From: tip-bot for Josh Poimboeuf <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: gregkh@linux-foundation.org, peterz@infradead.org,
keescook@google.com, dwmw@amazon.co.uk, jpoimboe@redhat.com,
mingo@kernel.org, torvalds@linux-foundation.org,
ak@linux.intel.com, jikos@kernel.org, riel@redhat.com,
tim.c.chen@linux.intel.com, dave.hansen@intel.com,
linux-kernel@vger.kernel.org, pjt@google.com,
luto@amacapital.net, tglx@linutronix.de, hpa@zytor.com
Subject: [tip:x86/pti] objtool: Allow alternatives to be ignored
Date: Thu, 11 Jan 2018 15:22:53 -0800 [thread overview]
Message-ID: <tip-258c76059cece01bebae098e81bacb1af2edad17@git.kernel.org> (raw)
In-Reply-To: <1515707194-20531-3-git-send-email-dwmw@amazon.co.uk>
Commit-ID: 258c76059cece01bebae098e81bacb1af2edad17
Gitweb: https://git.kernel.org/tip/258c76059cece01bebae098e81bacb1af2edad17
Author: Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Thu, 11 Jan 2018 21:46:24 +0000
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 12 Jan 2018 00:14:28 +0100
objtool: Allow alternatives to be ignored
Getting objtool to understand retpolines is going to be a bit of a
challenge. For now, take advantage of the fact that retpolines are
patched in with alternatives. Just read the original (sane)
non-alternative instruction, and ignore the patched-in retpoline.
This allows objtool to understand the control flow *around* the
retpoline, even if it can't yet follow what's inside. This means the
ORC unwinder will fail to unwind from inside a retpoline, but will work
fine otherwise.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: thomas.lendacky@amd.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@google.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: https://lkml.kernel.org/r/1515707194-20531-3-git-send-email-dwmw@amazon.co.uk
---
tools/objtool/check.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++-----
tools/objtool/check.h | 2 +-
2 files changed, 57 insertions(+), 7 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index de053fb..f40d46e 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -428,6 +428,40 @@ static void add_ignores(struct objtool_file *file)
}
/*
+ * FIXME: For now, just ignore any alternatives which add retpolines. This is
+ * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
+ * But it at least allows objtool to understand the control flow *around* the
+ * retpoline.
+ */
+static int add_nospec_ignores(struct objtool_file *file)
+{
+ struct section *sec;
+ struct rela *rela;
+ struct instruction *insn;
+
+ sec = find_section_by_name(file->elf, ".rela.discard.nospec");
+ if (!sec)
+ return 0;
+
+ list_for_each_entry(rela, &sec->rela_list, list) {
+ if (rela->sym->type != STT_SECTION) {
+ WARN("unexpected relocation symbol type in %s", sec->name);
+ return -1;
+ }
+
+ insn = find_insn(file, rela->sym->sec, rela->addend);
+ if (!insn) {
+ WARN("bad .discard.nospec entry");
+ return -1;
+ }
+
+ insn->ignore_alts = true;
+ }
+
+ return 0;
+}
+
+/*
* Find the destination instructions for all jumps.
*/
static int add_jump_destinations(struct objtool_file *file)
@@ -509,11 +543,18 @@ 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);
return -1;
}
+#endif
} else if (rela->sym->type == STT_SECTION) {
insn->call_dest = find_symbol_by_offset(rela->sym->sec,
rela->addend+4);
@@ -678,12 +719,6 @@ static int add_special_section_alts(struct objtool_file *file)
return ret;
list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
- alt = malloc(sizeof(*alt));
- if (!alt) {
- WARN("malloc failed");
- ret = -1;
- goto out;
- }
orig_insn = find_insn(file, special_alt->orig_sec,
special_alt->orig_off);
@@ -694,6 +729,10 @@ 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,
@@ -719,6 +758,13 @@ static int add_special_section_alts(struct objtool_file *file)
goto out;
}
+ alt = malloc(sizeof(*alt));
+ if (!alt) {
+ WARN("malloc failed");
+ ret = -1;
+ goto out;
+ }
+
alt->insn = new_insn;
list_add_tail(&alt->list, &orig_insn->alts);
@@ -1035,6 +1081,10 @@ static int decode_sections(struct objtool_file *file)
add_ignores(file);
+ ret = add_nospec_ignores(file);
+ if (ret)
+ return ret;
+
ret = add_jump_destinations(file);
if (ret)
return ret;
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index 47d9ea7..dbadb30 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -44,7 +44,7 @@ struct instruction {
unsigned int len;
unsigned char type;
