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>
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@ -100,9 +100,14 @@ extern void cpu_idle_on_new_stack(struct thread_info *old_ti,
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#else /* __ASSEMBLY__ */
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/* how to get the thread information struct from ASM */
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/*
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* How to get the thread information struct from assembly.
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* Note that we use different macros since different architectures
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* have different semantics in their "mm" instruction and we would
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* like to guarantee that the macro expands to exactly one instruction.
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*/
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#ifdef __tilegx__
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#define GET_THREAD_INFO(reg) move reg, sp; mm reg, zero, LOG2_THREAD_SIZE, 63
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#define EXTRACT_THREAD_INFO(reg) mm reg, zero, LOG2_THREAD_SIZE, 63
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#else
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#define GET_THREAD_INFO(reg) mm reg, sp, zero, LOG2_THREAD_SIZE, 31
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#endif
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@ -838,6 +838,18 @@ STD_ENTRY(interrupt_return)
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.Lresume_userspace:
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FEEDBACK_REENTER(interrupt_return)
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/*
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* Use r33 to hold whether we have already loaded the callee-saves
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* into ptregs. We don't want to do it twice in this loop, since
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* then we'd clobber whatever changes are made by ptrace, etc.
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* Get base of stack in r32.
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*/
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{
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GET_THREAD_INFO(r32)
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movei r33, 0
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}
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.Lretry_work_pending:
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/*
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* Disable interrupts so as to make sure we don't
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* miss an interrupt that sets any of the thread flags (like
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@ -848,9 +860,6 @@ STD_ENTRY(interrupt_return)
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IRQ_DISABLE(r20, r21)
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TRACE_IRQS_OFF /* Note: clobbers registers r0-r29 */
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/* Get base of stack in r32; note r30/31 are used as arguments here. */
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GET_THREAD_INFO(r32)
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/* Check to see if there is any work to do before returning to user. */
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{
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@ -866,16 +875,18 @@ STD_ENTRY(interrupt_return)
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/*
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* Make sure we have all the registers saved for signal
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* handling or single-step. Call out to C code to figure out
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* exactly what we need to do for each flag bit, then if
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* necessary, reload the flags and recheck.
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* handling, notify-resume, or single-step. Call out to C
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* code to figure out exactly what we need to do for each flag bit,
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* then if necessary, reload the flags and recheck.
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*/
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push_extra_callee_saves r0
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{
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PTREGS_PTR(r0, PTREGS_OFFSET_BASE)
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jal do_work_pending
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bnz r33, 1f
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}
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bnz r0, .Lresume_userspace
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push_extra_callee_saves r0
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movei r33, 1
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1: jal do_work_pending
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bnz r0, .Lretry_work_pending
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/*
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* In the NMI case we
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@ -1180,10 +1191,12 @@ handle_syscall:
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add r20, r20, tp
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lw r21, r20
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addi r21, r21, 1
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sw r20, r21
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{
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sw r20, r21
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GET_THREAD_INFO(r31)
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}
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/* Trace syscalls, if requested. */
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GET_THREAD_INFO(r31)
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addi r31, r31, THREAD_INFO_FLAGS_OFFSET
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lw r30, r31
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andi r30, r30, _TIF_SYSCALL_TRACE
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@ -1362,7 +1375,10 @@ handle_ill:
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3:
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/* set PC and continue */
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lw r26, r24
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sw r28, r26
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{
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sw r28, r26
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GET_THREAD_INFO(r0)
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}
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/*
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* Clear TIF_SINGLESTEP to prevent recursion if we execute an ill.
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@ -1370,7 +1386,6 @@ handle_ill:
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* need to clear it here and can't really impose on all other arches.
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* So what's another write between friends?
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*/
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GET_THREAD_INFO(r0)
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addi r1, r0, THREAD_INFO_FLAGS_OFFSET
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{
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@ -646,6 +646,20 @@ STD_ENTRY(interrupt_return)
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.Lresume_userspace:
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FEEDBACK_REENTER(interrupt_return)
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/*
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* Use r33 to hold whether we have already loaded the callee-saves
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* into ptregs. We don't want to do it twice in this loop, since
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* then we'd clobber whatever changes are made by ptrace, etc.
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*/
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{
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movei r33, 0
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move r32, sp
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}
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/* Get base of stack in r32. */
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EXTRACT_THREAD_INFO(r32)
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.Lretry_work_pending:
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/*
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* Disable interrupts so as to make sure we don't
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* miss an interrupt that sets any of the thread flags (like
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@ -656,9 +670,6 @@ STD_ENTRY(interrupt_return)
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IRQ_DISABLE(r20, r21)
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TRACE_IRQS_OFF /* Note: clobbers registers r0-r29 */
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/* Get base of stack in r32; note r30/31 are used as arguments here. */
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GET_THREAD_INFO(r32)
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/* Check to see if there is any work to do before returning to user. */
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{
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@ -674,16 +685,18 @@ STD_ENTRY(interrupt_return)
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/*
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* Make sure we have all the registers saved for signal
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* handling or single-step. Call out to C code to figure out
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* handling or notify-resume. Call out to C code to figure out
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* exactly what we need to do for each flag bit, then if
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* necessary, reload the flags and recheck.
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*/
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push_extra_callee_saves r0
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{
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PTREGS_PTR(r0, PTREGS_OFFSET_BASE)
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jal do_work_pending
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bnez r33, 1f
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}
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bnez r0, .Lresume_userspace
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push_extra_callee_saves r0
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movei r33, 1
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1: jal do_work_pending
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bnez r0, .Lretry_work_pending
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/*
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* In the NMI case we
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@ -968,11 +981,16 @@ handle_syscall:
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shl16insli r20, r20, hw0(irq_stat + IRQ_CPUSTAT_SYSCALL_COUNT_OFFSET)
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add r20, r20, tp
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ld4s r21, r20
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addi r21, r21, 1
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st4 r20, r21
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{
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addi r21, r21, 1
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move r31, sp
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}
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{
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st4 r20, r21
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EXTRACT_THREAD_INFO(r31)
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}
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/* Trace syscalls, if requested. */
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GET_THREAD_INFO(r31)
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addi r31, r31, THREAD_INFO_FLAGS_OFFSET
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ld r30, r31
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andi r30, r30, _TIF_SYSCALL_TRACE
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@ -567,6 +567,10 @@ struct task_struct *__sched _switch_to(struct task_struct *prev,
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*/
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int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
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{
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/* If we enter in kernel mode, do nothing and exit the caller loop. */
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if (!user_mode(regs))
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return 0;
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if (thread_info_flags & _TIF_NEED_RESCHED) {
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schedule();
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return 1;
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@ -589,8 +593,7 @@ int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
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return 1;
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}
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if (thread_info_flags & _TIF_SINGLESTEP) {
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if ((regs->ex1 & SPR_EX_CONTEXT_1_1__PL_MASK) == 0)
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single_step_once(regs);
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single_step_once(regs);
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return 0;
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}
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panic("work_pending: bad flags %#x\n", thread_info_flags);
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