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1/*
2 * Copyright 2011-2017 by the PaX Team <pageexec@freemail.hu>
3 * Modified by Alexander Popov <alex.popov@linux.com>
4 * Licensed under the GPL v2
5 *
6 * Note: the choice of the license means that the compilation process is
7 * NOT 'eligible' as defined by gcc's library exception to the GPL v3,
8 * but for the kernel it doesn't matter since it doesn't link against
9 * any of the gcc libraries
10 *
11 * This gcc plugin is needed for tracking the lowest border of the kernel stack.
12 * It instruments the kernel code inserting stackleak_track_stack() calls:
13 * - after alloca();
14 * - for the functions with a stack frame size greater than or equal
15 * to the "track-min-size" plugin parameter.
16 *
17 * This plugin is ported from grsecurity/PaX. For more information see:
18 * https://grsecurity.net/
19 * https://pax.grsecurity.net/
20 *
21 * Debugging:
22 * - use fprintf() to stderr, debug_generic_expr(), debug_gimple_stmt(),
23 * print_rtl() and print_simple_rtl();
24 * - add "-fdump-tree-all -fdump-rtl-all" to the plugin CFLAGS in
25 * Makefile.gcc-plugins to see the verbose dumps of the gcc passes;
26 * - use gcc -E to understand the preprocessing shenanigans;
27 * - use gcc with enabled CFG/GIMPLE/SSA verification (--enable-checking).
28 */
29
30#include "gcc-common.h"
31
32__visible int plugin_is_GPL_compatible;
33
34static int track_frame_size = -1;
35static const char track_function[] = "stackleak_track_stack";
36
37/*
38 * Mark these global variables (roots) for gcc garbage collector since
39 * they point to the garbage-collected memory.
40 */
41static GTY(()) tree track_function_decl;
42
43static struct plugin_info stackleak_plugin_info = {
44 .version = "201707101337",
45 .help = "track-min-size=nn\ttrack stack for functions with a stack frame size >= nn bytes\n"
46 "disable\t\tdo not activate the plugin\n"
47};
48
49static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after)
50{
51 gimple stmt;
52 gcall *stackleak_track_stack;
53 cgraph_node_ptr node;
54 int frequency;
55 basic_block bb;
56
57 /* Insert call to void stackleak_track_stack(void) */
58 stmt = gimple_build_call(track_function_decl, 0);
59 stackleak_track_stack = as_a_gcall(stmt);
60 if (after) {
61 gsi_insert_after(gsi, stackleak_track_stack,
62 GSI_CONTINUE_LINKING);
63 } else {
64 gsi_insert_before(gsi, stackleak_track_stack, GSI_SAME_STMT);
65 }
66
67 /* Update the cgraph */
68 bb = gimple_bb(stackleak_track_stack);
69 node = cgraph_get_create_node(track_function_decl);
70 gcc_assert(node);
71 frequency = compute_call_stmt_bb_frequency(current_function_decl, bb);
72 cgraph_create_edge(cgraph_get_node(current_function_decl), node,
73 stackleak_track_stack, bb->count, frequency);
74}
75
76static bool is_alloca(gimple stmt)
77{
78 if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA))
79 return true;
80
81#if BUILDING_GCC_VERSION >= 4007
82 if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA_WITH_ALIGN))
83 return true;
84#endif
85
86 return false;
87}
88
89/*
90 * Work with the GIMPLE representation of the code. Insert the
91 * stackleak_track_stack() call after alloca() and into the beginning
92 * of the function if it is not instrumented.
93 */
94static unsigned int stackleak_instrument_execute(void)
95{
96 basic_block bb, entry_bb;
97 bool prologue_instrumented = false, is_leaf = true;
98 gimple_stmt_iterator gsi;
99
100 /*
101 * ENTRY_BLOCK_PTR is a basic block which represents possible entry
102 * point of a function. This block does not contain any code and
103 * has a CFG edge to its successor.
104 */
105 gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
106 entry_bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
107
108 /*
109 * Loop through the GIMPLE statements in each of cfun basic blocks.
110 * cfun is a global variable which represents the function that is
111 * currently processed.
112 */
113 FOR_EACH_BB_FN(bb, cfun) {
114 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
115 gimple stmt;
116
117 stmt = gsi_stmt(gsi);
118
119 /* Leaf function is a function which makes no calls */
120 if (is_gimple_call(stmt))
121 is_leaf = false;
122
123 if (!is_alloca(stmt))
124 continue;
125
126 /* Insert stackleak_track_stack() call after alloca() */
127 stackleak_add_track_stack(&gsi, true);
128 if (bb == entry_bb)
129 prologue_instrumented = true;
130 }
131 }
132
133 if (prologue_instrumented)
134 return 0;
135
136 /*
137 * Special cases to skip the instrumentation.
