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GCC plugins updates for v5.9-rc1

Browse Source 
- Update URLs for HTTPS scheme where available (Alexander A. Klimov)
 - Improve STACKLEAK code generation on x86 (Alexander Popov)
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Merge tag 'gcc-plugins-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull gcc plugin updates from Kees Cook:
 "Primarily improvements to STACKLEAK from Alexander Popov, along with
  some additional cleanups.

    - Update URLs for HTTPS scheme where available (Alexander A. Klimov)

   - Improve STACKLEAK code generation on x86 (Alexander Popov)"

* tag 'gcc-plugins-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  gcc-plugins: Replace HTTP links with HTTPS ones
  gcc-plugins/stackleak: Add 'verbose' plugin parameter
  gcc-plugins/stackleak: Use asm instrumentation to avoid useless register saving
  ARM: vdso: Don't use gcc plugins for building vgettimeofday.c
  gcc-plugins/stackleak: Don't instrument itself
This commit is contained in:
Linus Torvalds 2020-08-04 13:26:06 -07:00
commit 3e4a12a1ba
9 changed files with 241 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/arm/vdso/Makefile
View File

@ -29,7 +29,7 @@ CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
CFLAGS_REMOVE_vdso.o = -pg
# Force -O2 to avoid libgcc dependencies
CFLAGS_REMOVE_vgettimeofday.o = -pg -Os
CFLAGS_REMOVE_vgettimeofday.o = -pg -Os $(GCC_PLUGINS_CFLAGS)
ifeq ($(c-gettimeofday-y),)
CFLAGS_vgettimeofday.o = -O2
else

13
include/linux/compiler_attributes.h
View File

@ -37,6 +37,7 @@
# define __GCC4_has_attribute___copy__ 0
# define __GCC4_has_attribute___designated_init__ 0
# define __GCC4_has_attribute___externally_visible__ 1
# define __GCC4_has_attribute___no_caller_saved_registers__ 0
# define __GCC4_has_attribute___noclone__ 1
# define __GCC4_has_attribute___nonstring__ 0
# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
@ -176,6 +177,18 @@
*/
#define __mode(x) __attribute__((__mode__(x)))
/*
* Optional: only supported since gcc >= 7
*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#index-no_005fcaller_005fsaved_005fregisters-function-attribute_002c-x86
* clang: https://clang.llvm.org/docs/AttributeReference.html#no-caller-saved-registers
*/
#if __has_attribute(__no_caller_saved_registers__)
# define __no_caller_saved_registers __attribute__((__no_caller_saved_registers__))
#else
# define __no_caller_saved_registers
#endif
/*
* Optional: not supported by clang
*

1
kernel/Makefile
View File

@ -125,6 +125,7 @@ obj-$(CONFIG_WATCH_QUEUE) += watch_queue.o
obj-$(CONFIG_SYSCTL_KUNIT_TEST) += sysctl-test.o
CFLAGS_stackleak.o += $(DISABLE_STACKLEAK_PLUGIN)
obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak.o
KASAN_SANITIZE_stackleak.o := n
KCSAN_SANITIZE_stackleak.o := n

16
kernel/stackleak.c
View File

@ -104,19 +104,9 @@ asmlinkage void notrace stackleak_erase(void)
}
NOKPROBE_SYMBOL(stackleak_erase);
void __used notrace stackleak_track_stack(void)
void __used __no_caller_saved_registers notrace stackleak_track_stack(void)
{
/*
* N.B. stackleak_erase() fills the kernel stack with the poison value,
* which has the register width. That code assumes that the value
* of 'lowest_stack' is aligned on the register width boundary.
*
* That is true for x86 and x86_64 because of the kernel stack
* alignment on these platforms (for details, see 'cc_stack_align' in
* arch/x86/Makefile). Take care of that when you port STACKLEAK to
* new platforms.
*/
unsigned long sp = (unsigned long)&sp;
unsigned long sp = current_stack_pointer;
/*
* Having CONFIG_STACKLEAK_TRACK_MIN_SIZE larger than
@ -125,6 +115,8 @@ void __used notrace stackleak_track_stack(void)
*/
BUILD_BUG_ON(CONFIG_STACKLEAK_TRACK_MIN_SIZE > STACKLEAK_SEARCH_DEPTH);
/* 'lowest_stack' should be aligned on the register width boundary */
sp = ALIGN(sp, sizeof(unsigned long));
if (sp < current->lowest_stack &&
sp >= (unsigned long)task_stack_page(current) +
sizeof(unsigned long)) {

