Re: [Xen-devel] [PATCH] fix the bug of gdb which debugs xen.

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

I don't know whether you intend this for immediate checkin, but anyway:

 * Don't delete the sysenter logic in traps.c, leave it.
 * I'm not sure about swap64() in gdbstub.c. The value may not be 64 bits
(e.g., running on i386), or the system may not be little endian. Might be
better to define an alternative to str2ulong() which is endian aware, like
gdb_write_to_packet_hex().

 -- Keir

On 12/08/2009 03:15, "Caz Yokoyama" <cazyokoyama@xxxxxxxxx> wrote:

> Hello,
> This patch fixes the bug of gdb which debugs Xen hypervisor, i.e. not domU. As
> Emre Can Sezer reported in
> http://lists.xensource.com/archives/html/xen-devel/2009-01/msg00885.html, once
> break point is hit, continue command produces SIGTRAP at restore_all_xen().
> This patch makes continue command resume Xen running. I still see other bugs
> like backtrace command does not show function name. But I hope this helps your
> debug.
> FYI, related postings.
> http://lists.xensource.com/archives/html/xen-devel/2007-12/msg00678.html
> http://www.filewatcher.com/p/xen_2.0.6.orig.tar.gz.2456215/xen-2.0/docs/misc/X
> enDebugger-HOWTO.html
>  
> connect gdb on step command
> --- a/xen/arch/x86/traps.c      Thu Aug 06 13:27:53 2009 +0100
> +++ b/xen/arch/x86/traps.c      Tue Aug 11 18:15:25 2009 -0700
> @@ -2977,13 +2977,7 @@
>         if ( regs->eflags & EF_TF )
>         {
>  #ifdef __x86_64__
> -           void sysenter_entry(void);
> -           void sysenter_eflags_saved(void);
> -           /* In SYSENTER entry path we can't zap TF until EFLAGS is saved.
> */
> -           if ( (regs->rip >= (unsigned long)sysenter_entry) &&
> -                (regs->rip < (unsigned long)sysenter_eflags_saved) )
> -               goto out;
> -           WARN_ON(regs->rip != (unsigned long)sysenter_eflags_saved);
> +           debugger_trap_fatal(TRAP_debug, regs);
>  #else
>             WARN_ON(1);
>  #endif
>  
> Value of gdb command is little endian.
> diff -r 13fe7f07df15 xen/common/gdbstub.c
> --- a/xen/common/gdbstub.c      Thu Aug 06 13:27:53 2009 +0100
> +++ b/xen/common/gdbstub.c      Tue Aug 11 18:15:25 2009 -0700
> @@ -53,6 +53,10 @@
>  
>  #define GDB_RETRY_MAX   10
>  
> +#define swap16(_v) ((((u16)(_v)>>8)&0xff)|(((u16)(_v)&0xff)<<8))
> +#define swap32(_v)
> (((u32)swap16((u16)(_v))<<16)|(u32)swap16((u32)((_v)>>16)))
> +#define swap64(_v)
> (((u64)swap32((u32)(_v))<<32)|(u64)swap32((u32)((_v)>>32)))
> +
>  struct gdb_cpu_info
>  {
>      atomic_t paused;
> @@ -489,6 +493,7 @@
>         }
>         ptr++;
>         val = str2ulong(ptr, sizeof(unsigned long));
> +       val = swap64(val);
>         gdb_arch_write_reg(addr, val, regs, ctx);
>         break;
>     case 'D':
>  
> Thank you.
> -Caz Yokoyama, caz at caztech dot com. 503-804-1028(m).
>  
> 



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