138 *
139 * Taking the address of static inline functions materializes them,
140 * but we mustn't instrument some of them as the resulting stack
141 * alignment required by the function call ABI will break other
142 * assumptions regarding the expected (but not otherwise enforced)
143 * register clobbering ABI.
144 *
145 * Case in point: native_save_fl on amd64 when optimized for size
146 * clobbers rdx if it were instrumented here.
147 *
148 * TODO: any more special cases?
149 */
150 if (is_leaf &&
151 !TREE_PUBLIC(current_function_decl) &&
152 DECL_DECLARED_INLINE_P(current_function_decl)) {
153 return 0;
154 }
155
156 if (is_leaf &&
157 !strncmp(IDENTIFIER_POINTER(DECL_NAME(current_function_decl)),
158 "_paravirt_", 10)) {
159 return 0;
160 }
161
162 /* Insert stackleak_track_stack() call at the function beginning */
163 bb = entry_bb;
164 if (!single_pred_p(bb)) {
165 /* gcc_assert(bb_loop_depth(bb) ||
166 (bb->flags & BB_IRREDUCIBLE_LOOP)); */
167 split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
168 gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
169 bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
170 }
171 gsi = gsi_after_labels(bb);
172 stackleak_add_track_stack(&gsi, false);
173
174 return 0;
175}
176
177static bool large_stack_frame(void)
178{
179#if BUILDING_GCC_VERSION >= 8000
180 return maybe_ge(get_frame_size(), track_frame_size);
181#else
182 return (get_frame_size() >= track_frame_size);
183#endif
184}
185
186/*
187 * Work with the RTL representation of the code.
188 * Remove the unneeded stackleak_track_stack() calls from the functions
189 * which don't call alloca() and don't have a large enough stack frame size.
190 */
191static unsigned int stackleak_cleanup_execute(void)
192{
193 rtx_insn *insn, *next;
194
195 if (cfun->calls_alloca)
196 return 0;
197
198 if (large_stack_frame())
199 return 0;
200
201 /*
202 * Find stackleak_track_stack() calls. Loop through the chain of insns,
203 * which is an RTL representation of the code for a function.
204 *
205 * The example of a matching insn:
206 * (call_insn 8 4 10 2 (call (mem (symbol_ref ("stackleak_track_stack")
207 * [flags 0x41] <function_decl 0x7f7cd3302a80 stackleak_track_stack>)
208 * [0 stackleak_track_stack S1 A8]) (0)) 675 {*call} (expr_list
209 * (symbol_ref ("stackleak_track_stack") [flags 0x41] <function_decl
210 * 0x7f7cd3302a80 stackleak_track_stack>) (expr_list (0) (nil))) (nil))
211 */
212 for (insn = get_insns(); insn; insn = next) {
213 rtx body;
214
215 next = NEXT_INSN(insn);
216
217 /* Check the expression code of the insn */
218 if (!CALL_P(insn))
219 continue;
220
221 /*
222 * Check the expression code of the insn body, which is an RTL
223 * Expression (RTX) describing the side effect performed by
224 * that insn.
225 */
226 body = PATTERN(insn);
227
228 if (GET_CODE(body) == PARALLEL)
229 body = XVECEXP(body, 0, 0);
230
231 if (GET_CODE(body) != CALL)
232 continue;
233
234 /*
235 * Check the first operand of the call expression. It should
236 * be a mem RTX describing the needed subroutine with a
237 * symbol_ref RTX.
