On Tue, Oct 16, 2012 at 02:41:42PM -0700, Xinliang David Li wrote:
> On Tue, Oct 16, 2012 at 7:58 AM, Jakub Jelinek <ja...@redhat.com> wrote:
> Why the above two condition? If the linker picks the larger size one,
> it is ok to do the instrumentation.
Added more comments, creation of local aliases when needed, and construction
of global var description strings.
Again, only very lightly tested.
__has_dynamic_init is still always 0, setting it to non-zero would require
dynamic initialization order support, which I'll happily leave to others.
And the addresses are still absolute (i.e. the global vars descriptor is
still likely .data.relro.local section for -fpic), both the __beg and
__name fields, but changing it would require first libasan changes.
Ok for asan?
2012-10-17 Jakub Jelinek <ja...@redhat.com>
* varasm.c: Include asan.h.
(assemble_noswitch_variable): Grow size by asan_red_zone_size
if decl is asan protected.
(place_block_symbol): Likewise.
(assemble_variable): If decl is asan protected, increase
DECL_ALIGN if needed, and for decls emitted using
assemble_variable_contents append padding zeros after it.
* Makefile.in (varasm.o): Depend on asan.h.
* asan.c: Include output.h.
(asan_pp, asan_pp_initialized): New variables.
(asan_pp_initialize, asan_pp_string): New functions.
(asan_emit_stack_protection): Use asan_pp{,_initialized}
instead of local pp{,_initialized} vars, use asan_pp_initialize
and asan_pp_string helpers.
(asan_needs_local_alias, asan_protect_global,
asan_global_struct, asan_add_global): New functions.
(asan_finish_file): Protect global vars that can be protected.
* asan.h (asan_protect_global): New prototype.
(asan_red_zone_size): New inline function.
--- gcc/varasm.c.jj 2012-10-11 19:10:39.000000000 +0200
+++ gcc/varasm.c 2012-10-16 15:40:37.075662625 +0200
@@ -51,6 +51,7 @@ along with GCC; see the file COPYING3.
#include "tree-mudflap.h"
#include "cgraph.h"
#include "pointer-set.h"
+#include "asan.h"
#ifdef XCOFF_DEBUGGING_INFO
#include "xcoffout.h" /* Needed for external data
@@ -1831,6 +1832,9 @@ assemble_noswitch_variable (tree decl, c
size = tree_low_cst (DECL_SIZE_UNIT (decl), 1);
rounded = size;
+ if (flag_asan && asan_protect_global (decl))
+ size += asan_red_zone_size (size);
+
/* Don't allocate zero bytes of common,
since that means "undefined external" in the linker. */
if (size == 0)
@@ -1897,6 +1901,7 @@ assemble_variable (tree decl, int top_le
const char *name;
rtx decl_rtl, symbol;
section *sect;
+ bool asan_protected = false;
/* This function is supposed to handle VARIABLES. Ensure we have one. */
gcc_assert (TREE_CODE (decl) == VAR_DECL);
@@ -1984,6 +1989,15 @@ assemble_variable (tree decl, int top_le
/* Compute the alignment of this data. */
align_variable (decl, dont_output_data);
+
+ if (flag_asan
+ && asan_protect_global (decl)
+ && DECL_ALIGN (decl) < ASAN_RED_ZONE_SIZE * BITS_PER_UNIT)
+ {
+ asan_protected = true;
+ DECL_ALIGN (decl) = ASAN_RED_ZONE_SIZE * BITS_PER_UNIT;
+ }
+
set_mem_align (decl_rtl, DECL_ALIGN (decl));
if (TREE_PUBLIC (decl))
@@ -2022,6 +2036,12 @@ assemble_variable (tree decl, int top_le
if (DECL_ALIGN (decl) > BITS_PER_UNIT)
ASM_OUTPUT_ALIGN (asm_out_file, floor_log2 (DECL_ALIGN_UNIT (decl)));
assemble_variable_contents (decl, name, dont_output_data);
+ if (asan_protected)
+ {
+ unsigned HOST_WIDE_INT int size
+ = tree_low_cst (DECL_SIZE_UNIT (decl), 1);
+ assemble_zeros (asan_red_zone_size (size));
+ }
}
}
@@ -6926,6 +6946,8 @@ place_block_symbol (rtx symbol)
decl = SYMBOL_REF_DECL (symbol);
alignment = DECL_ALIGN (decl);
size = tree_low_cst (DECL_SIZE_UNIT (decl), 1);
+ if (flag_asan && asan_protect_global (decl))
+ size += asan_red_zone_size (size);
}
/* Calculate the object's offset from the start of the block. */
--- gcc/Makefile.in.jj 2012-10-15 09:40:40.000000000 +0200
+++ gcc/Makefile.in 2012-10-17 13:00:02.995133686 +0200
@@ -2712,7 +2712,7 @@ varasm.o : varasm.c $(CONFIG_H) $(SYSTEM
output.h $(DIAGNOSTIC_CORE_H) xcoffout.h debug.h $(GGC_H) $(TM_P_H) \
$(HASHTAB_H) $(TARGET_H) langhooks.h gt-varasm.h $(BASIC_BLOCK_H) \
$(CGRAPH_H) $(TARGET_DEF_H) tree-mudflap.h \
- pointer-set.h $(COMMON_TARGET_H)
+ pointer-set.h $(COMMON_TARGET_H) asan.h
function.o : function.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H)
$(RTL_ERROR_H) \
$(TREE_H) $(GIMPLE_H) $(FLAGS_H) $(FUNCTION_H) $(EXPR_H) \
$(OPTABS_H) $(LIBFUNCS_H) $(REGS_H) hard-reg-set.h insn-config.h $(RECOG_H)
\
--- gcc/asan.c.jj 2012-10-16 12:18:41.000000000 +0200
+++ gcc/asan.c 2012-10-17 12:59:45.663228828 +0200
@@ -45,6 +45,7 @@ along with GCC; see the file COPYING3.
#include "target.h"
#include "expr.h"
#include "optabs.h"
+#include "output.h"
/*
AddressSanitizer finds out-of-bounds and use-after-free bugs
@@ -87,6 +88,34 @@ alias_set_type asan_shadow_set = -1;
alias set is used for all shadow memory accesses. */
static GTY(()) tree shadow_ptr_types[2];
+/* Asan pretty-printer, used for buidling of the description STRING_CSTs. */
+static pretty_printer asan_pp;
+static bool asan_pp_initialized;
+
+/* Initialize asan_pp. */
+
+static void
+asan_pp_initialize (void)
+{
+ pp_construct (&asan_pp, /* prefix */NULL, /* line-width */0);
+ asan_pp_initialized = true;
+}
+
+/* Create ADDR_EXPR of STRING_CST with asan_pp text. */
+
+static tree
+asan_pp_string (void)
+{
+ const char *buf = pp_base_formatted_text (&asan_pp);
+ size_t len = strlen (buf);
+ tree ret = build_string (len + 1, buf);
+ TREE_TYPE (ret)
+ = build_array_type (char_type_node, build_index_type (size_int (len)));
+ TREE_READONLY (ret) = 1;
+ TREE_STATIC (ret) = 1;
+ return build1 (ADDR_EXPR, build_pointer_type (char_type_node), ret);
+}
+
/* Return a CONST_INT representing 4 subsequent shadow memory bytes. */
static rtx
@@ -121,51 +150,38 @@ asan_emit_stack_protection (rtx base, HO
HOST_WIDE_INT last_offset, last_size;
int l;
unsigned char cur_shadow_byte = ASAN_STACK_MAGIC_LEFT;
- static pretty_printer pp;
- static bool pp_initialized;
- const char *buf;
- size_t len;
tree str_cst;
/* First of all, prepare the description string. */
- if (!pp_initialized)
- {
- pp_construct (&pp, /* prefix */NULL, /* line-width */0);
- pp_initialized = true;
- }
- pp_clear_output_area (&pp);
+ if (!asan_pp_initialized)
+ asan_pp_initialize ();
+
+ pp_clear_output_area (&asan_pp);
if (DECL_NAME (current_function_decl))
- pp_base_tree_identifier (&pp, DECL_NAME (current_function_decl));
+ pp_base_tree_identifier (&asan_pp, DECL_NAME (current_function_decl));
else
- pp_string (&pp, "<unknown>");
- pp_space (&pp);
- pp_decimal_int (&pp, length / 2 - 1);
- pp_space (&pp);
+ pp_string (&asan_pp, "<unknown>");
+ pp_space (&asan_pp);
+ pp_decimal_int (&asan_pp, length / 2 - 1);
+ pp_space (&asan_pp);
for (l = length - 2; l; l -= 2)
{
tree decl = decls[l / 2 - 1];
