From a845c7cf4b4cb5e9e3b2823867892b27646f3a98 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 29 Jan 2018 22:00:39 -0600 Subject: objtool: Improve retpoline alternative handling Currently objtool requires all retpolines to be: a) patched in with alternatives; and b) annotated with ANNOTATE_NOSPEC_ALTERNATIVE. If you forget to do both of the above, objtool segfaults trying to dereference a NULL 'insn->call_dest' pointer. Avoid that situation and print a more helpful error message: quirks.o: warning: objtool: efi_delete_dummy_variable()+0x99: unsupported intra-function call quirks.o: warning: objtool: If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE. Future improvements can be made to make objtool smarter with respect to retpolines, but this is a good incremental improvement for now. Reported-and-tested-by: Guenter Roeck Signed-off-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: David Woodhouse Cc: Greg Kroah-Hartman Cc: H. Peter Anvin Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/819e50b6d9c2e1a22e34c1a636c0b2057cc8c6e5.1517284349.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- tools/objtool/check.c | 36 ++++++++++++++++-------------------- 1 file changed, 16 insertions(+), 20 deletions(-) (limited to 'tools') diff --git a/tools/objtool/check.c b/tools/objtool/check.c index f40d46e24bcc..bc3490d929ff 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -543,18 +543,14 @@ static int add_call_destinations(struct objtool_file *file) dest_off = insn->offset + insn->len + insn->immediate; insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); - /* - * FIXME: Thanks to retpolines, it's now considered - * normal for a function to call within itself. So - * disable this warning for now. - */ -#if 0 - if (!insn->call_dest) { - WARN_FUNC("can't find call dest symbol at offset 0x%lx", - insn->sec, insn->offset, dest_off); + + if (!insn->call_dest && !insn->ignore) { + WARN_FUNC("unsupported intra-function call", + insn->sec, insn->offset); + WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); return -1; } -#endif + } else if (rela->sym->type == STT_SECTION) { insn->call_dest = find_symbol_by_offset(rela->sym->sec, rela->addend+4); @@ -648,6 +644,8 @@ static int handle_group_alt(struct objtool_file *file, last_new_insn = insn; + insn->ignore = orig_insn->ignore_alts; + if (insn->type != INSN_JUMP_CONDITIONAL && insn->type != INSN_JUMP_UNCONDITIONAL) continue; @@ -729,10 +727,6 @@ static int add_special_section_alts(struct objtool_file *file) goto out; } - /* Ignore retpoline alternatives. */ - if (orig_insn->ignore_alts) - continue; - new_insn = NULL; if (!special_alt->group || special_alt->new_len) { new_insn = find_insn(file, special_alt->new_sec, @@ -1089,11 +1083,11 @@ static int decode_sections(struct objtool_file *file) if (ret) return ret; - ret = add_call_destinations(file); + ret = add_special_section_alts(file); if (ret) return ret; - ret = add_special_section_alts(file); + ret = add_call_destinations(file); if (ret) return ret; @@ -1720,10 +1714,12 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, insn->visited = true; - list_for_each_entry(alt, &insn->alts, list) { - ret = validate_branch(file, alt->insn, state); - if (ret) - return 1; + if (!insn->ignore_alts) { + list_for_each_entry(alt, &insn->alts, list) { + ret = validate_branch(file, alt->insn, state); + if (ret) + return 1; + } } switch (insn->type) { -- cgit v1.2.3 From 17bc33914bcc98ba3c6b426fd1c49587a25c0597 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 29 Jan 2018 22:00:40 -0600 Subject: objtool: Add support for alternatives at the end of a section Now that the previous patch gave objtool the ability to read retpoline alternatives, it shows a new warning: arch/x86/entry/entry_64.o: warning: objtool: .entry_trampoline: don't know how to handle alternatives at end of section This is due to the JMP_NOSPEC in entry_SYSCALL_64_trampoline(). Previously, objtool ignored this situation because it wasn't needed, and it would have required a bit of extra code. Now that this case exists, add proper support for it. Signed-off-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: David Woodhouse Cc: Greg Kroah-Hartman Cc: Guenter Roeck Cc: H. Peter Anvin Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/2a30a3c2158af47d891a76e69bb1ef347e0443fd.1517284349.