2
scripts/Makefile.gcc-plugins
View File

@ -33,6 +33,8 @@ gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \
+= -DSTACKLEAK_PLUGIN
gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \
+= -fplugin-arg-stackleak_plugin-track-min-size=$(CONFIG_STACKLEAK_TRACK_MIN_SIZE)
gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \
+= -fplugin-arg-stackleak_plugin-arch=$(SRCARCH)
ifdef CONFIG_GCC_PLUGIN_STACKLEAK
DISABLE_STACKLEAK_PLUGIN += -fplugin-arg-stackleak_plugin-disable
endif

2
scripts/gcc-plugins/cyc_complexity_plugin.c
View File

@ -5,7 +5,7 @@
* Homepage:
* https://github.com/ephox-gcc-plugins/cyclomatic_complexity
*
* http://en.wikipedia.org/wiki/Cyclomatic_complexity
* https://en.wikipedia.org/wiki/Cyclomatic_complexity
* The complexity M is then defined as:
* M = E - N + 2P
* where

2
scripts/gcc-plugins/sancov_plugin.c
View File

@ -11,7 +11,7 @@
*
* You can read about it more here:
* https://gcc.gnu.org/viewcvs/gcc?limit_changes=0&view=revision&revision=231296
* http://lwn.net/Articles/674854/
* https://lwn.net/Articles/674854/
* https://github.com/google/syzkaller
* https://lwn.net/Articles/677764/
*

