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Unaligned loads: Only save working registers, use jump table to load non-working registers

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Angus Gratton 2015-08-11 15:29:53 +10:00
parent 8ea4ae27e2
commit 3b3f5ea771
1 changed files with 53 additions and 23 deletions
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76
core/exception_vectors.S
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@ -273,16 +273,6 @@ UserLoadStoreExceptionHandler:
s32i a3, sp, 0x0c
s32i a4, sp, 0x10
s32i a5, sp, 0x14
s32i a6, sp, 0x18
s32i a7, sp, 0x1c
s32i a8, sp, 0x20
s32i a9, sp, 0x24
s32i a10, sp, 0x28
s32i a11, sp, 0x2c
s32i a12, sp, 0x30
s32i a13, sp, 0x34
s32i a14, sp, 0x38
s32i a15, sp, 0x3c
rsr.sar a0 // save sar in a0
/* Load the instruction we failed to execute */
@ -324,8 +314,6 @@ TODO: the exception dump will have some wrong values in it */
/* verified an 8- or 16-bit read
a2 holds instruction, a5 holds mask to apply to read value
*/
extui a2, a2, 4, 4 /* a2 now destination register 0-15 */
slli a2, a2, 2 /* a2 now offset of destination register, relative to stack pointer */
rsr.excvaddr a3 // read faulting address
ssa8l a3 /* sar is now shift to extract a3's byte */
@ -344,11 +332,19 @@ TODO: the exception dump will have some wrong values in it */
bbci a5, 15, .Lextend_sign
.Lafter_extend_sign:
/* a4 holds the correctly read value */
extui a2, a2, 4, 4 /* a2 now destination register 0-15 */
/* write read value to register slot */
/* test if a4 needs to be written directly to a register (ie not a working register) */
bgei a2, 6, .Lwrite_value_direct_reg
/* test if a4 needs to be written to a0 */
beqz a2, .Lwrite_value_a0_reg
/* otherwise, a4 needs to be written to a saved working register 'slot' on the stack */
slli a2, a2, 2
add a5, sp, a2
s32i a4, a5, 0
.Lafter_write_value:
/* Footer*/
//Increment PC
rsr.epc1 a2
@ -363,16 +359,6 @@ TODO: the exception dump will have some wrong values in it */
l32i a3, sp, 0x0c
l32i a4, sp, 0x10
l32i a5, sp, 0x14
l32i a6, sp, 0x18
l32i a7, sp, 0x1c
l32i a8, sp, 0x20
l32i a9, sp, 0x24
l32i a10, sp, 0x28
l32i a11, sp, 0x2c
l32i a12, sp, 0x30
l32i a13, sp, 0x34
l32i a14, sp, 0x38
l32i a15, sp, 0x3c
addi sp, sp, 0x40
rfe
@ -383,6 +369,50 @@ TODO: the exception dump will have some wrong values in it */
or a4, a3, a4 /* set sign bit */
j .Lafter_extend_sign
.Lwrite_value_direct_reg:
/* Directly update register index a2, in range 6-15, using value in a4 */
addi a2, a2, -6
slli a2, a2, 3 /* offset from a6, x8 */
movi a3, .Ldirect_reg_jumptable
add a2, a2, a3
jx a2
.align 8
.Ldirect_reg_jumptable:
mov a6, a4
j .Lafter_write_value
.align 8
mov a7, a4
j .Lafter_write_value
.align 8
mov a8, a4
j .Lafter_write_value
.align 8
mov a9, a4
j .Lafter_write_value
.align 8
mov a10, a4
j .Lafter_write_value
.align 8
mov a11, a4
j .Lafter_write_value
.align 8
mov a12, a4
j .Lafter_write_value
.align 8
mov a13, a4
j .Lafter_write_value
.align 8
mov a14, a4
j .Lafter_write_value
.align 8
mov a15, a4
j .Lafter_write_value
.Lwrite_value_a0_reg:
/* a0 is saved in excsave1,so just update this with value */
wsr.excsave1 a4
j .Lafter_write_value
.global _xt_user_exit
.type _xt_user_exit, @function
_xt_user_exit: