Hi.
The patch adds new no_stack_protect attribute. The change is requested
from kernel folks and is direct equivalent of Clang's no_stack_protector.
Unlike Clang, I chose to name it no_stack_protect because we already
have stack_protect attribute (used with -fstack-protector-explicit).
First part of the patch contains a small refactoring of an enum, second
implements the functionality.
Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
Ready to be installed?
Thanks,
Martin
>From 6b3e9d32150fe17acb271b7bedee7dc95cad7dc8 Mon Sep 17 00:00:00 2001
From: Martin Liska <mli...@suse.cz>
Date: Fri, 15 May 2020 14:42:12 +0200
Subject: [PATCH 2/2] Implement no_stack_protect attribute.
gcc/ChangeLog:
2020-05-18 Martin Liska <mli...@suse.cz>
PR c/94722
* cfgexpand.c (stack_protect_decl_phase):
Guard with lookup_attribute("no_stack_protect") at
various places.
(expand_used_vars): Likewise here.
* doc/extend.texi: Document no_stack_protect attribute.
gcc/ada/ChangeLog:
2020-05-18 Martin Liska <mli...@suse.cz>
PR c/94722
* gcc-interface/utils.c (handle_no_stack_protect_attribute):
New.
(handle_stack_protect_attribute): Add error message for a
no_stack_protect function.
gcc/c-family/ChangeLog:
2020-05-18 Martin Liska <mli...@suse.cz>
PR c/94722
* c-attribs.c (handle_no_stack_protect_function_attribute): New.
(handle_stack_protect_attribute): Add error message for a
no_stack_protect function.
gcc/testsuite/ChangeLog:
2020-05-18 Martin Liska <mli...@suse.cz>
PR c/94722
* g++.dg/no-stack-protect-attr-2.C: New test.
* g++.dg/no-stack-protect-attr-3.C: New test.
* g++.dg/no-stack-protect-attr.C: New test.
---
gcc/ada/gcc-interface/utils.c | 32 ++++++++
gcc/c-family/c-attribs.c | 33 ++++++++
gcc/cfgexpand.c | 82 ++++++++++---------
gcc/doc/extend.texi | 4 +
.../g++.dg/no-stack-protect-attr-2.C | 7 ++
.../g++.dg/no-stack-protect-attr-3.C | 23 ++++++
gcc/testsuite/g++.dg/no-stack-protect-attr.C | 16 ++++
7 files changed, 158 insertions(+), 39 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/no-stack-protect-attr-2.C
create mode 100644 gcc/testsuite/g++.dg/no-stack-protect-attr-3.C
create mode 100644 gcc/testsuite/g++.dg/no-stack-protect-attr.C
diff --git a/gcc/ada/gcc-interface/utils.c b/gcc/ada/gcc-interface/utils.c
index 1527be4f6d1..144afe37d78 100644
--- a/gcc/ada/gcc-interface/utils.c
+++ b/gcc/ada/gcc-interface/utils.c
@@ -91,6 +91,7 @@ static tree handle_nonnull_attribute (tree *, tree, tree, int, bool *);
static tree handle_sentinel_attribute (tree *, tree, tree, int, bool *);
static tree handle_noreturn_attribute (tree *, tree, tree, int, bool *);
static tree handle_stack_protect_attribute (tree *, tree, tree, int, bool *);
+static tree handle_no_stack_protect_attribute (tree *, tree, tree, int, bool *);
static tree handle_noinline_attribute (tree *, tree, tree, int, bool *);
static tree handle_noclone_attribute (tree *, tree, tree, int, bool *);
static tree handle_noicf_attribute (tree *, tree, tree, int, bool *);
@@ -141,6 +142,8 @@ const struct attribute_spec gnat_internal_attribute_table[] =
handle_noreturn_attribute, NULL },
{ "stack_protect",0, 0, true, false, false, false,
handle_stack_protect_attribute, NULL },
+ { "no_stack_protect",0, 0, true, false, false, false,
+ handle_no_stack_protect_attribute, NULL },
{ "noinline", 0, 0, true, false, false, false,