- pp_wide_integer (&pp, offsets[l] - base_offset);
- pp_space (&pp);
- pp_wide_integer (&pp, offsets[l - 1] - offsets[l]);
- pp_space (&pp);
+ pp_wide_integer (&asan_pp, offsets[l] - base_offset);
+ pp_space (&asan_pp);
+ pp_wide_integer (&asan_pp, offsets[l - 1] - offsets[l]);
+ pp_space (&asan_pp);
if (DECL_P (decl) && DECL_NAME (decl))
{
- pp_decimal_int (&pp, IDENTIFIER_LENGTH (DECL_NAME (decl)));
- pp_space (&pp);
- pp_base_tree_identifier (&pp, DECL_NAME (decl));
+ pp_decimal_int (&asan_pp, IDENTIFIER_LENGTH (DECL_NAME (decl)));
+ pp_space (&asan_pp);
+ pp_base_tree_identifier (&asan_pp, DECL_NAME (decl));
}
else
- pp_string (&pp, "9 <unknown>");
- pp_space (&pp);
+ pp_string (&asan_pp, "9 <unknown>");
+ pp_space (&asan_pp);
}
- buf = pp_base_formatted_text (&pp);
- len = strlen (buf);
- str_cst = build_string (len + 1, buf);
- TREE_TYPE (str_cst)
- = build_array_type (char_type_node, build_index_type (size_int (len)));
- TREE_READONLY (str_cst) = 1;
- TREE_STATIC (str_cst) = 1;
- str_cst = build1 (ADDR_EXPR, build_pointer_type (char_type_node), str_cst);
+ str_cst = asan_pp_string ();
/* Emit the prologue sequence. */
base = expand_binop (Pmode, add_optab, base, GEN_INT (base_offset),
@@ -270,6 +286,75 @@ asan_emit_stack_protection (rtx base, HO
return ret;
}
+/* Return true if DECL, a global var, might be overridden and needs
+ therefore a local alias. */
+
+static bool
+asan_needs_local_alias (tree decl)
+{
+ return DECL_WEAK (decl) || !targetm.binds_local_p (decl);
+}
+
+/* Return true if DECL is a VAR_DECL that should be protected
+ by Address Sanitizer, by appending a red zone with protected
+ shadow memory after it and aligning it to at least
+ ASAN_RED_ZONE_SIZE bytes. */
+
+bool
+asan_protect_global (tree decl)
+{
+ rtx rtl, symbol;
+ section *sect;
+
+ if (TREE_CODE (decl) != VAR_DECL
+ /* TLS vars aren't statically protectable. */
+ || DECL_THREAD_LOCAL_P (decl)
+ /* Externs will be protected elsewhere. */
+ || DECL_EXTERNAL (decl)
+ || !TREE_ASM_WRITTEN (decl)
+ || !DECL_RTL_SET_P (decl)
+ /* Comdat vars pose an ABI problem, we can't know if
+ the var that is selected by the linker will have
+ padding or not. */
+ || DECL_ONE_ONLY (decl)
+ /* Similarly for common vars. People can use -fno-common. */
+ || DECL_COMMON (decl)
+ /* Don't protect if using user section, often vars placed
+ into user section from multiple TUs are then assumed
+ to be an array of such vars, putting padding in there
+ breaks this assumption. */
+ || (DECL_SECTION_NAME (decl) != NULL_TREE
+ && !DECL_HAS_IMPLICIT_SECTION_NAME_P (decl))
+ || DECL_SIZE (decl) == 0
+ || ASAN_RED_ZONE_SIZE * BITS_PER_UNIT > MAX_OFILE_ALIGNMENT
+ || !valid_constant_size_p (DECL_SIZE_UNIT (decl))
+ || DECL_ALIGN_UNIT (decl) > 2 * ASAN_RED_ZONE_SIZE)
+ return false;
+
+ rtl = DECL_RTL (decl);
+ if (!MEM_P (rtl) || GET_CODE (XEXP (rtl, 0)) != SYMBOL_REF)
+ return false;
+ symbol = XEXP (rtl, 0);
+
+ if (CONSTANT_POOL_ADDRESS_P (symbol)
+ || TREE_CONSTANT_POOL_ADDRESS_P (symbol))
+ return false;
+
+ sect = get_variable_section (decl, false);
+ if (sect->common.flags & SECTION_COMMON)
+ return false;
+
+ if (lookup_attribute ("weakref", DECL_ATTRIBUTES (decl)))
+ return false;
+
+#ifndef ASM_OUTPUT_DEF
+ if (asan_needs_local_alias (decl))
+ return false;
+#endif
+
+ return true;
+}
+
/* Construct a function tree for __asan_report_{load,store}{1,2,4,8,16}.
