Re: PING: PATCH: PR backtrace/14646: [x32] backtrace doesn't work

[Mark Kettenis <mark.kettenis@xs4all.nl>]

> Date: Mon, 8 Oct 2012 13:38:21 -0700
> From: "H.J. Lu" <hjl.tools@gmail.com>
> 
> On Mon, Oct 8, 2012 at 1:22 PM, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> >> Date: Mon, 8 Oct 2012 13:04:03 -0700
> >> From: "H.J. Lu" <hjl.tools@gmail.com>
> >>
> >> On Mon, Oct 8, 2012 at 12:48 PM, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> >> >> Date: Thu, 4 Oct 2012 06:57:22 -0700
> >> >> From: "H.J. Lu" <hjl.tools@gmail.com>
> >> >>
> >> >> On Wed, Oct 3, 2012 at 11:57 PM, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> >> >> >
> >> >> > Perhaps the user-regs.c mechanism can be used to establish eip -> pc
> >> >> > and esp -> sp mappings?
> >> >>
> >> >> It doesn't help as long as gdbarch_pc_regnum/gdbarch_sp_regnum
> >> >> are used for both frame pc/sp value and unwind pc/sp value.  For x32,
> >> >> we want eip/esp for frame pc/sp value and rip/rsp for unwind pc/sp
> >> >> value.
> >> >
> >> > That probably means we need to set gdbarch_pc_regnum (and
> >> > gdbarch_sp_regnum) to -1 for x32.
> >>
> >> We can't set gdbarch_pc_regnum/gdbarch_sp_regnum to -1:
> >>
> >>
> >> GNU gdb (GDB) 7.5.50.20121008-cvs
> >> Copyright (C) 2012 Free Software Foundation, Inc.
> >> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> >> This is free software: you are free to change and redistribute it.
> >> There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
> >> and "show warranty" for details.
> >> This GDB was configured as "x86_64-unknown-linux-gnu".
> >> For bug reporting instructions, please see:
> >> <http://www.gnu.org/software/gdb/bugs/>...
> >> Reading symbols from
> >> /export/build/gnu/glibc-x32/build-x86_64-linux/elf/sln...done.
> >> (gdb) b main
> >> Breakpoint 1 at 0x400c20: file sln.c, line 50.
> >> (gdb) r
> >> Starting program: /export/build/gnu/glibc-x32/build-x86_64-linux/elf/sln
> >> /export/gnu/import/git/gdb/gdb/regcache.c:1062: internal-error:
> >> regcache_read_pc: Unable to find PC
> >> A problem internal to GDB has been detected,
> >> further debugging may prove unreliable.
> >> Quit this debugging session? (y or n)
> >
> > Well, obviously you'll need to implement gdbarch_read_pc() for this to
> > work.  And probably a few more gdbarch methods.
> 
> What do we gain by setting gdbarch_pc_regnum/gdbarch_sp_regnum
> to -1?  PC and SP are RIP and RSP for x32.  We need them for
> stack unwind.  The only unusual part is they are 64-bit although
> x32 is a 32-bit environment.   How about this change?

Did you even try that change?

> diff --git a/gdb/features/i386/x32-core.xml b/gdb/features/i386/x32-core.xml
> index 1e41417..392ce24 100644
> --- a/gdb/features/i386/x32-core.xml
> +++ b/gdb/features/i386/x32-core.xml
> @@ -34,7 +34,7 @@
>    <reg name="rsi" bitsize="64" type="int64"/>
>    <reg name="rdi" bitsize="64" type="int64"/>
>    <reg name="rbp" bitsize="64" type="int64"/>
> -  <reg name="rsp" bitsize="64" type="int64"/>
> +  <reg name="rsp" bitsize="64" type="data_ptr"/>
>    <reg name="r8" bitsize="64" type="int64"/>
>    <reg name="r9" bitsize="64" type="int64"/>
>    <reg name="r10" bitsize="64" type="int64"/>
> @@ -44,7 +44,7 @@
>    <reg name="r14" bitsize="64" type="int64"/>
>    <reg name="r15" bitsize="64" type="int64"/>
> 
> -  <reg name="rip" bitsize="64" type="uint64"/>
> +  <reg name="rip" bitsize="64" type="code_ptr"/>
>    <reg name="eflags" bitsize="32" type="i386_eflags"/>
>    <reg name="cs" bitsize="32" type="int32"/>
>    <reg name="ss" bitsize="32" type="int32"/>