Commit ff0ab8af authored by Al Viro's avatar Al Viro
Browse files

parisc: optimizations in copy_thread() and friends 



* in user thread case the registers had been copied as part of task_struct
already; no need to do it in copy_thread().
* no need to store kernel stack pointer into regs->r21; we know its offset
anyway.
* no need to clobber r3 in sys_fork_wrapper and friends - r28 will do just
as well and *it* will be overwritten anyway.
* no need to mess with storing the return address for child - it should just
use syscall_exit.
* no need to bother with separate stack frame for sys_clone() - just branch
there and be done with that.
* no need to bother with wrapper_exit - we need it only on the child_return,
so let's just do it there.
* use the same ksp for kernel threads and userland ones, while we are at it,
and let ret_from_kernel_execve() go through the normal syscall_exit.  More
straightforward is better here...

[fixes from jejb folded]

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 7f1f311a

arch/parisc/kernel/entry.S

+19 −67
Original line number Diff line number Diff line
@@ -719,7 +719,7 @@ ENTRY(ret_from_kernel_thread) 
	BL	schedule_tail, %r2

	nop



	LDREG	TI_TASK-THREAD_SZ_ALGN(%r30), %r1

	LDREG	TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30), %r1

	LDREG	TASK_PT_GR25(%r1), %r26

#ifdef CONFIG_64BIT

	LDREG	TASK_PT_GR27(%r1), %r27
@@ -743,9 +743,8 @@ ENDPROC(ret_from_kernel_thread) 


ENTRY(ret_from_kernel_execve)

	mfctl   %cr30, %r1

	ldo	THREAD_SZ_ALGN(%r1), %r30

	b	intr_return	/* forward */

	copy	%r26,%r16	/* pt_regs into r16 */

	b	syscall_exit	/* forward */

	ldo	THREAD_SZ_ALGN+FRAME_SIZE(%r1), %r30

ENDPROC(ret_from_kernel_execve)
@@ -1709,39 +1708,13 @@ ENTRY(sys_fork_wrapper) 
	LDREG	TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30), %r1

	ldo	TASK_REGS(%r1),%r1

	reg_save %r1

	mfctl	%cr27, %r3

	STREG	%r3, PT_CR27(%r1)



	STREG	%r2,-RP_OFFSET(%r30)

	ldo	FRAME_SIZE(%r30),%r30

#ifdef CONFIG_64BIT

	ldo	-16(%r30),%r29		/* Reference param save area */

#endif



	/* These are call-clobbered registers and therefore

	   also syscall-clobbered (we hope). */

	STREG	%r2,PT_GR19(%r1)	/* save for child */

	STREG	%r30,PT_GR21(%r1)

	mfctl	%cr27, %r28

	STREG	%r28, PT_CR27(%r1)



	LDREG	PT_GR30(%r1),%r25

	copy	%r1,%r24

	BL	sys_clone,%r2

	b	sys_clone

	ldi	SIGCHLD,%r26



	LDREG	-RP_OFFSET-FRAME_SIZE(%r30),%r2

wrapper_exit:

	ldo	-FRAME_SIZE(%r30),%r30		/* get the stackframe */

	LDREG	TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1

	ldo	TASK_REGS(%r1),%r1	 /* get pt regs */



	LDREG	PT_CR27(%r1), %r3

	mtctl	%r3, %cr27

	reg_restore %r1



	/* strace expects syscall # to be preserved in r20 */

	ldi	__NR_fork,%r20

	bv %r0(%r2)

	STREG	%r20,PT_GR20(%r1)

ENDPROC(sys_fork_wrapper)



	/* Set the return value for the child */
@@ -1749,9 +1722,13 @@ ENTRY(child_return) 
	BL	schedule_tail, %r2

	nop



	LDREG	TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE-FRAME_SIZE(%r30), %r1

	LDREG	TASK_PT_GR19(%r1),%r2

	b	wrapper_exit

	LDREG	TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30), %r1

	ldo	TASK_REGS(%r1),%r1	 /* get pt regs */



	LDREG	PT_CR27(%r1), %r3

	mtctl	%r3, %cr27

	reg_restore %r1

	b	syscall_exit

	copy	%r0,%r28

ENDPROC(child_return)
@@ -1760,23 +1737,10 @@ ENTRY(sys_clone_wrapper) 
	LDREG	TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1

	ldo	TASK_REGS(%r1),%r1	/* get pt regs */

	reg_save %r1

	mfctl	%cr27, %r3

	STREG	%r3, PT_CR27(%r1)



