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Commit fbf7192b authored by David Mosberger-Tang's avatar David Mosberger-Tang Committed by Tony Luck
Browse files

[IA64] Annotate fsys_bubble_down() with McKinley dispatch info. 



This patch changes comments & formatting only.  There is no code
change.

Signed-off-by: default avatarDavid Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent 1ba7be7d

arch/ia64/kernel/fsys.S

+74 −44
Original line number Diff line number Diff line
@@ -531,84 +531,114 @@ GLOBAL_ENTRY(fsys_bubble_down) 
	.altrp b6

	.body

	/*

	 * We get here for syscalls that don't have a lightweight handler.  For those, we

	 * need to bubble down into the kernel and that requires setting up a minimal

	 * pt_regs structure, and initializing the CPU state more or less as if an

	 * interruption had occurred.  To make syscall-restarts work, we setup pt_regs

	 * such that cr_iip points to the second instruction in syscall_via_break.

	 * Decrementing the IP hence will restart the syscall via break and not

	 * decrementing IP will return us to the caller, as usual.  Note that we preserve

	 * the value of psr.pp rather than initializing it from dcr.pp.  This makes it

	 * possible to distinguish fsyscall execution from other privileged execution.

	 * We get here for syscalls that don't have a lightweight

	 * handler.  For those, we need to bubble down into the kernel

	 * and that requires setting up a minimal pt_regs structure,

	 * and initializing the CPU state more or less as if an

	 * interruption had occurred.  To make syscall-restarts work,

	 * we setup pt_regs such that cr_iip points to the second

	 * instruction in syscall_via_break.  Decrementing the IP

	 * hence will restart the syscall via break and not

	 * decrementing IP will return us to the caller, as usual.

	 * Note that we preserve the value of psr.pp rather than

	 * initializing it from dcr.pp.  This makes it possible to

	 * distinguish fsyscall execution from other privileged

	 * execution.

	 *

	 * On entry:

	 *	- normal fsyscall handler register usage, except that we also have:

	 *	- normal fsyscall handler register usage, except

	 *	  that we also have:

	 *	- r18: address of syscall entry point

	 *	- r21: ar.fpsr

	 *	- r26: ar.pfs

	 *	- r27: ar.rsc

	 *	- r29: psr

	 *

	 * We used to clear some PSR bits here but that requires slow

	 * serialization.  Fortuntely, that isn't really necessary.

	 * The rationale is as follows: we used to clear bits

	 * ~PSR_PRESERVED_BITS in PSR.L.  Since

	 * PSR_PRESERVED_BITS==PSR.{UP,MFL,MFH,PK,DT,PP,SP,RT,IC}, we

	 * ended up clearing PSR.{BE,AC,I,DFL,DFH,DI,DB,SI,TB}.

	 * However,

	 *

	 * PSR.BE : already is turned off in __kernel_syscall_via_epc()

	 * PSR.AC : don't care (kernel normally turns PSR.AC on)

	 * PSR.I  : already turned off by the time fsys_bubble_down gets

	 *	    invoked

	 * PSR.DFL: always 0 (kernel never turns it on)

	 * PSR.DFH: don't care --- kernel never touches f32-f127 on its own

	 *	    initiative

	 * PSR.DI : always 0 (kernel never turns it on)

	 * PSR.SI : always 0 (kernel never turns it on)

	 * PSR.DB : don't care --- kernel never enables kernel-level

	 *	    breakpoints

	 * PSR.TB : must be 0 already; if it wasn't zero on entry to

	 *          __kernel_syscall_via_epc, the branch to fsys_bubble_down

	 *          will trigger a taken branch; the taken-trap-handler then

	 *          converts the syscall into a break-based system-call.

	 */

	/*

	 * Reading psr.l gives us only bits 0-31, psr.it, and psr.mc.  The rest we have

	 * to synthesize.

	 * Reading psr.l gives us only bits 0-31, psr.it, and psr.mc.

	 * The rest we have to synthesize.

	 */

#	define PSR_ONE_BITS		((3 << IA64_PSR_CPL0_BIT) | (0x1 << IA64_PSR_RI_BIT) \

#	define PSR_ONE_BITS		((3 << IA64_PSR_CPL0_BIT)	\

					 | (0x1 << IA64_PSR_RI_BIT)	\

					 | IA64_PSR_BN | IA64_PSR_I)



	invala

	movl r14=ia64_ret_from_syscall

	invala					// M0|1

	movl r14=ia64_ret_from_syscall		// X



	nop.m 0

	movl r28=__kernel_syscall_via_break

	movl r28=__kernel_syscall_via_break	// X	create cr.iip

	;;



	mov r2=r16			// copy current task addr to addl-addressable register

	adds r16=IA64_TASK_THREAD_ON_USTACK_OFFSET,r16

	mov r31=pr			// save pr (2 cyc)

	mov r2=r16				// A    get task addr to addl-addressable register

	adds r16=IA64_TASK_THREAD_ON_USTACK_OFFSET,r16 // A

	mov r31=pr				// I0   save pr (2 cyc)

