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Commit fc327e26 authored by Chris Metcalf's avatar Chris Metcalf
Browse files

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: default avatarAl Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
parent 36be5051

arch/tile/include/asm/thread_info.h

+7 −2
Original line number Original line Diff line number Diff line
@@ -100,9 +100,14 @@ extern void cpu_idle_on_new_stack(struct thread_info *old_ti, 




#else /* __ASSEMBLY__ */

#else /* __ASSEMBLY__ */





/* how to get the thread information struct from ASM */

/*

 * How to get the thread information struct from assembly.

 * Note that we use different macros since different architectures

 * have different semantics in their "mm" instruction and we would

 * like to guarantee that the macro expands to exactly one instruction.

 */

#ifdef __tilegx__

#ifdef __tilegx__

#define GET_THREAD_INFO(reg) move reg, sp; mm reg, zero, LOG2_THREAD_SIZE, 63

#define EXTRACT_THREAD_INFO(reg) mm reg, zero, LOG2_THREAD_SIZE, 63

#else

#else

#define GET_THREAD_INFO(reg) mm reg, sp, zero, LOG2_THREAD_SIZE, 31

#define GET_THREAD_INFO(reg) mm reg, sp, zero, LOG2_THREAD_SIZE, 31

#endif

#endif

arch/tile/kernel/intvec_32.S

+28 −13
Original line number Original line Diff line number Diff line
@@ -838,6 +838,18 @@ STD_ENTRY(interrupt_return) 
.Lresume_userspace:

.Lresume_userspace:

	FEEDBACK_REENTER(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

	 * Disable interrupts so as to make sure we don't

	 * miss an interrupt that sets any of the thread flags (like

	 * miss an interrupt that sets any of the thread flags (like
@@ -848,9 +860,6 @@ STD_ENTRY(interrupt_return) 
	IRQ_DISABLE(r20, r21)

	IRQ_DISABLE(r20, r21)

	TRACE_IRQS_OFF  /* Note: clobbers registers r0-r29 */

	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. */

	/* Check to see if there is any work to do before returning to user. */

	{

	{
@@ -866,16 +875,18 @@ STD_ENTRY(interrupt_return) 




	/*

	/*

	 * Make sure we have all the registers saved for signal

	 * Make sure we have all the registers saved for signal

	 * handling or single-step.  Call out to C code to figure out

	 * handling, notify-resume, or single-step.  Call out to C

	 * exactly what we need to do for each flag bit, then if

	 * code to figure out exactly what we need to do for each flag bit,

	 * necessary, reload the flags and recheck.

	 * then if necessary, reload the flags and recheck.

	 */

	 */

	push_extra_callee_saves r0

	{

	{

	 PTREGS_PTR(r0, PTREGS_OFFSET_BASE)

	 PTREGS_PTR(r0, PTREGS_OFFSET_BASE)

	 jal    do_work_pending

	 bnz    r33, 1f

	}

	}

	bnz     r0, .Lresume_userspace

	push_extra_callee_saves r0

	movei   r33, 1

1:	jal     do_work_pending

	bnz     r0, .Lretry_work_pending





	/*

	/*

	 * In the NMI case we

	 * In the NMI case we
@@ -1180,10 +1191,12 @@ handle_syscall: 
	add     r20, r20, tp

	add     r20, r20, tp

	lw      r21, r20

	lw      r21, r20

	addi    r21, r21, 1

	addi    r21, r21, 1

	{

	 sw     r20, r21

	 sw     r20, r21

	 GET_THREAD_INFO(r31)

	}





	/* Trace syscalls, if requested. */

	/* Trace syscalls, if requested. */

	GET_THREAD_INFO(r31)

	addi	r31, r31, THREAD_INFO_FLAGS_OFFSET

	addi	r31, r31, THREAD_INFO_FLAGS_OFFSET

	lw	r30, r31

	lw	r30, r31

	andi    r30, r30, _TIF_SYSCALL_TRACE

	andi    r30, r30, _TIF_SYSCALL_TRACE
@@ -1362,7 +1375,10 @@ handle_ill: 
3:

3:

	/* set PC and continue */

	/* set PC and continue */

	lw      r26, r24

	lw      r26, r24

	{

	 sw     r28, r26

	 sw     r28, r26

	 GET_THREAD_INFO(r0)

	}





	/*

	/*

	 * Clear TIF_SINGLESTEP to prevent recursion if we execute an ill.

