| /* |
| * Copyright 2011-2017 by the PaX Team <pageexec@freemail.hu> |
| * Modified by Alexander Popov <alex.popov@linux.com> |
| * Licensed under the GPL v2 |
| * |
| * Note: the choice of the license means that the compilation process is |
| * NOT 'eligible' as defined by gcc's library exception to the GPL v3, |
| * but for the kernel it doesn't matter since it doesn't link against |
| * any of the gcc libraries |
| * |
| * This gcc plugin is needed for tracking the lowest border of the kernel stack. |
| * It instruments the kernel code inserting stackleak_track_stack() calls: |
| * - after alloca(); |
| * - for the functions with a stack frame size greater than or equal |
| * to the "track-min-size" plugin parameter. |
| * |
| * This plugin is ported from grsecurity/PaX. For more information see: |
| * https://grsecurity.net/ |
| * https://pax.grsecurity.net/ |
| * |
| * Debugging: |
| * - use fprintf() to stderr, debug_generic_expr(), debug_gimple_stmt(), |
| * 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; |
| * - use gcc with enabled CFG/GIMPLE/SSA verification (--enable-checking). |
| */ |
| |
| #include "gcc-common.h" |
| |
| __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 |
| * they point to the garbage-collected memory. |
| */ |
| static GTY(()) tree track_function_decl; |
| |
| static struct plugin_info stackleak_plugin_info = { |
| .version = PLUGIN_VERSION, |
| .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 add_stack_tracking_gcall(gimple_stmt_iterator *gsi, bool after) |
| { |
| gimple stmt; |
| gcall *gimple_call; |
| cgraph_node_ptr node; |
| basic_block bb; |
| |
| /* Insert calling stackleak_track_stack() */ |
| stmt = gimple_build_call(track_function_decl, 0); |
| 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(gimple_call); |
| node = cgraph_get_create_node(track_function_decl); |
| gcc_assert(node); |
| cgraph_create_edge(cgraph_get_node(current_function_decl), node, |
| gimple_call, bb->count, |
| compute_call_stmt_bb_frequency(current_function_decl, bb)); |
| } |
| |
| static bool is_alloca(gimple stmt) |
| { |
| if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA)) |
| return true; |
| |
| if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA_WITH_ALIGN)) |
| return true; |
| |
| 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 |
| * of the function if it is not instrumented. |
| */ |
| static unsigned int stackleak_instrument_execute(void) |
| { |
| basic_block bb, entry_bb; |
| bool prologue_instrumented = false, is_leaf = true; |
| gimple_stmt_iterator gsi = { 0 }; |
| |
| /* |
| * ENTRY_BLOCK_PTR is a basic block which represents possible entry |
| * point of a function. This block does not contain any code and |
| * has a CFG edge to its successor. |
| */ |
| gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun))); |
| entry_bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)); |
| |
| /* |
| * Loop through the GIMPLE statements in each of cfun basic blocks. |
| * cfun is a global variable which represents the function that is |
| * currently processed. |
| */ |
| FOR_EACH_BB_FN(bb, cfun) { |
| for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) { |
| gimple stmt; |
| |
| stmt = gsi_stmt(gsi); |
| |
| /* Leaf function is a function which makes no calls */ |
| if (is_gimple_call(stmt)) |
| is_leaf = false; |
| |
| 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() */ |
| add_stack_tracking(&gsi, true); |
| if (bb == entry_bb) |
| prologue_instrumented = true; |
| } |
| } |
| |
| if (prologue_instrumented) |
| return 0; |
| |
| /* |
| * Special cases to skip the instrumentation. |
| * |
| * Taking the address of static inline functions materializes them, |
| * but we mustn't instrument some of them as the resulting stack |
| * alignment required by the function call ABI will break other |
| * assumptions regarding the expected (but not otherwise enforced) |
| * register clobbering ABI. |
| * |
| * Case in point: native_save_fl on amd64 when optimized for size |
| * clobbers rdx if it were instrumented here. |
| * |
| * TODO: any more special cases? |
| */ |
| if (is_leaf && |
| !TREE_PUBLIC(current_function_decl) && |
| DECL_DECLARED_INLINE_P(current_function_decl)) { |
| return 0; |
| } |
| |
| if (is_leaf && |