238 */
239 body = XEXP(body, 0);
240 if (GET_CODE(body) != MEM)
241 continue;
242
243 body = XEXP(body, 0);
244 if (GET_CODE(body) != SYMBOL_REF)
245 continue;
246
247 if (SYMBOL_REF_DECL(body) != track_function_decl)
248 continue;
249
250 /* Delete the stackleak_track_stack() call */
251 delete_insn_and_edges(insn);
252#if BUILDING_GCC_VERSION >= 4007 && BUILDING_GCC_VERSION < 8000
253 if (GET_CODE(next) == NOTE &&
254 NOTE_KIND(next) == NOTE_INSN_CALL_ARG_LOCATION) {
255 insn = next;
256 next = NEXT_INSN(insn);
257 delete_insn_and_edges(insn);
258 }
259#endif
260 }
261
262 return 0;
263}
264
265static bool stackleak_gate(void)
266{
267 tree section;
268
269 section = lookup_attribute("section",
270 DECL_ATTRIBUTES(current_function_decl));
271 if (section && TREE_VALUE(section)) {
272 section = TREE_VALUE(TREE_VALUE(section));
273
274 if (!strncmp(TREE_STRING_POINTER(section), ".init.text", 10))
275 return false;
276 if (!strncmp(TREE_STRING_POINTER(section), ".devinit.text", 13))
277 return false;
278 if (!strncmp(TREE_STRING_POINTER(section), ".cpuinit.text", 13))
279 return false;
280 if (!strncmp(TREE_STRING_POINTER(section), ".meminit.text", 13))
281 return false;
282 }
283
284 return track_frame_size >= 0;
285}
286
287/* Build the function declaration for stackleak_track_stack() */
288static void stackleak_start_unit(void *gcc_data __unused,
289 void *user_data __unused)
290{
291 tree fntype;
292
293 /* void stackleak_track_stack(void) */
294 fntype = build_function_type_list(void_type_node, NULL_TREE);
295 track_function_decl = build_fn_decl(track_function, fntype);
296 DECL_ASSEMBLER_NAME(track_function_decl); /* for LTO */
297 TREE_PUBLIC(track_function_decl) = 1;
298 TREE_USED(track_function_decl) = 1;
299 DECL_EXTERNAL(track_function_decl) = 1;
300 DECL_ARTIFICIAL(track_function_decl) = 1;
301 DECL_PRESERVE_P(track_function_decl) = 1;
302}
303
304/*
305 * Pass gate function is a predicate function that gets executed before the
306 * corresponding pass. If the return value is 'true' the pass gets executed,
307 * otherwise, it is skipped.
308 */
309static bool stackleak_instrument_gate(void)
310{
311 return stackleak_gate();
312}
313
314#define PASS_NAME stackleak_instrument
315#define PROPERTIES_REQUIRED PROP_gimple_leh | PROP_cfg
316#define TODO_FLAGS_START TODO_verify_ssa | TODO_verify_flow | TODO_verify_stmts
317#define TODO_FLAGS_FINISH TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func \
318 | TODO_update_ssa | TODO_rebuild_cgraph_edges
319#include "gcc-generate-gimple-pass.h"
320
321static bool stackleak_cleanup_gate(void)
322{
323 return stackleak_gate();
324}
325
326#define PASS_NAME stackleak_cleanup
327#define TODO_FLAGS_FINISH TODO_dump_func
328#include "gcc-generate-rtl-pass.h"
329
330/*
331 * Every gcc plugin exports a plugin_init() function that is called right
332 * after the plugin is loaded. This function is responsible for registering
333 * the plugin callbacks and doing other required initialization.
334 */
335__visible int plugin_init(struct plugin_name_args *plugin_info,
336 struct plugin_gcc_version *version)
337{
338 const char * const plugin_name = plugin_info->base_name;
339 const int argc = plugin_info->argc;
340 const struct plugin_argument * const argv = plugin_info->argv;
341 int i = 0;
342
343 /* Extra GGC root tables describing our GTY-ed data */
344 static const struct ggc_root_tab gt_ggc_r_gt_stackleak[] = {
345 {
346 .base = &track_function_decl,
347 .nelt = 1,
348 .stride = sizeof(track_function_decl),
349 .cb = >_ggc_mx_tree_node,
350 .pchw = >_pch_nx_tree_node
351 },
352 LAST_GGC_ROOT_TAB
353 };
354
355 /*
356 * The stackleak_instrument pass should be executed before the
357 * "optimized" pass, which is the control flow graph cleanup that is
358 * performed just before expanding gcc trees to the RTL. In former
359 * versions of the plugin this new pass was inserted before the
360 * "tree_profile" pass, which is currently called "profile".
361 */
362 PASS_INFO(stackleak_instrument, "optimized", 1,
363 PASS_POS_INSERT_BEFORE);
364
365 /*
366 * The stackleak_cleanup pass should be executed before the "*free_cfg"
367 * pass. It's the moment when the stack frame size is already final,
368 * function prologues and epilogues are generated, and the
369 * machine-dependent code transformations are not done.
