From d9e9d2300681d68a775c28de6aa6e5290ae17796 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 14 Jun 2022 23:15:38 +0200 Subject: x86,objtool: Create .return_sites Find all the return-thunk sites and record them in a .return_sites section such that the kernel can undo this. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov --- tools/objtool/arch/x86/decode.c | 5 +++ tools/objtool/check.c | 74 +++++++++++++++++++++++++++++++++ tools/objtool/include/objtool/arch.h | 1 + tools/objtool/include/objtool/elf.h | 1 + tools/objtool/include/objtool/objtool.h | 1 + tools/objtool/objtool.c | 1 + 6 files changed, 83 insertions(+) (limited to 'tools/objtool') diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index 8b990a52aada..c260006106be 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -787,3 +787,8 @@ bool arch_is_retpoline(struct symbol *sym) { return !strncmp(sym->name, "__x86_indirect_", 15); } + +bool arch_is_rethunk(struct symbol *sym) +{ + return !strcmp(sym->name, "__x86_return_thunk"); +} diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 864bb9dd3584..f6d4ffa82432 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -749,6 +749,52 @@ static int create_retpoline_sites_sections(struct objtool_file *file) return 0; } +static int create_return_sites_sections(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, ".return_sites"); + if (sec) { + WARN("file already has .return_sites, skipping"); + return 0; + } + + idx = 0; + list_for_each_entry(insn, &file->return_thunk_list, call_node) + idx++; + + if (!idx) + return 0; + + sec = elf_create_section(file->elf, ".return_sites", 0, + sizeof(int), idx); + if (!sec) { + WARN("elf_create_section: .return_sites"); + return -1; + } + + idx = 0; + list_for_each_entry(insn, &file->return_thunk_list, call_node) { + + int *site = (int *)sec->data->d_buf + idx; + *site = 0; + + if (elf_add_reloc_to_insn(file->elf, sec, + idx * sizeof(int), + R_X86_64_PC32, + insn->sec, insn->offset)) { + WARN("elf_add_reloc_to_insn: .return_sites"); + return -1; + } + + idx++; + } + + return 0; +} + static int create_ibt_endbr_seal_sections(struct objtool_file *file) { struct instruction *insn; @@ -1083,6 +1129,11 @@ __weak bool arch_is_retpoline(struct symbol *sym) return false; } +__weak bool arch_is_rethunk(struct symbol *sym) +{ + return false; +} + #define NEGATIVE_RELOC ((void *)-1L) static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn) @@ -1250,6 +1301,18 @@ static void add_retpoline_call(struct objtool_file *file, struct instruction *in annotate_call_site(file, insn, false); } +static void add_return_call(struct objtool_file *file, struct instruction *insn) +{ + /* + * Return thunk tail calls are really just returns in disguise, + * so convert them accordingly. + */ + insn->type = INSN_RETURN; + insn->retpoline_safe = true; + + list_add_tail(&insn->call_node, &file->return_thunk_list); +} + static bool same_function(struct instruction *insn1, struct instruction *insn2) { return insn1->func->pfunc == insn2->func->pfunc; @@ -1302,6 +1365,9 @@ static int add_jump_destinations(struct objtool_file *file) } else if (reloc->sym->retpoline_thunk) { add_retpoline_call(file, insn); continue; + } else if (reloc->sym->return_thunk) { + add_return_call(file, insn); + continue; } else if (insn->func) { /* * External sibling call or internal sibling call with @@ -2184,6 +2250,9 @@ static int classify_symbols(struct objtool_file *file) if (arch_is_retpoline(func)) func->retpoline_thunk = true; + if (arch_is_rethunk(func)) + func->return_thunk = true; + if (!strcmp(func->name, "__fentry__")) func->fentry = true; @@ -3972,6 +4041,11 @@ int check(struct objtool_file *file) if (ret < 0) goto out; warnings += ret; + + ret = create_return_sites_sections(file); + if (ret < 0) + goto out; + warnings += ret; } if (opts.mcount) { diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h index 9b19cc304195..beb2f3aa94ff 100644 --- a/tools/objtool/include/objtool/arch.h +++ b/tools/objtool/include/objtool/arch.h @@ -89,6 +89,7 @@ const char *arch_ret_insn(int len); int arch_decode_hint_reg(u8 sp_reg, int *base); bool arch_is_retpoline(struct symbol *sym); +bool arch_is_rethunk(struct symbol *sym); int arch_rewrite_retpolines(struct objtool_file *file); diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h index adebfbc2b518..16f4067b82ae 100644 --- a/tools/objtool/include/objtool/elf.h +++ b/tools/objtool/include/objtool/elf.h @@ -57,6 +57,7 @@ struct symbol { u8 uaccess_safe : 1; u8 static_call_tramp : 1; u8 retpoline_thunk : 1; + u8 return_thunk : 1; u8 fentry : 1; u8 profiling_func : 1; struct list_head pv_target; diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h index a6e72d916807..7f2d1b095333 100644 --- a/tools/objtool/include/objtool/objtool.h +++ b/tools/objtool/include/objtool/objtool.h @@ -24,6 +24,7 @@ struct objtool_file { struct list_head insn_list; DECLARE_HASHTABLE(insn_hash, 20); struct list_head retpoline_call_list; + struct list_head return_thunk_list; struct list_head static_call_list; struct list_head mcount_loc_list; struct list_head endbr_list; diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c index 512669ce064c..a7ecc32e3512 100644 --- a/tools/objtool/objtool.c +++ b/tools/objtool/objtool.c @@ -102,6 +102,7 @@ struct objtool_file *objtool_open_read(const char *_objname) INIT_LIST_HEAD(&file.insn_list); hash_init(file.insn_hash); INIT_LIST_HEAD(&file.retpoline_call_list); + INIT_LIST_HEAD(&file.return_thunk_list); INIT_LIST_HEAD(&file.static_call_list); INIT_LIST_HEAD(&file.mcount_loc_list); INIT_LIST_HEAD(&file.endbr_list); -- cgit v1.2.3 From 951ddecf435659553ed15a9214e153a3af43a9a1 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 14 Jun 2022 23:15:47 +0200 Subject: objtool: Treat .text.__x86.* as noinstr Needed because zen_untrain_ret() will be called from noinstr code. Also makes sense since the thunks MUST NOT contain instrumentation nor be poked with dynamic instrumentation. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov --- tools/objtool/check.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'tools/objtool') diff --git a/tools/objtool/check.c b/tools/objtool/check.c index f6d4ffa82432..b98fd68013c3 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -376,7 +376,8 @@ static int decode_instructions(struct objtool_file *file) sec->text = true; if (!strcmp(sec->name, ".noinstr.text") || - !strcmp(sec->name, ".entry.text")) + !strcmp(sec->name, ".entry.text") || + !strncmp(sec->name, ".text.__x86.", 12)) sec->noinstr = true; for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) { -- cgit v1.2.3 From a149180fbcf336e97ce4eb2cdc13672727feb94d Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 14 Jun 2022 23:15:48 +0200 Subject: x86: Add magic AMD return-thunk Note: needs to be in a section distinct from Retpolines such that the Retpoline RET substitution cannot possibly use immediate jumps. ORC unwinding for zen_untrain_ret() and __x86_return_thunk() is a little tricky but works due to the fact that zen_untrain_ret() doesn't have any stack ops and as such will emit a single ORC entry at the start (+0x3f). Meanwhile, unwinding an IP, including the __x86_return_thunk() one (+0x40) will search for the largest ORC entry smaller or equal to the IP, these will find the one ORC entry (+0x3f) and all works. [ Alexandre: SVM part. ] [ bp: Build fix, massages. ] Suggested-by: Andrew Cooper Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov --- tools/objtool/check.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) (limited to 'tools/objtool') diff --git a/tools/objtool/check.c b/tools/objtool/check.c index b98fd68013c3..4252cd05dfc4 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1302,7 +1302,7 @@ static void add_retpoline_call(struct objtool_file *file, struct instruction *in annotate_call_site(file, insn, false); } -static void add_return_call(struct objtool_file *file, struct instruction *insn) +static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add) { /* * Return thunk tail calls are really just returns in disguise, @@ -1311,7 +1311,8 @@ static void add_return_call(struct objtool_file *file, struct instruction *insn) insn->type = INSN_RETURN; insn->retpoline_safe = true; - list_add_tail(&insn->call_node, &file->return_thunk_list); + if (add) + list_add_tail(&insn->call_node, &file->return_thunk_list); } static bool same_function(struct instruction *insn1, struct instruction *insn2) @@ -1367,7 +1368,7 @@ static int add_jump_destinations(struct objtool_file *file) add_retpoline_call(file, insn); continue; } else if (reloc->sym->return_thunk) { - add_return_call(file, insn); + add_return_call(file, insn, true); continue; } else if (insn->func) { /* @@ -1387,6 +1388,21 @@ static int add_jump_destinations(struct objtool_file *file) jump_dest = find_insn(file, dest_sec, dest_off); if (!jump_dest) { + struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off); + + /* + * This is a special case for zen_untrain_ret(). + * It jumps to __x86_return_thunk(), but objtool + * can't find the thunk's starting RET + * instruction, because the RET is also in the + * middle of another instruction. Objtool only + * knows about the outer instruction. + */ + if (sym && sym->return_thunk) { + add_return_call(file, insn, false); + continue; + } + WARN_FUNC("can't find jump dest instruction at %s+0x%lx", insn->sec, insn->offset, dest_sec->name, dest_off); -- cgit v1.2.3 From 9bb2ec608a209018080ca262f771e6a9ff203b6f Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 14 Jun 2022 23:15:59 +0200 Subject: objtool: Update Retpoline validation Update retpoline validation with the new CONFIG_RETPOLINE requirement of not having bare naked RET instructions. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov --- tools/objtool/check.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) (limited to 'tools/objtool') diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 4252cd05dfc4..7dc378156a63 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2115,8 +2115,9 @@ static int read_retpoline_hints(struct objtool_file *file) } if (insn->type != INSN_JUMP_DYNAMIC && - insn->type != INSN_CALL_DYNAMIC) { - WARN_FUNC("retpoline_safe hint not an indirect jump/call", + insn->type != INSN_CALL_DYNAMIC && + insn->type != INSN_RETURN) { + WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret", insn->sec, insn->offset); return -1; } @@ -3526,7 +3527,8 @@ static int validate_retpoline(struct objtool_file *file) for_each_insn(file, insn) { if (insn->type != INSN_JUMP_DYNAMIC && - insn->type != INSN_CALL_DYNAMIC) + insn->type != INSN_CALL_DYNAMIC && + insn->type != INSN_RETURN) continue; if (insn->retpoline_safe) @@ -3541,9 +3543,14 @@ static int validate_retpoline(struct objtool_file *file) if (!strcmp(insn->sec->name, ".init.text") && !opts.module) continue; - WARN_FUNC("indirect %s found in RETPOLINE build", - insn->sec, insn->offset, - insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); + if (insn->type == INSN_RETURN) { + WARN_FUNC("'naked' return found in RETPOLINE build", + insn->sec, insn->offset); + } else { + WARN_FUNC("indirect %s found in RETPOLINE build", + insn->sec, insn->offset, + insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); + } warnings++; } -- cgit v1.2.3 From a09a6e2399ba0595c3042b3164f3ca68a3cff33e Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 14 Jun 2022 23:16:03 +0200 Subject: objtool: Add entry UNRET validation Since entry asm is tricky, add a validation pass that ensures the retbleed mitigation has been done before the first actual RET instruction. Entry points are those that either have UNWIND_HINT_ENTRY, which acts as UNWIND_HINT_EMPTY but marks the instruction as an entry point, or those that have UWIND_HINT_IRET_REGS at +0. This is basically a variant of validate_branch() that is intra-function and it will simply follow all branches from marked entry points and ensures that all paths lead to ANNOTATE_UNRET_END. If a path hits RET or an indirection the path is a fail and will be reported. There are 3 ANNOTATE_UNRET_END instances: - UNTRAIN_RET itself - exception from-kernel; this path doesn't need UNTRAIN_RET - all early exceptions; these also don't need UNTRAIN_RET Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov --- tools/objtool/builtin-check.c | 6 ++ tools/objtool/check.c | 177 ++++++++++++++++++++++++++++++-- tools/objtool/include/objtool/builtin.h | 1 + tools/objtool/include/objtool/check.h | 11 +- 4 