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Fetching buffer arguments from user space.

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This commit is contained in:
Yifan Wu 2020-12-06 13:56:13 +08:00
parent d38b24a9cb
commit 9366099b28
20 changed files with 405 additions and 82 deletions
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44
os/src/trap/trap.S
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@ -5,16 +5,14 @@
.macro LOAD_GP n
ld x\n, \n*8(sp)
.endm
.section .text
.section .text.trampoline
.globl __alltraps
.globl __restore
.align 2
__alltraps:
csrrw sp, sscratch, sp
# now sp->kernel stack, sscratch->user stack
# allocate a TrapContext on kernel stack
addi sp, sp, -34*8
# save general-purpose registers
# now sp->*TrapContext in user space, sscratch->user stack
# save other general purpose registers
sd x1, 1*8(sp)
# skip sp(x2), we will save it later
sd x3, 3*8(sp)
@ -25,28 +23,40 @@ __alltraps:
SAVE_GP %n
.set n, n+1
.endr
# we can use t0/t1/t2 freely, because they were saved on kernel stack
# we can use t0/t1/t2 freely, because they have been saved in TrapContext
csrr t0, sstatus
csrr t1, sepc
sd t0, 32*8(sp)
sd t1, 33*8(sp)
# read user stack from sscratch and save it on the kernel stack
# read user stack from sscratch and save it in TrapContext
csrr t2, sscratch
sd t2, 2*8(sp)
# set input argument of trap_handler(cx: &mut TrapContext)
mv a0, sp
call trap_handler
# load kernel_satp into t0
ld t0, 34*8(sp)
# load trap_handler into t1
ld t1, 36*8(sp)
# move to kernel_sp
ld sp, 35*8(sp)
# switch to kernel space
csrw satp, t0
sfence.vma
# jump to trap_handler
jr t1
__restore:
# now sp->kernel stack(after allocated), sscratch->user stack
# a0: *TrapContext in user space(Constant); a1: user space token
# switch to user space
csrw satp, a1
sfence.vma
csrw sscratch, a0
mv sp, a0
# now sp points to TrapContext in user space, start restoring based on it
# restore sstatus/sepc
ld t0, 32*8(sp)
ld t1, 33*8(sp)
ld t2, 2*8(sp)
csrw sstatus, t0
csrw sepc, t1
csrw sscratch, t2
# restore general-purpuse registers except sp/tp
# restore general purpose registers except x0/sp/tp
ld x1, 1*8(sp)
ld x3, 3*8(sp)
.set n, 5
@ -54,8 +64,6 @@ __restore:
LOAD_GP %n
.set n, n+1
.endr
# release TrapContext on kernel stack
addi sp, sp, 34*8
# now sp->kernel stack, sscratch->user stack
csrrw sp, sscratch, sp
# back to user stack
ld sp, 2*8(sp)
sret