From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 13675 invoked by alias); 7 Dec 2010 21:45:55 -0000 Received: (qmail 13568 invoked by uid 22791); 7 Dec 2010 21:45:53 -0000 X-SWARE-Spam-Status: No, hits=-2.0 required=5.0 tests=AWL,BAYES_00,TW_EG,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from sibelius.xs4all.nl (HELO glazunov.sibelius.xs4all.nl) (83.163.83.176) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 07 Dec 2010 21:45:47 +0000 Received: from glazunov.sibelius.xs4all.nl (kettenis@localhost [127.0.0.1]) by glazunov.sibelius.xs4all.nl (8.14.3/8.14.3) with ESMTP id oB7LjS1Y008469; Tue, 7 Dec 2010 22:45:28 +0100 (CET) Received: (from kettenis@localhost) by glazunov.sibelius.xs4all.nl (8.14.3/8.14.3/Submit) id oB7LjQO3026426; Tue, 7 Dec 2010 22:45:26 +0100 (CET) Date: Tue, 07 Dec 2010 21:45:00 -0000 Message-Id: <201012072145.oB7LjQO3026426@glazunov.sibelius.xs4all.nl> From: Mark Kettenis To: kevinb@redhat.com CC: gdb-patches@sourceware.org In-reply-to: <20101207132806.67a0baa2@mesquite.lan> (message from Kevin Buettner on Tue, 7 Dec 2010 13:28:06 -0700) Subject: Re: [RFC] mips-tdep.c: Sign extend values placed into registers for inferior function calls References: <20101207132806.67a0baa2@mesquite.lan> Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2010-12/txt/msg00078.txt.bz2 > Date: Tue, 7 Dec 2010 13:28:06 -0700 > From: Kevin Buettner > > Here is an example, taken from the log file, of one failure fixed by > this patch: > > p t_short_values(10,-23) > UNPREDICTABLE: PC = 0x800209d4 > Quit > (gdb) FAIL: gdb.base/callfuncs.exp: p t_short_values(10,-23) > > In creating the inferior function call, gdb is placing a negative > value, -23, sign extended only to 32-bits, into one of the 64-bit > argument registers. When the simulator executes a move instruction > in the course of executing t_short_values(), it first checks to make > sure that the register value is correctly sign extended. I.e. it looks > at bits 32-63 and makes sure that they all match the value in bit 31. > If it's not correctly sign extended, it outputs the "UNPREDICTABLE" > message. It then aborts back to GDB, often causing further problems > for later tests. So do I understand correctly that this is a problem with the simulator, and that real hardware doesn't really care what is in the unused upper half of the register? Did you test this on real hardware? > Comments? > > Kevin > > * mips-tdep.c (mips_eabi_push_dummy_call): Place signed, rather > than unsigned, values in registers. > > Index: mips-tdep.c > =================================================================== > RCS file: /cvs/src/src/gdb/mips-tdep.c,v > retrieving revision 1.508 > diff -u -p -r1.508 mips-tdep.c > --- mips-tdep.c 28 Nov 2010 04:31:24 -0000 1.508 > +++ mips-tdep.c 7 Dec 2010 19:52:14 -0000 > @@ -2755,7 +2755,7 @@ mips_eabi_push_dummy_call (struct gdbarc > fprintf_unfiltered (gdb_stdlog, > "mips_eabi_push_dummy_call: struct_return reg=%d %s\n", > argreg, paddress (gdbarch, struct_addr)); > - regcache_cooked_write_unsigned (regcache, argreg++, struct_addr); > + regcache_cooked_write_signed (regcache, argreg++, struct_addr); This one makes sense, func_addr and bp_addr are already written signed. > @@ -2834,7 +2834,7 @@ mips_eabi_push_dummy_call (struct gdbarc > if (mips_debug) > fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s", > float_argreg, phex (regval, 4)); > - regcache_cooked_write_unsigned (regcache, float_argreg++, regval); > + regcache_cooked_write_signed (regcache, float_argreg++, regval); > > /* Write the high word of the double to the odd register(s). */ > regval = extract_unsigned_integer (val + 4 - low_offset, > @@ -2842,7 +2842,7 @@ mips_eabi_push_dummy_call (struct gdbarc > if (mips_debug) > fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s", > float_argreg, phex (regval, 4)); > - regcache_cooked_write_unsigned (regcache, float_argreg++, regval); > + regcache_cooked_write_signed (regcache, float_argreg++, regval); These two are odd though, since the values are still read using extract_integer_unsigned. That's a bit odd. > } > else > { > @@ -2854,7 +2854,7 @@ mips_eabi_push_dummy_call (struct gdbarc > if (mips_debug) > fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s", > float_argreg, phex (regval, len)); > - regcache_cooked_write_unsigned (regcache, float_argreg++, regval); > + regcache_cooked_write_signed (regcache, float_argreg++, regval); same here > @@ -2937,13 +2937,13 @@ mips_eabi_push_dummy_call (struct gdbarc > && !fp_register_arg_p (gdbarch, typecode, arg_type)) > { > LONGEST regval = > - extract_unsigned_integer (val, partial_len, byte_order); > + extract_signed_integer (val, partial_len, byte_order); > > if (mips_debug) > fprintf_filtered (gdb_stdlog, " - reg=%d val=%s", > argreg, > phex (regval, regsize)); > - regcache_cooked_write_unsigned (regcache, argreg, regval); > + regcache_cooked_write_signed (regcache, argreg, regval); > argreg++; > } > > >