370 */
371 PASS_INFO(stackleak_cleanup, "*free_cfg", 1, PASS_POS_INSERT_BEFORE);
372
373 if (!plugin_default_version_check(version, &gcc_version)) {
374 error(G_("incompatible gcc/plugin versions"));
375 return 1;
376 }
377
378 /* Parse the plugin arguments */
379 for (i = 0; i < argc; i++) {
380 if (!strcmp(argv[i].key, "disable"))
381 return 0;
382
383 if (!strcmp(argv[i].key, "track-min-size")) {
384 if (!argv[i].value) {
385 error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
386 plugin_name, argv[i].key);
387 return 1;
388 }
389
390 track_frame_size = atoi(argv[i].value);
391 if (track_frame_size < 0) {
392 error(G_("invalid option argument '-fplugin-arg-%s-%s=%s'"),
393 plugin_name, argv[i].key, argv[i].value);
394 return 1;
395 }
396 } else {
397 error(G_("unknown option '-fplugin-arg-%s-%s'"),
398 plugin_name, argv[i].key);
399 return 1;
400 }
401 }
402
403 /* Give the information about the plugin */
404 register_callback(plugin_name, PLUGIN_INFO, NULL,
405 &stackleak_plugin_info);
406
407 /* Register to be called before processing a translation unit */
408 register_callback(plugin_name, PLUGIN_START_UNIT,
409 &stackleak_start_unit, NULL);
410
411 /* Register an extra GCC garbage collector (GGC) root table */
412 register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS, NULL,
413 (void *)>_ggc_r_gt_stackleak);
414
415 /*
416 * Hook into the Pass Manager to register new gcc passes.
417 *
418 * The stack frame size info is available only at the last RTL pass,
419 * when it's too late to insert complex code like a function call.
420 * So we register two gcc passes to instrument every function at first
421 * and remove the unneeded instrumentation later.
422 */
423 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
424 &stackleak_instrument_pass_info);
425 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
426 &stackleak_cleanup_pass_info);
427
428 return 0;
429}
1/*
2 * Copyright 2011-2017 by the PaX Team <pageexec@freemail.hu>
3 * Modified by Alexander Popov <alex.popov@linux.com>
4 * Licensed under the GPL v2
5 *
6 * Note: the choice of the license means that the compilation process is
7 * NOT 'eligible' as defined by gcc's library exception to the GPL v3,
8 * but for the kernel it doesn't matter since it doesn't link against
9 * any of the gcc libraries
10 *
11 * This gcc plugin is needed for tracking the lowest border of the kernel stack.
12 * It instruments the kernel code inserting stackleak_track_stack() calls:
13 * - after alloca();
14 * - for the functions with a stack frame size greater than or equal
15 * to the "track-min-size" plugin parameter.
16 *
17 * This plugin is ported from grsecurity/PaX. For more information see:
18 * https://grsecurity.net/
19 * https://pax.grsecurity.net/
20 *
21 * Debugging:
22 * - use fprintf() to stderr, debug_generic_expr(), debug_gimple_stmt(),
23 * print_rtl_single() and debug_rtx();
24 * - add "-fdump-tree-all -fdump-rtl-all" to the plugin CFLAGS in
25 * Makefile.gcc-plugins to see the verbose dumps of the gcc passes;
26 * - use gcc -E to understand the preprocessing shenanigans;
27 * - use gcc with enabled CFG/GIMPLE/SSA verification (--enable-checking).
28 */
29
30#include "gcc-common.h"
31
32__visible int plugin_is_GPL_compatible;
33
34static int track_frame_size = -1;
35static bool build_for_x86 = false;
36static const char track_function[] = "stackleak_track_stack";
37static bool disable = false;
38static bool verbose = false;
39
40/*
41 * Mark these global variables (roots) for gcc garbage collector since
42 * they point to the garbage-collected memory.
43 */
44static GTY(()) tree track_function_decl;
45
46static struct plugin_info stackleak_plugin_info = {
47 .version = "201707101337",
48 .help = "track-min-size=nn\ttrack stack for functions with a stack frame size >= nn bytes\n"
49 "arch=target_arch\tspecify target build arch\n"
50 "disable\t\tdo not activate the plugin\n"
51 "verbose\t\tprint info about the instrumentation\n"
52};
53
54static void add_stack_tracking_gcall(gimple_stmt_iterator *gsi, bool after)
55{
56 gimple stmt;
57 gcall *gimple_call;
58 cgraph_node_ptr node;
59 basic_block bb;
60
61 /* Insert calling stackleak_track_stack() */
62 stmt = gimple_build_call(track_function_decl, 0);
63 gimple_call = as_a_gcall(stmt);
64 if (after)
65 gsi_insert_after(gsi, gimple_call, GSI_CONTINUE_LINKING);
66 else
67 gsi_insert_before(gsi, gimple_call, GSI_SAME_STMT);
68
69 /* Update the cgraph */
70 bb = gimple_bb(gimple_call);
71 node = cgraph_get_create_node(track_function_decl);
72 gcc_assert(node);
73 cgraph_create_edge(cgraph_get_node(current_function_decl), node,