248
scripts/gcc-plugins/stackleak_plugin.c
View File

@ -20,7 +20,7 @@
*
* Debugging:
* - use fprintf() to stderr, debug_generic_expr(), debug_gimple_stmt(),
* print_rtl() and print_simple_rtl();
* print_rtl_single() and debug_rtx();
* - add "-fdump-tree-all -fdump-rtl-all" to the plugin CFLAGS in
* Makefile.gcc-plugins to see the verbose dumps of the gcc passes;
* - use gcc -E to understand the preprocessing shenanigans;
@ -32,7 +32,10 @@
__visible int plugin_is_GPL_compatible;
static int track_frame_size = -1;
static bool build_for_x86 = false;
static const char track_function[] = "stackleak_track_stack";
static bool disable = false;
static bool verbose = false;
/*
* Mark these global variables (roots) for gcc garbage collector since
@ -43,32 +46,32 @@ static GTY(()) tree track_function_decl;
static struct plugin_info stackleak_plugin_info = {
.version = "201707101337",
.help = "track-min-size=nn\ttrack stack for functions with a stack frame size >= nn bytes\n"
"arch=target_arch\tspecify target build arch\n"
"disable\t\tdo not activate the plugin\n"
"verbose\t\tprint info about the instrumentation\n"
};
static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after)
static void add_stack_tracking_gcall(gimple_stmt_iterator *gsi, bool after)
{
gimple stmt;
gcall *stackleak_track_stack;
gcall *gimple_call;
cgraph_node_ptr node;
basic_block bb;
/* Insert call to void stackleak_track_stack(void) */
/* Insert calling stackleak_track_stack() */
stmt = gimple_build_call(track_function_decl, 0);
stackleak_track_stack = as_a_gcall(stmt);
if (after) {
gsi_insert_after(gsi, stackleak_track_stack,
GSI_CONTINUE_LINKING);
} else {
gsi_insert_before(gsi, stackleak_track_stack, GSI_SAME_STMT);
}
gimple_call = as_a_gcall(stmt);
if (after)
gsi_insert_after(gsi, gimple_call, GSI_CONTINUE_LINKING);
else
gsi_insert_before(gsi, gimple_call, GSI_SAME_STMT);
/* Update the cgraph */
bb = gimple_bb(stackleak_track_stack);
bb = gimple_bb(gimple_call);
node = cgraph_get_create_node(track_function_decl);
gcc_assert(node);
cgraph_create_edge(cgraph_get_node(current_function_decl), node,
stackleak_track_stack, bb->count,
gimple_call, bb->count,
compute_call_stmt_bb_frequency(current_function_decl, bb));
}
@ -85,6 +88,83 @@ static bool is_alloca(gimple stmt)
return false;
}
static tree get_current_stack_pointer_decl(void)
{
varpool_node_ptr node;
FOR_EACH_VARIABLE(node) {
tree var = NODE_DECL(node);
tree name = DECL_NAME(var);
if (DECL_NAME_LENGTH(var) != sizeof("current_stack_pointer") - 1)
continue;
if (strcmp(IDENTIFIER_POINTER(name), "current_stack_pointer"))
continue;
return var;
}
if (verbose) {
fprintf(stderr, "stackleak: missing current_stack_pointer in %s()\n",
DECL_NAME_POINTER(current_function_decl));
}
return NULL_TREE;
}
static void add_stack_tracking_gasm(gimple_stmt_iterator *gsi, bool after)
{
gasm *asm_call = NULL;
tree sp_decl, input;
vec<tree, va_gc> *inputs = NULL;
/* 'no_caller_saved_registers' is currently supported only for x86 */
gcc_assert(build_for_x86);
/*
* Insert calling stackleak_track_stack() in asm:
* asm volatile("call stackleak_track_stack"
* :: "r" (current_stack_pointer))
* Use ASM_CALL_CONSTRAINT trick from arch/x86/include/asm/asm.h.
* This constraint is taken into account during gcc shrink-wrapping
* optimization. It is needed to be sure that stackleak_track_stack()
* call is inserted after the prologue of the containing function,
* when the stack frame is prepared.
*/
sp_decl = get_current_stack_pointer_decl();
if (sp_decl == NULL_TREE) {
add_stack_tracking_gcall(gsi, after);
return;
}
input = build_tree_list(NULL_TREE, build_const_char_string(2, "r"));
input = chainon(NULL_TREE, build_tree_list(input, sp_decl));
vec_safe_push(inputs, input);
asm_call = gimple_build_asm_vec("call stackleak_track_stack",
inputs, NULL, NULL, NULL);
gimple_asm_set_volatile(asm_call, true);
if (after)
gsi_insert_after(gsi, asm_call, GSI_CONTINUE_LINKING);
else
gsi_insert_before(gsi, asm_call, GSI_SAME_STMT);
update_stmt(asm_call);
}
static void add_stack_tracking(gimple_stmt_iterator *gsi, bool after)
{
/*
* The 'no_caller_saved_registers' attribute is used for
* stackleak_track_stack(). If the compiler supports this attribute for
* the target arch, we can add calling stackleak_track_stack() in asm.
* That improves performance: we avoid useless operations with the
* caller-saved registers in the functions from which we will remove
* stackleak_track_stack() call during the stackleak_cleanup pass.
*/
if (lookup_attribute_spec(get_identifier("no_caller_saved_registers")))
add_stack_tracking_gasm(gsi, after);
else
add_stack_tracking_gcall(gsi, after);
}
/*
* Work with the GIMPLE representation of the code. Insert the
* stackleak_track_stack() call after alloca() and into the beginning
@ -94,7 +174,7 @@ static unsigned int stackleak_instrument_execute(void)
{
basic_block bb, entry_bb;
bool prologue_instrumented = false, is_leaf = true;
gimple_stmt_iterator gsi;
gimple_stmt_iterator gsi = { 0 };
/*
* ENTRY_BLOCK_PTR is a basic block which represents possible entry
@ -122,8 +202,13 @@ static unsigned int stackleak_instrument_execute(void)