| !strncmp(IDENTIFIER_POINTER(DECL_NAME(current_function_decl)), |
| "_paravirt_", 10)) { |
| return 0; |
| } |
| |
| /* Insert stackleak_track_stack() call at the function beginning */ |
| bb = entry_bb; |
| if (!single_pred_p(bb)) { |
| /* gcc_assert(bb_loop_depth(bb) || |
| (bb->flags & BB_IRREDUCIBLE_LOOP)); */ |
| split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun))); |
| gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun))); |
| bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)); |
| } |
| gsi = gsi_after_labels(bb); |
| add_stack_tracking(&gsi, false); |
| |
| return 0; |
| } |
| |
| static bool large_stack_frame(void) |
| { |
| #if BUILDING_GCC_VERSION >= 8000 |
| return maybe_ge(get_frame_size(), track_frame_size); |
| #else |
| return (get_frame_size() >= track_frame_size); |
| #endif |
| } |
| |
| static void remove_stack_tracking_gcall(void) |
| { |
| rtx_insn *insn, *next; |
| |
| /* |
| * Find stackleak_track_stack() calls. Loop through the chain of insns, |
| * which is an RTL representation of the code for a function. |
| * |
| * The example of a matching insn: |
| * (call_insn 8 4 10 2 (call (mem (symbol_ref ("stackleak_track_stack") |
| * [flags 0x41] <function_decl 0x7f7cd3302a80 stackleak_track_stack>) |
| * [0 stackleak_track_stack S1 A8]) (0)) 675 {*call} (expr_list |
| * (symbol_ref ("stackleak_track_stack") [flags 0x41] <function_decl |
| * 0x7f7cd3302a80 stackleak_track_stack>) (expr_list (0) (nil))) (nil)) |
| */ |
| for (insn = get_insns(); insn; insn = next) { |
| rtx body; |
| |
| next = NEXT_INSN(insn); |
| |
| /* Check the expression code of the insn */ |
| if (!CALL_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) |
| body = XVECEXP(body, 0, 0); |
| |
| if (GET_CODE(body) != CALL) |
| continue; |
| |
| /* |
| * Check the first operand of the call expression. It should |
| * be a mem RTX describing the needed subroutine with a |
| * symbol_ref RTX. |
| */ |
| body = XEXP(body, 0); |
| if (GET_CODE(body) != MEM) |
| continue; |
| |
| body = XEXP(body, 0); |
| if (GET_CODE(body) != SYMBOL_REF) |
| continue; |
| |
| if (SYMBOL_REF_DECL(body) != track_function_decl) |
| continue; |
| |
| /* Delete the stackleak_track_stack() call */ |
| delete_insn_and_edges(insn); |
| #if BUILDING_GCC_VERSION < 8000 |
| if (GET_CODE(next) == NOTE && |
| NOTE_KIND(next) == NOTE_INSN_CALL_ARG_LOCATION) { |
| insn = next; |
| next = NEXT_INSN(insn); |
| delete_insn_and_edges(insn); |
| } |
| #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; |
| } |
| |
| /* |
| * STRING_CST may or may not be NUL terminated: |
| * https://gcc.gnu.org/onlinedocs/gccint/Constant-expressions.html |
| */ |
| static inline bool string_equal(tree node, const char *string, int length) |
| { |
| if (TREE_STRING_LENGTH(node) < length) |
| return false; |
| if (TREE_STRING_LENGTH(node) > length + 1) |
| return false; |
| if (TREE_STRING_LENGTH(node) == length + 1 && |
| TREE_STRING_POINTER(node)[length] != '\0') |
| return false; |
| return !memcmp(TREE_STRING_POINTER(node), string, length); |
| } |
| #define STRING_EQUAL(node, str) string_equal(node, str, strlen(str)) |
| |
| static bool stackleak_gate(void) |
| { |
| tree section; |
| |
| section = lookup_attribute("section", |
| DECL_ATTRIBUTES(current_function_decl)); |
| if (section && TREE_VALUE(section)) { |
| section = TREE_VALUE(TREE_VALUE(section)); |
| |
| if (STRING_EQUAL(section, ".init.text")) |
| return false; |
| if (STRING_EQUAL(section, ".devinit.text")) |
| return false; |
| if (STRING_EQUAL(section, ".cpuinit.text")) |
| return false; |
| if (STRING_EQUAL(section, ".meminit.text")) |
| return false; |
| if (STRING_EQUAL(section, ".noinstr.text")) |
| return false; |
| if (STRING_EQUAL(section, ".entry.text")) |
| return false; |
| } |
| |
| return track_frame_size >= 0; |
| } |
| |
| /* Build the function declaration for stackleak_track_stack() */ |
| static void stackleak_start_unit(void *gcc_data __unused, |
| void *user_data __unused) |
| { |
| tree fntype; |
| |
| /* void stackleak_track_stack(void) */ |
| fntype = build_function_type_list(void_type_node, NULL_TREE); |
| track_function_decl = build_fn_decl(track_function, fntype); |
| DECL_ASSEMBLER_NAME(track_function_decl); /* for LTO */ |
| TREE_PUBLIC(track_function_decl) = 1; |
| TREE_USED(track_function_decl) = 1; |
