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i386 copyout_fast: improve detection of a fault on accessing userspace

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Do not blindly account a page fault occuring on the trampoline area,
as the userspace access fault.  Check that it occured exactly in the
instruction that does that.

This avoids unneeded switches of address space on faults not needing the
switch, effectively converting machine resets due to tripple faults,
into regular panics.

Reviewed by:	jhb
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D36302
This commit is contained in:
Konstantin Belousov 2022-08-09 03:56:54 +03:00
parent 0a9b374ecc
commit 95f773e594
2 changed files with 36 additions and 12 deletions
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16
sys/i386/i386/copyout_fast.s
View File

@ -93,7 +93,7 @@ ENTRY(copyout_fast)
popl %ecx
popl %edi
popl %esi
rep; movsb
pf_x1: rep; movsb
movl %ebx,%cr3
movl %eax,%esp
@ -150,7 +150,7 @@ ENTRY(copyin_fast)
popl %ecx
popl %edi
popl %esi
rep; movsb
pf_x2: rep; movsb
movl %ebx,%cr3
@ -197,7 +197,7 @@ ENTRY(fueword_fast)
cli
movl PCPU(TRAMPSTK),%esp
movl %eax,%cr3
movl (%ecx),%eax
pf_x3: movl (%ecx),%eax
movl %ebx,%cr3
movl %esi,%esp
sti
@ -226,7 +226,7 @@ ENTRY(fuword16_fast)
cli
movl PCPU(TRAMPSTK),%esp
movl %eax,%cr3
movzwl (%ecx),%eax
pf_x4: movzwl (%ecx),%eax
movl %ebx,%cr3
movl %esi,%esp
sti
@ -252,7 +252,7 @@ ENTRY(fubyte_fast)
cli
movl PCPU(TRAMPSTK),%esp
movl %eax,%cr3
movzbl (%ecx),%eax
pf_x5: movzbl (%ecx),%eax
movl %ebx,%cr3
movl %esi,%esp
sti
@ -291,7 +291,7 @@ ENTRY(suword_fast)
cli
movl PCPU(TRAMPSTK),%esp
movl %eax,%cr3
movl %edi,(%ecx)
pf_x6: movl %edi,(%ecx)
movl %ebx,%cr3
movl %esi,%esp
sti
@ -319,7 +319,7 @@ ENTRY(suword16_fast)
cli
movl PCPU(TRAMPSTK),%esp
movl %eax,%cr3
movw %di,(%ecx)
pf_x7: movw %di,(%ecx)
movl %ebx,%cr3
movl %esi,%esp
sti
@ -348,7 +348,7 @@ ENTRY(subyte_fast)
movl PCPU(TRAMPSTK),%esp
movl %eax,%cr3
movl %edi,%eax
movb %al,(%ecx)
pf_x8: movb %al,(%ecx)
movl %ebx,%cr3
movl %esi,%esp
sti

32
sys/i386/i386/exception.s
View File

@ -130,17 +130,41 @@ IDTVEC(prot)
jmp irettraps
IDTVEC(page)
testl $PSL_VM, TF_EFLAGS-TF_ERR(%esp)
jnz 1f
jnz 4f
testb $SEL_RPL_MASK, TF_CS-TF_ERR(%esp)
jnz 1f
jnz 4f
cmpl $PMAP_TRM_MIN_ADDRESS, TF_EIP-TF_ERR(%esp)
jb 1f
jb 4f
pushl %eax
movl TF_EIP-TF_ERR+4(%esp), %eax
addl $1f, %eax
call 5f
1: cmpl $pf_x1, %eax
je 2f
cmpl $pf_x2, %eax
je 2f
cmpl $pf_x3, %eax
je 2f
cmpl $pf_x4, %eax
je 2f
cmpl $pf_x5, %eax
je 2f
cmpl $pf_x6, %eax
je 2f
cmpl $pf_x7, %eax
je 2f
cmpl $pf_x8, %eax
jne 3f
2: popl %eax
movl %ebx, %cr3
movl %edx, TF_EIP-TF_ERR(%esp)
addl $4, %esp
iret
1: pushl $T_PAGEFLT
3: popl %eax
4: pushl $T_PAGEFLT
jmp alltraps
5: subl (%esp), %eax
retl
IDTVEC(rsvd_pti)
IDTVEC(rsvd)
pushl $0; TRAP(T_RESERVED)