files changed, 184 insertions(+), 11 deletions(-) (limited to 'tools/objtool') diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c index f4c3a5091737..c063e1ff96b2 100644 --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -68,6 +68,7 @@ const struct option check_options[] = { OPT_BOOLEAN('n', "noinstr", &opts.noinstr, "validate noinstr rules"), OPT_BOOLEAN('o', "orc", &opts.orc, "generate ORC metadata"), OPT_BOOLEAN('r', "retpoline", &opts.retpoline, "validate and annotate retpoline usage"), + OPT_BOOLEAN(0, "unret", &opts.unret, "validate entry unret placement"), OPT_BOOLEAN('l', "sls", &opts.sls, "validate straight-line-speculation mitigations"), OPT_BOOLEAN('s', "stackval", &opts.stackval, "validate frame pointer rules"), OPT_BOOLEAN('t', "static-call", &opts.static_call, "annotate static calls"), @@ -163,6 +164,11 @@ static bool link_opts_valid(struct objtool_file *file) return false; } + if (opts.unret) { + ERROR("--unret requires --link"); + return false; + } + return true; } diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 7dc378156a63..822a490e6d87 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2032,16 +2032,24 @@ static int read_unwind_hints(struct objtool_file *file) insn->hint = true; - if (opts.ibt && hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) { + if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) { struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset); - if (sym && sym->bind == STB_GLOBAL && - insn->type != INSN_ENDBR && !insn->noendbr) { - WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR", - insn->sec, insn->offset); + if (sym && sym->bind == STB_GLOBAL) { + if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) { + WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR", + insn->sec, insn->offset); + } + + insn->entry = 1; } } + if (hint->type == UNWIND_HINT_TYPE_ENTRY) { + hint->type = UNWIND_HINT_TYPE_CALL; + insn->entry = 1; + } + if (hint->type == UNWIND_HINT_TYPE_FUNC) { insn->cfi = &func_cfi; continue; @@ -2116,8 +2124,9 @@ static int read_retpoline_hints(struct objtool_file *file) if (insn->type != INSN_JUMP_DYNAMIC && insn->type != INSN_CALL_DYNAMIC && - insn->type != INSN_RETURN) { - WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret", + insn->type != INSN_RETURN && + insn->type != INSN_NOP) { + WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret/nop", insn->sec, insn->offset); return -1; } @@ -3305,8 +3314,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, return 1; } - visited = 1 << state.uaccess; - if (insn->visited) { + visited = VISITED_BRANCH << state.uaccess; + if (insn->visited & VISITED_BRANCH_MASK) { if (!insn->hint && !insn_cfi_match(insn, &state.cfi)) return 1; @@ -3520,6 +3529,145 @@ static int validate_unwind_hints(struct objtool_file *file, struct section *sec) return warnings; } +/* + * Validate rethunk entry constraint: must untrain RET before the first RET. + * + * Follow every branch (intra-function) and ensure ANNOTATE_UNRET_END comes + * before an actual RET instruction. + */ +static int validate_entry(struct objtool_file *file, struct instruction *insn) +{ + struct instruction *next, *dest; + int ret, warnings = 0; + + for (;;) { + next = next_insn_to_validate(file, insn); + + if (insn->visited & VISITED_ENTRY) + return 0; + + insn->visited |= VISITED_ENTRY; + + if (!insn->ignore_alts && !list_empty(&insn->alts)) { + struct alternative *alt; + bool skip_orig = false; + + list_for_each_entry(alt, &insn->alts, list) { + if (alt->skip_orig) + skip_orig = true; + + ret = validate_entry(file, alt->insn); + if (ret) { + if (opts.backtrace) + BT_FUNC("(alt)", insn); + return ret; + } + } + + if (skip_orig) + return 0; + } + + switch (insn->type) { + + case INSN_CALL_DYNAMIC: + case INSN_JUMP_DYNAMIC: + case INSN_JUMP_DYNAMIC_CONDITIONAL: + WARN_FUNC("early indirect call", insn->sec, insn->offset); + return 1; + + case INSN_JUMP_UNCONDITIONAL: + case INSN_JUMP_CONDITIONAL: + if (!is_sibling_call(insn)) { + if (!insn->jump_dest) { + WARN_FUNC("unresolved jump target after linking?!?", + insn->sec, insn->offset); + return -1; + } + ret = validate_entry(file, insn->jump_dest); + if (ret) { + if (opts.backtrace) { + BT_FUNC("(branch%s)", insn, + insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : ""); + } + return ret; + } + + if (insn->type == INSN_JUMP_UNCONDITIONAL) + return 0; + + break; + } + + /* fallthrough */ + case INSN_CALL: + dest = find_insn(file, insn->call_dest->sec, + insn->call_dest->offset); + if (!dest) { + WARN("Unresolved function after linking!?: %s", + insn->call_dest->name); + return -1; + } + + ret = validate_entry(file, dest); + if (ret) { + if (opts.backtrace) + BT_FUNC("(call)", insn); + return ret; + } + /* + * If a call returns without error, it must have seen UNTRAIN_RET. + * Therefore any non-error return is a success. + */ + return 0; + + case INSN_RETURN: + WARN_FUNC("RET before UNTRAIN", insn->sec, insn->offset); + return 1; + + case INSN_NOP: + if (insn->retpoline_safe) + return 0; + break; + + default: + break; + } + + if (!next) { + WARN_FUNC("teh end!", insn->sec, insn->offset); + return -1; + } + insn = next; + } + + return warnings; +} + +/* + * Validate that all branches starting at 'insn->entry' encounter UNRET_END + * before RET. + */ +static int validate_unret(struct objtool_file *file) +{ + struct instruction *insn; + int ret, warnings = 0; + + for_each_insn(file, insn) { + if (!insn->entry) + continue; + + ret = validate_entry(file, insn); + if (ret < 0) { + WARN_FUNC("Failed UNRET validation", insn->sec, insn->offset); + return ret; + } + warnings += ret; + } + + return warnings; +} + static int validate_retpoline(struct objtool_file *file) { struct instruction *insn; @@ -4039,6 +4187,17 @@ int check(struct objtool_file *file) warnings += ret; } + if (opts.unret) { + /* + * Must be after validate_branch() and friends, it plays + * further games with insn->visited. + */ + ret = validate_unret(file); + if (ret < 0) + return ret; + warnings += ret; + } + if (opts.ibt) { ret = validate_ibt(file); if (ret < 0) diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h index 280ea18b7f2b..0c476b0b40a3 100644 --- a/tools/objtool/include/objtool/builtin.h +++ b/tools/objtool/include/objtool/builtin.h @@ -19,6 +19,7 @@ struct opts { bool noinstr; bool orc; bool retpoline; + bool unret; bool sls; bool stackval; bool static_call; diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h index f10d7374f388..0eeedeacbefb 100644 --- a/tools/objtool/include/objtool/check.h +++ b/tools/objtool/include/objtool/check.h @@ -51,8 +51,10 @@ struct instruction { ignore_alts : 1, hint : 1, retpoline_safe : 1, - noendbr : 1; - /* 2 bit hole */ + noendbr : 1, + entry : 1; + /* 1 bit hole */ + s8 instr; u8 visited; /* u8 hole */ @@ -69,6 +71,11 @@ struct instruction { struct cfi_state *cfi; }; +#define VISITED_BRANCH 0x01 +#define VISITED_BRANCH_UACCESS 0x02 +#define VISITED_BRANCH_MASK 0x03 +#define VISITED_ENTRY 0x04 + static inline bool is_static_jump(struct instruction *insn) { return insn->type == INSN_JUMP_CONDITIONAL || -- cgit v1.2.3 From 8faea26e611189e933ea2281975ff4dc7c1106b6 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 24 Jun 2022 12:52:40 +0200 Subject: objtool: Re-add UNWIND_HINT_{SAVE_RESTORE} Commit c536ed2fffd5 ("objtool: Remove SAVE/RESTORE hints") removed the save/restore unwind hints because they were no longer needed. Now they're going to be needed again so re-add them. Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov --- tools/objtool/check.c | 40 +++++++++++++++++++++++++++++++++++ tools/objtool/include/objtool/check.h | 19 +++++++++-------- 2 files changed, 50 insertions(+), 9 deletions(-) (limited to 'tools/objtool') diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 822a490e6d87..ddfdd138cc2a 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2032,6 +2032,17 @@ static int read_unwind_hints(struct objtool_file *file) insn->hint = true; + if (hint->type == UNWIND_HINT_TYPE_SAVE) { + insn->hint = false; + insn->save = true; + continue; + } + + if (hint->type == UNWIND_HINT_TYPE_RESTORE) { + insn->restore = true; + continue; + } + if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) { struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset); @@ -3329,6 +3340,35 