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[linuxsh-dev] FPU use in kernel
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From: NIIBE Y. <gn...@m1...> - 2001-12-20 02:56:58
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Here's a patch to remove FPU usage support in kernel, which I talked summer
or spring. It took so long, because I needed to be conservative to sync.
2001-12-20 NIIBE Yutaka <gn...@m1...>
* include/asm-sh/processor.h (unlazy_fpu): Don't need to grab_fpu.
* arch/sh/kernel/entry.S (PF_USEDFPU, __PF_USEDFPU): Removed.
(restore_all, handle_exception): Simplified.
(__fpu_prepare_fd, __init_task_flags): Removed
* arch/sh/kernel/fpu.c (enable_fpu_in_danger): Removed.
(fpu_prepare_fd): Removed.
Index: arch/sh/kernel/entry.S
===================================================================
RCS file: /cvsroot/linuxsh/linux/arch/sh/kernel/entry.S,v
retrieving revision 1.1.1.1
diff -u -3 -p -r1.1.1.1 entry.S
--- arch/sh/kernel/entry.S 2001/10/15 20:44:47 1.1.1.1
+++ arch/sh/kernel/entry.S 2001/12/20 02:51:09
@@ -66,7 +66,6 @@ need_resched = 20
tsk_ptrace = 24
PT_TRACESYS = 0x00000002
-PF_USEDFPU = 0x00100000
ENOSYS = 38
EINVAL = 22
@@ -567,12 +566,6 @@ __irq_stat:
.align 2
restore_all:
-#if defined(__SH4__)
- mov.l __fpu_prepare_fd, r0
- jsr @r0
- stc sr, r4
-#endif
- !
mov.l @r15+, r0
mov.l @r15+, r1
mov.l @r15+, r2
@@ -585,7 +578,7 @@ restore_all:
stc sr, r8
mov.l __blrb_flags, r9 ! BL =1, RB=1
or r9, r8
- ldc r8, sr ! here, change the register bank
+ ldc r8, sr ! here, change the register bank
!
mov.l @r15+, r8
mov.l @r15+, r9
@@ -594,25 +587,25 @@ restore_all:
mov.l @r15+, r12
mov.l @r15+, r13
mov.l @r15+, r14
- mov.l @r15+, k4 ! original stack pointer
+ mov.l @r15+, k4 ! original stack pointer
ldc.l @r15+, spc
lds.l @r15+, pr
- mov.l @r15+, k3 ! original SR
+ mov.l @r15+, k3 ! original SR
ldc.l @r15+, gbr
lds.l @r15+, mach
lds.l @r15+, macl
- add #4, r15 ! Skip syscall number
+ add #4, r15 ! Skip syscall number
!
! Calculate new SR value
- mov k3, k2 ! original SR value
+ mov k3, k2 ! original SR value
mov.l 1f, k1
stc sr, k0
- and k1, k0 ! Get current FD-bit
+ and k1, k0 ! Get current FD-bit
mov.l 2f, k1
- and k1, k2 ! Mask orignal SR value
- or k0, k2 ! Inherit current FD-bit
+ and k1, k2 ! Mask orignal SR value
+ or k0, k2 ! Inherit current FD-bit
!
- mov k3, k0 ! Calculate IMASK-bits
+ mov k3, k0 ! Calculate IMASK-bits
shlr2 k0
and #0x3c, k0
cmp/eq #0x3c, k0
@@ -620,69 +613,15 @@ restore_all:
shll2 k0
mov g_imask, k0
!
-7: or k0, k2 ! Set the IMASK-bits
+7: or k0, k2 ! Set the IMASK-bits
ldc k2, ssr
!
-#if defined(__SH4__)
- shll k2
- shll k2
- bf 9f ! user mode
- /* Kernel to kernel transition */
- mov.l 1f, k1
- tst k1, k3
- bf 9f ! it hadn't FPU
- ! Kernel to kernel and FPU was used
- ! There's the case we don't get FPU now
- stc sr, k2
- tst k1, k2
- bt 8f
- ! We need to grab FPU here
- xor k1, k2
- ldc k2, sr ! Grab FPU
- mov.l __init_task_flags, k1
- mov.l @k1, k2
- mov.l __PF_USEDFPU, k0
- or k0, k2
- mov.l k2, @k1 ! Set init_task.flags |= PF_USEDFPU
- !
- ! Restoring FPU...
- !
