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Diffstat (limited to 'gcc_plugin/afl-gcc-pass.so.cc')
| -rw-r--r-- | gcc_plugin/afl-gcc-pass.so.cc | 505 |
1 files changed, 505 insertions, 0 deletions
diff --git a/gcc_plugin/afl-gcc-pass.so.cc b/gcc_plugin/afl-gcc-pass.so.cc new file mode 100644 index 00000000..f0f5b30b --- /dev/null +++ b/gcc_plugin/afl-gcc-pass.so.cc @@ -0,0 +1,505 @@ +// +// There are some TODOs in this file: +// - fix instrumentation via external call +// - fix inline instrumentation +// - implement whitelist feature +// - dont instrument blocks that are uninteresting +// - implement neverZero +// + +/* + american fuzzy lop - GCC instrumentation pass + --------------------------------------------- + + Written by Austin Seipp <aseipp@pobox.com> with bits from + Emese Revfy <re.emese@gmail.com> + + Fixed by Heiko Eißfeldt 2019 for AFL++ + + GCC integration design is based on the LLVM design, which comes + from Laszlo Szekeres. Some of the boilerplate code below for + afl_pass to adapt to different GCC versions was taken from Emese + Revfy's Size Overflow plugin for GCC, licensed under the GPLv2/v3. + + (NOTE: this plugin code is under GPLv3, in order to comply with the + GCC runtime library exception, which states that you may distribute + "Target Code" from the compiler under a license of your choice, as + long as the "Compilation Process" is "Eligible", and contains no + GPL-incompatible software in GCC "during the process of + transforming high level code to target code". In this case, the + plugin will be used to generate "Target Code" during the + "Compilation Process", and thus it must be GPLv3 to be "eligible".) + + Copyright (C) 2015 Austin Seipp + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. + + */ + +#define BUILD_INLINE_INST + +#include "../config.h" +#include "../include/debug.h" + +/* clear helper AFL types pulls in, which intervene with gcc-plugin geaders from GCC-8 */ +#ifdef likely +#undef likely +#endif +#ifdef unlikely +#undef unlikely +#endif + + +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> + +#include <list> +#include <string> +#include <fstream> + +#include <gcc-plugin.h> +#include <plugin-version.h> +#include <diagnostic.h> +#include <tree.h> +#include <tree-ssa.h> +#include <tree-pass.h> +#include <tree-ssa-alias.h> +#include <basic-block.h> +#include <gimple-expr.h> +#include <gimple.h> +#include <gimple-iterator.h> +#include <gimple-ssa.h> +#include <version.h> +#include <toplev.h> +#include <intl.h> +#include <context.h> +#include <stringpool.h> +#include <cgraph.h> +#include <cfgloop.h> + +/* -------------------------------------------------------------------------- */ +/* -- AFL instrumentation pass ---------------------------------------------- */ + +static int be_quiet = 0; +static unsigned int inst_ratio = 100; +static bool inst_ext = true; +static std::list<std::string> myWhitelist; + +static unsigned int ext_call_instrument(function *fun) { + /* Instrument all the things! */ + basic_block bb; + unsigned finst_blocks = 0; + unsigned fcnt_blocks = 0; + + tree fntype = build_function_type_list( + void_type_node, /* return */ + uint32_type_node, /* args */ + NULL_TREE); /* done */ + tree fndecl = build_fn_decl("__afl_trace", fntype); + TREE_STATIC(fndecl) = 1; /* Defined elsewhere */ + TREE_PUBLIC(fndecl) = 1; /* Public */ + DECL_EXTERNAL(fndecl) = 1; /* External linkage */ + DECL_ARTIFICIAL(fndecl) = 1; /* Injected by compiler */ + + FOR_EACH_BB_FN(bb, fun) { + gimple_seq fcall; + gimple_seq seq = NULL; + gimple_stmt_iterator bentry; + ++fcnt_blocks; + + // only instrument if this basic block is the destination of a previous + // basic block that has multiple successors + // this gets rid of ~5-10% of instrumentations that are unnecessary + // result: a little more speed and less map pollution + + int more_than_one = -1; + edge ep; + edge_iterator eip; + FOR_EACH_EDGE (ep, eip, bb->preds) { + int count = 0; + if (more_than_one == -1) + more_than_one = 0; + + basic_block Pred = ep->src; + edge es; + edge_iterator eis; + FOR_EACH_EDGE (es, eis, Pred->succs) { + basic_block Succ = es->dest; + if (Succ != NULL) count++; + } + if (count > 1) + more_than_one = 1; + } + if (more_than_one != 1) + continue; + + /* Bail on this block if we trip the specified ratio */ + if (R(100) >= inst_ratio) continue; + + /* Make up cur_loc */ + unsigned int rand_loc = R(MAP_SIZE); + tree cur_loc = build_int_cst(uint32_type_node, rand_loc); + + /* Update bitmap via external call */ + /* to quote: + * /+ Trace a basic block with some ID +/ + * void __afl_trace(u32 x); + */ + + fcall = gimple_build_call(fndecl, 1, cur_loc); /* generate the function _call_ to above built reference, with *1* parameter -> the random const for the location */ + gimple_seq_add_stmt(&seq, fcall); /* and insert into a sequence */ + + /* Done - grab the entry to the block and insert sequence */ + bentry = gsi_after_labels(bb); + gsi_insert_seq_before(&bentry, seq, GSI_SAME_STMT); + + ++finst_blocks; + } + + /* Say something nice. */ + if (!be_quiet) { + if (!finst_blocks) + WARNF(G_("No instrumentation targets found in " cBRI "%s" cRST ), + function_name(fun)); + else if (finst_blocks < fcnt_blocks) + OKF(G_("Instrumented %2u /%2u locations in " cBRI "%s" cRST ), + finst_blocks, fcnt_blocks, + function_name(fun)); + else + OKF(G_("Instrumented %2u locations in " cBRI "%s" cRST ), + finst_blocks, + function_name(fun)); + } + + return 0; +} + +static unsigned int inline_instrument(function *fun) { + + /* Instrument all the things! */ + basic_block bb; + unsigned finst_blocks = 0; + unsigned fcnt_blocks = 0; + + /* Set up global type declarations */ + tree map_type = build_pointer_type(unsigned_char_type_node); + tree map_ptr_g = build_decl(UNKNOWN_LOCATION, VAR_DECL, + get_identifier_with_length("__afl_area_ptr", 14), map_type); + TREE_USED(map_ptr_g) = 1; + TREE_STATIC(map_ptr_g) = 1; /* Defined elsewhere */ + DECL_EXTERNAL(map_ptr_g) = 1; /* External linkage */ + DECL_PRESERVE_P(map_ptr_g) = 1; + DECL_ARTIFICIAL(map_ptr_g) = 1; /* Injected by compiler */ + rest_of_decl_compilation(map_ptr_g, 1, 0); + + tree prev_loc_g = build_decl(UNKNOWN_LOCATION, VAR_DECL, + get_identifier_with_length("__afl_prev_loc", 14), uint32_type_node); + TREE_USED(prev_loc_g) = 1; + TREE_STATIC(prev_loc_g) = 1; /* Defined elsewhere */ + DECL_EXTERNAL(prev_loc_g) = 1; /* External linkage */ + DECL_PRESERVE_P(prev_loc_g) = 1; + DECL_ARTIFICIAL(prev_loc_g) = 1; /* Injected by compiler */ + rest_of_decl_compilation(prev_loc_g, 1, 0); + + FOR_EACH_BB_FN(bb, fun) { + gimple_seq seq = NULL; + gimple_stmt_iterator bentry; + ++fcnt_blocks; + + // only instrument if this basic block is the destination of a previous + // basic block that has multiple successors + // this gets rid of ~5-10% of instrumentations that are unnecessary + // result: a little more speed and less map pollution + + int more_than_one = -1; + edge ep; + edge_iterator eip; + FOR_EACH_EDGE (ep, eip, bb->preds) { + int count = 0; + if (more_than_one == -1) + more_than_one = 0; + + basic_block Pred = ep->src; + edge es; + edge_iterator eis; + FOR_EACH_EDGE (es, eis, Pred->succs) { + basic_block Succ = es->dest; + if (Succ != NULL) count++; + } + if (count > 1) + more_than_one = 1; + } + if (more_than_one != 1) + continue; + + /* Bail on this block if we trip the specified ratio */ + if (R(100) >= inst_ratio) continue; + + /* Make up cur_loc */ + + unsigned int rand_loc = R(MAP_SIZE); + tree cur_loc = build_int_cst(uint32_type_node, rand_loc); + + /* Load prev_loc, xor with cur_loc */ + // gimple_assign <var_decl, prev_loc.0_1, prev_loc, NULL, NULL> + tree prev_loc = create_tmp_var_raw(uint32_type_node, "prev_loc"); + gassign *g = gimple_build_assign(prev_loc, VAR_DECL, prev_loc_g); + gimple_seq_add_stmt(&seq, g); // load prev_loc + update_stmt(g); + + // gimple_assign <bit_xor_expr, _2, prev_loc.0_1, 47231, NULL> + tree area_off = create_tmp_var_raw(uint32_type_node, "area_off"); + g = gimple_build_assign(area_off, BIT_XOR_EXPR, prev_loc, cur_loc); + gimple_seq_add_stmt(&seq, g); // area_off = prev_loc ^ cur_loc + update_stmt(g); + + /* Update bitmap */ + + tree one = build_int_cst(unsigned_char_type_node, 1); +// tree zero = build_int_cst(unsigned_char_type_node, 0); + + // gimple_assign <addr_expr, p_6, &map[_2], NULL, NULL> + tree map_ptr = create_tmp_var(map_type, "map_ptr"); + tree map_ptr2 = create_tmp_var(map_type, "map_ptr2"); + + g = gimple_build_assign(map_ptr, map_ptr_g); + gimple_seq_add_stmt(&seq, g); // map_ptr = __afl_area_ptr + update_stmt(g); + +#if 0 + tree addr = build2(ADDR_EXPR, map_type, map_ptr, area_off); + g = gimple_build_assign(map_ptr2, MODIFY_EXPR, addr); + gimple_seq_add_stmt(&seq, g); // map_ptr2 = map_ptr + area_off + update_stmt(g); +#else + g = gimple_build_assign(map_ptr2, PLUS_EXPR, map_ptr, area_off); + gimple_seq_add_stmt(&seq, g); // map_ptr2 = map_ptr + area_off + update_stmt(g); +#endif + // gimple_assign <mem_ref, _3, *p_6, NULL, NULL> + tree tmp1 = create_tmp_var_raw(unsigned_char_type_node, "tmp1"); + g = gimple_build_assign(tmp1, MEM_REF, map_ptr2); + gimple_seq_add_stmt(&seq, g); // tmp1 = *map_ptr2 + update_stmt(g); + + // gimple_assign <plus_expr, _4, _3, 1, NULL> + tree tmp2 = create_tmp_var_raw(unsigned_char_type_node, "tmp2"); + g = gimple_build_assign(tmp2, PLUS_EXPR, tmp1, one); + gimple_seq_add_stmt(&seq, g); // tmp2 = tmp1 + 1 + update_stmt(g); + + // TODO: neverZero: here we have to check if tmp3 == 0 + // and add 1 if so + + // gimple_assign <ssa_name, *p_6, _4, NULL, NULL> +// tree map_ptr3 = create_tmp_var_raw(map_type, "map_ptr3"); + g = gimple_build_assign(map_ptr_g, INDIRECT_REF, tmp2); + gimple_seq_add_stmt(&seq, g); // *map_ptr3 = tmp2 + update_stmt(g); + + /* Set prev_loc to cur_loc >> 1 */ + + // gimple_assign <integer_cst, prev_loc, 23615, NULL, NULL> + tree shifted_loc = build_int_cst(TREE_TYPE(prev_loc_g), rand_loc >> 1); + tree prev_loc2 = create_tmp_var_raw(uint32_type_node, "prev_loc2"); + g = gimple_build_assign(prev_loc2, shifted_loc); + gimple_seq_add_stmt(&seq, g); // __afl_prev_loc = cur_loc >> 1 + update_stmt(g); + g = gimple_build_assign(prev_loc_g, prev_loc2); + gimple_seq_add_stmt(&seq, g); // __afl_prev_loc = cur_loc >> 1 + update_stmt(g); + + /* Done - grab the entry to the block and insert sequence */ + + bentry = gsi_after_labels(bb); + gsi_insert_seq_before(&bentry, seq, GSI_NEW_STMT); + + ++finst_blocks; + } + + /* Say something nice. */ + if (!be_quiet) { + if (!finst_blocks) + WARNF(G_("No instrumentation targets found in " cBRI "%s" cRST ), + function_name(fun)); + else if (finst_blocks < fcnt_blocks) + OKF(G_("Instrumented %2u /%2u locations in " cBRI "%s" cRST ), + finst_blocks, fcnt_blocks, + function_name(fun)); + else + OKF(G_("Instrumented %2u locations in " cBRI "%s" cRST ), + finst_blocks, + function_name(fun)); + } + + + return 0; +} + +/* -------------------------------------------------------------------------- */ +/* -- Boilerplate and initialization ---------------------------------------- */ + +static const struct pass_data afl_pass_data = { + + .type = GIMPLE_PASS, + .name = "afl-inst", + .optinfo_flags = OPTGROUP_NONE, + + .tv_id = TV_NONE, + .properties_required = 0, + .properties_provided = 0, + .properties_destroyed = 0, + .todo_flags_start = 0, + // NOTE(aseipp): it's very, very important to include + // at least 'TODO_update_ssa' here so that GCC will + // properly update the resulting SSA form, e.g., to + // include new PHI nodes for newly added symbols or + // names. Do not remove this. Do not taunt Happy Fun + // Ball. + .todo_flags_finish = TODO_update_ssa | TODO_verify_il | TODO_cleanup_cfg, +}; + +namespace { + +class afl_pass : public gimple_opt_pass { +private: + bool do_ext_call; + +public: + afl_pass(bool ext_call, gcc::context *g) : gimple_opt_pass(afl_pass_data, g), do_ext_call(ext_call) {} + + virtual