74 gimple_call, bb->count,
75 compute_call_stmt_bb_frequency(current_function_decl, bb));
76}
77
78static bool is_alloca(gimple stmt)
79{
80 if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA))
81 return true;
82
83 if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA_WITH_ALIGN))
84 return true;
85
86 return false;
87}
88
89static tree get_current_stack_pointer_decl(void)
90{
91 varpool_node_ptr node;
92
93 FOR_EACH_VARIABLE(node) {
94 tree var = NODE_DECL(node);
95 tree name = DECL_NAME(var);
96
97 if (DECL_NAME_LENGTH(var) != sizeof("current_stack_pointer") - 1)
98 continue;
99
100 if (strcmp(IDENTIFIER_POINTER(name), "current_stack_pointer"))
101 continue;
102
103 return var;
104 }
105
106 if (verbose) {
107 fprintf(stderr, "stackleak: missing current_stack_pointer in %s()\n",
108 DECL_NAME_POINTER(current_function_decl));
109 }
110 return NULL_TREE;
111}
112
113static void add_stack_tracking_gasm(gimple_stmt_iterator *gsi, bool after)
114{
115 gasm *asm_call = NULL;
116 tree sp_decl, input;
117 vec<tree, va_gc> *inputs = NULL;
118
119 /* 'no_caller_saved_registers' is currently supported only for x86 */
120 gcc_assert(build_for_x86);
121
122 /*
123 * Insert calling stackleak_track_stack() in asm:
124 * asm volatile("call stackleak_track_stack"
125 * :: "r" (current_stack_pointer))
126 * Use ASM_CALL_CONSTRAINT trick from arch/x86/include/asm/asm.h.
127 * This constraint is taken into account during gcc shrink-wrapping
128 * optimization. It is needed to be sure that stackleak_track_stack()
129 * call is inserted after the prologue of the containing function,
130 * when the stack frame is prepared.
131 */
132 sp_decl = get_current_stack_pointer_decl();
133 if (sp_decl == NULL_TREE) {
134 add_stack_tracking_gcall(gsi, after);
135 return;
136 }
137 input = build_tree_list(NULL_TREE, build_const_char_string(2, "r"));
138 input = chainon(NULL_TREE, build_tree_list(input, sp_decl));
139 vec_safe_push(inputs, input);
140 asm_call = gimple_build_asm_vec("call stackleak_track_stack",
141 inputs, NULL, NULL, NULL);
142 gimple_asm_set_volatile(asm_call, true);
143 if (after)
144 gsi_insert_after(gsi, asm_call, GSI_CONTINUE_LINKING);
145 else
146 gsi_insert_before(gsi, asm_call, GSI_SAME_STMT);
147 update_stmt(asm_call);
148}
149
150static void add_stack_tracking(gimple_stmt_iterator *gsi, bool after)
151{
152 /*
153 * The 'no_caller_saved_registers' attribute is used for
154 * stackleak_track_stack(). If the compiler supports this attribute for
155 * the target arch, we can add calling stackleak_track_stack() in asm.
156 * That improves performance: we avoid useless operations with the
157 * caller-saved registers in the functions from which we will remove
158 * stackleak_track_stack() call during the stackleak_cleanup pass.
159 */
160 if (lookup_attribute_spec(get_identifier("no_caller_saved_registers")))
161 add_stack_tracking_gasm(gsi, after);
162 else
163 add_stack_tracking_gcall(gsi, after);
164}
165
166/*
167 * Work with the GIMPLE representation of the code. Insert the
168 * stackleak_track_stack() call after alloca() and into the beginning
169 * of the function if it is not instrumented.
170 */
171static unsigned int stackleak_instrument_execute(void)
172{
173 basic_block bb, entry_bb;
174 bool prologue_instrumented = false, is_leaf = true;
175 gimple_stmt_iterator gsi = { 0 };
176
177 /*
178 * ENTRY_BLOCK_PTR is a basic block which represents possible entry
179 * point of a function. This block does not contain any code and
180 * has a CFG edge to its successor.
181 */
182 gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
183 entry_bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
184
185 /*
186 * Loop through the GIMPLE statements in each of cfun basic blocks.
187 * cfun is a global variable which represents the function that is
188 * currently processed.
189 */
190 FOR_EACH_BB_FN(bb, cfun) {
191 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
192 gimple stmt;
193
194 stmt = gsi_stmt(gsi);
195
196 /* Leaf function is a function which makes no calls */
197 if (is_gimple_call(stmt))
198 is_leaf = false;
199
200 if (!is_alloca(stmt))
201 continue;
202
203 if (verbose) {
204 fprintf(stderr, "stackleak: be careful, alloca() in %s()\n",
205 DECL_NAME_POINTER(current_function_decl));
206 }
207
208 /* Insert stackleak_track_stack() call after alloca() */
209 add_stack_tracking(&gsi, true);
210 if (bb == entry_bb)
211 prologue_instrumented = true;
212 }
213 }
214
215 if (prologue_instrumented)
216 return 0;
217
218 /*
219 * Special cases to skip the instrumentation.
