PATCH: Check section size for valid core sections

["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?

Thanks.


H.J.
---
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)