	;;

	st1 [r16]=r0			// clear current->thread.on_ustack flag

	addl r22=IA64_RBS_OFFSET,r2	// compute base of RBS

	add r3=TI_FLAGS+IA64_TASK_SIZE,r2

	st1 [r16]=r0				// M2|3 clear current->thread.on_ustack flag

	addl r22=IA64_RBS_OFFSET,r2		// A    compute base of RBS

	add r3=TI_FLAGS+IA64_TASK_SIZE,r2	// A

	;;

	ld4 r3=[r3]				// r2 = current_thread_info()->flags

	lfetch.fault.excl.nt1 [r22]

	ld4 r3=[r3]				// M0|1 r3 = current_thread_info()->flags

	lfetch.fault.excl.nt1 [r22]		// M0|1 prefetch register backing-store

	nop.i 0

	;;

	mov ar.rsc=0			// set enforced lazy mode, pl 0, little-endian, loadrs=0

	mov ar.rsc=0				// M2   set enforced lazy mode, pl 0, LE, loadrs=0

	nop.m 0

	nop.i 0

	;;

	mov r23=ar.bspstore		// save ar.bspstore (12 cyc)

	mov.m r24=ar.rnat		// read ar.rnat (5 cyc lat)

	mov r23=ar.bspstore			// M2 (12 cyc) save ar.bspstore

	mov.m r24=ar.rnat			// M2 (5 cyc) read ar.rnat (dual-issues!)

	nop.i 0

	;;

	mov ar.bspstore=r22		// switch to kernel RBS

	mov ar.bspstore=r22			// M2 (6 cyc) switch to kernel RBS

	movl r8=PSR_ONE_BITS			// X

	;;

	mov r25=ar.unat			// save ar.unat (5 cyc)

	mov r19=b6			// save b6 (2 cyc)

	mov r20=r1			// save caller's gp in r20

	mov r25=ar.unat				// M2 (5 cyc) save ar.unat

	mov r19=b6				// I0   save b6 (2 cyc)

	mov r20=r1				// A    save caller's gp in r20

	;;

	or r29=r8,r29			// construct cr.ipsr value to save

	mov b6=r18			// copy syscall entry-point to b6 (7 cyc)

	addl r1=IA64_STK_OFFSET-IA64_PT_REGS_SIZE,r2	// compute base of memory stack

	or r29=r8,r29				// A    construct cr.ipsr value to save

	mov b6=r18				// I0   copy syscall entry-point to b6 (7 cyc)

	addl r1=IA64_STK_OFFSET-IA64_PT_REGS_SIZE,r2 // A compute base of memory stack



	mov r18=ar.bsp			// save (kernel) ar.bsp (12 cyc)

	cmp.ne pKStk,pUStk=r0,r0	// set pKStk <- 0, pUStk <- 1

	br.call.sptk.many b7=ia64_syscall_setup

	mov r18=ar.bsp				// M2   save (kernel) ar.bsp (12 cyc)

	cmp.ne pKStk,pUStk=r0,r0		// A    set pKStk <- 0, pUStk <- 1

	br.call.sptk.many b7=ia64_syscall_setup	// B

	;;

	mov ar.rsc=0x3			// set eager mode, pl 0, little-endian, loadrs=0

	mov rp=r14				// set the real return addr

	mov ar.rsc=0x3				// M2   set eager mode, pl 0, LE, loadrs=0

	mov rp=r14				// I0   set the real return addr

	nop.i 0

	;;

	ssm psr.i

	tbit.z p8,p0=r3,TIF_SYSCALL_TRACE

(p10)	br.cond.spnt.many ia64_ret_from_syscall	// p10==true means out registers are more than 8

	ssm psr.i				// M2   we're on kernel stacks now, reenable irqs

	tbit.z p8,p0=r3,TIF_SYSCALL_TRACE	// I0

(p10)	br.cond.spnt.many ia64_ret_from_syscall	// B    return if bad call-frame or r15 is a NaT



	nop.m 0

(p8)	br.call.sptk.many b6=b6		// ignore this return addr

	br.cond.spnt ia64_trace_syscall

(p8)	br.call.sptk.many b6=b6			// B    (ignore return address)

	br.cond.spnt ia64_trace_syscall		// B

END(fsys_bubble_down)



	.rodata