220 *
221 * Taking the address of static inline functions materializes them,
222 * but we mustn't instrument some of them as the resulting stack
223 * alignment required by the function call ABI will break other
224 * assumptions regarding the expected (but not otherwise enforced)
225 * register clobbering ABI.
226 *
227 * Case in point: native_save_fl on amd64 when optimized for size
228 * clobbers rdx if it were instrumented here.
229 *
230 * TODO: any more special cases?
231 */
232 if (is_leaf &&
233 !TREE_PUBLIC(current_function_decl) &&
234 DECL_DECLARED_INLINE_P(current_function_decl)) {
235 return 0;
236 }
237
238 if (is_leaf &&
239 !strncmp(IDENTIFIER_POINTER(DECL_NAME(current_function_decl)),
240 "_paravirt_", 10)) {
241 return 0;
242 }
243
244 /* Insert stackleak_track_stack() call at the function beginning */
245 bb = entry_bb;
246 if (!single_pred_p(bb)) {
247 /* gcc_assert(bb_loop_depth(bb) ||
248 (bb->flags & BB_IRREDUCIBLE_LOOP)); */
249 split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
250 gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
251 bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
252 }
253 gsi = gsi_after_labels(bb);
254 add_stack_tracking(&gsi, false);
255
256 return 0;
257}
258
259static bool large_stack_frame(void)
260{
261#if BUILDING_GCC_VERSION >= 8000
262 return maybe_ge(get_frame_size(), track_frame_size);
263#else
264 return (get_frame_size() >= track_frame_size);
265#endif
266}
267
268static void remove_stack_tracking_gcall(void)
269{
270 rtx_insn *insn, *next;
271
272 /*
273 * Find stackleak_track_stack() calls. Loop through the chain of insns,
274 * which is an RTL representation of the code for a function.
275 *
276 * The example of a matching insn:
277 * (call_insn 8 4 10 2 (call (mem (symbol_ref ("stackleak_track_stack")
278 * [flags 0x41] <function_decl 0x7f7cd3302a80 stackleak_track_stack>)
279 * [0 stackleak_track_stack S1 A8]) (0)) 675 {*call} (expr_list
280 * (symbol_ref ("stackleak_track_stack") [flags 0x41] <function_decl
281 * 0x7f7cd3302a80 stackleak_track_stack>) (expr_list (0) (nil))) (nil))
282 */
283 for (insn = get_insns(); insn; insn = next) {
284 rtx body;
285
286 next = NEXT_INSN(insn);
287
288 /* Check the expression code of the insn */
289 if (!CALL_P(insn))
290 continue;
291
292 /*
293 * Check the expression code of the insn body, which is an RTL
294 * Expression (RTX) describing the side effect performed by
295 * that insn.
296 */
297 body = PATTERN(insn);
298
299 if (GET_CODE(body) == PARALLEL)
300 body = XVECEXP(body, 0, 0);
301
302 if (GET_CODE(body) != CALL)
303 continue;
304
305 /*
306 * Check the first operand of the call expression. It should
307 * be a mem RTX describing the needed subroutine with a
308 * symbol_ref RTX.
309 */
310 body = XEXP(body, 0);
311 if (GET_CODE(body) != MEM)
312 continue;
313
314 body = XEXP(body, 0);
315 if (GET_CODE(body) != SYMBOL_REF)
316 continue;
317
318 if (SYMBOL_REF_DECL(body) != track_function_decl)
319 continue;
320
321 /* Delete the stackleak_track_stack() call */
322 delete_insn_and_edges(insn);
323#if BUILDING_GCC_VERSION < 8000
324 if (GET_CODE(next) == NOTE &&
325 NOTE_KIND(next) == NOTE_INSN_CALL_ARG_LOCATION) {
326 insn = next;
327 next = NEXT_INSN(insn);
328 delete_insn_and_edges(insn);
329 }
330#endif
331 }
332}
333
334static bool remove_stack_tracking_gasm(void)
335{
336 bool removed = false;
337 rtx_insn *insn, *next;
338
339 /* 'no_caller_saved_registers' is currently supported only for x86 */
340 gcc_assert(build_for_x86);
341
342 /*
343 * Find stackleak_track_stack() asm calls. Loop through the chain of
344 * insns, which is an RTL representation of the code for a function.
