From aea6303d6c5fa276ea10887dab968ee0f3c79328 Mon Sep 17 00:00:00 2001

From: Stefan Liebler <stli@linux.vnet.ibm.com>

Date: Thu, 8 Oct 2015 10:30:00 +0200

Subject: [PATCH 04/30] S390: Fix handling of DXC-byte in FPC-register.

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upstream-commit-id: 5d96fe8c0dc3450bafe6c2aae2dabc76819df3e0

https://www.sourceware.org/ml/libc-alpha/2015-07/msg00074.html

On s390, the DXC(data-exception-code)-byte in FPC(floating-point-control)-

register contains a code of the last occured exception.

If bits 6 and 7 of DXC-byte are zero, the bits 0-5 correspond to the

ieee-exception flag bits.

The current implementation always uses these bits as ieee-exception flag bits.

fetestexcept() reports any exception after the first usage of a

vector-instruction in a process, because it raises an "vector instruction

exception" with DXC-code 0xFE.

This patch fixes the handling of the DXC-byte. The DXC-Byte is only handled

if bits 6 and 7 are zero.

The #define _FPU_RESERVED is extended by the DXC-Byte.

Otherwise the tests math/test-fpucw-static and math/test-fpucw-ieee-static

fails, because DXC-Byte contains the vector instruction exception when reaching

main(). This exception was triggered by strrchr() call in __init_misc().

__init_misc() is called after __setfpucw () in __libc_init_first().

The field __ieee_instruction_pointer in struct fenv_t is renamed to __unused

because it is a relict from commit "Remove PTRACE_PEEKUSER"

(87b9b50f0d4b92248905e95a06a13c513dc45e59) and isn´t used anymore.

ChangeLog:

	[BZ #18610]

	* sysdeps/s390/fpu/bits/fenv.h (fenv_t): Rename

	__ieee_instruction_pointer to __unused.

	* sysdeps/s390/fpu/fesetenv.c (__fesetenv): Remove usage of

	__ieee_instruction_pointer.

	* sysdeps/s390/fpu/fclrexcpt.c (feclearexcept): Fix dxc-field handling.

	* sysdeps/s390/fpu/fgetexcptflg.c (fegetexceptflag): Likewise.

	* sysdeps/s390/fpu/fsetexcptflg.c (fesetexceptflag): Likewise.

	* sysdeps/s390/fpu/ftestexcept.c (fetestexcept): Likewise.

	* sysdeps/s390/fpu/fpu_control.h (_FPU_RESERVED):

	Mark dxc-field as reserved.

---

 sysdeps/s390/fpu/bits/fenv.h    |  6 ++++--

 sysdeps/s390/fpu/fclrexcpt.c    |  7 ++++++-

 sysdeps/s390/fpu/fesetenv.c     |  2 --

 sysdeps/s390/fpu/fgetexcptflg.c |  8 +++++++-

 sysdeps/s390/fpu/fpu_control.h  |  6 +++---

 sysdeps/s390/fpu/fsetexcptflg.c | 15 ++++++++++++---

 sysdeps/s390/fpu/ftestexcept.c  | 12 +++++++++---

 7 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/sysdeps/s390/fpu/bits/fenv.h b/sysdeps/s390/fpu/bits/fenv.h

index 88c6f7a..93177dc 100644

--- a/sysdeps/s390/fpu/bits/fenv.h

+++ b/sysdeps/s390/fpu/bits/fenv.h

@@ -77,8 +77,10 @@ typedef unsigned int fexcept_t; /* size of fpc */

 typedef struct

 {

   fexcept_t __fpc;

-  void *__ieee_instruction_pointer;

-  /* failing instruction for ieee exceptions */

+  void *__unused;

+  /* The field __unused (formerly __ieee_instruction_pointer) is a relict from

+     commit "Remove PTRACE_PEEKUSER" (87b9b50f0d4b92248905e95a06a13c513dc45e59)

+     and isn´t used anymore.  */

 } fenv_t;

 /* If the default argument is used we use this value.  */

diff --git a/sysdeps/s390/fpu/fclrexcpt.c b/sysdeps/s390/fpu/fclrexcpt.c

index 3e8d9bb..c2647ba 100644

--- a/sysdeps/s390/fpu/fclrexcpt.c

+++ b/sysdeps/s390/fpu/fclrexcpt.c

@@ -29,7 +29,12 @@ feclearexcept (int excepts)

   _FPU_GETCW (temp);

   /* Clear the relevant bits.  */

-  temp &= ~((excepts << FPC_DXC_SHIFT)|(excepts << FPC_FLAGS_SHIFT));

+  temp &= ~(excepts << FPC_FLAGS_SHIFT);

+  if ((temp & FPC_NOT_FPU_EXCEPTION) == 0)

+    /* Bits 6, 7 of dxc-byte are zero,

+       thus bits 0-5 of dxc-byte correspond to the flag-bits.

