Re: [Patch] / 0 should send SIGFPE not SIGTRAP...

[David Daney <ddaney at avtrex dot com>]

Maciej W. Rozycki wrote:

> On Fri, 11 Jun 2004 cgd@broadcom.com wrote:
>  
>
> > Unfortunately, at this point, Linux should probably accept the
> > divide-by-zero code in both locations.
> >    
>
> I think that's not a big trouble for Linux -- the path is rare and not
> critical for performance.
>
>  
How about the attached (lightly tested) patch?

David Daney.
*** ../linux-avtrex/linux/arch/mips/kernel/traps.c	2004-02-26 11:14:09.000000000 -0800
--- arch/mips/kernel/traps.c	2004-06-11 13:43:00.000000000 -0700
***************
*** 597,615 ****
  	 * There is the ancient bug in the MIPS assemblers that the break
  	 * code starts left to bit 16 instead to bit 6 in the opcode.
  	 * Gas is bug-compatible ...
! 	 */
! 	bcode = ((opcode >> 16) & ((1 << 20) - 1));
! 
! 	/*
  	 * (A short test says that IRIX 5.3 sends SIGTRAP for all break
  	 * insns, even for break codes that indicate arithmetic failures.
  	 * Weird ...)
  	 * But should we continue the brokenness???  --macro
  	 */
  	switch (bcode) {
! 	case 6:
! 	case 7:
! 		if (bcode == 7)
  			info.si_code = FPE_INTDIV;
  		else
  			info.si_code = FPE_INTOVF;
--- 597,621 ----
  	 * There is the ancient bug in the MIPS assemblers that the break
  	 * code starts left to bit 16 instead to bit 6 in the opcode.
  	 * Gas is bug-compatible ...
! 	 *
  	 * (A short test says that IRIX 5.3 sends SIGTRAP for all break
  	 * insns, even for break codes that indicate arithmetic failures.
  	 * Weird ...)
  	 * But should we continue the brokenness???  --macro
+          *
+          * It seems some assemblers (binutils-2.15 for example) assemble
+          * break correctly.  So we check for the break code in either
+          * position.
+          *
  	 */
+ 
+ 	bcode = ((opcode >> 6) & ((1 << 20) - 1));
  	switch (bcode) {
! 	case 0x0006:
! 	case 0x0007:
!         case 0x1800: /* 6 << 10 */
!         case 0x1c00: /* 7 << 10 */
! 		if (bcode == 0x7 || bcode == 0x1c00)
  			info.si_code = FPE_INTDIV;
  		else
  			info.si_code = FPE_INTOVF;
***************
*** 633,639 ****
  
  	/* Immediate versions don't provide a code.  */
  	if (!(opcode & OPCODE))
! 		tcode = ((opcode >> 6) & ((1 << 20) - 1));
  
  	/*
  	 * (A short test says that IRIX 5.3 sends SIGTRAP for all trap
--- 639,645 ----
  
  	/* Immediate versions don't provide a code.  */
  	if (!(opcode & OPCODE))
! 		tcode = ((opcode >> 6) & ((1 << 10) - 1));
  
  	/*
  	 * (A short test says that IRIX 5.3 sends SIGTRAP for all trap