unsigned long immediate;
- bool alt_group, visited, dead_end, ignore, hint, save, restore;
+ bool alt_group, visited, dead_end, ignore, hint, save, restore, ignore_alts;
struct symbol *call_dest;
struct instruction *jump_dest;
struct list_head alts;
next prev parent reply other threads:[~2018-01-11 23:29 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-11 21:46 [PATCH v8 00/12] Retpoline: Avoid speculative indirect calls in kernel David Woodhouse
2018-01-11 21:46 ` [PATCH v8 01/12] objtool: Detect jumps to retpoline thunks David Woodhouse
2018-01-11 23:22 ` [tip:x86/pti] " tip-bot for Josh Poimboeuf
2018-01-11 21:46 ` [PATCH v8 02/12] objtool: Allow alternatives to be ignored David Woodhouse
2018-01-11 23:22 ` tip-bot for Josh Poimboeuf [this message]
2018-01-18 19:09 ` [v8,02/12] " Guenter Roeck
2018-01-18 19:33 ` Josh Poimboeuf
2018-01-18 19:41 ` Guenter Roeck
2018-01-22 19:34 ` David Woodhouse
2018-01-22 20:25 ` Guenter Roeck
2018-01-22 20:27 ` David Woodhouse
2018-01-28 21:06 ` Josh Poimboeuf
2018-01-29 1:26 ` Guenter Roeck
2018-01-29 17:15 ` Guenter Roeck
2018-01-29 17:30 ` Josh Poimboeuf
2018-01-22 19:27 ` Guenter Roeck
2018-01-11 21:46 ` [PATCH v8 03/12] x86/retpoline: Add initial retpoline support David Woodhouse
2018-01-11 23:23 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 23:58 ` [PATCH v8 03/12] " Tom Lendacky
2018-01-12 10:28 ` David Woodhouse
2018-01-12 14:02 ` Tom Lendacky
2018-01-14 15:02 ` Borislav Petkov
2018-01-14 15:53 ` Josh Poimboeuf
2018-01-14 15:59 ` Borislav Petkov
2018-01-11 21:46 ` [PATCH v8 04/12] x86/spectre: Add boot time option to select Spectre v2 mitigation David Woodhouse
2018-01-11 23:23 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-23 22:40 ` [PATCH v8 04/12] " Borislav Petkov
2018-01-23 22:53 ` David Woodhouse
2018-01-23 23:05 ` Andi Kleen
2018-01-23 22:55 ` Jiri Kosina
2018-01-23 23:05 ` Borislav Petkov
2018-01-24 0:32 ` Kees Cook
2018-01-24 9:58 ` Borislav Petkov
2018-01-23 23:06 ` Jiri Kosina
2018-01-23 23:21 ` Andi Kleen
2018-01-23 23:24 ` Jiri Kosina
2018-01-23 23:45 ` Andi Kleen
2018-01-23 23:49 ` Jiri Kosina
2018-01-24 4:26 ` Greg Kroah-Hartman
2018-01-24 9:56 ` Jiri Kosina
2018-01-24 13:58 ` Greg Kroah-Hartman
2018-01-24 14:03 ` Jiri Kosina
2018-01-24 14:22 ` Greg Kroah-Hartman
2018-01-11 21:46 ` [PATCH v8 05/12] x86/retpoline/crypto: Convert crypto assembler indirect jumps David Woodhouse
2018-01-11 23:24 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 06/12] x86/retpoline/entry: Convert entry " David Woodhouse
2018-01-11 23:24 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 07/12] x86/retpoline/ftrace: Convert ftrace " David Woodhouse
2018-01-11 23:25 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 08/12] x86/retpoline/hyperv: Convert " David Woodhouse
2018-01-11 23:25 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 09/12] x86/retpoline/xen: Convert Xen hypercall " David Woodhouse
2018-01-11 23:25 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 10/12] x86/retpoline/checksum32: Convert assembler " David Woodhouse
2018-01-11 23:26 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 11/12] x86/retpoline/irq32: " David Woodhouse
2018-01-11 23:26 ` [tip:x86/pti] " tip-bot for Andi Kleen
2018-01-11 21:46 ` [PATCH v8 12/12] x86/retpoline: Fill return stack buffer on vmexit David Woodhouse
2018-01-11 23:27 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 23:51 ` [PATCH v8 12/12] " Andi Kleen
2018-01-12 11:11 ` [PATCH v8.1 " David Woodhouse
2018-01-12 11:15 ` Thomas Gleixner
2018-01-12 11:21 ` Woodhouse, David
2018-01-12 11:37 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-14 14:50 ` Borislav Petkov
2018-01-14 15:28 ` Thomas Gleixner
2018-01-14 15:35 ` Borislav Petkov
2018-01-25 12:07 ` Borislav Petkov
2018-01-25 12:20 ` David Woodhouse
2018-01-25 12:45 ` Borislav Petkov
2018-01-25 15:10 ` Josh Poimboeuf
2018-01-25 15:51 ` Borislav Petkov
2018-01-25 16:03 ` David Woodhouse
2018-01-25 16:56 ` Josh Poimboeuf
2018-01-25 17:00 ` David Woodhouse
2018-01-25 17:05 ` Andy Lutomirski
2018-01-25 17:44 ` Josh Poimboeuf
2018-01-25 18:41 ` Jiri Kosina
2018-01-25 17:10 ` Thomas Gleixner
2018-01-25 17:32 ` Josh Poimboeuf
2018-01-25 17:53 ` Borislav Petkov
2018-01-25 18:04 ` David Woodhouse
2018-01-25 18:32 ` Josh Poimboeuf
2018-01-25 19:07 ` Borislav Petkov
2018-01-25 19:10 ` Borislav Petkov
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