unsigned int execute(function *fun) { + + if (!myWhitelist.empty()) { + bool instrumentBlock = false; + + /* EXPR_FILENAME + This macro returns the name of the file in which the entity was declared, as + a char*. For an entity declared implicitly by the compiler (like __builtin_ + memcpy), this will be the string "<internal>". + */ + const char *fname = DECL_SOURCE_FILE(fun->decl); + + if (0 != strncmp("<internal>", fname, 10) + && 0 != strncmp("<built-in>", fname, 10)) + { + std::string instFilename(fname); + + /* Continue only if we know where we actually are */ + if (!instFilename.empty()) { + for (std::list<std::string>::iterator it = myWhitelist.begin(); it != myWhitelist.end(); ++it) { + /* We don't check for filename equality here because + * filenames might actually be full paths. Instead we + * check that the actual filename ends in the filename + * specified in the list. */ + if (instFilename.length() >= it->length()) { + if (instFilename.compare(instFilename.length() - it->length(), it->length(), *it) == 0) { + instrumentBlock = true; + break; + } + } + } + } + } + + /* Either we couldn't figure out our location or the location is + * not whitelisted, so we skip instrumentation. */ + if (!instrumentBlock) return 0;; + } + + return do_ext_call ? ext_call_instrument(fun) : inline_instrument(fun); + } +}; /* class afl_pass */ + +} /* anon namespace */ + +static struct opt_pass *make_afl_pass(bool ext_call, gcc::context *ctxt) { + return new afl_pass(ext_call, ctxt); +} + +/* -------------------------------------------------------------------------- */ +/* -- Initialization -------------------------------------------------------- */ + +int plugin_is_GPL_compatible = 1; + +static struct plugin_info afl_plugin_info = { + .version = "20191015", + .help = "AFL++ gcc plugin\n", +}; + +int plugin_init(struct plugin_name_args *plugin_info, + struct plugin_gcc_version *version) { + + struct register_pass_info afl_pass_info; + struct timeval tv; + struct timezone tz; + u32 rand_seed; + + /* Setup random() so we get Actually Random(TM) outputs from R() */ + gettimeofday(&tv, &tz); + rand_seed = tv.tv_sec ^ tv.tv_usec ^ getpid(); + srandom(rand_seed); + + /* Pass information */ + afl_pass_info.pass = make_afl_pass(inst_ext, g); + afl_pass_info.reference_pass_name = "ssa"; + afl_pass_info.ref_pass_instance_number = 1; + afl_pass_info.pos_op = PASS_POS_INSERT_AFTER; + + if (!plugin_default_version_check(version, &gcc_version)) { + FATAL(G_("Incompatible gcc/plugin versions!")); + } + + /* Show a banner */ + if (isatty(2) && !getenv("AFL_QUIET")) { + SAYF(G_(cCYA "afl-gcc-pass " cBRI VERSION cRST " initially by <aseipp@pobox.com>, maintainer: hexcoder-\n")); + } else + be_quiet = 1; + + /* Decide instrumentation ratio */ + char* inst_ratio_str = getenv("AFL_INST_RATIO"); + + if (inst_ratio_str) { + if (sscanf(inst_ratio_str, "%u", &inst_ratio) != 1 || !inst_ratio || inst_ratio > 100) + FATAL(G_("Bad value of AFL_INST_RATIO (must be between 1 and 100)")); + else { + if (!be_quiet) + ACTF(G_("%s instrumentation at ratio of %u%% in %s mode."), + inst_ext ? G_("Call-based") : G_("Inline"), + inst_ratio, + getenv("AFL_HARDEN") ? G_("hardened") : G_("non-hardened")); + } + } + + char* instWhiteListFilename = getenv("AFL_GCC_WHITELIST"); + if (instWhiteListFilename) { + std::string line; + std::ifstream fileStream; + fileStream.open(instWhiteListFilename); + if (!fileStream) + fatal_error(0, "Unable to open AFL_GCC_WHITELIST"); + getline(fileStream, line); + while (fileStream) { + myWhitelist.push_back(line); + getline(fileStream, line); + } + } else if (!be_quiet && getenv("AFL_LLVM_WHITELIST")) + SAYF(cYEL "[-] " cRST "AFL_LLVM_WHITELIST environment variable detected - did you mean AFL_GCC_WHITELIST?\n"); + + /* Go go gadget */ + register_callback(plugin_info->base_name, PLUGIN_INFO, NULL, &afl_plugin_info); + register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &afl_pass_info); + return 0; +} |