From patchwork Wed Jul 11 20:36:37 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Popov X-Patchwork-Id: 10520481 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 52302600CA for ; Wed, 11 Jul 2018 20:37:59 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2EC3B206E2 for ; Wed, 11 Jul 2018 20:37:59 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 20D7D28DE3; Wed, 11 Jul 2018 20:37:59 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 8933E206E2 for ; Wed, 11 Jul 2018 20:37:56 +0000 (UTC) Received: (qmail 3663 invoked by uid 550); 11 Jul 2018 20:37:46 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 3558 invoked from network); 11 Jul 2018 20:37:45 -0000 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references; bh=Ux1zNk8HOooSq9cUpKaITOk6GhFcqigwhtqDK6hiCLE=; b=b41nN72s/K7XhuNfqhuUbrbbEBMBW/Zuo87tcn6yNmnMUS9gyYVIwatwJlR8WXZuvR g3nDAAelisFL7FIvGumCgE0AuWVeGOPAYLZAGRv/EggyGHp37emqf+P3itVXyf/opoHS JRAevSROkHAodCD7C8JJ76sflx7ADQr+13hIZuQCJIrNjWWgC+OPmFby43O6IScrafM3 IYv9Mu8gftwxMJ8iWax/wZCmAbfEKaFKIiwmXUtmjJFi+IchxztQ1DhssbPUeB4Sjg8v /Y3xOn2QKyuNl5GJds/SEezZ1zff9/6wHpQfqbqJN4Nl7G+S0yvM/Ela/LSP8DLiqFor xqzA== X-Gm-Message-State: AOUpUlHfxoh/uD2IzHWciNs134ekOOXS2cObaBy3+5GeDiLTakcfTUU9 PxwH+Ue5CSVusSMQCrTrHr/wT9oLqtk= X-Google-Smtp-Source: AAOMgpf5pR1go7Qd98NsoyfIBse19GX8FTwwisnciHhib1p7QtX9AcozJcNiNSLHD0dk8GMDFkKNUw== X-Received: by 2002:a19:2207:: with SMTP id i7-v6mr81132lfi.69.1531341453580; Wed, 11 Jul 2018 13:37:33 -0700 (PDT) From: Alexander Popov To: kernel-hardening@lists.openwall.com, Kees Cook , PaX Team , Brad Spengler , Ingo Molnar , Andy Lutomirski , Tycho Andersen , Laura Abbott , Mark Rutland , Ard Biesheuvel , Borislav Petkov , Richard Sandiford , Thomas Gleixner , "H . Peter Anvin" , Peter Zijlstra , "Dmitry V . Levin" , Emese Revfy , Jonathan Corbet , Andrey Ryabinin , "Kirill A . Shutemov" , Thomas Garnier , Andrew Morton , Alexei Starovoitov , Josef Bacik , Masami Hiramatsu , Nicholas Piggin , Al Viro , "David S . Miller" , Ding Tianhong , David Woodhouse , Josh Poimboeuf , Steven Rostedt , Dominik Brodowski , Juergen Gross , Linus Torvalds , Greg Kroah-Hartman , Dan Williams , Dave Hansen , Mathias Krause , Vikas Shivappa , Kyle Huey , Dmitry Safonov , Will Deacon , Arnd Bergmann , Florian Weimer , Boris Lukashev , Andrey Konovalov , x86@kernel.org, linux-kernel@vger.kernel.org, alex.popov@linux.com Subject: [PATCH v14 3/6] gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack Date: Wed, 11 Jul 2018 23:36:37 +0300 Message-Id: <1531341400-12077-4-git-send-email-alex.popov@linux.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1531341400-12077-1-git-send-email-alex.popov@linux.com> References: <1531341400-12077-1-git-send-email-alex.popov@linux.com> X-Virus-Scanned: ClamAV using ClamSMTP The STACKLEAK feature erases the kernel stack before returning from syscalls. That reduces the information which kernel stack leak bugs can reveal and blocks some uninitialized stack variable attacks. Moreover, STACKLEAK blocks kernel stack depth overflow caused by alloca(), aka Stack Clash attack. This commit introduces the STACKLEAK gcc plugin. It is needed for: - tracking the lowest border of the kernel stack, which is important for the code erasing the used part of the kernel stack at the end of syscalls (comes in a separate commit); - checking that alloca() calls don't cause stack overflow. So this plugin instruments the kernel code inserting: - the stackleak_check_alloca() call before alloca() and the stackleak_track_stack() call after it; - the stackleak_track_stack() call for the functions with a stack frame size greater than or equal to CONFIG_STACKLEAK_TRACK_MIN_SIZE. The STACKLEAK feature is ported from grsecurity/PaX. More information at: https://grsecurity.net/ https://pax.grsecurity.net/ This code is modified from Brad Spengler/PaX Team's code in the last public patch of grsecurity/PaX based on our understanding of the code. Changes or omissions from the original code are ours and don't reflect the original grsecurity/PaX code. Signed-off-by: Alexander Popov --- arch/Kconfig | 14 + arch/x86/kernel/dumpstack.c | 31 +++ kernel/stackleak.c | 28 ++ scripts/Makefile.gcc-plugins | 8 +- scripts/gcc-plugins/stackleak_plugin.c | 480 +++++++++++++++++++++++++++++++++ 5 files changed, 560 insertions(+), 1 deletion(-) create mode 100644 scripts/gcc-plugins/stackleak_plugin.c diff --git a/arch/Kconfig b/arch/Kconfig index 07c8929..aa9374b 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -560,6 +560,8 @@ config GCC_PLUGIN_STACKLEAK bool "Erase the kernel stack before returning from syscalls" depends on GCC_PLUGINS depends on HAVE_ARCH_STACKLEAK + imply VMAP_STACK + imply SCHED_STACK_END_CHECK help This option makes the kernel erase the kernel stack before returning from