-8: mov.l 3f, k1
- lds k1, fpscr
- fmov.s @r15+, fr0
- fmov.s @r15+, fr1
- fmov.s @r15+, fr2
- fmov.s @r15+, fr3
- fmov.s @r15+, fr4
- fmov.s @r15+, fr5
- fmov.s @r15+, fr6
- fmov.s @r15+, fr7
- fmov.s @r15+, fr8
- fmov.s @r15+, fr9
- fmov.s @r15+, fr10
- fmov.s @r15+, fr11
- fmov.s @r15+, fr12
- fmov.s @r15+, fr13
- fmov.s @r15+, fr14
- fmov.s @r15+, fr15
- lds.l @r15+, fpscr
- lds.l @r15+, fpul
-9:
-#endif
mov k4, r15
rte
nop
.align 2
__blrb_flags: .long 0x30000000
-#if defined(__SH4__)
-__fpu_prepare_fd:
- .long SYMBOL_NAME(fpu_prepare_fd)
-__init_task_flags:
- .long SYMBOL_NAME(init_task_union)+4
-__PF_USEDFPU:
- .long PF_USEDFPU
-#endif
1: .long 0x00008000 ! FD
2: .long 0xffff7f0f ! ~(IMASK+FD)
3: .long 0x00080000 ! SZ=0, PR=1
@@ -732,61 +671,21 @@ handle_exception:
! Using k0, k1 for scratch registers (r0_bank1, r1_bank),
! save all registers onto stack.
!
- stc ssr, k0 ! from kernel space?
- shll k0 ! Check MD bit (bit30) by shifting it into the T bit
- shll k0
-#if defined(__SH4__)
- bf/s 8f ! it's from user to kernel transition
- mov r15, k0 ! save original stack to k0
- /* It's a kernel to kernel transition. */
- /* Is the FPU disabled? */
- mov.l 2f, k1
- stc ssr, k0
- tst k1, k0
- mov.l 4f, k1
- bf/s 9f ! FPU is not enabled, no need to save it
- mov r15, k0 ! save original stack to k0
- ! FPU is enabled, save it
- ! /* XXX: Need to save another bank of FPU if all FPU feature is used */
- ! /* Currently it's not the case for GCC (only udivsi3_i4, divsi3_i4) */
- sts.l fpul, @-r15
- sts.l fpscr, @-r15
- mov.l 6f, k1
- lds k1, fpscr
- mov.l 3f, k1
- fmov.s fr15, @-r15
- fmov.s fr14, @-r15
- fmov.s fr13, @-r15
- fmov.s fr12, @-r15
- fmov.s fr11, @-r15
- fmov.s fr10, @-r15
- fmov.s fr9, @-r15
- fmov.s fr8, @-r15
- fmov.s fr7, @-r15
- fmov.s fr6, @-r15
- fmov.s fr5, @-r15
- fmov.s fr4, @-r15
- fmov.s fr3, @-r15
- fmov.s fr2, @-r15
- fmov.s fr1, @-r15
- bra 9f
- fmov.s fr0, @-r15
-#else
- mov.l 3f, k1
- bt/s 9f ! it's a kernel to kernel transition, and skip the FPU save.
- mov r15, k0 ! save original stack to k0 anyway
-#endif
-8: /* User space to kernel */
+ stc ssr, k0 ! Is it from kernel space?
+ shll k0 ! Check MD bit (bit30) by shifting it into...
+ shll k0 ! ...the T bit
+ bt/s 9f ! It's a kernel to kernel transition.
+ mov r15, k0 ! save original stack to k0
+ /* User space to kernel */
mov #0x20, k1
- shll8 k1 ! k1 <= 8192 == THREAD_SIZE
+ shll8 k1 ! k1 <= 8192 == THREAD_SIZE
add current, k1
mov k1, r15 ! change to kernel stack
!
- mov.l 4f, k1 ! let kernel release FPU
-9: ! Save the user registers on the stack.
- ! At this point, k1 should have been set to the new SR value
- mov #-1, k4
- mov.l k4, @-r15 ! syscall_nr (default: -1)
+9: mov #-1, k4
+ mov.l 3f, k1
+ ! Save the user registers on the stack.
+ mov.l k4, @-r15 ! syscall_nr (default: -1)
!
sts.l macl, @-r15
sts.l mach, @-r15
@@ -806,11 +705,11 @@ handle_exception:
mov.l r9, @-r15
mov.l r8, @-r15
!
- stc sr, r8 ! Back to normal register bank, and
- or k1, r8 ! Block all interrupts, may release FPU
+ stc sr, r8 ! Back to normal register bank, and
+ or k1, r8 ! Block all interrupts
mov.l 5f, k1
- and k1, r8 ! ...
