NetBSD Problem Report #57949

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Date: Mon, 19 Feb 2024 21:23:36 +0000 (UTC)
From: campbell+netbsd@mumble.net
Reply-To: campbell+netbsd@mumble.net
To: gnats-bugs@NetBSD.org
Subject: fetestexcept disables all floating-point exception traps as a side effect
X-Send-Pr-Version: www-1.0

>Number:         57949
>Category:       port-amd64
>Synopsis:       fetestexcept disables all floating-point exception traps as a side effect
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Feb 19 21:25:00 +0000 2024
>Closed-Date:    Fri Feb 23 19:11:09 +0000 2024
>Last-Modified:  Fri Feb 23 19:11:09 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current, 10, 9, 8, 7, 6
>Organization:
The NetBSD Exception
>Environment:
amd64
>Description:
fetestexcept uses fnstenv, which has the side effect of masking all x87 floating-point exception traps.

There's no need to use this; it should just use fnstcw (and stmxcsr).
>How-To-Repeat:
	unsigned enabled0, raised, enabled1;

	feclearexcept(FE_ALL_EXCEPT);
	fedisableexcept(FE_ALL_EXCEPT);

	feenableexcept(FE_ALL_EXCEPT);
	enabled0 = fegetexcept();
	raised = fetestexcept(FE_ALL_EXCEPT);
	enabled1 = fegetexcept();

	printf("enabled0:	0x%x\n", enabled0);
	printf("raised:		0x%x\n", raised);
	printf("enabled1:	0x%x\n", enabled1);

Expected enabled0 and enabled1 to both be 0x3d, but instead enabled0 is 0x3d and enabled1 is 0.
>Fix:
Yes, please!

>Release-Note:

>Audit-Trail:
From: "Taylor R Campbell" <riastradh@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/57949 CVS commit: src/tests/lib/libm
Date: Mon, 19 Feb 2024 23:19:11 +0000

 Module Name:	src
 Committed By:	riastradh
 Date:		Mon Feb 19 23:19:11 UTC 2024

 Modified Files:
 	src/tests/lib/libm: t_fenv.c

 Log Message:
 fenv(3): Add test for PR port-amd64/57949.


 To generate a diff of this commit:
 cvs rdiff -u -r1.13 -r1.14 src/tests/lib/libm/t_fenv.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

From: Taylor R Campbell <riastradh@NetBSD.org>
To: gnats-bugs@NetBSD.org
Cc: netbsd-bugs@NetBSD.org
Subject: Re: port-amd64/57949: fetestexcept disables all floating-point exception traps as a side effect
Date: Mon, 19 Feb 2024 23:58:07 +0000

 This is a multi-part message in MIME format.
 --=_fvz4bw6Sgb7EvIjKFB6Nr1oMeWUc8Daj

 The attached patch should fix this -- I'll commit once the releng
 testbed has confirmed my test is working to detect the problem.

 --=_fvz4bw6Sgb7EvIjKFB6Nr1oMeWUc8Daj
 Content-Type: text/plain; charset="ISO-8859-1"; name="pr57949-x86fetestexcept"
 Content-Transfer-Encoding: quoted-printable
 Content-Disposition: attachment; filename="pr57949-x86fetestexcept.patch"

 From 8af3bc587abd07af6d32acf4f5dc7803ac28ec23 Mon Sep 17 00:00:00 2001
 From: Taylor R Campbell <riastradh@NetBSD.org>
 Date: Mon, 19 Feb 2024 23:24:13 +0000
 Subject: [PATCH] fenv(3): Fix fetestexcept to avoid side effects on trap
  state.

 PR port-amd64/57949
 ---
  lib/libm/arch/x86_64/fenv.c | 10 +---------
  tests/lib/libm/t_fenv.c     |  3 ---
  2 files changed, 1 insertion(+), 12 deletions(-)

 diff --git a/lib/libm/arch/x86_64/fenv.c b/lib/libm/arch/x86_64/fenv.c
 index cd09c8bbd597..7d1816c15a72 100644
 --- a/lib/libm/arch/x86_64/fenv.c
 +++ b/lib/libm/arch/x86_64/fenv.c
 @@ -259,7 +259,6 @@ fesetexceptflag(const fexcept_t *flagp, int excepts)
  int
  fetestexcept(int excepts)
  {
 -	fenv_t fenv;
  	uint32_t mxcsr;
  	uint16_t status;
  	int ex;
 @@ -268,17 +267,10 @@ fetestexcept(int excepts)
 =20
  	ex =3D excepts & FE_ALL_EXCEPT;
 =20
 -	/* Store the current x87 floating-point environment */
 -	memset(&fenv, 0, sizeof(fenv));
 -
 -	__fnstenv(&fenv);
  	__fnstsw(&status);
 -
 -	/* Store the MXCSR register state */
 -	__stmxcsr(&fenv.mxcsr);
  	__stmxcsr(&mxcsr);
 =20
 -	return ((fenv.x87.status | fenv.mxcsr) & ex);
 +	return ((status | mxcsr) & ex);
  }
 =20
  /*
 diff --git a/tests/lib/libm/t_fenv.c b/tests/lib/libm/t_fenv.c
 index 038da828c7c6..deacead62b6f 100644
 --- a/tests/lib/libm/t_fenv.c
 +++ b/tests/lib/libm/t_fenv.c
 @@ -364,9 +364,6 @@ ATF_TC_BODY(fetestexcept_trap, tc)
  	    "fegetexcept()=3D0x%x FE_ALL_EXCEPT=3D0x%x", except, FE_ALL_EXCEPT);
 =20
  	(void)fetestexcept(FE_ALL_EXCEPT);
 -#ifdef __x86_64__
 -	atf_tc_expect_fail("PR port-amd64/57949");
 -#endif
  	ATF_CHECK_EQ_MSG((except =3D fegetexcept()), FE_ALL_EXCEPT,
  	    "fegetexcept()=3D0x%x FE_ALL_EXCEPT=3D0x%x", except, FE_ALL_EXCEPT);
  }

