git: 95f773e59482 - main - i386 copyout_fast: improve detection of a fault on accessing userspace

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=95f773e59482b1a3462d2fe3901532d51fb053b3

commit 95f773e59482b1a3462d2fe3901532d51fb053b3
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2022-08-09 00:56:54 +0000
Commit:     Konstantin Belousov <kib@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)