	 * Clear TIF_SINGLESTEP to prevent recursion if we execute an ill.
@@ -1370,7 +1386,6 @@ handle_ill: 
	 * need to clear it here and can't really impose on all other arches.

	 * need to clear it here and can't really impose on all other arches.

	 * So what's another write between friends?

	 * So what's another write between friends?

	 */

	 */

	GET_THREAD_INFO(r0)





	addi    r1, r0, THREAD_INFO_FLAGS_OFFSET

	addi    r1, r0, THREAD_INFO_FLAGS_OFFSET

	{

	{

arch/tile/kernel/intvec_64.S

+28 −10
Original line number Original line Diff line number Diff line
@@ -646,6 +646,20 @@ STD_ENTRY(interrupt_return) 
.Lresume_userspace:

.Lresume_userspace:

	FEEDBACK_REENTER(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

	 * Disable interrupts so as to make sure we don't

	 * miss an interrupt that sets any of the thread flags (like

	 * miss an interrupt that sets any of the thread flags (like
@@ -656,9 +670,6 @@ STD_ENTRY(interrupt_return) 
	IRQ_DISABLE(r20, r21)

	IRQ_DISABLE(r20, r21)

	TRACE_IRQS_OFF  /* Note: clobbers registers r0-r29 */

	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. */

	/* 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

	 * 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

	 * exactly what we need to do for each flag bit, then if

	 * necessary, reload the flags and recheck.

	 * necessary, reload the flags and recheck.

	 */

	 */

	push_extra_callee_saves r0

	{

	{

	 PTREGS_PTR(r0, PTREGS_OFFSET_BASE)

	 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

	 * In the NMI case we
@@ -968,11 +981,16 @@ handle_syscall: 
	shl16insli r20, r20, hw0(irq_stat + IRQ_CPUSTAT_SYSCALL_COUNT_OFFSET)

	shl16insli r20, r20, hw0(irq_stat + IRQ_CPUSTAT_SYSCALL_COUNT_OFFSET)

	add     r20, r20, tp

	add     r20, r20, tp

	ld4s    r21, r20

	ld4s    r21, r20

	{

	 addi   r21, r21, 1

	 addi   r21, r21, 1

	 move   r31, sp

	}

	{

	 st4    r20, r21

	 st4    r20, r21

	 EXTRACT_THREAD_INFO(r31)

	}





	/* Trace syscalls, if requested. */

	/* Trace syscalls, if requested. */

	GET_THREAD_INFO(r31)

	addi	r31, r31, THREAD_INFO_FLAGS_OFFSET

	addi	r31, r31, THREAD_INFO_FLAGS_OFFSET

	ld	r30, r31

	ld	r30, r31

	andi    r30, r30, _TIF_SYSCALL_TRACE

	andi    r30, r30, _TIF_SYSCALL_TRACE

arch/tile/kernel/process.c

+5 −2
Original line number Original line Diff line number Diff line
@@ -567,6 +567,10 @@ struct task_struct *__sched _switch_to(struct task_struct *prev, 
 */

 */

int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)

int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)

{

{

	/* If we enter in kernel mode, do nothing and exit the caller loop. */

	if (!user_mode(regs))

		return 0;



	if (thread_info_flags & _TIF_NEED_RESCHED) {

	if (thread_info_flags & _TIF_NEED_RESCHED) {

		schedule();

		schedule();

		return 1;

		return 1;
@@ -589,7 +593,6 @@ int do_work_pending(struct pt_regs *regs, u32 thread_info_flags) 
		return 1;

		return 1;

	}

	}

	if (thread_info_flags & _TIF_SINGLESTEP) {

	if (thread_info_flags & _TIF_SINGLESTEP) {

		if ((regs->ex1 & SPR_EX_CONTEXT_1_1__PL_MASK) == 0)

		single_step_once(regs);

		single_step_once(regs);

		return 0;

		return 0;

	}

	}