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i386 copyout/in_fast: handle page fault from KVA access

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by delegating the work to the slow path.

Some kernel memory, like pipe buffers, is pageable.  We must not enable
interrupts, and consequently, preemption, while in critical section in
the fast copyout path, because we use pcpu buffers.  If page fault
occurs while copying from the pcpu copyout_buf to kernel memory, abort
fast path and delegate work to the slow implementation.

In collaboration with:	pho, tijl
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2022-09-08 23:15:32 +03:00
parent fd25c62278
commit 49587b8fb4
2 changed files with 24 additions and 22 deletions
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21
sys/i386/i386/copyout_fast.s
View File

@ -47,32 +47,30 @@ ENTRY(copyout_fast)
pushl %ebx
movl 20(%ebp),%ebx /* KCR3 */
movl PCPU(CURPCB),%edx
movl PCB_CR3(%edx),%edx /* UCR3 */
/* bcopy(%esi = kaddr, %edi = PCPU(copyout_buf), %ecx = len) */
movl 16(%ebp),%ecx
movl 8(%ebp),%esi
movl %esp,%eax
movl $copyout_fault,%edx
cli
movl PCPU(COPYOUT_BUF),%edi
rep; movsb
pf_y1: rep; movsb
movl 16(%ebp),%ecx /* len */
movl PCPU(COPYOUT_BUF),%esi /* kaddr */
movl 12(%ebp),%edi /* uaddr */
movl %esp,%eax
movl PCPU(TRAMPSTK),%esp
movl PCPU(CURPCB),%edx
movl PCB_CR3(%edx),%edx /* UCR3 */
movl %edx,%cr3
movl $copyout_fault,%edx
/* bcopy(%esi = PCPU(copyout_buf), %edi = udaddr, %ecx = len) */
pf_x1: rep; movsb
movl %ebx,%cr3
movl %eax,%esp
sti
xorl %eax,%eax
popl %ebx
popl %edi
@ -93,10 +91,10 @@ ENTRY(copyin_fast)
movl PCB_CR3(%eax),%edx /* UCR3 */
movl 16(%ebp),%ecx /* len */
movl 8(%ebp),%esi /* udaddr */
movl %esp,%eax
cli
movl PCPU(COPYOUT_BUF),%edi /* kaddr */
movl %esp,%eax
movl PCPU(TRAMPSTK),%esp
movl %edx,%cr3
movl $copyout_fault,%edx
@ -110,10 +108,9 @@ pf_x2: rep; movsb
movl 16(%ebp),%ecx
movl 12(%ebp),%edi
movl PCPU(COPYOUT_BUF),%esi
rep; movsb
pf_y2: rep; movsb
sti
xorl %eax,%eax
popl %ebx
popl %edi

25
sys/i386/i386/exception.s
View File

@ -130,15 +130,15 @@ IDTVEC(prot)
jmp irettraps
IDTVEC(page)
testl $PSL_VM, TF_EFLAGS-TF_ERR(%esp)
jnz 4f
jnz 5f
testb $SEL_RPL_MASK, TF_CS-TF_ERR(%esp)
jnz 4f
jnz 5f
cmpl $PMAP_TRM_MIN_ADDRESS, TF_EIP-TF_ERR(%esp)
jb 4f
jb 5f
pushl %eax
movl TF_EIP-TF_ERR+4(%esp), %eax
addl $1f, %eax
call 5f
call 6f
1: cmpl $pf_x1, %eax
je 2f
cmpl $pf_x2, %eax
@ -154,16 +154,21 @@ IDTVEC(page)
cmpl $pf_x7, %eax
je 2f
cmpl $pf_x8, %eax
jne 3f
2: popl %eax
movl %ebx, %cr3
je 2f
cmpl $pf_y1, %eax
je 3f
cmpl $pf_y2, %eax
je 3f
jmp 4f
2: movl %ebx, %cr3
3: popl %eax
movl %edx, TF_EIP-TF_ERR(%esp)
addl $4, %esp
iret
3: popl %eax
4: pushl $T_PAGEFLT
4: popl %eax
5: pushl $T_PAGEFLT
jmp alltraps
5: subl (%esp), %eax
6: subl (%esp), %eax
retl
IDTVEC(rsvd_pti)
IDTVEC(rsvd)