system calls. That reduces the information which @@ -576,6 +578,18 @@ config GCC_PLUGIN_STACKLEAK * https://grsecurity.net/ * https://pax.grsecurity.net/ +config STACKLEAK_TRACK_MIN_SIZE + int "Minimum stack frame size of functions tracked by STACKLEAK" + default 100 + range 0 4096 + depends on GCC_PLUGIN_STACKLEAK + help + The STACKLEAK gcc plugin instruments the kernel code for tracking + the lowest border of the kernel stack (and for some other purposes). + It inserts the stackleak_track_stack() call for the functions with + a stack frame size greater than or equal to this parameter. + If unsure, leave the default value 100. + config HAVE_STACKPROTECTOR bool help diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 666a284..df6f61c 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -418,3 +418,34 @@ void show_regs(struct pt_regs *regs) if (!user_mode(regs)) show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT); } + +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +void __used stackleak_check_alloca(unsigned long size) +{ + unsigned long sp = (unsigned long)&sp; + struct stack_info stack_info = {0}; + unsigned long visit_mask = 0; + unsigned long stack_left; + + BUG_ON(get_stack_info(&sp, current, &stack_info, &visit_mask)); + + stack_left = sp - (unsigned long)stack_info.begin; + + if (size >= stack_left) { + /* + * Kernel stack depth overflow is detected, let's report that. + * If CONFIG_VMAP_STACK is enabled, we can safely use BUG(). + * If CONFIG_VMAP_STACK is disabled, BUG() handling can corrupt + * the neighbour memory. CONFIG_SCHED_STACK_END_CHECK calls + * panic() in a similar situation, so let's do the same if that + * option is on. Otherwise just use BUG() and hope for the best. + */ +#if !defined(CONFIG_VMAP_STACK) && defined(CONFIG_SCHED_STACK_END_CHECK) + panic("alloca() over the kernel stack boundary\n"); +#else + BUG(); +#endif + } +} +EXPORT_SYMBOL(stackleak_check_alloca); +#endif diff --git a/kernel/stackleak.c b/kernel/stackleak.c index bc3ad49..659dcc9 100644 --- a/kernel/stackleak.c +++ b/kernel/stackleak.c @@ -60,3 +60,31 @@ asmlinkage void stackleak_erase(void) current->lowest_stack = current_top_of_stack() - THREAD_SIZE/64; } +void __used 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; + + /* + * Having CONFIG_STACKLEAK_TRACK_MIN_SIZE larger than + * STACKLEAK_SEARCH_DEPTH makes the poison search in + * stackleak_erase() unreliable. Let's prevent that. + */ + BUILD_BUG_ON(CONFIG_STACKLEAK_TRACK_MIN_SIZE > STACKLEAK_SEARCH_DEPTH); + + if (sp < current->lowest_stack && + sp >= (unsigned long)task_stack_page(current) + + sizeof(unsigned long)) { + current->lowest_stack = sp; + } +} +EXPORT_SYMBOL(stackleak_track_stack); diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index c961b9a..091fd33 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -17,10 +17,16 @@ gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) += randomize_layout_plugin.so gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) += -DRANDSTRUCT_PLUGIN gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE) += -fplugin-arg-randomize_layout_plugin-performance-mode +gcc-plugin-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak_plugin.so +gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) += -DSTACKLEAK_PLUGIN -fplugin-arg-stackleak_plugin-track-min-size=$(CONFIG_STACKLEAK_TRACK_MIN_SIZE) +ifdef CONFIG_GCC_PLUGIN_STACKLEAK + DISABLE_STACKLEAK_PLUGIN += -fplugin-arg-stackleak_plugin-disable +endif + GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y)) export GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR -export DISABLE_LATENT_ENTROPY_PLUGIN +export DISABLE_LATENT_ENTROPY_PLUGIN DISABLE_STACKLEAK_PLUGIN # sancov_plugin.so can be only in CFLAGS_KCOV because avoid duplication. GCC_PLUGINS_CFLAGS := $(filter-out %/sancov_plugin.so, $(GCC_PLUGINS_CFLAGS)) diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c new file mode 100644 index 0000000..66eabf4 --- /dev/null +++ b/scripts/gcc-plugins/stackleak_plugin.c @@ -0,0 +1,480 @@ +/* + * Copyright 2011-2017 by the PaX Team + * Modified by Alexander Popov + * 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 + * and checking that alloca() calls don't cause stack overflow. It instruments + * the kernel code inserting: + * - the stackleak_check_alloca() call before alloca() and the + * stackleak_track_stack() call after it; + * - the stackleak_track_stack() call 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() and print_simple_rtl(); + * - 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 const char track_function[] = "stackleak_track_stack"; +static const char check_function[] = "stackleak_check_alloca"; + +/* + * Mark these global variables (roots) for gcc garbage collector since + * they point to the garbage-collected