if (!is_alloca(stmt))
continue;
if (verbose) {
fprintf(stderr, "stackleak: be careful, alloca() in %s()\n",
DECL_NAME_POINTER(current_function_decl));
}
/* Insert stackleak_track_stack() call after alloca() */
stackleak_add_track_stack(&gsi, true);
add_stack_tracking(&gsi, true);
if (bb == entry_bb)
prologue_instrumented = true;
}
@ -168,7 +253,7 @@ static unsigned int stackleak_instrument_execute(void)
bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
}
gsi = gsi_after_labels(bb);
stackleak_add_track_stack(&gsi, false);
add_stack_tracking(&gsi, false);
return 0;
}
@ -182,21 +267,10 @@ static bool large_stack_frame(void)
#endif
}
/*
* Work with the RTL representation of the code.
* Remove the unneeded stackleak_track_stack() calls from the functions
* which don't call alloca() and don't have a large enough stack frame size.
*/
static unsigned int stackleak_cleanup_execute(void)
static void remove_stack_tracking_gcall(void)
{
rtx_insn *insn, *next;
if (cfun->calls_alloca)
return 0;
if (large_stack_frame())
return 0;
/*
* Find stackleak_track_stack() calls. Loop through the chain of insns,
* which is an RTL representation of the code for a function.
@ -257,6 +331,102 @@ static unsigned int stackleak_cleanup_execute(void)
}
#endif
}
}
static bool remove_stack_tracking_gasm(void)
{
bool removed = false;
rtx_insn *insn, *next;
/* 'no_caller_saved_registers' is currently supported only for x86 */
gcc_assert(build_for_x86);
/*
* Find stackleak_track_stack() asm calls. Loop through the chain of
* insns, which is an RTL representation of the code for a function.
*
* The example of a matching insn:
* (insn 11 5 12 2 (parallel [ (asm_operands/v
* ("call stackleak_track_stack") ("") 0
* [ (reg/v:DI 7 sp [ current_stack_pointer ]) ]
* [ (asm_input:DI ("r")) ] [])
* (clobber (reg:CC 17 flags)) ]) -1 (nil))
*/
for (insn = get_insns(); insn; insn = next) {
rtx body;
next = NEXT_INSN(insn);
/* Check the expression code of the insn */
if (!NONJUMP_INSN_P(insn))
continue;
/*
* Check the expression code of the insn body, which is an RTL
* Expression (RTX) describing the side effect performed by
* that insn.
*/
body = PATTERN(insn);
if (GET_CODE(body) != PARALLEL)
continue;
body = XVECEXP(body, 0, 0);
if (GET_CODE(body) != ASM_OPERANDS)
continue;
if (strcmp(ASM_OPERANDS_TEMPLATE(body),
"call stackleak_track_stack")) {
continue;
}
delete_insn_and_edges(insn);
gcc_assert(!removed);
removed = true;
}
return removed;
}
/*
* Work with the RTL representation of the code.
* Remove the unneeded stackleak_track_stack() calls from the functions
* which don't call alloca() and don't have a large enough stack frame size.
*/
static unsigned int stackleak_cleanup_execute(void)
{
const char *fn = DECL_NAME_POINTER(current_function_decl);
bool removed = false;
/*
* Leave stack tracking in functions that call alloca().
* Additional case:
* gcc before version 7 called allocate_dynamic_stack_space() from
* expand_stack_vars() for runtime alignment of constant-sized stack
* variables. That caused cfun->calls_alloca to be set for functions
* that in fact don't use alloca().
* For more info see gcc commit 7072df0aae0c59ae437e.
* Let's leave such functions instrumented as well.
*/
if (cfun->calls_alloca) {
if (verbose)
fprintf(stderr, "stackleak: instrument %s(): calls_alloca\n", fn);
return 0;
}
/* Leave stack tracking in functions with large stack frame */
if (large_stack_frame()) {
if (verbose)
fprintf(stderr, "stackleak: instrument %s()\n", fn);
return 0;
}
if (lookup_attribute_spec(get_identifier("no_caller_saved_registers")))
removed = remove_stack_tracking_gasm();
if (!removed)
remove_stack_tracking_gcall();
return 0;
}
@ -376,9 +546,6 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
/* Parse the plugin arguments */
for (i = 0; i < argc; i++) {
if (!strcmp(argv[i].key, "disable"))
return 0;
if (!strcmp(argv[i].key, "track-min-size")) {
if (!argv[i].value) {
error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
@ -392,6 +559,19 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
plugin_name, argv[i].key, argv[i].value);
return 1;
}
} else if (!strcmp(argv[i].key, "arch")) {
if (!argv[i].value) {
error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
plugin_name, argv[i].key);
return 1;
}
if (!strcmp(argv[i].value, "x86"))
build_for_x86 = true;
} else if (!strcmp(argv[i].key, "disable")) {
disable = true;
} else if (!strcmp(argv[i].key, "verbose")) {
verbose = true;
} else {
error(G_("unknown option '-fplugin-arg-%s-%s'"),
plugin_name, argv[i].key);
@ -399,6 +579,12 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
}
}
if (disable) {
if (verbose)
fprintf(stderr, "stackleak: disabled for this translation unit\n");
return 0;
}
/* Give the information about the plugin */
register_callback(plugin_name, PLUGIN_INFO, NULL,
&stackleak_plugin_info);

2
scripts/gcc-plugins/structleak_plugin.c
View File

@ -11,7 +11,7 @@
* otherwise leak kernel stack to userland if they aren't properly initialized
* by later code
*
* Homepage: http://pax.grsecurity.net/
* Homepage: https://pax.grsecurity.net/
*
* Options:
* -fplugin-arg-structleak_plugin-disable