Hi, I'm trying to debug a userspace application with gdb-6.3 / gdbserver. Objdump -p reports: private flags = 20001107: [abi=O32] [mips3] [32bitmode] With gdb-6.0 from an older toolchain this works, but gdb-6.3 reports the infamous "Reply contains invalid hex digit 59". The reason for this is that gdb and gdbserver disagree about the register size. Gdbserver seems to be hardcoded to 32bit register size (regformats/reg-mips.dat), while gdb-6.3 assumes that mips3 binaries use 64bit registers. (Actually E_MIPS_ARCH_3 gets transformed into bfd_mach_mips4000 in bfd/elfxx-mips.c, which has 64bit registers according to bfd/cpu-mips.c). (I briefly checked gdb-6.4, it seems to do the same.) The workaround given in this posting seems to work for userspace, too: http://www.linux-mips.org/archives/linux-mips/2005-11/msg00154.html I.e. "set architecture mips:isa32" overrides the register size which gdb uses to talk to gdbserver. However, I wonder why gdb doesn't evaluate the 32bitmode flag from the ELF e_flags header. To be honest, I also wonder what the exact semantics of this flag are. The NUBI document says: "32BIT_MODE: (e_flags&EF_MIPS_32BITMODE) - 1 when code assumes 32-bit registers only. Always set for NUBI32, but NUBI-compliant software should not rely on it." I think (maybe in error ;-), that all binaries compiled for a 32bit ABI, but a 64bit ISA, have this flag set, as the kernel will refuse to execute 64bt code (i.e. not o32 or n32 ABI). Therefore, shouldn't gdb also evaluate this flag when deciding about the ISA register size? How about this patch: --- gdb-6.3/gdb/mips-tdep.c.orig 2004-10-15 09:25:03.000000000 +0200 +++ gdb-6.3/gdb/mips-tdep.c 2006-01-30 21:13:09.000000000 +0100 @@ -258,6 +258,15 @@ mips_abi (struct gdbarch *gdbarch) int mips_isa_regsize (struct gdbarch *gdbarch) { + struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch); + if (tdep != NULL) + { + int ef_mips_32bitmode; + ef_mips_32bitmode = (tdep->elf_flags & EF_MIPS_32BITMODE); + if (ef_mips_32bitmode) + return 4; + } + return (gdbarch_bfd_arch_info (gdbarch)->bits_per_word / gdbarch_bfd_arch_info (gdbarch)->bits_per_byte); } I also considered if adding 64bit support to gdbserver would be the right thing, but I think not as o32 ABI executables don't have 64bit registers, right? Please don't be too hard on me, my understanding of gdb etc. is pretty limited. I'm especially confused by this ISA regsize vs. ABI regsize thing ;-/. Thus my patch looks at the 32bitmode flag and not at the o32 ABI to decide about this register size, however I'm not sure if any of this makes actually sense. It seems to work for me, though ;-) But I'd be willing to do some work to get this fixed properly in upstream gdb, if I get some guidance. Thanks, Johannes