+       Clear the relevant bits in flags and dxc-field.  */

+    temp &= ~(excepts << FPC_DXC_SHIFT);

   /* Put the new data in effect.  */

   _FPU_SETCW (temp);

diff --git a/sysdeps/s390/fpu/fesetenv.c b/sysdeps/s390/fpu/fesetenv.c

index b534205..a4a0bb5 100644

--- a/sysdeps/s390/fpu/fesetenv.c

+++ b/sysdeps/s390/fpu/fesetenv.c

@@ -32,12 +32,10 @@ fesetenv (const fenv_t *envp)

   if (envp == FE_DFL_ENV)

     {

       env.__fpc = _FPU_DEFAULT;

-      env.__ieee_instruction_pointer = 0;

     }

   else if (envp == FE_NOMASK_ENV)

     {

       env.__fpc = FPC_EXCEPTION_MASK;

-      env.__ieee_instruction_pointer = 0;

     }

   else

     env = (*envp);

diff --git a/sysdeps/s390/fpu/fgetexcptflg.c b/sysdeps/s390/fpu/fgetexcptflg.c

index 7457678..7941904 100644

--- a/sysdeps/s390/fpu/fgetexcptflg.c

+++ b/sysdeps/s390/fpu/fgetexcptflg.c

@@ -27,7 +27,13 @@ fegetexceptflag (fexcept_t *flagp, int excepts)

   /* Get the current exceptions.  */

   _FPU_GETCW (temp);

-  newexcepts = (excepts << FPC_DXC_SHIFT) | (excepts << FPC_FLAGS_SHIFT);

+  newexcepts = excepts << FPC_FLAGS_SHIFT;

+  if ((temp & FPC_NOT_FPU_EXCEPTION) == 0)

+    /* Bits 6, 7 of dxc-byte are zero,

+       thus bits 0-5 of dxc-byte correspond to the flag-bits.

+       Evaluate flags and last dxc-exception-code.  */

+    newexcepts |= excepts << FPC_DXC_SHIFT;

+

   *flagp = temp & newexcepts;

   /* Success.  */

diff --git a/sysdeps/s390/fpu/fpu_control.h b/sysdeps/s390/fpu/fpu_control.h

index af81bc2..dba904d 100644

--- a/sysdeps/s390/fpu/fpu_control.h

+++ b/sysdeps/s390/fpu/fpu_control.h

@@ -19,12 +19,12 @@

    <http://www.gnu.org/licenses/>.  */

 #ifndef _FPU_CONTROL_H

-# define _FPU_CONTROL_H

+#define _FPU_CONTROL_H

-# include <features.h>

+#include <features.h>

 /* These bits are reserved are not changed.  */

-# define _FPU_RESERVED 0x070700FC

+#define _FPU_RESERVED 0x0707FFFC

 /* The fdlibm code requires no interrupts for exceptions.  Don't

    change the rounding mode, it would break long double I/O!  */

diff --git a/sysdeps/s390/fpu/fsetexcptflg.c b/sysdeps/s390/fpu/fsetexcptflg.c

index aada675..85c68e8 100644

--- a/sysdeps/s390/fpu/fsetexcptflg.c

+++ b/sysdeps/s390/fpu/fsetexcptflg.c

@@ -24,16 +24,25 @@

 int

 fesetexceptflag (const fexcept_t *flagp, int excepts)

 {

-  fexcept_t temp,newexcepts;

+  fexcept_t temp, newexcepts;

   /* Get the current environment.  We have to do this since we cannot

      separately set the status word.  */

   _FPU_GETCW (temp);

   /* Install the new exception bits in the Accrued Exception Byte.  */

   excepts = excepts & FE_ALL_EXCEPT;

-  newexcepts = (excepts << FPC_DXC_SHIFT) | (excepts << FPC_FLAGS_SHIFT);

+  newexcepts = excepts << FPC_FLAGS_SHIFT;

   temp &= ~newexcepts;

-  temp |= *flagp & newexcepts;

+  if ((temp & FPC_NOT_FPU_EXCEPTION) == 0)

+    /* Bits 6, 7 of dxc-byte are zero,

+       thus bits 0-5 of dxc-byte correspond to the flag-bits.

+       Clear given exceptions in dxc-field.  */

+    temp &= ~(excepts << FPC_DXC_SHIFT);

+

+  /* Integrate dxc-byte of flagp into flags. The dxc-byte of flagp contains

+     either an ieee-exception or 0 (see fegetexceptflag).  */

+  temp |= (*flagp | ((*flagp >> FPC_DXC_SHIFT) << FPC_FLAGS_SHIFT))

+    & newexcepts;

   /* Store the new status word (along with the rest of the environment.

      Possibly new exceptions are set but they won't get executed unless

diff --git a/sysdeps/s390/fpu/ftestexcept.c b/sysdeps/s390/fpu/ftestexcept.c

index 5594994..c36aefd 100644

--- a/sysdeps/s390/fpu/ftestexcept.c

+++ b/sysdeps/s390/fpu/ftestexcept.c

@@ -23,11 +23,17 @@

 int

 fetestexcept (int excepts)

 {

-  fexcept_t temp;

+  fexcept_t temp, res;

   /* Get current exceptions.  */

   _FPU_GETCW (temp);

-  temp = (temp >> FPC_DXC_SHIFT) | (temp >> FPC_FLAGS_SHIFT);

-  return temp & excepts & FE_ALL_EXCEPT;

+  res = temp >> FPC_FLAGS_SHIFT;

+  if ((temp & FPC_NOT_FPU_EXCEPTION) == 0)

+    /* Bits 6, 7 of dxc-byte are zero,

+       thus bits 0-5 of dxc-byte correspond to the flag-bits.

+       Evaluate flags and last dxc-exception-code.  */

+    res |= temp >> FPC_DXC_SHIFT;

+

+  return res & excepts & FE_ALL_EXCEPT;

 }

 libm_hidden_def (fetestexcept)

-- 

2.3.0