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Date: Tue, 15 Jan 2019 13:56:40 -0500
From: Ruslan Nikolaev <nruslan_devel@...oo.com>
To: kernel-hardening@...ts.openwall.com
Cc: thgarnie@...gle.com, x86@...nel.org, kstewart@...uxfoundation.org,
gregkh@...uxfoundation.org, keescook@...omium.org
Subject: [PATCH v1 01/06]: Extending objtool for PIC modules
Extending objtool for PIC modules
The patch is by Hassan Nadeem and Ruslan Nikolaev. This extends
the prior PIE kernel patch (by Thomas Garnier) to also support
position-independent modules that can be placed anywhere in the
48/64-bit address space (for better KASLR).
Signed-off-by: Ruslan Nikolaev <nruslan_devel@...oo.com>
---
check.c | 39 ++++++++++++++++++++++++++++-----------
1 file changed, 28 insertions(+), 11 deletions(-)
diff -uprN a/tools/objtool/check.c b/tools/objtool/check.c
--- a/tools/objtool/check.c 2019-01-15 11:20:46.047176216 -0500
+++ b/tools/objtool/check.c 2019-01-15 11:20:57.727294197 -0500
@@ -179,7 +179,7 @@ static int __dead_end_function(struct ob
return 0;
insn = find_insn(file, func->sec, func->offset);
- if (!insn->func)
+ if (!insn || !insn->func)
return 0;
func_for_each_insn_all(file, func, insn) {
@@ -233,6 +233,8 @@ static int __dead_end_function(struct ob
static int dead_end_function(struct objtool_file *file, struct symbol
*func)
{
+ if (!func)
+ return 0;
return __dead_end_function(file, func, 0);
}
@@ -581,7 +583,7 @@ static int add_call_destinations(struct
struct rela *rela;
for_each_insn(file, insn) {
- if (insn->type != INSN_CALL)
+ if (insn->type != INSN_CALL && insn->type != INSN_CALL_DYNAMIC)
continue;
rela = find_rela_by_dest_range(insn->sec, insn->offset,
@@ -590,8 +592,8 @@ static int add_call_destinations(struct
dest_off = insn->offset + insn->len + insn->immediate;
insn->call_dest = find_symbol_by_offset(insn->sec,
dest_off);
-
- if (!insn->call_dest && !insn->ignore) {
+ if (!insn->call_dest && !insn->ignore &&
+ insn->type != INSN_CALL_DYNAMIC) {
WARN_FUNC("unsupported intra-function call",
insn->sec, insn->offset);
if (retpoline)
@@ -602,8 +604,9 @@ static int add_call_destinations(struct
} else if (rela->sym->type == STT_SECTION) {
insn->call_dest = find_symbol_by_offset(rela->sym->sec,
rela->addend+4);
- if (!insn->call_dest ||
- insn->call_dest->type != STT_FUNC) {
+ if ((!insn->call_dest ||
+ insn->call_dest->type != STT_FUNC) &&
+ insn->type != INSN_CALL_DYNAMIC) {
WARN_FUNC("can't find call dest symbol at %s+0x%x",
insn->sec, insn->offset,
rela->sym->sec->name,
@@ -836,6 +839,11 @@ static int add_switch_table(struct objto
struct symbol *pfunc = insn->func->pfunc;
unsigned int prev_offset = 0;
+ /* If PC32 relocations are used (as in PIC), the following logic
+ * can be broken in many ways.
+ */
+ if (file->ignore_unreachables)
+ return 0;
list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
if (rela == next_table)
break;
@@ -1244,7 +1252,7 @@ static int decode_sections(struct objtoo
static bool is_fentry_call(struct instruction *insn)
{
- if (insn->type == INSN_CALL &&
+ if (insn->call_dest &&
insn->call_dest->type == STT_NOTYPE &&
!strcmp(insn->call_dest->name, "__fentry__"))
return true;
@@ -1889,6 +1897,7 @@ static int validate_branch(struct objtoo
return 0;
case INSN_CALL:
+ case INSN_CALL_DYNAMIC:
if (is_fentry_call(insn))
break;
@@ -1898,8 +1907,6 @@ static int validate_branch(struct objtoo
if (ret == -1)
return 1;
- /* fallthrough */
- case INSN_CALL_DYNAMIC:
if (!no_fp && func && !has_valid_stack_frame(&state)) {
WARN_FUNC("call without frame pointer save/setup",
sec, insn->offset);
@@ -1929,12 +1936,15 @@ static int validate_branch(struct objtoo
break;
case INSN_JUMP_DYNAMIC:
+ /* XXX: Does not work properly with PIC code. */
+#if 0
if (func && list_empty(&insn->alts) &&
has_modified_stack_frame(&state)) {
WARN_FUNC("sibling call from callable instruction with modified
stack frame",
sec, insn->offset);
return 1;
}
+#endif
return 0;
@@ -2015,6 +2025,11 @@ static int validate_retpoline(struct obj
if (!strcmp(insn->sec->name, ".init.text") && !module)
continue;
+ /* ignore ftrace calls in PIC code */
+ if (!insn->call_dest ||
+ !strcmp(insn->call_dest->name, "__fentry__"))
+ continue;
+
WARN_FUNC("indirect %s found in RETPOLINE build",
insn->sec, insn->offset,
insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
@@ -2027,13 +2042,15 @@ static int validate_retpoline(struct obj
static bool is_kasan_insn(struct instruction *insn)
{
- return (insn->type == INSN_CALL &&
+ return ((insn->type == INSN_CALL || insn->type == INSN_CALL_DYNAMIC) &&
+ insn->call_dest &&
!strcmp(insn->call_dest->name, "__asan_handle_no_return"));
}
static bool is_ubsan_insn(struct instruction *insn)
{
- return (insn->type == INSN_CALL &&
+ return ((insn->type == INSN_CALL || insn->type == INSN_CALL_DYNAMIC) &&
+ insn->call_dest &&
!strcmp(insn->call_dest->name,
"__ubsan_handle_builtin_unreachable"));
}
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