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, state.instr += insn->instr; if (insn->hint) { + if (insn->restore) { + struct instruction *save_insn, *i; + + i = insn; + save_insn = NULL; + + sym_for_each_insn_continue_reverse(file, func, i) { + if (i->save) { + save_insn = i; + break; + } + } + + if (!save_insn) { + WARN_FUNC("no corresponding CFI save for CFI restore", + sec, insn->offset); + return 1; + } + + if (!save_insn->visited) { + WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", + sec, insn->offset); + return 1; + } + + insn->cfi = save_insn->cfi; + nr_cfi_reused++; + } + state.cfi = *insn->cfi; } else { /* XXX track if we actually changed state.cfi */ diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h index 0eeedeacbefb..036129cebeee 100644 --- a/tools/objtool/include/objtool/check.h +++ b/tools/objtool/include/objtool/check.h @@ -46,18 +46,19 @@ struct instruction { enum insn_type type; unsigned long immediate; - u8 dead_end : 1, - ignore : 1, - ignore_alts : 1, - hint : 1, - retpoline_safe : 1, - noendbr : 1, - entry : 1; - /* 1 bit hole */ + u16 dead_end : 1, + ignore : 1, + ignore_alts : 1, + hint : 1, + save : 1, + restore : 1, + retpoline_safe : 1, + noendbr : 1, + entry : 1; + /* 7 bit hole */ s8 instr; u8 visited; - /* u8 hole */ struct alt_group *alt_group; struct symbol *call_dest; -- cgit v1.2.3 From f43b9876e857c739d407bc56df288b0ebe1a9164 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 27 Jun 2022 22:21:17 +0000 Subject: x86/retbleed: Add fine grained Kconfig knobs Do fine-grained Kconfig for all the various retbleed parts. NOTE: if your compiler doesn't support return thunks this will silently 'upgrade' your mitigation to IBPB, you might not like this. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov --- tools/objtool/builtin-check.c | 7 +++++++ tools/objtool/check.c | 9 +++++++-- tools/objtool/include/objtool/builtin.h | 1 + 3 files changed, 15 insertions(+), 2 deletions(-) (limited to 'tools/objtool') diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c index c063e1ff96b2..24fbe803a0d3 100644 --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -68,6 +68,7 @@ const struct option check_options[] = { OPT_BOOLEAN('n', "noinstr", &opts.noinstr, "validate noinstr rules"), OPT_BOOLEAN('o', "orc", &opts.orc, "generate ORC metadata"), OPT_BOOLEAN('r', "retpoline", &opts.retpoline, "validate and annotate retpoline usage"), + OPT_BOOLEAN(0, "rethunk", &opts.rethunk, "validate and annotate rethunk usage"), OPT_BOOLEAN(0, "unret", &opts.unret, "validate entry unret placement"), OPT_BOOLEAN('l', "sls", &opts.sls, "validate straight-line-speculation mitigations"), OPT_BOOLEAN('s', "stackval", &opts.stackval, "validate frame pointer rules"), @@ -124,6 +125,7 @@ static bool opts_valid(void) opts.noinstr || opts.orc || opts.retpoline || + opts.rethunk || opts.sls || opts.stackval || opts.static_call || @@ -136,6 +138,11 @@ static bool opts_valid(void) return true; } + if (opts.unret && !opts.rethunk) { + ERROR("--unret requires --rethunk"); + return false; + } + if (opts.dump_orc) return true; diff --git a/tools/objtool/check.c b/tools/objtool/check.c index ddfdd138cc2a..7bebdb8867cd 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -3732,8 +3732,11 @@ static int validate_retpoline(struct objtool_file *file) continue; if (insn->type == INSN_RETURN) { - WARN_FUNC("'naked' return found in RETPOLINE build", - insn->sec, insn->offset); + if (opts.rethunk) { + WARN_FUNC("'naked' return found in RETHUNK build", + insn->sec, insn->offset); + } else + continue; } else { WARN_FUNC("indirect %s found in RETPOLINE build", insn->sec, insn->offset, @@ -4264,7 +4267,9 @@ int check(struct objtool_file *file) if (ret < 0) goto out; warnings += ret; + } + if (opts.rethunk) { ret = create_return_sites_sections(file); if (ret < 0) goto out; diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h index 0c476b0b40a3..42a52f1a0add 100644 --- a/tools/objtool/include/objtool/builtin.h +++ b/tools/objtool/include/objtool/builtin.h @@ -19,6 +19,7 @@ struct opts { bool noinstr; bool orc; bool retpoline; + bool rethunk; bool unret; bool sls; bool stackval; -- cgit v1.2.3