 --=_fvz4bw6Sgb7EvIjKFB6Nr1oMeWUc8Daj--

From: "Taylor R Campbell" <riastradh@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/57949 CVS commit: src
Date: Tue, 20 Feb 2024 03:53:49 +0000

 Module Name:	src
 Committed By:	riastradh
 Date:		Tue Feb 20 03:53:49 UTC 2024

 Modified Files:
 	src/lib/libm/arch/x86_64: fenv.c
 	src/tests/lib/libm: t_fenv.c

 Log Message:
 fenv(3): Fix fetestexcept to avoid side effects on trap state.

 PR port-amd64/57949


 To generate a diff of this commit:
 cvs rdiff -u -r1.10 -r1.11 src/lib/libm/arch/x86_64/fenv.c
 cvs rdiff -u -r1.14 -r1.15 src/tests/lib/libm/t_fenv.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->pending-pullups
State-Changed-By: riastradh@NetBSD.org
State-Changed-When: Thu, 22 Feb 2024 14:54:24 +0000
State-Changed-Why:
pullup-10 #602 https://releng.netbsd.org/cgi-bin/req-10.cgi?show=602
pullup-9 #1801 https://releng.netbsd.org/cgi-bin/req-9.cgi?show=1801
pullup-8 #1937 https://releng.netbsd.org/cgi-bin/req-8.cgi?show=1937


From: "Martin Husemann" <martin@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/57949 CVS commit: [netbsd-10] src
Date: Fri, 23 Feb 2024 18:09:23 +0000

 Module Name:	src
 Committed By:	martin
 Date:		Fri Feb 23 18:09:23 UTC 2024

 Modified Files:
 	src/lib/libm/arch/x86_64 [netbsd-10]: fenv.c
 	src/tests/lib/libm [netbsd-10]: t_fenv.c

 Log Message:
 Pull up following revision(s) (requested by riastradh in ticket #603):

 	tests/lib/libm/t_fenv.c: revision 1.14
 	tests/lib/libm/t_fenv.c: revision 1.15
 	lib/libm/arch/x86_64/fenv.c: revision 1.11

 fenv(3): Add test for PR port-amd64/57949.

 fenv(3): Fix fetestexcept to avoid side effects on trap state.

 PR port-amd64/57949


 To generate a diff of this commit:
 cvs rdiff -u -r1.10 -r1.10.2.1 src/lib/libm/arch/x86_64/fenv.c
 cvs rdiff -u -r1.6 -r1.6.10.1 src/tests/lib/libm/t_fenv.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

From: "Martin Husemann" <martin@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/57949 CVS commit: [netbsd-9] src
Date: Fri, 23 Feb 2024 18:13:54 +0000

 Module Name:	src
 Committed By:	martin
 Date:		Fri Feb 23 18:13:54 UTC 2024

 Modified Files:
 	src/lib/libm/arch/x86_64 [netbsd-9]: fenv.c
 	src/tests/lib/libm [netbsd-9]: t_fenv.c

 Log Message:
 Pull up following revision(s) (requested by riastradh in ticket #1801):

 	tests/lib/libm/t_fenv.c: revision 1.14
 	tests/lib/libm/t_fenv.c: revision 1.15
 	lib/libm/arch/x86_64/fenv.c: revision 1.11

 fenv(3): Add test for PR port-amd64/57949.

 fenv(3): Fix fetestexcept to avoid side effects on trap state.

 PR port-amd64/57949


 To generate a diff of this commit:
 cvs rdiff -u -r1.7 -r1.7.14.1 src/lib/libm/arch/x86_64/fenv.c
 cvs rdiff -u -r1.6 -r1.6.2.1 src/tests/lib/libm/t_fenv.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

From: "Martin Husemann" <martin@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/57949 CVS commit: [netbsd-8] src
Date: Fri, 23 Feb 2024 18:15:53 +0000

 Module Name:	src
 Committed By:	martin
 Date:		Fri Feb 23 18:15:53 UTC 2024

 Modified Files:
 	src/lib/libm/arch/x86_64 [netbsd-8]: fenv.c
 	src/tests/lib/libm [netbsd-8]: t_fenv.c

 Log Message:
 Pull up following revision(s) (requested by riastradh in ticket #1937):

 	tests/lib/libm/t_fenv.c: revision 1.14
 	tests/lib/libm/t_fenv.c: revision 1.15
 	lib/libm/arch/x86_64/fenv.c: revision 1.11

 fenv(3): Add test for PR port-amd64/57949.

 fenv(3): Fix fetestexcept to avoid side effects on trap state.

 PR port-amd64/57949


 To generate a diff of this commit:
 cvs rdiff -u -r1.7 -r1.7.4.1 src/lib/libm/arch/x86_64/fenv.c
 cvs rdiff -u -r1.3 -r1.3.8.1 src/tests/lib/libm/t_fenv.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: pending-pullups->closed
State-Changed-By: riastradh@NetBSD.org
State-Changed-When: Fri, 23 Feb 2024 19:11:09 +0000
State-Changed-Why:
fixed and pulled up to 10, 9, 8


>Unformatted:

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