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RE: [PATCH][GCC][front-end][build-machinery][opt-framework] Allow setting of stack-clash via configure options. [Patch (4/6)]


HI Alexandre,

Thanks for the review. Attached is the updated patch and new changelog below:

Thanks,
Tamar

gcc/
2018-07-25  Tamar Christina  <tamar.christina@arm.com>

	PR target/86486
	* configure.ac: Add stack-clash-protection-guard-size.
	* doc/install.texi: Document it.
	* config.in (DEFAULT_STK_CLASH_GUARD_SIZE): New.
	* params.def: Update comment for guard-size.
	(PARAM_STACK_CLASH_PROTECTION_GUARD_SIZE,
	PARAM_STACK_CLASH_PROTECTION_PROBE_INTERVAL): Update description.
	* configure: Regenerate.

> -----Original Message-----
> From: Alexandre Oliva <oliva@gnu.org>
> Sent: Tuesday, July 24, 2018 20:24
> To: Tamar Christina <Tamar.Christina@arm.com>
> Cc: Joseph Myers <joseph@codesourcery.com>; Jeff Law
> <law@redhat.com>; gcc-patches@gcc.gnu.org; nd <nd@arm.com>;
> bonzini@gnu.org; dj@redhat.com; neroden@gcc.gnu.org;
> Ralf.Wildenhues@gmx.de
> Subject: Re: [PATCH][GCC][front-end][build-machinery][opt-framework]
> Allow setting of stack-clash via configure options. [Patch (4/6)]
> 
> Hello, Christina,
> 
> On Jul 24, 2018, Tamar Christina <Tamar.Christina@arm.com> wrote:
> 
> > gcc/
> > 2018-07-24  Tamar Christina  <tamar.christina@arm.com>
> 
> > 	PR target/86486
> > 	* configure.ac: Add stack-clash-protection-guard-size.
> > 	* doc/install.texi: Document it.
> > 	* config.in (DEFAULT_STK_CLASH_GUARD_SIZE): New.
> > 	* params.def: Update comment for guard-size.
> > 	* configure: Regenerate.
> 
> The configury bits look almost good to me.
> 
> I wish the help message, comments and docs expressed somehow that the
> given power of two expresses a size in bytes, rather than in kilobytes, bits or
> any other unit that might be reasonably assumed to express stack sizes.  I'm
> afraid I don't know the best way to accomplish that in a few words.
> 
> > +stk_clash_default=12
> 
> This seems to be left-over from an earlier patch, as it is now unused AFAICT.
> 
> Thanks,
> 
> --
> Alexandre Oliva, freedom fighter   https://FSFLA.org/blogs/lxo
> Be the change, be Free!         FSF Latin America board member
> GNU Toolchain Engineer                Free Software Evangelist
diff --git a/gcc/config.in b/gcc/config.in
index 2856e72d627df537a301a6c7ab6b5bbb75f6b43f..32118ef1f94cece06a1d870416c3a1705716d21b 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -55,6 +55,13 @@
 #endif
 
 
+/* Define to larger than zero set to the default stack clash protector size as
+   a power of two in bytes. */
+#ifndef USED_FOR_TARGET
+#undef DEFAULT_STK_CLASH_GUARD_SIZE
+#endif
+
+
 /* Define if you want to use __cxa_atexit, rather than atexit, to register C++
    destructors for local statics and global objects. This is essential for
    fully standards-compliant handling of destructors, but requires
diff --git a/gcc/configure b/gcc/configure
index 60d373982fd38fe51c285e2b02941754d1b833d6..77ed62d199b272dfe39de156771dfb774184dd7d 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -905,6 +905,7 @@ enable_valgrind_annotations
 with_stabs
 enable_multilib
 enable_multiarch
+with_stack_clash_protection_guard_size
 enable___cxa_atexit
 enable_decimal_float
 enable_fixed_point
@@ -1724,6 +1725,9 @@ Optional Packages:
   --with-gnu-as           arrange to work with GNU as
   --with-as               arrange to use the specified as (full pathname)
   --with-stabs            arrange to use stabs instead of host debug format
+  --with-stack-clash-protection-guard-size=size
+                          Set the default stack clash protection guard size
+                          for specific targets as a power of two in bytes.
   --with-dwarf2           force the default debug format to be DWARF 2
   --with-specs=SPECS      add SPECS to driver command-line processing
   --with-pkgversion=PKG   Use PKG in the version string in place of "GCC"
@@ -7436,6 +7440,34 @@ $as_echo "$enable_multiarch$ma_msg_suffix" >&6; }
 
 
 
