Date: Wed, 19 Jan 1994 21:51:55 +0100
From: Stefan Eckart <S_Eckart AT lis DOT e-technik DOT tu-muenchen DOT de>
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: -pg bug mostly fixed

Thanks to the advice from Charles Sandmann and DJ Delorie I can
report the following:

This patch solves two of three known problems when compiling with
the -pg profiling option:

a) segmentation violation during disk transfers

b) zero time entries in the gprof report under certain circumstances
   (e.g. large global data arrays)

Problem a) was caused by DS not being valid during timer interrupts,
the reason for b) was gas assembling 'cmp $1,%ax' as 'cmpl $1,%eax'
instead of 'cmpw $1,%eax'.

The third problem still remains:

c) system crashes when profiling a program that pages to disk

In this case the system hangs (CTRL-ALT-DEL doesn't work) and the
topline displays the R and m> flags.

This is a bug one probably can live with, because profiling a paging
program doesn't make much sense anyway...

Bye,

Stefan.


*** \djgpp\lib\crt0.s	Tue Nov 30 02:23:02 1993
--- crt0.s	Wed Jan 19 20:10:00 1994
***************
*** 139,146 ****
  mcount_isr_init:
  	movw	__go32_info_block+36, %ax	/* run mode */
! 	cmp	$1,%ax
  	jb	skip_mcount
! 	cmp	$3,%ax
  	ja	skip_mcount
  	
  	movw	$16,%ax
--- 139,148 ----
  mcount_isr_init:
  	movw	__go32_info_block+36, %ax	/* run mode */
! 	cmpw	$1,%ax
  	jb	skip_mcount
! 	cmpw	$3,%ax
  	ja	skip_mcount
+ 
+ 	movw	%ds,__ds_sav
  	
  	movw	$16,%ax
***************
*** 175,181 ****
  mcount_isr:
  	pushl	%eax
  	cmpl	$1,mcount_skip
  	je	L0
! 	movl	4(%esp),%eax /* get the PC */
  	subl	$0x1020,%eax /* to fit in low..high */
  	andl	$0xfffffffc,%eax
--- 177,185 ----
  mcount_isr:
  	pushl	%eax
+ 	pushl	%ds
+ 	movw	%cs:__ds_sav,%ds
  	cmpl	$1,mcount_skip
  	je	L0
! 	movl	8(%esp),%eax /* get the PC */
  	subl	$0x1020,%eax /* to fit in low..high */
  	andl	$0xfffffffc,%eax
***************
*** 184,190 ****
  	incw	(%eax)
  L0:
  	popl	%eax
! 	ljmp	mc_chain /* chain to the next timer vector */
  	iret
  #endif
  
--- 188,198 ----
  	incw	(%eax)
  L0:
+ 	popl	%ds
  	popl	%eax
! 	ljmp	%cs:mc_chain /* chain to the next timer vector */
  	iret
+ 	.align	2
+ __ds_sav:
+ 	.short	0
  #endif