345 *
346 * The example of a matching insn:
347 * (insn 11 5 12 2 (parallel [ (asm_operands/v
348 * ("call stackleak_track_stack") ("") 0
349 * [ (reg/v:DI 7 sp [ current_stack_pointer ]) ]
350 * [ (asm_input:DI ("r")) ] [])
351 * (clobber (reg:CC 17 flags)) ]) -1 (nil))
352 */
353 for (insn = get_insns(); insn; insn = next) {
354 rtx body;
355
356 next = NEXT_INSN(insn);
357
358 /* Check the expression code of the insn */
359 if (!NONJUMP_INSN_P(insn))
360 continue;
361
362 /*
363 * Check the expression code of the insn body, which is an RTL
364 * Expression (RTX) describing the side effect performed by
365 * that insn.
366 */
367 body = PATTERN(insn);
368
369 if (GET_CODE(body) != PARALLEL)
370 continue;
371
372 body = XVECEXP(body, 0, 0);
373
374 if (GET_CODE(body) != ASM_OPERANDS)
375 continue;
376
377 if (strcmp(ASM_OPERANDS_TEMPLATE(body),
378 "call stackleak_track_stack")) {
379 continue;
380 }
381
382 delete_insn_and_edges(insn);
383 gcc_assert(!removed);
384 removed = true;
385 }
386
387 return removed;
388}
389
390/*
391 * Work with the RTL representation of the code.
392 * Remove the unneeded stackleak_track_stack() calls from the functions
393 * which don't call alloca() and don't have a large enough stack frame size.
394 */
395static unsigned int stackleak_cleanup_execute(void)
396{
397 const char *fn = DECL_NAME_POINTER(current_function_decl);
398 bool removed = false;
399
400 /*
401 * Leave stack tracking in functions that call alloca().
402 * Additional case:
403 * gcc before version 7 called allocate_dynamic_stack_space() from
404 * expand_stack_vars() for runtime alignment of constant-sized stack
405 * variables. That caused cfun->calls_alloca to be set for functions
406 * that in fact don't use alloca().
407 * For more info see gcc commit 7072df0aae0c59ae437e.
408 * Let's leave such functions instrumented as well.
409 */
410 if (cfun->calls_alloca) {
411 if (verbose)
412 fprintf(stderr, "stackleak: instrument %s(): calls_alloca\n", fn);
413 return 0;
414 }
415
416 /* Leave stack tracking in functions with large stack frame */
417 if (large_stack_frame()) {
418 if (verbose)
419 fprintf(stderr, "stackleak: instrument %s()\n", fn);
420 return 0;
421 }
422
423 if (lookup_attribute_spec(get_identifier("no_caller_saved_registers")))
424 removed = remove_stack_tracking_gasm();
425
426 if (!removed)
427 remove_stack_tracking_gcall();
428
429 return 0;
430}
431
432static bool stackleak_gate(void)
433{
434 tree section;
435
436 section = lookup_attribute("section",
437 DECL_ATTRIBUTES(current_function_decl));
438 if (section && TREE_VALUE(section)) {
439 section = TREE_VALUE(TREE_VALUE(section));
440
441 if (!strncmp(TREE_STRING_POINTER(section), ".init.text", 10))
442 return false;
443 if (!strncmp(TREE_STRING_POINTER(section), ".devinit.text", 13))
444 return false;
445 if (!strncmp(TREE_STRING_POINTER(section), ".cpuinit.text", 13))
446 return false;
447 if (!strncmp(TREE_STRING_POINTER(section), ".meminit.text", 13))
448 return false;
449 }
450
451 return track_frame_size >= 0;
452}
453
454/* Build the function declaration for stackleak_track_stack() */
455static void stackleak_start_unit(void *gcc_data __unused,
456 void *user_data __unused)
457{
458 tree fntype;
459
460 /* void stackleak_track_stack(void) */
461 fntype = build_function_type_list(void_type_node, NULL_TREE);
462 track_function_decl = build_fn_decl(track_function, fntype);
463 DECL_ASSEMBLER_NAME(track_function_decl); /* for LTO */
464 TREE_PUBLIC(track_function_decl) = 1;
465 TREE_USED(track_function_decl) = 1;
466 DECL_EXTERNAL(track_function_decl) = 1;
467 DECL_ARTIFICIAL(track_function_decl) = 1;
468 DECL_PRESERVE_P(track_function_decl) = 1;
469}
470
471/*
472 * Pass gate function is a predicate function that gets executed before the
473 * corresponding pass. If the return value is 'true' the pass gets executed,
474 * otherwise, it is skipped.
