git: 91aae953cb80 - main - amd64: clear PSL.AC in the right frame

[Konstantin Belousov]

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=91aae953cb807d6fb7a70782b323bf9beb60d7c9

commit 91aae953cb807d6fb7a70782b323bf9beb60d7c9
Author:     Konstantin Belousov <kib at FreeBSD.org>
AuthorDate: 2021-05-22 19:48:36 +0000
Commit:     Konstantin Belousov <kib at FreeBSD.org>
CommitDate: 2021-05-25 15:20:46 +0000

    amd64: clear PSL.AC in the right frame
    
    If copyin family of routines fault, kernel does clear PSL.AC on the
    fault entry, but the AC flag of the faulted frame is kept intact.  Since
    onfault handler is effectively jump, AC survives until syscall exit.
    
    Reported by:    m00nbsd, via Sony
    Reviewed by:    markj
    Sponsored by:   The FreeBSD Foundation
    admbugs:        975
---
 sys/amd64/amd64/support.S           | 18 ++++++++++++------
 sys/amd64/linux/linux_support.s     |  5 ++++-
 sys/amd64/linux32/linux32_support.s |  5 ++++-
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/sys/amd64/amd64/support.S b/sys/amd64/amd64/support.S
index 0db6f2f04099..d511fe265996 100644
--- a/sys/amd64/amd64/support.S
+++ b/sys/amd64/amd64/support.S
@@ -919,9 +919,11 @@ ENTRY(copyin_smap_erms)
 END(copyin_smap_erms)
 
 	ALIGN_TEXT
-	/* Trap entry clears PSL.AC */
 copy_fault:
-	movq	$0,PCB_ONFAULT(%r11)
+	testl	$CPUID_STDEXT_SMAP,cpu_stdext_feature(%rip)
+	je	1f
+	clac
+1:	movq	$0,PCB_ONFAULT(%r11)
 	movl	$EFAULT,%eax
 	POP_FRAME_POINTER
 	ret
@@ -1358,9 +1360,11 @@ ENTRY(subyte_smap)
 END(subyte_smap)
 
 	ALIGN_TEXT
-	/* Fault entry clears PSL.AC */
 fusufault:
-	movq	PCPU(CURPCB),%rcx
+	testl	$CPUID_STDEXT_SMAP,cpu_stdext_feature(%rip)
+	je	1f
+	clac
+1:	movq	PCPU(CURPCB),%rcx
 	xorl	%eax,%eax
 	movq	%rax,PCB_ONFAULT(%rcx)
 	decq	%rax
@@ -1443,8 +1447,10 @@ ENTRY(copyinstr_smap)
 END(copyinstr_smap)
 
 cpystrflt:
-	/* Fault entry clears PSL.AC */
-	movl	$EFAULT,%eax
+	testl	$CPUID_STDEXT_SMAP,cpu_stdext_feature(%rip)
+	je	1f
+	clac
+1:	movl	$EFAULT,%eax
 cpystrflt_x:
 	/* set *lencopied and return %eax */
 	movq	$0,PCB_ONFAULT(%r9)
diff --git a/sys/amd64/linux/linux_support.s b/sys/amd64/linux/linux_support.s
index 45eb565f667d..bb1c218bdf89 100644
--- a/sys/amd64/linux/linux_support.s
+++ b/sys/amd64/linux/linux_support.s
@@ -34,7 +34,10 @@
 #include "assym.inc"
 
 futex_fault:
-	movq	$0,PCB_ONFAULT(%r8)
+	testl	$CPUID_STDEXT_SMAP,cpu_stdext_feature(%rip)
+	je	1f
+	clac
+1:	movq	$0,PCB_ONFAULT(%r8)
 	movl	$-EFAULT,%eax
 	ret
 
diff --git a/sys/amd64/linux32/linux32_support.s b/sys/amd64/linux32/linux32_support.s
index da076010c13c..86f3d11b552b 100644
--- a/sys/amd64/linux32/linux32_support.s
+++ b/sys/amd64/linux32/linux32_support.s
@@ -34,7 +34,10 @@
 #include "assym.inc"
 
 futex_fault:
-	movq	$0,PCB_ONFAULT(%r8)
+	testl	$CPUID_STDEXT_SMAP,cpu_stdext_feature(%rip)
+	je	1f
+	clac
+1:	movq	$0,PCB_ONFAULT(%r8)
 	movl	$-EFAULT,%eax
 	ret