The branch main has been updated by kib:
URL:
https://cgit.FreeBSD.org/src/commit/?id=95f773e59482b1a3462d2fe3901532d51fb053b3
commit 95f773e59482b1a3462d2fe3901532d51fb053b3
Author: Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2022-08-09 00:56:54 +0000
Commit: Konstantin Belousov <k...@freebsd.org>
CommitDate: 2022-08-24 19:11:40 +0000
i386 copyout_fast: improve detection of a fault on accessing userspace
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
---
sys/i386/i386/copyout_fast.s | 16 ++++++++--------
sys/i386/i386/exception.s | 32 ++++++++++++++++++++++++++++----
2 files changed, 36 insertions(+), 12 deletions(-)
diff --git a/sys/i386/i386/copyout_fast.s b/sys/i386/i386/copyout_fast.s
index 715952f5fe20..d1d17f775872 100644
--- a/sys/i386/i386/copyout_fast.s
+++ b/sys/i386/i386/copyout_fast.s
@@ -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
diff --git a/sys/i386/i386/exception.s b/sys/i386/i386/exception.s
index f4135548fd81..42e9c474c3cd 100644
--- a/sys/i386/i386/exception.s
+++ b/sys/i386/i386/exception.s
@@ -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)
