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xtensa: introduce spill_registers_kernel macro

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Most in-kernel users want registers spilled on the kernel stack and
don't require PS.EXCM to be set. That means that they don't need fixup
routine and could reuse regular window overflow mechanism for that,
which makes spill routine very simple.

Cc: stable@vger.kernel.org
Suggested-by: Chris Zankel <chris@zankel.net>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
This commit is contained in:
Max Filippov 2014-01-22 08:04:43 +04:00
parent 45ec8860be
commit e2fd1374c7
2 changed files with 77 additions and 29 deletions
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46
arch/xtensa/include/asm/traps.h
View file

@ -23,25 +23,37 @@ void secondary_trap_init(void);
static inline void spill_registers(void)
{
#if XCHAL_NUM_AREGS > 16
__asm__ __volatile__ (
"movi a14, "__stringify((1 << PS_EXCM_BIT) | LOCKLEVEL)"\n\t"
"mov a12, a0\n\t"
"rsr a13, sar\n\t"
"xsr a14, ps\n\t"
"movi a0, _spill_registers\n\t"
"rsync\n\t"
"callx0 a0\n\t"
"mov a0, a12\n\t"
"wsr a13, sar\n\t"
"wsr a14, ps\n\t"
: :
#if defined(CONFIG_FRAME_POINTER)
: "a2", "a3", "a4", "a11", "a12", "a13", "a14", "a15",
#else
: "a2", "a3", "a4", "a7", "a11", "a12", "a13", "a14", "a15",
" call12 1f\n"
" _j 2f\n"
" retw\n"
" .align 4\n"
"1:\n"
" _entry a1, 48\n"
" addi a12, a0, 3\n"
#if XCHAL_NUM_AREGS > 32
" .rept (" __stringify(XCHAL_NUM_AREGS) " - 32) / 12\n"
" _entry a1, 48\n"
" mov a12, a0\n"
" .endr\n"
#endif
" _entry a1, 48\n"
#if XCHAL_NUM_AREGS % 12 == 0
" mov a8, a8\n"
#elif XCHAL_NUM_AREGS % 12 == 4
" mov a12, a12\n"
#elif XCHAL_NUM_AREGS % 12 == 8
" mov a4, a4\n"
#endif
" retw\n"
"2:\n"
: : : "a12", "a13", "memory");
#else
__asm__ __volatile__ (
" mov a12, a12\n"
: : : "memory");
#endif
"memory");
}
#endif /* _XTENSA_TRAPS_H */

60
arch/xtensa/kernel/entry.S
View file

@ -1794,6 +1794,43 @@ ENTRY(system_call)
ENDPROC(system_call)
/*
* Spill live registers on the kernel stack macro.
*
* Entry condition: ps.woe is set, ps.excm is cleared
* Exit condition: windowstart has single bit set
* May clobber: a12, a13
*/
.macro spill_registers_kernel
#if XCHAL_NUM_AREGS > 16
call12 1f
_j 2f
retw
.align 4
1:
_entry a1, 48
addi a12, a0, 3
#if XCHAL_NUM_AREGS > 32
.rept (XCHAL_NUM_AREGS - 32) / 12
_entry a1, 48
mov a12, a0
.endr
#endif
_entry a1, 48
#if XCHAL_NUM_AREGS % 12 == 0
mov a8, a8
#elif XCHAL_NUM_AREGS % 12 == 4
mov a12, a12
#elif XCHAL_NUM_AREGS % 12 == 8
mov a4, a4
#endif
retw
2:
#else
mov a12, a12
#endif
.endm
/*
* Task switch.
@ -1806,21 +1843,20 @@ ENTRY(_switch_to)
entry a1, 16
mov a12, a2 # preserve 'prev' (a2)
mov a13, a3 # and 'next' (a3)
mov a10, a2 # preserve 'prev' (a2)
mov a11, a3 # and 'next' (a3)
l32i a4, a2, TASK_THREAD_INFO
l32i a5, a3, TASK_THREAD_INFO
save_xtregs_user a4 a6 a8 a9 a10 a11 THREAD_XTREGS_USER
save_xtregs_user a4 a6 a8 a9 a12 a13 THREAD_XTREGS_USER
s32i a0, a12, THREAD_RA # save return address
s32i a1, a12, THREAD_SP # save stack pointer
s32i a0, a10, THREAD_RA # save return address
s32i a1, a10, THREAD_SP # save stack pointer
/* Disable ints while we manipulate the stack pointer. */
movi a14, (1 << PS_EXCM_BIT) | LOCKLEVEL
xsr a14, ps
rsil a14, LOCKLEVEL
rsr a3, excsave1
rsync
s32i a3, a3, EXC_TABLE_FIXUP /* enter critical section */
@ -1835,7 +1871,7 @@ ENTRY(_switch_to)
/* Flush register file. */
call0 _spill_registers # destroys a3, a4, and SAR
spill_registers_kernel
/* Set kernel stack (and leave critical section)
* Note: It's save to set it here. The stack will not be overwritten
@ -1851,13 +1887,13 @@ ENTRY(_switch_to)
/* restore context of the task 'next' */
l32i a0, a13, THREAD_RA # restore return address
l32i a1, a13, THREAD_SP # restore stack pointer
l32i a0, a11, THREAD_RA # restore return address
l32i a1, a11, THREAD_SP # restore stack pointer
load_xtregs_user a5 a6 a8 a9 a10 a11 THREAD_XTREGS_USER
load_xtregs_user a5 a6 a8 a9 a12 a13 THREAD_XTREGS_USER
wsr a14, ps
mov a2, a12 # return 'prev'
mov a2, a10 # return 'prev'
rsync
retw