handle_noinline_attribute, NULL },
{ "noclone", 0, 0, true, false, false, false,
@@ -6523,10 +6526,39 @@ handle_stack_protect_attribute (tree *node, tree name, tree, int,
warning (OPT_Wattributes, "%qE attribute ignored", name);
*no_add_attrs = true;
}
+ else if (lookup_attribute ("no_stack_protect", DECL_ATTRIBUTES (*node)))
+ {
+ warning (OPT_Wattributes, "%qE attribute ignored due to conflict "
+ "with %qs attribute", name, "no_stack_protect");
+ *no_add_attrs = true;
+ }
+
+ return NULL_TREE;
+}
+
+/* Handle a "no_stack_protect" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_no_stack_protect_attribute (tree *node, tree name, tree, int,
+ bool *no_add_attrs)
+{
+ if (TREE_CODE (*node) != FUNCTION_DECL)
+ {
+ warning (OPT_Wattributes, "%qE attribute ignored", name);
+ *no_add_attrs = true;
+ }
+ else if (lookup_attribute ("stack_protect", DECL_ATTRIBUTES (*node)))
+ {
+ warning (OPT_Wattributes, "%qE attribute ignored due to conflict "
+ "with %qs attribute", name, "stack_protect");
+ *no_add_attrs = true;
+ }
return NULL_TREE;
}
+
/* Handle a "noinline" attribute; arguments as in
struct attribute_spec.handler. */
diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index 7a6fb9af6da..3c22576035b 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -63,6 +63,8 @@ static tree handle_no_sanitize_undefined_attribute (tree *, tree, tree, int,
static tree handle_asan_odr_indicator_attribute (tree *, tree, tree, int,
bool *);
static tree handle_stack_protect_attribute (tree *, tree, tree, int, bool *);
+static tree handle_no_stack_protect_function_attribute (tree *, tree,
+ tree, int, bool *);
static tree handle_noinline_attribute (tree *, tree, tree, int, bool *);
static tree handle_noclone_attribute (tree *, tree, tree, int, bool *);
static tree handle_nocf_check_attribute (tree *, tree, tree, int, bool *);
@@ -273,6 +275,9 @@ const struct attribute_spec c_common_attribute_table[] =
handle_noreturn_attribute, NULL },
{ "stack_protect", 0, 0, true, false, false, false,
handle_stack_protect_attribute, NULL },
+ { "no_stack_protect", 0, 0, true, false, false, false,
+ handle_no_stack_protect_function_attribute,
+ NULL },
{ "noinline", 0, 0, true, false, false, false,
handle_noinline_attribute,
attr_noinline_exclusions },
@@ -1017,6 +1022,34 @@ handle_stack_protect_attribute (tree *node, tree name, tree, int,
warning (OPT_Wattributes, "%qE attribute ignored", name);
*no_add_attrs = true;
}
+ else if (lookup_attribute ("no_stack_protect", DECL_ATTRIBUTES (*node)))
+ {
+ warning (OPT_Wattributes, "%qE attribute ignored due to conflict "
+ "with %qs attribute", name, "no_stack_protect");
+ *no_add_attrs = true;
+ }
+
+ return NULL_TREE;
+}
+
+/* Handle a "no_stack_protect" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_no_stack_protect_function_attribute (tree *node, tree name, tree,
+ int, bool *no_add_attrs)
+{
+ if (TREE_CODE (*node) != FUNCTION_DECL)
+ {
+ warning (OPT_Wattributes, "%qE attribute ignored", name);
+ *no_add_attrs = true;
+ }
+ else if (lookup_attribute ("stack_protect", DECL_ATTRIBUTES (*node)))
+ {
+ warning (OPT_Wattributes, "%qE attribute ignored due to conflict "
+ "with %qs attribute", name, "stack_protect");
+ *no_add_attrs = true;
+ }
return NULL_TREE;
}
