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-rw-r--r--scripts/gcc-plugins/stackleak_plugin.c633
1 files changed, 633 insertions, 0 deletions
diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c
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index 0000000000..c5c2ce113c
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+++ b/scripts/gcc-plugins/stackleak_plugin.c
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+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2011-2017 by the PaX Team <pageexec@freemail.hu>
+ * Modified by Alexander Popov <alex.popov@linux.com>
+ *
+ * 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 = &gt_ggc_mx_tree_node,
+ .pchw = &gt_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 *)&gt_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;
+}