[PATCH 2/3] x86: Use correct .reg-xstate section size

[Andreas Arnez <arnez at linux dot vnet dot ibm dot com>]

When reading the XSAVE extended state from an i386 or AMD64 core file,
the respective regset iterator requests a minimum section size of
zero.  Since the respective regset supply function does not check the
size either, this may lead to accessing data out of range if the
section is too short.

In write mode, the iterator always uses the maximum supported size for
the XSAVE extended state.

This is now changed such that the iterator always requests the
expected size of this section based on xcr0, both for reading and
writing.

gdb/ChangeLog:

	* amd64-linux-tdep.c (amd64_linux_iterate_over_regset_sections):
	For ".reg-xstate", explicitly specify the requested section size
	via X86_XSTATE_SIZE instead of just 0 on input and
	X86_XSTATE_MAX_SIZE on output.
	* i386-linux-tdep.c (i386_linux_iterate_over_regset_sections):
	Likewise.
---
 gdb/amd64-linux-tdep.c | 2 +-
 gdb/i386-linux-tdep.c  | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/gdb/amd64-linux-tdep.c b/gdb/amd64-linux-tdep.c
index 42d884e..5db04c0 100644
--- a/gdb/amd64-linux-tdep.c
+++ b/gdb/amd64-linux-tdep.c
@@ -1639,7 +1639,7 @@ amd64_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
 
   cb (".reg", 27 * 8, &i386_gregset, NULL, cb_data);
   cb (".reg2", 512, &amd64_fpregset, NULL, cb_data);
-  cb (".reg-xstate",  regcache ? X86_XSTATE_MAX_SIZE : 0,
+  cb (".reg-xstate",  X86_XSTATE_SIZE (tdep->xcr0),
       &amd64_linux_xstateregset, "XSAVE extended state", cb_data);
 }
 
diff --git a/gdb/i386-linux-tdep.c b/gdb/i386-linux-tdep.c
index 8a5209a..4a0ce60 100644
--- a/gdb/i386-linux-tdep.c
+++ b/gdb/i386-linux-tdep.c
@@ -690,8 +690,7 @@ i386_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
   cb (".reg", 68, &i386_gregset, NULL, cb_data);
 
   if (tdep->xcr0 & X86_XSTATE_AVX)
-    /* Use max size for writing, accept any size when reading.  */
-    cb (".reg-xstate", regcache ? X86_XSTATE_MAX_SIZE : 0,
+    cb (".reg-xstate", X86_XSTATE_SIZE (tdep->xcr0),
 	&i386_linux_xstateregset, "XSAVE extended state", cb_data);
   else if (tdep->xcr0 & X86_XSTATE_SSE)
     cb (".reg-xfp", 512, &i386_fpregset, "extended floating-point",
-- 
1.8.4.2