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index b66c3e5f7af..6e8687c392c 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -1831,11 +1831,12 @@ stack_protect_decl_phase (tree decl)
if (bits & SPCT_HAS_SMALL_CHAR_ARRAY)
has_short_buffer = true;
- if (flag_stack_protect == SPCT_FLAG_ALL
- || flag_stack_protect == SPCT_FLAG_STRONG
- || (flag_stack_protect == SPCT_FLAG_EXPLICIT
- && lookup_attribute ("stack_protect",
- DECL_ATTRIBUTES (current_function_decl))))
+ tree attribs = DECL_ATTRIBUTES (current_function_decl);
+ if (!lookup_attribute ("no_stack_protect", attribs)
+ && (flag_stack_protect == SPCT_FLAG_ALL
+ || flag_stack_protect == SPCT_FLAG_STRONG
+ || (flag_stack_protect == SPCT_FLAG_EXPLICIT
+ && lookup_attribute ("stack_protect", attribs))))
{
if ((bits & (SPCT_HAS_SMALL_CHAR_ARRAY | SPCT_HAS_LARGE_CHAR_ARRAY))
&& !(bits & SPCT_HAS_AGGREGATE))
@@ -2136,6 +2137,7 @@ expand_used_vars (void)
set are actually used by the optimized function. Lay them out. */
expand_used_vars_for_block (outer_block, true);
+ tree attribs = DECL_ATTRIBUTES (current_function_decl);
if (stack_vars_num > 0)
{
bool has_addressable_vars = false;
@@ -2145,10 +2147,10 @@ expand_used_vars (void)
/* If stack protection is enabled, we don't share space between
vulnerable data and non-vulnerable data. */
if (flag_stack_protect != 0
+ && !lookup_attribute ("no_stack_protect", attribs)
&& (flag_stack_protect != SPCT_FLAG_EXPLICIT
|| (flag_stack_protect == SPCT_FLAG_EXPLICIT
- && lookup_attribute ("stack_protect",
- DECL_ATTRIBUTES (current_function_decl)))))
+ && lookup_attribute ("stack_protect", attribs))))
has_addressable_vars = add_stack_protection_conflicts ();
if (flag_stack_protect == SPCT_FLAG_STRONG && has_addressable_vars)
@@ -2161,38 +2163,40 @@ expand_used_vars (void)
dump_stack_var_partition ();
}
- switch (flag_stack_protect)
- {
- case SPCT_FLAG_ALL:
- create_stack_guard ();
- break;
- case SPCT_FLAG_STRONG:
- if (gen_stack_protect_signal
- || cfun->calls_alloca
- || has_protected_decls
- || lookup_attribute ("stack_protect",
- DECL_ATTRIBUTES (current_function_decl)))
+ if (!lookup_attribute ("no_stack_protect", attribs))
+ switch (flag_stack_protect)
+ {
+ case SPCT_FLAG_ALL:
create_stack_guard ();
- break;
+ break;
- case SPCT_FLAG_DEFAULT:
- if (cfun->calls_alloca
- || has_protected_decls
- || lookup_attribute ("stack_protect",
- DECL_ATTRIBUTES (current_function_decl)))
- create_stack_guard ();
- break;
+ case SPCT_FLAG_STRONG:
+ if (gen_stack_protect_signal
+ || cfun->calls_alloca
+ || has_protected_decls
+ || lookup_attribute ("stack_protect",
+ DECL_ATTRIBUTES (current_function_decl)))
+ create_stack_guard ();
+ break;
- case SPCT_FLAG_EXPLICIT:
- if (lookup_attribute ("stack_protect",
- DECL_ATTRIBUTES (current_function_decl)))
- create_stack_guard ();
- break;
+ case SPCT_FLAG_DEFAULT:
+ if (cfun->calls_alloca
+ || has_protected_decls
+ || lookup_attribute ("stack_protect",
+ DECL_ATTRIBUTES (current_function_decl)))
+ create_stack_guard ();
+ break;
- default:
- break;
- }
+ case SPCT_FLAG_EXPLICIT:
+ if (lookup_attribute ("stack_protect",
+ DECL_ATTRIBUTES (current_function_decl)))
+ create_stack_guard ();
+ break;
+
+ default:
+ break;
+ }
/* Assign rtl to each variable based on these partitions. */
if (stack_vars_num > 0)
@@ -2213,11 +2217,11 @@ expand_used_vars (void)
expand_stack_vars (stack_protect_decl_phase_1, &data);
