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author | Chris Metcalf <cmetcalf@ezchip.com> | 2015-09-22 18:49:41 (GMT) |
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committer | Chris Metcalf <cmetcalf@ezchip.com> | 2016-01-18 19:49:09 (GMT) |
commit | 583b24a210ada7e88fc12aaf50024975ec882816 (patch) | |
tree | b396bc95a44f29d9dd2c8bab86fcd0d0728b24b1 /arch/tile/kernel/intvec_32.S | |
parent | 65a792e84f25d1436698f999224b2cf5d7594546 (diff) | |
download | linux-583b24a210ada7e88fc12aaf50024975ec882816.tar.xz |
arch/tile: adopt prepare_exit_to_usermode() model from x86
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 c5c46f59e4e7 ("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>
Diffstat (limited to 'arch/tile/kernel/intvec_32.S')
-rw-r--r-- | arch/tile/kernel/intvec_32.S | 46 |
1 files changed, 14 insertions, 32 deletions
diff --git a/arch/tile/kernel/intvec_32.S b/arch/tile/kernel/intvec_32.S index fbbe2ea..33d4881 100644 --- a/arch/tile/kernel/intvec_32.S +++ b/arch/tile/kernel/intvec_32.S @@ -846,18 +846,6 @@ 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. - * Get base of stack in r32. - */ - { - GET_THREAD_INFO(r32) - movei r33, 0 - } - -.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. @@ -867,33 +855,27 @@ 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. */ + /* + * 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. + */ + GET_THREAD_INFO(r21) { - addi r29, r32, THREAD_INFO_FLAGS_OFFSET - moveli r1, lo16(_TIF_ALLWORK_MASK) + addi r22, r21, THREAD_INFO_FLAGS_OFFSET + moveli r20, lo16(_TIF_ALLWORK_MASK) } { - lw r29, r29 - auli r1, r1, ha16(_TIF_ALLWORK_MASK) + lw r22, r22 + auli r20, r20, ha16(_TIF_ALLWORK_MASK) } - and r1, r29, r1 - bzt r1, .Lrestore_all - - /* - * Make sure we have all the registers saved for signal - * handling, notify-resume, or single-step. 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. - */ + and r1, r22, r20 { PTREGS_PTR(r0, PTREGS_OFFSET_BASE) - bnz r33, 1f + bzt r1, .Lrestore_all } push_extra_callee_saves r0 - movei r33, 1 -1: jal do_work_pending - bnz r0, .Lretry_work_pending + jal prepare_exit_to_usermode /* * In the NMI case we @@ -1327,7 +1309,7 @@ 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) |