exit_to_usermode
/*
* In the NMI case we
@@ -1411,7 +1392,7 @@ STD_ENTRY(ret_from_kernel_thread)
FEEDBACK_REENTER(ret_from_kernel_thread)
{
movei r30, 0 /* not an NMI */
j .Lresume_userspace /* jump into middle of interrupt_return */
j interrupt_return
}
STD_ENDPROC(ret_from_kernel_thread)