/* Phase 2 contains other kinds of arrays. */
- if (flag_stack_protect == SPCT_FLAG_ALL
- || flag_stack_protect == SPCT_FLAG_STRONG
- || (flag_stack_protect == SPCT_FLAG_EXPLICIT
- && lookup_attribute ("stack_protect",
- DECL_ATTRIBUTES (current_function_decl))))
+ if (!lookup_attribute ("no_stack_protect", attribs)
+ && (flag_stack_protect == SPCT_FLAG_ALL
+ || flag_stack_protect == SPCT_FLAG_STRONG
+ || (flag_stack_protect == SPCT_FLAG_EXPLICIT
+ && lookup_attribute ("stack_protect", attribs))))
expand_stack_vars (stack_protect_decl_phase_2, &data);
}
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index c80848e9061..604bf37e916 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -3671,6 +3671,10 @@ This attribute adds stack protection code to the function if
flags @option{-fstack-protector}, @option{-fstack-protector-strong}
or @option{-fstack-protector-explicit} are set.
+@item no_stack_protect
+@cindex @code{no_stack_protect} function attribute
+This attribute prevents stack protection code for the function.
+
@item target (@var{string}, @dots{})
@cindex @code{target} function attribute
Multiple target back ends implement the @code{target} attribute
diff --git a/gcc/testsuite/g++.dg/no-stack-protect-attr-2.C b/gcc/testsuite/g++.dg/no-stack-protect-attr-2.C
new file mode 100644
index 00000000000..dcac6f9d389
--- /dev/null
+++ b/gcc/testsuite/g++.dg/no-stack-protect-attr-2.C
@@ -0,0 +1,7 @@
+/* PR c/94722 */
+/* { dg-do compile } */
+
+int __attribute__((no_stack_protect, stack_protect)) c() /* { dg-warning "'stack_protect' attribute ignored due to conflict with 'no_stack_protect' attribute" } */
+{
+ return 0;
+}
diff --git a/gcc/testsuite/g++.dg/no-stack-protect-attr-3.C b/gcc/testsuite/g++.dg/no-stack-protect-attr-3.C
new file mode 100644
index 00000000000..a6b702ba5ea
--- /dev/null
+++ b/gcc/testsuite/g++.dg/no-stack-protect-attr-3.C
@@ -0,0 +1,23 @@
+/* PR c/94722 */
+/* Test that stack protection is disabled via no_stack_protect attribute. */
+
+/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
+/* { dg-options "-O2 -fstack-protector-explicit" } */
+
+/* { dg-do compile } */
+
+int __attribute__((no_stack_protect)) foo()
+{
+ int a;
+ char b[34];
+ return 0;
+}
+
+int __attribute__((stack_protect)) bar()
+{
+ int a;
+ char b[34];
+ return 0;
+}
+
+/* { dg-final { scan-assembler-times "stack_chk_fail" 1 } } */
diff --git a/gcc/testsuite/g++.dg/no-stack-protect-attr.C b/gcc/testsuite/g++.dg/no-stack-protect-attr.C
new file mode 100644
index 00000000000..8332e5b276d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/no-stack-protect-attr.C
@@ -0,0 +1,16 @@
+/* PR c/94722 */
+/* Test that stack protection is disabled via no_stack_protect attribute. */
+
+/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
+/* { dg-options "-O2 -fstack-protector-all" } */
+
+/* { dg-do compile } */
+
+int __attribute__((no_stack_protect)) c()
+{
+ int a;
+ char b[34];
+ return 0;
+}
+
+/* { dg-final { scan-assembler-not "stack_chk_fail" } } */
--
2.26.2
>From 2465dd4f502824548472a4c303cde25c157215ef Mon Sep 17 00:00:00 2001
From: Martin Liska <mli...@suse.cz>
Date: Fri, 15 May 2020 14:51:24 +0200
Subject: [PATCH 1/2] Come up with stack_protector enum.
gcc/ChangeLog:
2020-05-15 Martin Liska <mli...@suse.cz>
* cfgexpand.c: Move the enum to ...