| DECL_EXTERNAL(track_function_decl) = 1; |
| DECL_ARTIFICIAL(track_function_decl) = 1; |
| DECL_PRESERVE_P(track_function_decl) = 1; |
| } |
| |
| /* |
| * Pass gate function is a predicate function that gets executed before the |
| * corresponding pass. If the return value is 'true' the pass gets executed, |
| * otherwise, it is skipped. |
| */ |
| static bool stackleak_instrument_gate(void) |
| { |
| return stackleak_gate(); |
| } |
| |
| #define PASS_NAME stackleak_instrument |
| #define PROPERTIES_REQUIRED PROP_gimple_leh | PROP_cfg |
| #define TODO_FLAGS_START TODO_verify_ssa | TODO_verify_flow | TODO_verify_stmts |
| #define TODO_FLAGS_FINISH TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func \ |
| | TODO_update_ssa | TODO_rebuild_cgraph_edges |
| #include "gcc-generate-gimple-pass.h" |
| |
| static bool stackleak_cleanup_gate(void) |
| { |
| return stackleak_gate(); |
| } |
| |
| #define PASS_NAME stackleak_cleanup |
| #define TODO_FLAGS_FINISH TODO_dump_func |
| #include "gcc-generate-rtl-pass.h" |
| |
| /* |
| * Every gcc plugin exports a plugin_init() function that is called right |
| * after the plugin is loaded. This function is responsible for registering |
| * the plugin callbacks and doing other required initialization. |
| */ |
| __visible int plugin_init(struct plugin_name_args *plugin_info, |
| struct plugin_gcc_version *version) |
| { |
| const char * const plugin_name = plugin_info->base_name; |
| const int argc = plugin_info->argc; |
| const struct plugin_argument * const argv = plugin_info->argv; |
| int i = 0; |
| |
| /* Extra GGC root tables describing our GTY-ed data */ |
| static const struct ggc_root_tab gt_ggc_r_gt_stackleak[] = { |
| { |
| .base = &track_function_decl, |
| .nelt = 1, |
| .stride = sizeof(track_function_decl), |
| .cb = >_ggc_mx_tree_node, |
| .pchw = >_pch_nx_tree_node |
| }, |
| LAST_GGC_ROOT_TAB |
| }; |
| |
| /* |
| * The stackleak_instrument pass should be executed before the |
| * "optimized" pass, which is the control flow graph cleanup that is |
| * performed just before expanding gcc trees to the RTL. In former |
| * versions of the plugin this new pass was inserted before the |
| * "tree_profile" pass, which is currently called "profile". |
| */ |
| PASS_INFO(stackleak_instrument, "optimized", 1, |
| PASS_POS_INSERT_BEFORE); |
| |
| /* |
| * The stackleak_cleanup pass should be executed before the "*free_cfg" |
| * pass. It's the moment when the stack frame size is already final, |
| * function prologues and epilogues are generated, and the |
| * machine-dependent code transformations are not done. |
| */ |
| PASS_INFO(stackleak_cleanup, "*free_cfg", 1, PASS_POS_INSERT_BEFORE); |
| |
| if (!plugin_default_version_check(version, &gcc_version)) { |
| error(G_("incompatible gcc/plugin versions")); |
| return 1; |
| } |
| |
| /* Parse the plugin arguments */ |
| for (i = 0; i < argc; i++) { |
| if (!strcmp(argv[i].key, "track-min-size")) { |
| if (!argv[i].value) { |
| error(G_("no value supplied for option '-fplugin-arg-%s-%s'"), |
| plugin_name, argv[i].key); |
| return 1; |
| } |
| |
| track_frame_size = atoi(argv[i].value); |
| if (track_frame_size < 0) { |
| error(G_("invalid option argument '-fplugin-arg-%s-%s=%s'"), |
| 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); |
| return 1; |
| } |
| } |
| |
| 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); |
| |
| /* Register to be called before processing a translation unit */ |
| register_callback(plugin_name, PLUGIN_START_UNIT, |
| &stackleak_start_unit, NULL); |
| |
| /* Register an extra GCC garbage collector (GGC) root table */ |
| register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS, NULL, |
| (void *)>_ggc_r_gt_stackleak); |
| |
| /* |
| * Hook into the Pass Manager to register new gcc passes. |
| * |
| * The stack frame size info is available only at the last RTL pass, |
| * when it's too late to insert complex code like a function call. |
| * So we register two gcc passes to instrument every function at first |
| * and remove the unneeded instrumentation later. |
| */ |
| register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, |
| &stackleak_instrument_pass_info); |
| register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, |
| &stackleak_cleanup_pass_info); |
| |
| return 0; |
| } |