Problems with egcs-1.0.1-/gcc-2.8.0-inline assembly [causes a kernel-oops in de4x5-driver]

[Franz Sirl]

This is probably due to a bug in the string macros of Linux, see
< http://linuxwww.db.erau.edu/mail_archives/linux-kernel/Jan_98/2155.html >
for patches and
< http://linuxwww.db.erau.edu/mail_archives/linux-kernel/Jan_98/2151.html >
for an explanation.

How about an entry for the FAQ?

Bye,
Franz.



At 16:28 19.01.98 , Bernd Nottelmann wrote:
>Hi,
>
>consider the following C-program (a very very simplified version
>of de4x5.c :-):
>
>-----------------------snip-----------------------
>
>
>
>extern inline char * strstr(const char * cs,const char * ct)
>{
>register char * __res;
>__asm__ __volatile__(
> "cld\n\t" \
> "movl %4,%%edi\n\t"
> "repne\n\t"
> "scasb\n\t"
> "notl %%ecx\n\t"
> "decl %%ecx\n\t" /* NOTE! This also sets Z if searchstring='' */
> "movl %%ecx,%%edx\n"
> "1:\tmovl %4,%%edi\n\t"
> "movl %%esi,%%eax\n\t"
> "movl %%edx,%%ecx\n\t"
> "repe\n\t"   /* <- SEGMENTATION FAULT HERE */
> "cmpsb\n\t"
> "je 2f\n\t"  /* also works for empty string, see above */
> "xchgl %%eax,%%esi\n\t"
> "incl %%esi\n\t"
> "cmpb $0,-1(%%eax)\n\t"
> "jne 1b\n\t"
> "xorl %%eax,%%eax\n\t"
> "2:"
> :"=a" (__res):"0" (0),"c" (0xffffffff),"S" (cs),"g" (ct)
> :"cx","dx","di","si");
>return __res;
>}
>
>#include <stdio.h>
>
>main() {
>  int i, siglen;
>  char ManCode[8];
>  const char *signatures[]={"DE425","DE434","DE435","DE450","DE500"};
>  siglen = sizeof(signatures)/sizeof(const char *);
>  ManCode[0]='_'; ManCode[1]='_';
>  ManCode[2]='?'; ManCode[3]='?'; ManCode[5]='?';
>  ManCode[6]='\0';
>
>  for (i=0;i<siglen;i++)
>    if (strstr(ManCode, signatures[i]) != NULL)
>      printf("Found\n");
>    else
>      printf("Not found\n");
>}
>
>-----------------------snip-----------------------
>
>Compiled with
>gcc strtst.c -o strtst
>it runs without any error messages:
>
># ./strtst
>Not found
>Not found
>Not found
>Not found
>Not found
>
>but when I compile it with -O and higher optimizations
>it gives a seg fault (it occurs in the assembler line with
>the corresponding comment).
>My egcs has been only build from the gcc-subtree
>I hope I have given enough information to you.
>
>Bernd
>
>	.file	"strtst.c"
>	.version	"01.01"
>/ GNU C version egcs-2.90.23 980102 (egcs-1.0.1 release)
(i686-pc-linux-gnulibc1) compiled by GNU C version egcs-2.90.23 980102
(egcs-1.0.1 release).
>/ options passed: 
>/ options enabled:  -fpeephole -ffunction-cse -fkeep-static-consts
>/ -fpcc-struct-return -fsched-interblock -fsched-spec -fcommon
>/ -fverbose-asm -fgnu-linker -fargument-alias -m80387 -mhard-float
>/ -mno-soft-float -mieee-fp -mfp-ret-in-387 -mschedule-prologue
>/ -mcpu=pentiumpro -march=pentium
>
>gcc2_compiled.:
>.section	.rodata
>.LC0:
>	.string	"DE425"
>.LC1:
>	.string	"DE434"
>.LC2:
>	.string	"DE435"
>.LC3:
>	.string	"DE450"
>.LC4:
>	.string	"DE500"
>.LC5:
>	.string	"Found\n"
>.LC6:
>	.string	"Not found\n"
>.text
>	.align 4
>.globl main
>	.type	main,@function
>main:
>	pushl %ebp
>	movl %esp,%ebp
>	subl $36,%esp
>	leal -36(%ebp),%eax
>	movl $.LC0,-36(%ebp)
>	movl $.LC1,-32(%ebp)
>	movl $.LC2,-28(%ebp)
>	movl $.LC3,-24(%ebp)
>	movl $.LC4,-20(%ebp)
>	movl $5,-8(%ebp)
>	movb $95,-16(%ebp)
>	movb $95,-15(%ebp)
>	movb $63,-15(%ebp)
>	movb $63,-15(%ebp)
>	movb $63,-15(%ebp)
>	movb $0,-10(%ebp)
>	movl $0,-4(%ebp)
>.L3:
>	movl -4(%ebp),%eax
>	cmpl %eax,-8(%ebp)
>	jg .L6
>	jmp .L4
>	.align 4
>.L6:
>	movl -4(%ebp),%eax
>	movl %eax,%edx
>	leal 0(,%edx,4),%eax
>	leal -36(%ebp),%edx