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- tools/objtool/check.c | 53 ++++++++++++++++++++++++++++++--------------------- 1 file changed, 31 insertions(+), 22 deletions(-) (limited to 'tools') diff --git a/tools/objtool/check.c b/tools/objtool/check.c index bc3490d929ff..9cd028aa1509 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -594,7 +594,7 @@ static int handle_group_alt(struct objtool_file *file, struct instruction *orig_insn, struct instruction **new_insn) { - struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump; + struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL; unsigned long dest_off; last_orig_insn = NULL; @@ -610,28 +610,30 @@ static int handle_group_alt(struct objtool_file *file, last_orig_insn = insn; } - if (!next_insn_same_sec(file, last_orig_insn)) { - WARN("%s: don't know how to handle alternatives at end of section", - special_alt->orig_sec->name); - return -1; - } - - fake_jump = malloc(sizeof(*fake_jump)); - if (!fake_jump) { - WARN("malloc failed"); - return -1; + if (next_insn_same_sec(file, last_orig_insn)) { + fake_jump = malloc(sizeof(*fake_jump)); + if (!fake_jump) { + WARN("malloc failed"); + return -1; + } + memset(fake_jump, 0, sizeof(*fake_jump)); + INIT_LIST_HEAD(&fake_jump->alts); + clear_insn_state(&fake_jump->state); + + fake_jump->sec = special_alt->new_sec; + fake_jump->offset = -1; + fake_jump->type = INSN_JUMP_UNCONDITIONAL; + fake_jump->jump_dest = list_next_entry(last_orig_insn, list); + fake_jump->ignore = true; } - memset(fake_jump, 0, sizeof(*fake_jump)); - INIT_LIST_HEAD(&fake_jump->alts); - clear_insn_state(&fake_jump->state); - - fake_jump->sec = special_alt->new_sec; - fake_jump->offset = -1; - fake_jump->type = INSN_JUMP_UNCONDITIONAL; - fake_jump->jump_dest = list_next_entry(last_orig_insn, list); - fake_jump->ignore = true; if (!special_alt->new_len) { + if (!fake_jump) { + WARN("%s: empty alternative at end of section", + special_alt->orig_sec->name); + return -1; + } + *new_insn = fake_jump; return 0; } @@ -654,8 +656,14 @@ static int handle_group_alt(struct objtool_file *file, continue; dest_off = insn->offset + insn->len + insn->immediate; - if (dest_off == special_alt->new_off + special_alt->new_len) + if (dest_off == special_alt->new_off + special_alt->new_len) { + if (!fake_jump) { + WARN("%s: alternative jump to end of section", + special_alt->orig_sec->name); + return -1; + } insn->jump_dest = fake_jump; + } if (!insn->jump_dest) { WARN_FUNC("can't find alternative jump destination", @@ -670,7 +678,8 @@ static int handle_group_alt(struct objtool_file *file, return -1; } - list_add(&fake_jump->list, &last_new_insn->list); + if (fake_jump) + list_add(&fake_jump->list, &last_new_insn->list); return 0; } -- cgit v1.2.3 From 830c1e3d16b2c1733cd1ec9c8f4d47a398ae31bc Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 29 Jan 2018 22:00:41 -0600 Subject: objtool: Warn on stripped section symbol With the following fix: 2a0098d70640 ("objtool: Fix seg fault with gold linker") ... a seg fault was avoided, but the original seg fault condition in objtool wasn't fixed. Replace the seg fault with an error message. Suggested-by: Ingo Molnar Signed-off-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: David Woodhouse Cc: Greg Kroah-Hartman Cc: Guenter Roeck Cc: H. Peter Anvin Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/dc4585a70d6b975c99fc51d1957ccdde7bd52f3a.1517284349.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- tools/objtool/orc_gen.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'tools') diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c index e61fe703197b..18384d9be4e1 100644 --- a/tools/objtool/orc_gen.c +++ b/tools/objtool/orc_gen.c @@ -98,6 +98,11 @@ static int create_orc_entry(struct section *u_sec, struct section *ip_relasec, struct orc_entry *orc; struct rela *rela; + if (!insn_sec->sym) { + WARN("missing symbol for section %s", insn_sec->name); + return -1; + } + /* populate ORC data */ orc = (struct orc_entry *)u_sec->data->d_buf + idx; memcpy(orc, o, sizeof(*orc)); -- cgit v1.2.3