IS_STORE is either 1 (for a store) or 0 (for a load).
SIZE_IN_BYTES is one of 1, 2, 4, 8, 16. */
@@ -568,6 +653,101 @@ transform_statements (void)
}
}
+/* Build
+ struct __asan_global
+ {
+ const void *__beg;
+ uptr __size;
+ uptr __size_with_redzone;
+ const void *__name;
+ uptr __has_dynamic_init;
+ } type. */
+
+static tree
+asan_global_struct (void)
+{
+ static const char *field_names[5]
+ = { "__beg", "__size", "__size_with_redzone",
+ "__name", "__has_dynamic_init" };
+ tree fields[5], ret;
+ int i;
+
+ ret = make_node (RECORD_TYPE);
+ for (i = 0; i < 5; i++)
+ {
+ fields[i]
+ = build_decl (UNKNOWN_LOCATION, FIELD_DECL,
+ get_identifier (field_names[i]),
+ (i == 0 || i == 3) ? const_ptr_type_node
+ : build_nonstandard_integer_type (POINTER_SIZE, 1));
+ DECL_CONTEXT (fields[i]) = ret;
+ if (i)
+ DECL_CHAIN (fields[i - 1]) = fields[i];
+ }
+ TYPE_FIELDS (ret) = fields[0];
+ TYPE_NAME (ret) = get_identifier ("__asan_global");
+ layout_type (ret);
+ return ret;
+}
+
+/* Append description of a single global DECL into vector V.
+ TYPE is __asan_global struct type as returned by asan_global_struct. */
+
+static void
+asan_add_global (tree decl, tree type, VEC(constructor_elt, gc) *v)
+{
+ tree init, uptr = TREE_TYPE (DECL_CHAIN (TYPE_FIELDS (type)));
+ unsigned HOST_WIDE_INT size;
+ tree str_cst, refdecl = decl;
+ VEC(constructor_elt, gc) *vinner = NULL;
+
+ if (!asan_pp_initialized)
+ asan_pp_initialize ();
+
+ pp_clear_output_area (&asan_pp);
+ if (DECL_NAME (decl))
+ pp_base_tree_identifier (&asan_pp, DECL_NAME (decl));
+ else
+ pp_string (&asan_pp, "<unknown>");
+ pp_space (&asan_pp);
+ pp_left_paren (&asan_pp);
+ pp_string (&asan_pp, main_input_filename);
+ pp_right_paren (&asan_pp);
+ str_cst = asan_pp_string ();
+
+ if (asan_needs_local_alias (decl))
+ {
+ char buf[20];
+ ASM_GENERATE_INTERNAL_LABEL (buf, "LASAN",
+ VEC_length (constructor_elt, v) + 1);
+ refdecl = build_decl (DECL_SOURCE_LOCATION (decl),
+ VAR_DECL, get_identifier (buf), TREE_TYPE (decl));
+ TREE_ADDRESSABLE (refdecl) = TREE_ADDRESSABLE (decl);
+ TREE_READONLY (refdecl) = TREE_READONLY (decl);
+ TREE_THIS_VOLATILE (refdecl) = TREE_THIS_VOLATILE (decl);
+ DECL_GIMPLE_REG_P (refdecl) = DECL_GIMPLE_REG_P (decl);
+ DECL_ARTIFICIAL (refdecl) = DECL_ARTIFICIAL (decl);
+ DECL_IGNORED_P (refdecl) = DECL_IGNORED_P (decl);
+ TREE_STATIC (refdecl) = 1;
+ TREE_PUBLIC (refdecl) = 0;
+ TREE_USED (refdecl) = 1;
+ assemble_alias (refdecl, DECL_ASSEMBLER_NAME (decl));
+ }
+
+ CONSTRUCTOR_APPEND_ELT (vinner, NULL_TREE,
+ fold_convert (const_ptr_type_node,
+ build_fold_addr_expr (refdecl)));
+ size = tree_low_cst (DECL_SIZE_UNIT (decl), 1);
+ CONSTRUCTOR_APPEND_ELT (vinner, NULL_TREE, build_int_cst (uptr, size));
+ size += asan_red_zone_size (size);
+ CONSTRUCTOR_APPEND_ELT (vinner, NULL_TREE, build_int_cst (uptr, size));
+ CONSTRUCTOR_APPEND_ELT (vinner, NULL_TREE,
+ fold_convert (const_ptr_type_node, str_cst));
+ CONSTRUCTOR_APPEND_ELT (vinner, NULL_TREE, build_int_cst (uptr, 0));
+ init = build_constructor (type, vinner);
+ CONSTRUCTOR_APPEND_ELT (v, NULL_TREE, init);
+}
+
/* Module-level instrumentation.