* coretypes.h (enum stack_protector): ... here.
* function.c (assign_parm_adjust_stack_rtl): Use the stack_protector
enum.
gcc/c-family/ChangeLog:
2020-05-15 Martin Liska <mli...@suse.cz>
* c-cppbuiltin.c (c_cpp_builtins): Use the stack_protector enum.
---
gcc/c-family/c-cppbuiltin.c | 8 ++++----
gcc/cfgexpand.c | 7 -------
gcc/coretypes.h | 8 ++++++++
gcc/function.c | 2 +-
4 files changed, 13 insertions(+), 12 deletions(-)
diff --git a/gcc/c-family/c-cppbuiltin.c b/gcc/c-family/c-cppbuiltin.c
index a7d65d63934..9164400a046 100644
--- a/gcc/c-family/c-cppbuiltin.c
+++ b/gcc/c-family/c-cppbuiltin.c
@@ -1425,13 +1425,13 @@ c_cpp_builtins (cpp_reader *pfile)
/* Make the choice of the stack protector runtime visible to source code.
The macro names and values here were chosen for compatibility with an
earlier implementation, i.e. ProPolice. */
- if (flag_stack_protect == 4)
+ if (flag_stack_protect == SPCT_FLAG_EXPLICIT)
cpp_define (pfile, "__SSP_EXPLICIT__=4");
- if (flag_stack_protect == 3)
+ if (flag_stack_protect == SPCT_FLAG_STRONG)
cpp_define (pfile, "__SSP_STRONG__=3");
- if (flag_stack_protect == 2)
+ if (flag_stack_protect == SPCT_FLAG_ALL)
cpp_define (pfile, "__SSP_ALL__=2");
- else if (flag_stack_protect == 1)
+ else if (flag_stack_protect == SPCT_FLAG_DEFAULT)
cpp_define (pfile, "__SSP__=1");
if (flag_openacc)
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 2f6ec97ed04..b66c3e5f7af 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -1762,13 +1762,6 @@ clear_tree_used (tree block)
clear_tree_used (t);
}
-enum {
- SPCT_FLAG_DEFAULT = 1,
- SPCT_FLAG_ALL = 2,
- SPCT_FLAG_STRONG = 3,
- SPCT_FLAG_EXPLICIT = 4
-};
-
/* Examine TYPE and determine a bit mask of the following features. */
#define SPCT_HAS_LARGE_CHAR_ARRAY 1
diff --git a/gcc/coretypes.h b/gcc/coretypes.h
index cda22697cc3..323b1cf0f1e 100644
--- a/gcc/coretypes.h
+++ b/gcc/coretypes.h
@@ -219,6 +219,14 @@ enum profile_reproducibility {
PROFILE_REPRODUCIBILITY_MULTITHREADED
};
+/* Type of -fstack-protector-*. */
+enum stack_protector {
+ SPCT_FLAG_DEFAULT = 1,
+ SPCT_FLAG_ALL = 2,
+ SPCT_FLAG_STRONG = 3,
+ SPCT_FLAG_EXPLICIT = 4
+};
+
/* Types of unwind/exception handling info that can be generated. */
enum unwind_info_type
diff --git a/gcc/function.c b/gcc/function.c
index 9eee9b59bfd..fe5c91809f3 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -2841,7 +2841,7 @@ assign_parm_adjust_stack_rtl (struct assign_parm_data_one *data)
/* If stack protection is in effect for this function, don't leave any
pointers in their passed stack slots. */
else if (crtl->stack_protect_guard
- && (flag_stack_protect == 2
+ && (flag_stack_protect == SPCT_FLAG_ALL
|| data->arg.pass_by_reference
|| POINTER_TYPE_P (data->nominal_type)))
stack_parm = NULL;
--
2.26.2
