Bug in get_insn_opcode.

Bug in get_insn_opcode.

[Carsten Langgaard]

There is a bug in the function get_insn_opcode in traps.c

As 'epc' is an int pointer here, it should only be increased by 1 (4
byte) and not by 4 (4*4 = 16 bytes).
See the patch below.

/Carsten

Index: arch/mips/kernel/traps.c
===================================================================
RCS file: /home/repository/sw/linux-2.4.0/arch/mips/kernel/traps.c,v
retrieving revision 1.10
diff -u -r1.10 traps.c
--- traps.c     2001/02/28 13:46:43     1.10
+++ traps.c     2001/03/02 16:50:27
@@ -410,7 +410,7 @@

        epc = (unsigned int *) (unsigned long) regs->cp0_epc;
        if (regs->cp0_cause & CAUSEF_BD)
-               epc += 4;
+               epc++;

        if (verify_area(VERIFY_READ, epc, 4)) {
                force_sig(SIGSEGV, current);
Index: arch/mips64/kernel/traps.c
===================================================================
RCS file: /home/repository/sw/linux-2.4.0/arch/mips64/kernel/traps.c,v
retrieving revision 1.5
diff -u -r1.5 traps.c
--- traps.c     2001/02/19 16:02:52     1.5
+++ traps.c     2001/03/02 16:50:13
@@ -371,7 +371,7 @@

        epc = (unsigned int *) (unsigned long) regs->cp0_epc;
        if (regs->cp0_cause & CAUSEF_BD)
-               epc += 4;
+               epc++;

        if (verify_area(VERIFY_READ, epc, 4)) {
                force_sig(SIGSEGV, current);




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Re: Bug in get_insn_opcode.

[Jun Sun]

On Fri, Mar 02, 2001 at 05:56:48PM +0100, Carsten Langgaard wrote:
> There is a bug in the function get_insn_opcode in traps.c
> 
> As 'epc' is an int pointer here, it should only be increased by 1 (4
> byte) and not by 4 (4*4 = 16 bytes).
> See the patch below.
> 
> /Carsten
>

Good catch!

I am surprised that trap on branch delay slot is rare that we only discover
this bug now ...

Jun 

Re: Bug in get_insn_opcode.

[Ralf Baechle]

On Fri, Mar 02, 2001 at 05:56:48PM +0100, Carsten Langgaard wrote:
> Date:   Fri, 02 Mar 2001 17:56:48 +0100
> From: Carsten Langgaard <carstenl@mips.com>
> To: linux-mips@oss.sgi.com
> Subject: Bug in get_insn_opcode.
> 
> There is a bug in the function get_insn_opcode in traps.c
> 
> As 'epc' is an int pointer here, it should only be increased by 1 (4
> byte) and not by 4 (4*4 = 16 bytes).
> See the patch below.

> Index: arch/mips/kernel/traps.c
> ===================================================================
> RCS file: /home/repository/sw/linux-2.4.0/arch/mips/kernel/traps.c,v
> retrieving revision 1.10
> diff -u -r1.10 traps.c
> --- traps.c     2001/02/28 13:46:43     1.10
> +++ traps.c     2001/03/02 16:50:27

Patch will behave (un-)funny on a cvs diff generated patch like this which
lacks full pathnames in the --- and +++ lines.  Patches for this
behaviour are available on ftp.cyclic.com (so it still exists ...) or in
more recent cvs rpms.

Applied anyway, of course.

  Ralf

Re: Bug in get_insn_opcode.

[Geert Uytterhoeven]

On Sat, 3 Mar 2001, Ralf Baechle wrote:
> On Fri, Mar 02, 2001 at 05:56:48PM +0100, Carsten Langgaard wrote:
> > Index: arch/mips/kernel/traps.c
> > ===================================================================
> > RCS file: /home/repository/sw/linux-2.4.0/arch/mips/kernel/traps.c,v
> > retrieving revision 1.10
> > diff -u -r1.10 traps.c
> > --- traps.c     2001/02/28 13:46:43     1.10
> > +++ traps.c     2001/03/02 16:50:27
> 
> Patch will behave (un-)funny on a cvs diff generated patch like this which
> lacks full pathnames in the --- and +++ lines.  Patches for this
> behaviour are available on ftp.cyclic.com (so it still exists ...) or in
> more recent cvs rpms.

Isn't patch supposed to look at the `Index' line?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: Bug in get_insn_opcode.

[Ralf Baechle]

On Sat, Mar 03, 2001 at 04:15:05PM +0100, Geert Uytterhoeven wrote:

> > > Index: arch/mips/kernel/traps.c
> > > ===================================================================
> > > RCS file: /home/repository/sw/linux-2.4.0/arch/mips/kernel/traps.c,v
> > > retrieving revision 1.10
> > > diff -u -r1.10 traps.c
> > > --- traps.c     2001/02/28 13:46:43     1.10
> > > +++ traps.c     2001/03/02 16:50:27
> > 
> > Patch will behave (un-)funny on a cvs diff generated patch like this which
> > lacks full pathnames in the --- and +++ lines.  Patches for this
> > behaviour are available on ftp.cyclic.com (so it still exists ...) or in
> > more recent cvs rpms.
> 
> Isn't patch supposed to look at the `Index' line?

Only when the environment variable POSIXLY_CORRECT is set to y which has
a ton of other unwanted side effects, so patch would need wrapper scripts
or what not else.

  Ralf