- Insert __asan_init() into the list of CTORs.
- TODO: insert redzones around globals.
@@ -577,10 +757,61 @@ void
asan_finish_file (void)
{
tree ctor_statements = NULL_TREE;
+ struct varpool_node *vnode;
+ unsigned HOST_WIDE_INT gcount = 0;
+
append_to_statement_list (build_call_expr (asan_init_func (), 0),
- &ctor_statements);
+ &ctor_statements);
+ FOR_EACH_DEFINED_VARIABLE (vnode)
+ if (asan_protect_global (vnode->symbol.decl))
+ ++gcount;
+ if (gcount)
+ {
+ tree type = asan_global_struct (), var, ctor, decl;
+ tree uptr = build_nonstandard_integer_type (POINTER_SIZE, 1);
+ tree dtor_statements = NULL_TREE;
+ VEC(constructor_elt, gc) *v;
+ char buf[20];
+
+ type = build_array_type_nelts (type, gcount);
+ ASM_GENERATE_INTERNAL_LABEL (buf, "LASAN", 0);
+ var = build_decl (UNKNOWN_LOCATION, VAR_DECL, get_identifier (buf),
+ type);
+ TREE_STATIC (var) = 1;
+ TREE_PUBLIC (var) = 0;
+ DECL_ARTIFICIAL (var) = 1;
+ DECL_IGNORED_P (var) = 1;
+ v = VEC_alloc (constructor_elt, gc, gcount);
+ FOR_EACH_DEFINED_VARIABLE (vnode)
+ if (asan_protect_global (vnode->symbol.decl))
+ asan_add_global (vnode->symbol.decl, TREE_TYPE (type), v);
+ ctor = build_constructor (type, v);
+ TREE_CONSTANT (ctor) = 1;
+ TREE_STATIC (ctor) = 1;
+ DECL_INITIAL (var) = ctor;
+ varpool_assemble_decl (varpool_node (var));
+
+ type = build_function_type_list (void_type_node,
+ build_pointer_type (TREE_TYPE (type)),
+ uptr, NULL_TREE);
+ decl = build_fn_decl ("__asan_register_globals", type);
+ TREE_NOTHROW (decl) = 1;
+ append_to_statement_list (build_call_expr (decl, 2,
+ build_fold_addr_expr (var),
+ build_int_cst (uptr, gcount)),
+ &ctor_statements);
+
+ decl = build_fn_decl ("__asan_unregister_globals", type);
+ TREE_NOTHROW (decl) = 1;
+ append_to_statement_list (build_call_expr (decl, 2,
+ build_fold_addr_expr (var),
+ build_int_cst (uptr, gcount)),
+ &dtor_statements);
+ cgraph_build_static_cdtor ('D', dtor_statements,
+ MAX_RESERVED_INIT_PRIORITY - 1);
+ }
cgraph_build_static_cdtor ('I', ctor_statements,
- MAX_RESERVED_INIT_PRIORITY - 1);
+ MAX_RESERVED_INIT_PRIORITY - 1);
}
/* Initialize shadow_ptr_types array. */
--- gcc/asan.h.jj 2012-10-17 11:01:17.720950926 +0200
+++ gcc/asan.h 2012-10-17 11:01:05.669018002 +0200
@@ -23,6 +23,7 @@ along with GCC; see the file COPYING3.
extern void asan_finish_file (void);
extern rtx asan_emit_stack_protection (rtx, HOST_WIDE_INT *, tree *, int);
+extern bool asan_protect_global (tree);
/* Alias set for accessing the shadow memory. */
extern alias_set_type asan_shadow_set;
@@ -56,4 +57,14 @@ asan_protect_stack_decl (tree decl)
return DECL_P (decl) && !DECL_ARTIFICIAL (decl);
}
+/* Return the size of padding needed to insert after a protected
+ decl of SIZE. */
+
+static inline unsigned int
+asan_red_zone_size (unsigned int size)
+{
+ unsigned int c = size & (ASAN_RED_ZONE_SIZE - 1);
+ return c ? 2 * ASAN_RED_ZONE_SIZE - c : ASAN_RED_ZONE_SIZE;
+}
+
#endif /* TREE_ASAN */
Jakub