>	movl (%eax,%edx),%eax
>	pushl %eax
>	leal -16(%ebp),%eax
>	pushl %eax
>	call strstr
>	addl $8,%esp
>	movl %eax,%eax
>	testl %eax,%eax
>	je .L7
>	pushl $.LC5
>	call printf
>	addl $4,%esp
>	jmp .L5
>	.align 4
>.L7:
>	pushl $.LC6
>	call printf
>	addl $4,%esp
>.L8:
>.L5:
>	incl -4(%ebp)
>	jmp .L3
>	.align 4
>.L4:
>.L2:
>	movl %ebp,%esp
>	popl %ebp
>	ret
>.Lfe1:
>	.size	main,.Lfe1-main
>	.ident	"GCC: (GNU) egcs-2.90.23 980102 (egcs-1.0.1 release)"
>	.file	"strtst.c"
>	.version	"01.01"
>/ GNU C version egcs-2.90.23 980102 (egcs-1.0.1 release)
(i686-pc-linux-gnulibc1) compiled by GNU C version egcs-2.90.23 980102
(egcs-1.0.1 release).
>/ options passed:  -O
>/ options enabled:  -fdefer-pop -fthread-jumps -fpeephole -ffunction-cse
>/ -finline -fkeep-static-consts -fpcc-struct-return -fsched-interblock
>/ -fsched-spec -fcommon -fverbose-asm -fgnu-linker -falias-check
>/ -fargument-alias -m80387 -mhard-float -mno-soft-float -mieee-fp
>/ -mfp-ret-in-387 -mschedule-prologue -mcpu=pentiumpro -march=pentium
>
>gcc2_compiled.:
>.section	.rodata
>.LC0:
>	.string	"DE425"
>.LC1:
>	.string	"DE434"
>.LC2:
>	.string	"DE435"
>.LC3:
>	.string	"DE450"
>.LC4:
>	.string	"DE500"
>.LC5:
>	.string	"Found\n"
>.LC6:
>	.string	"Not found\n"
>.text
>	.align 4
>.globl main
>	.type	main,@function
>main:
>	pushl %ebp
>	movl %esp,%ebp
>	subl $40,%esp
>	pushl %edi
>	pushl %esi
>	pushl %ebx
>	movl $.LC0,-28(%ebp)
>	movl $.LC1,-24(%ebp)
>	movl $.LC2,-20(%ebp)
>	movl $.LC3,-16(%ebp)
>	movl $.LC4,-12(%ebp)
>	movb $95,-8(%ebp)
>	movb $63,-7(%ebp)
>	movb $0,-2(%ebp)
>	movl $0,-40(%ebp)
>	leal -28(%ebp),%edx
>	movl %edx,-32(%ebp)
>	leal -8(%ebp),%ecx
>	movl %ecx,-36(%ebp)
>	.align 4
>.L6:
>	xorl %eax,%eax
>	movl $-1,%ecx
>	movl -36(%ebp),%esi
>	movl -40(%ebp),%edx
>	movl -32(%ebp),%ebx
>#APP
>	cld
>	movl (%ebx,%edx,4),%edi
>	repne
>	scasb
>	notl %ecx
>	decl %ecx
>	movl %ecx,%edx
>1:	movl (%ebx,%edx,4),%edi
>	movl %esi,%eax
>	movl %edx,%ecx
>	repe
>	cmpsb
>	je 2f
>	xchgl %eax,%esi
>	incl %esi
>	cmpb $0,-1(%eax)
>	jne 1b
>	xorl %eax,%eax
>	2:
>#NO_APP
>	testl %eax,%eax
>	je .L7
>	pushl $.LC5
>	jmp .L11
>	.align 4
>.L7:
>	pushl $.LC6
>.L11:
>	call printf
>	addl $4,%esp
>	incl -40(%ebp)
>	cmpl $5,-40(%ebp)
>	jl .L6
>	leal -52(%ebp),%esp
>	popl %ebx
>	popl %esi
>	popl %edi
>	movl %ebp,%esp
>	popl %ebp
>	ret
>.Lfe1:
>	.size	main,.Lfe1-main
>	.ident	"GCC: (GNU) egcs-2.90.23 980102 (egcs-1.0.1 release)"
>