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parisc: optimizations in copy_thread() and friends

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* 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: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2012-10-05 18:55:57 -04:00
parent 7f1f311ac7
commit ff0ab8af9c
2 changed files with 27 additions and 87 deletions
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86
arch/parisc/kernel/entry.S
View File

@ -719,7 +719,7 @@ ENTRY(ret_from_kernel_thread)
BL schedule_tail, %r2 BL schedule_tail, %r2
nop 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 LDREG TASK_PT_GR25(%r1), %r26
#ifdef CONFIG_64BIT #ifdef CONFIG_64BIT
LDREG TASK_PT_GR27(%r1), %r27 LDREG TASK_PT_GR27(%r1), %r27
@ -743,9 +743,8 @@ ENDPROC(ret_from_kernel_thread)
ENTRY(ret_from_kernel_execve) ENTRY(ret_from_kernel_execve)
mfctl %cr30, %r1 mfctl %cr30, %r1
ldo THREAD_SZ_ALGN(%r1), %r30 b syscall_exit /* forward */
b intr_return /* forward */ ldo THREAD_SZ_ALGN+FRAME_SIZE(%r1), %r30
copy %r26,%r16 /* pt_regs into r16 */
ENDPROC(ret_from_kernel_execve) ENDPROC(ret_from_kernel_execve)
@ -1709,39 +1708,13 @@ ENTRY(sys_fork_wrapper)
LDREG TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30), %r1 LDREG TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30), %r1
ldo TASK_REGS(%r1),%r1 ldo TASK_REGS(%r1),%r1
reg_save %r1 reg_save %r1
mfctl %cr27, %r3 mfctl %cr27, %r28
STREG %r3, PT_CR27(%r1) STREG %r28, 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)
LDREG PT_GR30(%r1),%r25 LDREG PT_GR30(%r1),%r25
copy %r1,%r24 copy %r1,%r24
BL sys_clone,%r2 b sys_clone
ldi SIGCHLD,%r26 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) ENDPROC(sys_fork_wrapper)
/* Set the return value for the child */ /* Set the return value for the child */
@ -1749,9 +1722,13 @@ ENTRY(child_return)
BL schedule_tail, %r2 BL schedule_tail, %r2
nop nop
LDREG TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE-FRAME_SIZE(%r30), %r1 LDREG TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30), %r1
LDREG TASK_PT_GR19(%r1),%r2 ldo TASK_REGS(%r1),%r1 /* get pt regs */
b wrapper_exit
LDREG PT_CR27(%r1), %r3
mtctl %r3, %cr27
reg_restore %r1
b syscall_exit
copy %r0,%r28 copy %r0,%r28
ENDPROC(child_return) ENDPROC(child_return)
@ -1760,23 +1737,10 @@ ENTRY(sys_clone_wrapper)
LDREG TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 LDREG TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1
ldo TASK_REGS(%r1),%r1 /* get pt regs */ ldo TASK_REGS(%r1),%r1 /* get pt regs */
reg_save %r1 reg_save %r1
mfctl %cr27, %r3 mfctl %cr27, %r28
STREG %r3, PT_CR27(%r1) STREG %r28, PT_CR27(%r1)
b sys_clone
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
copy %r1,%r24 copy %r1,%r24
b wrapper_exit
LDREG -RP_OFFSET-FRAME_SIZE(%r30),%r2
ENDPROC(sys_clone_wrapper) ENDPROC(sys_clone_wrapper)
@ -1784,23 +1748,11 @@ ENTRY(sys_vfork_wrapper)
LDREG TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 LDREG TI_TASK-THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1
ldo TASK_REGS(%r1),%r1 /* get pt regs */ ldo TASK_REGS(%r1),%r1 /* get pt regs */
reg_save %r1 reg_save %r1
mfctl %cr27, %r3 mfctl %cr27, %r28
STREG %r3, PT_CR27(%r1) STREG %r28, PT_CR27(%r1)
STREG %r2,-RP_OFFSET(%r30) b sys_vfork
ldo FRAME_SIZE(%r30),%r30
#ifdef CONFIG_64BIT
ldo -16(%r30),%r29 /* Reference param save area */
#endif
STREG %r2,PT_GR19(%r1) /* save for child */
STREG %r30,PT_GR21(%r1)
BL sys_vfork,%r2
copy %r1,%r26 copy %r1,%r26
b wrapper_exit
LDREG -RP_OFFSET-FRAME_SIZE(%r30),%r2
ENDPROC(sys_vfork_wrapper) ENDPROC(sys_vfork_wrapper)

28
arch/parisc/kernel/process.c
View File

@ -52,6 +52,7 @@
#include <asm/io.h> #include <asm/io.h>
#include <asm/asm-offsets.h> #include <asm/asm-offsets.h>
#include <asm/assembly.h>
#include <asm/pdc.h> #include <asm/pdc.h>
#include <asm/pdc_chassis.h> #include <asm/pdc_chassis.h>
#include <asm/pgalloc.h> #include <asm/pgalloc.h>
@ -253,14 +254,16 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
#ifdef CONFIG_HPUX #ifdef CONFIG_HPUX
extern void * const hpux_child_return; extern void * const hpux_child_return;
#endif #endif
if (unlikely(p->flags & PF_KTHREAD)) {
if (unlikely((p->flags & PF_KTHREAD) && usp != 0)) {
memset(cregs, 0, sizeof(struct pt_regs)); memset(cregs, 0, sizeof(struct pt_regs));
if (!usp) /* idle thread */
return 0;
/* kernel thread */ /* kernel thread */
cregs->ksp = (unsigned long)stack + THREAD_SZ_ALGN;
/* Must exit via ret_from_kernel_thread in order /* Must exit via ret_from_kernel_thread in order
* to call schedule_tail() * to call schedule_tail()
*/ */
cregs->ksp = (unsigned long)stack + THREAD_SZ_ALGN + FRAME_SIZE;
cregs->kpc = (unsigned long) &ret_from_kernel_thread; cregs->kpc = (unsigned long) &ret_from_kernel_thread;
/* /*
* Copy function and argument to be called from * 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; cregs->gr[25] = arg;
} else { } else {
/* user thread */ /* 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->gr[30] = usp;
cregs->ksp = (unsigned long)stack + THREAD_SZ_ALGN + FRAME_SIZE;
if (personality(p->personality) == PER_HPUX) { if (personality(p->personality) == PER_HPUX) {
#ifdef CONFIG_HPUX #ifdef CONFIG_HPUX
cregs->kpc = (unsigned long) &hpux_child_return; cregs->kpc = (unsigned long) &hpux_child_return;
@ -302,8 +291,7 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
} }
/* Setup thread TLS area from the 4th parameter in clone */ /* Setup thread TLS area from the 4th parameter in clone */
if (clone_flags & CLONE_SETTLS) if (clone_flags & CLONE_SETTLS)
cregs->cr27 = pregs->gr[23]; cregs->cr27 = pregs->gr[23];
} }
return 0; return 0;