475 */
476static bool stackleak_instrument_gate(void)
477{
478 return stackleak_gate();
479}
480
481#define PASS_NAME stackleak_instrument
482#define PROPERTIES_REQUIRED PROP_gimple_leh | PROP_cfg
483#define TODO_FLAGS_START TODO_verify_ssa | TODO_verify_flow | TODO_verify_stmts
484#define TODO_FLAGS_FINISH TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func \
485 | TODO_update_ssa | TODO_rebuild_cgraph_edges
486#include "gcc-generate-gimple-pass.h"
487
488static bool stackleak_cleanup_gate(void)
489{
490 return stackleak_gate();
491}
492
493#define PASS_NAME stackleak_cleanup
494#define TODO_FLAGS_FINISH TODO_dump_func
495#include "gcc-generate-rtl-pass.h"
496
497/*
498 * Every gcc plugin exports a plugin_init() function that is called right
499 * after the plugin is loaded. This function is responsible for registering
500 * the plugin callbacks and doing other required initialization.
501 */
502__visible int plugin_init(struct plugin_name_args *plugin_info,
503 struct plugin_gcc_version *version)
504{
505 const char * const plugin_name = plugin_info->base_name;
506 const int argc = plugin_info->argc;
507 const struct plugin_argument * const argv = plugin_info->argv;
508 int i = 0;
509
510 /* Extra GGC root tables describing our GTY-ed data */
511 static const struct ggc_root_tab gt_ggc_r_gt_stackleak[] = {
512 {
513 .base = &track_function_decl,
514 .nelt = 1,
515 .stride = sizeof(track_function_decl),
516 .cb = >_ggc_mx_tree_node,
517 .pchw = >_pch_nx_tree_node
518 },
519 LAST_GGC_ROOT_TAB
520 };
521
522 /*
523 * The stackleak_instrument pass should be executed before the
524 * "optimized" pass, which is the control flow graph cleanup that is
525 * performed just before expanding gcc trees to the RTL. In former
526 * versions of the plugin this new pass was inserted before the
527 * "tree_profile" pass, which is currently called "profile".
528 */
529 PASS_INFO(stackleak_instrument, "optimized", 1,
530 PASS_POS_INSERT_BEFORE);
531
532 /*
533 * The stackleak_cleanup pass should be executed before the "*free_cfg"
534 * pass. It's the moment when the stack frame size is already final,
535 * function prologues and epilogues are generated, and the
536 * machine-dependent code transformations are not done.
537 */
538 PASS_INFO(stackleak_cleanup, "*free_cfg", 1, PASS_POS_INSERT_BEFORE);
539
540 if (!plugin_default_version_check(version, &gcc_version)) {
541 error(G_("incompatible gcc/plugin versions"));
542 return 1;
543 }
544
545 /* Parse the plugin arguments */
546 for (i = 0; i < argc; i++) {
547 if (!strcmp(argv[i].key, "track-min-size")) {
548 if (!argv[i].value) {
549 error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
550 plugin_name, argv[i].key);
551 return 1;
552 }
553
554 track_frame_size = atoi(argv[i].value);
555 if (track_frame_size < 0) {
556 error(G_("invalid option argument '-fplugin-arg-%s-%s=%s'"),
557 plugin_name, argv[i].key, argv[i].value);
558 return 1;
559 }
560 } else if (!strcmp(argv[i].key, "arch")) {
561 if (!argv[i].value) {
562 error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
563 plugin_name, argv[i].key);
564 return 1;
565 }
566
567 if (!strcmp(argv[i].value, "x86"))
568 build_for_x86 = true;
569 } else if (!strcmp(argv[i].key, "disable")) {
570 disable = true;
571 } else if (!strcmp(argv[i].key, "verbose")) {
572 verbose = true;
573 } else {
574 error(G_("unknown option '-fplugin-arg-%s-%s'"),
575 plugin_name, argv[i].key);
576 return 1;
577 }
578 }
579
580 if (disable) {
581 if (verbose)
582 fprintf(stderr, "stackleak: disabled for this translation unit\n");
583 return 0;
584 }
585
586 /* Give the information about the plugin */
587 register_callback(plugin_name, PLUGIN_INFO, NULL,
588 &stackleak_plugin_info);
589
590 /* Register to be called before processing a translation unit */
591 register_callback(plugin_name, PLUGIN_START_UNIT,
592 &stackleak_start_unit, NULL);
593
594 /* Register an extra GCC garbage collector (GGC) root table */
595 register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS, NULL,
596 (void *)>_ggc_r_gt_stackleak);
597
598 /*
599 * Hook into the Pass Manager to register new gcc passes.
600 *
601 * The stack frame size info is available only at the last RTL pass,
602 * when it's too late to insert complex code like a function call.
603 * So we register two gcc passes to instrument every function at first
604 * and remove the unneeded instrumentation later.
605 */
606 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
607 &stackleak_instrument_pass_info);
608 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
609 &stackleak_cleanup_pass_info);
610
611 return 0;
612}