memory. + */ +static GTY(()) tree track_function_decl; +static GTY(()) tree check_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" + "disable\t\tdo not activate the plugin\n" +}; + +static void stackleak_add_check_alloca(gimple_stmt_iterator *gsi) +{ + gimple stmt; + gcall *stackleak_check_alloca; + tree alloca_size; + cgraph_node_ptr node; + int frequency; + basic_block bb; + + /* Insert call to void stackleak_check_alloca(unsigned long size) */ + alloca_size = gimple_call_arg(gsi_stmt(*gsi), 0); + stmt = gimple_build_call(check_function_decl, 1, alloca_size); + stackleak_check_alloca = as_a_gcall(stmt); + gsi_insert_before(gsi, stackleak_check_alloca, GSI_SAME_STMT); + + /* Update the cgraph */ + bb = gimple_bb(stackleak_check_alloca); + node = cgraph_get_create_node(check_function_decl); + gcc_assert(node); + frequency = compute_call_stmt_bb_frequency(current_function_decl, bb); + cgraph_create_edge(cgraph_get_node(current_function_decl), node, + stackleak_check_alloca, bb->count, frequency); +} + +static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after) +{ + gimple stmt; + gcall *stackleak_track_stack; + cgraph_node_ptr node; + int frequency; + basic_block bb; + + /* Insert call to void stackleak_track_stack(void) */ + 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); + } + + /* Update the cgraph */ + bb = gimple_bb(stackleak_track_stack); + node = cgraph_get_create_node(track_function_decl); + gcc_assert(node); + frequency = compute_call_stmt_bb_frequency(current_function_decl, bb); + cgraph_create_edge(cgraph_get_node(current_function_decl), node, + stackleak_track_stack, bb->count, frequency); +} + +static bool is_alloca(gimple stmt) +{ + if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA)) + return true; + +#if BUILDING_GCC_VERSION >= 4007 + if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA_WITH_ALIGN)) + return true; +#endif + + return false; +} + +/* + * Work with the GIMPLE representation of the code. Insert the + * stackleak_check_alloca() call before alloca() and stackleak_track_stack() + * call after it. Also insert stackleak_track_stack() call 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; + + /* + * 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; + + /* Insert stack overflow check before alloca() */ + stackleak_add_check_alloca(&gsi); + + /* Insert stackleak_track_stack() call after alloca() */ + stackleak_add_track_stack(&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); + stackleak_add_track_stack(&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 +} + +/* + * 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) +{ + 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. + * + * The example of a matching insn: + * (call_insn 8 4 10 2 (call (mem (symbol_ref ("stackleak_track_stack") + * [flags 0x41] ) + * [0 stackleak_track_stack S1 A8]) (0)) 675 {*call} (expr_list + * (symbol_ref ("stackleak_track_stack") [flags 0x41] ) (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 >= 4007 && 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 + } + + return 0; +} + +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 (!strncmp(TREE_STRING_POINTER(section), ".init.text", 10)) + return false; + if (!strncmp(TREE_STRING_POINTER(section), ".devinit.text", 13)) + return false; + if (!strncmp(TREE_STRING_POINTER(section), ".cpuinit.text", 13)) + return false; + if (!strncmp(TREE_STRING_POINTER(section), ".meminit.text", 13)) + return false; + } + + return track_frame_size >= 0; +} + +/* + * Build function declarations for stackleak_track_stack() and + * stackleak_check_alloca(). + */ +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; + + /* void stackleak_check_alloca(unsigned long) */ + fntype = build_function_type_list(void_type_node, + long_unsigned_type_node, NULL_TREE); + check_function_decl = build_fn_decl(check_function, fntype); + DECL_ASSEMBLER_NAME(check_function_decl); /* for LTO */ + TREE_PUBLIC(check_function_decl) = 1; + TREE_USED(check_function_decl) = 1; + DECL_EXTERNAL(check_function_decl) = 1; + DECL_ARTIFICIAL(check_function_decl) = 1; + DECL_PRESERVE_P(check_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 + }, + { + .base = &check_function_decl, + .nelt = 1, + .stride = sizeof(check_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 after the + * "reload" pass, when the stack frame size is final. + */ + PASS_INFO(stackleak_cleanup, "reload", 1, PASS_POS_INSERT_AFTER); + + 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, "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'"), + 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 { + error(G_("unknown option '-fplugin-arg-%s-%s'"), + plugin_name, argv[i].key); + return 1; + } + } + + /* 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; +}