- ldc r8, sr ! ...changed here.
+ and k1, r8 ! ...
+ ldc r8, sr ! ...changed here.
!
mov.l r7, @-r15
mov.l r6, @-r15
@@ -831,9 +730,7 @@ handle_exception:
nop
.align 2
1: .long SYMBOL_NAME(exception_handling_table)
-2: .long 0x00008000 ! FD=1
3: .long 0x000000f0 ! FD=0, IMASK=15
-4: .long 0x000080f0 ! FD=1, IMASK=15
5: .long 0xcfffffff ! RB=0, BL=0
6: .long 0x00080000 ! SZ=0, PR=1
Index: arch/sh/kernel/fpu.c
===================================================================
RCS file: /cvsroot/linuxsh/linux/arch/sh/kernel/fpu.c,v
retrieving revision 1.1.1.1
diff -u -3 -p -r1.1.1.1 fpu.c
--- arch/sh/kernel/fpu.c 2001/10/15 20:44:48 1.1.1.1
+++ arch/sh/kernel/fpu.c 2001/12/20 02:51:09
@@ -181,102 +181,12 @@ do_fpu_state_restore(unsigned long r4, u
{
struct task_struct *tsk = current;
- if (!user_mode(®s)) {
- if (tsk != &init_task) {
- unlazy_fpu(tsk);
- }
- tsk = &init_task;
- if (tsk->flags & PF_USEDFPU) {
- /*
- * This weird situation can be occurred.
- *
- * There's race condition in __cli:
- *
- * (1) SR --> register
- * (2) Set IMASK of register
- * (3) SR <-- register
- *
- * Between (1) and (2), or (2) and (3) getting
- * interrupt, and interrupt handler (or
- * softirq) may use FPU.
- *
- * Then, SR.FD is overwritten by (3).
- *
- * This results init_task.PF_USEDFPU is on,
- * with SR.FD == 1.
- *
- */
- release_fpu();
- return;
- }
- }
-
grab_fpu();
- if (tsk->used_math) {
- /* Using the FPU again. */
- restore_fpu(tsk);
- } else {
- /* First time FPU user. */
- fpu_init();
- tsk->used_math = 1;
- }
- tsk->flags |= PF_USEDFPU;
- release_fpu();
-}
-
-/*
- * Change current FD flag to set FD flag back to exception
- */
-asmlinkage void
-fpu_prepare_fd(unsigned long sr, unsigned long r5, unsigned long r6,
- unsigned long r7, struct pt_regs regs)
-{
- __cli();
if (!user_mode(®s)) {
- if (init_task.flags & PF_USEDFPU)
- grab_fpu();
- else {
- if (!(sr & SR_FD)) {
- BUG();
- release_fpu();
- }
- }
+ printk(KERN_ERR "BUG: FPU is used in kernel mode.\n");
return;
}
- if (sr & SR_FD) { /* Kernel doesn't grab FPU */
- if (current->flags & PF_USEDFPU)
- grab_fpu();
- else {
- if (init_task.flags & PF_USEDFPU) {
- /*
- * This weird situation can be occurred.
- * See the comment in do_fpu_state_restore.
- */
- grab_fpu();
- save_fpu(&init_task);
- }
- }
- } else {
- if (init_task.flags & PF_USEDFPU)
- save_fpu(&init_task);
- else {
- BUG();
- release_fpu();
- }
- }
-}
-
-/* Short cut for the FPU exception */
-asmlinkage void
-enable_fpu_in_danger(void)
-{
- struct task_struct *tsk = current;
-
- if (tsk != &init_task)
- unlazy_fpu(tsk);
-
- tsk = &init_task;
if (tsk->used_math) {
/* Using the FPU again. */
restore_fpu(tsk);
Index: include/asm-sh/processor.h
===================================================================
RCS file: /cvsroot/linuxsh/linux/include/asm-sh/processor.h,v
retrieving revision 1.1.1.1
diff -u -3 -p -r1.1.1.1 processor.h
--- include/asm-sh/processor.h 2001/10/15 20:45:10 1.1.1.1
+++ include/asm-sh/processor.h 2001/12/20 02:51:09
@@ -184,7 +184,6 @@ extern void save_fpu(struct task_struct
#define unlazy_fpu(tsk) do { \
if ((tsk)->flags & PF_USEDFPU) { \
- grab_fpu(); \
save_fpu(tsk); \
} \
} while (0)
--
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