Re: PATCH: Check section size for valid core sections

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

> Date: Sun, 7 Feb 2010 09:42:13 -0800
> From: "H.J. Lu" <hongjiu.lu@intel.com>
> 
> I added a new core section, .reg-xstate, to support x86 XSAVE extended
> state.  We can read it on any machine. But we can only write it on
> machines with x86 XSAVE extended state. I have
> 
> /* Supported register note sections.  */
> static struct core_regset_section amd64_linux_regset_sections[] =
> {
>   { ".reg", 144, "general-purpose" },
>   { ".reg2", 512, "floating-point" },
>   { ".reg-xstate", 0, "XSAVE extended state" },
>   { NULL, 0 }
> };
> 
> I update its size with
> 
>  /* Update the XSAVE extended state size on Linux/x86 host.  Need it
>     for "gcore".  */
>   i386_xstate_init ();
>   amd64_linux_regset_sections[2].size = i386_xstate.size;
> 
> If the machine suppors XSAVE, size will be non-zero. We can still
> read the core section since size is only used for gcore. OK to install?

Sorry, but this makes no sense to me.

> 2010-02-07  H.J. Lu  <hongjiu.lu@intel.com>
>  
> 	* linux-nat.c (linux_nat_do_thread_registers): Check section
> 	size instead of section name for valid core sections.
> 
> diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
> index 7fc9584..44a3288 100644
> --- a/gdb/linux-nat.c
> +++ b/gdb/linux-nat.c
> @@ -4112,9 +4112,12 @@ linux_nat_do_thread_registers (bfd *obfd, ptid_t ptid,
>    /* The loop below uses the new struct core_regset_section, which stores
>       the supported section names and sizes for the core file.  Note that
>       note PRSTATUS needs to be treated specially.  But the other notes are
> -     structurally the same, so they can benefit from the new struct.  */
> +     structurally the same, so they can benefit from the new struct.  We
> +     check section size instead of section name for valid core sections
> +     since we can read x86 XSAVE extended state core section, but we can
> +     write it only if x86 XSAVE extended state is available natively.  */
>    if (core_regset_p && sect_list != NULL)
> -    while (sect_list->sect_name != NULL)
> +    while (sect_list->size != 0)
>        {
>  	/* .reg was already handled above.  */
>  	if (strcmp (sect_list->sect_name, ".reg") == 0)
>