	STREG	%r2,-RP_OFFSET(%r30)

	ldo	FRAME_SIZE(%r30),%r30

#ifdef CONFIG_64BIT

	ldo	-16(%r30),%r29		/* Reference param save area */

#endif



	/* WARNING - Clobbers r19 and r21, userspace must save these! */

	STREG	%r2,PT_GR19(%r1)	/* save for child */

	STREG	%r30,PT_GR21(%r1)

	BL	sys_clone,%r2

	mfctl	%cr27, %r28

	STREG	%r28, PT_CR27(%r1)

	b	sys_clone

	copy	%r1,%r24



	b	wrapper_exit

	LDREG	-RP_OFFSET-FRAME_SIZE(%r30),%r2

ENDPROC(sys_clone_wrapper)
@@ -1784,23 +1748,11 @@ ENTRY(sys_vfork_wrapper) 
	LDREG	TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1

	ldo	TASK_REGS(%r1),%r1	/* get pt regs */

	reg_save %r1

	mfctl	%cr27, %r3

	STREG	%r3, PT_CR27(%r1)



	STREG	%r2,-RP_OFFSET(%r30)

	ldo	FRAME_SIZE(%r30),%r30

#ifdef CONFIG_64BIT

	ldo	-16(%r30),%r29		/* Reference param save area */

#endif

	mfctl	%cr27, %r28

	STREG	%r28, PT_CR27(%r1)



	STREG	%r2,PT_GR19(%r1)	/* save for child */

	STREG	%r30,PT_GR21(%r1)



	BL	sys_vfork,%r2

	b	sys_vfork

	copy	%r1,%r26



	b	wrapper_exit

	LDREG	-RP_OFFSET-FRAME_SIZE(%r30),%r2

ENDPROC(sys_vfork_wrapper)

arch/parisc/kernel/process.c

+8 −20
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ 


#include <asm/io.h>

#include <asm/asm-offsets.h>

#include <asm/assembly.h>

#include <asm/pdc.h>

#include <asm/pdc_chassis.h>

#include <asm/pgalloc.h>
@@ -253,14 +254,16 @@ copy_thread(unsigned long clone_flags, unsigned long usp, 
#ifdef CONFIG_HPUX

	extern void * const hpux_child_return;

#endif



	if (unlikely((p->flags & PF_KTHREAD) && usp != 0)) {

	if (unlikely(p->flags & PF_KTHREAD)) {

		memset(cregs, 0, sizeof(struct pt_regs));

		if (!usp) /* idle thread */

			return 0;



		/* kernel thread */

		cregs->ksp = (unsigned long)stack + THREAD_SZ_ALGN;

		/* Must exit via ret_from_kernel_thread in order

		 * to call schedule_tail()

		 */

		cregs->ksp = (unsigned long)stack + THREAD_SZ_ALGN + FRAME_SIZE;

		cregs->kpc = (unsigned long) &ret_from_kernel_thread;

		/*

		 * Copy function and argument to be called from
@@ -275,22 +278,8 @@ copy_thread(unsigned long clone_flags, unsigned long usp, 
		cregs->gr[25] = arg;

	} else {

		/* user thread */

		/*

		 * Note that the fork wrappers are responsible

		 * for setting gr[21].

		 */



		*cregs = *pregs;



		/* Set the return value for the child.  Note that this is not

		   actually restored by the syscall exit path, but we put it

		   here for consistency in case of signals. */

		cregs->gr[28] = 0; /* child */



		/* Use same stack depth as parent */

		cregs->ksp = (unsigned long)stack

			+ (pregs->gr[21] & (THREAD_SIZE - 1));

		cregs->gr[30] = usp;

		cregs->ksp = (unsigned long)stack + THREAD_SZ_ALGN + FRAME_SIZE;

		if (personality(p->personality) == PER_HPUX) {

#ifdef CONFIG_HPUX

			cregs->kpc = (unsigned long) &hpux_child_return;
@@ -303,7 +292,6 @@ copy_thread(unsigned long clone_flags, unsigned long usp, 
		/* Setup thread TLS area from the 4th parameter in clone */

		if (clone_flags & CLONE_SETTLS)

			cregs->cr27 = pregs->gr[23];

	

	}



	return 0;

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