+# default stack clash protection guard size as power of twos in bytes.
+# Please keep these in sync with params.def.
+stk_clash_min=12
+stk_clash_max=30
+
+# Keep the default value when the option is not used to 0, this allows us to
+# distinguish between the cases where the user specifially set a value via
+# configure and when the normal default value is used.
+
+# Check whether --with-stack-clash-protection-guard-size was given.
+if test "${with_stack_clash_protection_guard_size+set}" = set; then :
+  withval=$with_stack_clash_protection_guard_size; DEFAULT_STK_CLASH_GUARD_SIZE="$with_stack_clash_protection_guard_size"
+else
+  DEFAULT_STK_CLASH_GUARD_SIZE=0
+fi
+
+if test $DEFAULT_STK_CLASH_GUARD_SIZE -ne 0 \
+     && (test $DEFAULT_STK_CLASH_GUARD_SIZE -lt $stk_clash_min \
+	 || test $DEFAULT_STK_CLASH_GUARD_SIZE -gt $stk_clash_max); then
+  as_fn_error "Invalid value $DEFAULT_STK_CLASH_GUARD_SIZE for --with-stack-clash-protection-guard-size. Must be between $stk_clash_min and $stk_clash_max." "$LINENO" 5
+fi
+
+
+cat >>confdefs.h <<_ACEOF
+#define DEFAULT_STK_CLASH_GUARD_SIZE $DEFAULT_STK_CLASH_GUARD_SIZE
+_ACEOF
+
+
 # Enable __cxa_atexit for C++.
 # Check whether --enable-__cxa_atexit was given.
 if test "${enable___cxa_atexit+set}" = set; then :
@@ -18448,7 +18480,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 18451 "configure"
+#line 18483 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -18554,7 +18586,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 18557 "configure"
+#line 18589 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 010ecd2ccf609ded1f4d2849a2acc13aba43b55b..0bf75e14bf77054d7c5cafd9d686eb0964999227 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -811,6 +811,29 @@ AC_MSG_RESULT($enable_multiarch$ma_msg_suffix)
 AC_SUBST(with_cpu)
 AC_SUBST(with_float)
 
+# default stack clash protection guard size as power of twos in bytes.
+# Please keep these in sync with params.def.
+stk_clash_min=12
+stk_clash_max=30
+
+# Keep the default value when the option is not used to 0, this allows us to
+# distinguish between the cases where the user specifially set a value via
+# configure and when the normal default value is used.
+AC_ARG_WITH(stack-clash-protection-guard-size,
+[AS_HELP_STRING([--with-stack-clash-protection-guard-size=size],
+[Set the default stack clash protection guard size for specific targets as a power of two in bytes.])],
+[DEFAULT_STK_CLASH_GUARD_SIZE="$with_stack_clash_protection_guard_size"], [DEFAULT_STK_CLASH_GUARD_SIZE=0])
+if test $DEFAULT_STK_CLASH_GUARD_SIZE -ne 0 \
+     && (test $DEFAULT_STK_CLASH_GUARD_SIZE -lt $stk_clash_min \
+	 || test $DEFAULT_STK_CLASH_GUARD_SIZE -gt $stk_clash_max); then
+  AC_MSG_ERROR(m4_normalize([
+		Invalid value $DEFAULT_STK_CLASH_GUARD_SIZE for --with-stack-clash-protection-guard-size. \
+		Must be between $stk_clash_min and $stk_clash_max.]))
+fi
+
+AC_DEFINE_UNQUOTED(DEFAULT_STK_CLASH_GUARD_SIZE, $DEFAULT_STK_CLASH_GUARD_SIZE,
+	[Define to larger than zero set the default stack clash protector size.])
+
 # Enable __cxa_atexit for C++.
 AC_ARG_ENABLE(__cxa_atexit,
 [AS_HELP_STRING([--enable-__cxa_atexit], [enable __cxa_atexit for C++])],
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 7c5cdc762d3ecca2b37c1ebc8caf99d22ff351b9..8aa7bed0d25081afc859bc3421dc71c68e516cde 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1410,6 +1410,11 @@ These features are extensions to the traditional
 SVR4-based MIPS ABIs and require support from GNU binutils
 and the runtime C library.
 
+@item --with-stack-clash-protection-guard-size=@var{size}
+On certain targets this option sets the default stack clash protection guard
+size as a power of two in bytes.  On AArch64 @var{size} is required to be either
+12 (4KB) or 16 (64KB).
+
 @item --enable-__cxa_atexit
 Define if you want to use __cxa_atexit, rather than atexit, to
 register C++ destructors for local statics and global objects.
diff --git a/gcc/params.def b/gcc/params.def
index a3906c268814bdc3a813416a60b9f666d1568f0a..762a38ca07b9a3ed5784d64ab3eab9955e0cb246 100644
--- a/gcc/params.def
+++ b/gcc/params.def
@@ -213,14 +213,15 @@ DEFPARAM(PARAM_STACK_FRAME_GROWTH,
 	 "Maximal stack frame growth due to inlining (in percent).",
 	 1000, 0, 0)
 
+/* Keep these up to date with those in configure.ac.  */
 DEFPARAM(PARAM_STACK_CLASH_PROTECTION_GUARD_SIZE,
 	 "stack-clash-protection-guard-size",
-	 "Size of the stack guard expressed as a power of two.",
+	 "Size of the stack guard expressed as a power of two in bytes.",
 	 12, 12, 30)
 
 DEFPARAM(PARAM_STACK_CLASH_PROTECTION_PROBE_INTERVAL,
 	 "stack-clash-protection-probe-interval",
-	 "Interval in which to probe the stack expressed as a power of two.",
+	 "Interval in which to probe the stack expressed as a power of two in bytes.",
 	 12, 10, 16)
 
 /* The GCSE optimization will be disabled if it would require


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