[PATCH 0/4] objtool: fix some objtool warnings

[PATCH 0/4] objtool: fix some objtool warnings

[Josh Poimboeuf]

Some objtool warning fixes, most of which were reported by Arnd.

The first patch fixes an issue which is specific to GCC 7.  It has been
around a while.

The second patch fixes an issue which has theoretically always existed
in objtool, but was only recently uncovered due to some recent function
whitelist changes associated with objtool 2.0.

The third and fourth patches are fixes for the recent objtool 2.0 and
ORC support.

Josh Poimboeuf (4):
  objtool: Assume unannotated 'ud2' instructions are dead ends
  objtool: Skip unreachable warnings for 'alt' instructions
  objtool: Fix '-mtune=atom' decoding support in objtool 2.0
  objtool: Disable GCC '-Wpacked' warnings

 include/linux/compiler-gcc.h    | 16 -----------
 include/linux/compiler.h        | 25 +++++++++++++++-
 tools/objtool/Makefile          |  3 +-
 tools/objtool/arch.h            |  5 ++--
 tools/objtool/arch/x86/decode.c | 43 +++++++++++++++++++++++----
 tools/objtool/check.c           | 64 +++++++++++++++++++++++++++++++++++++++--
 6 files changed, 127 insertions(+), 29 deletions(-)

-- 
2.13.3

[PATCH 1/4] objtool: Assume unannotated 'ud2' instructions are dead ends

[Josh Poimboeuf]

Arnd reported some false positive warnings with GCC 7:

  drivers/hid/wacom_wac.o: warning: objtool: wacom_bpt3_touch()+0x2a5: stack state mismatch: cfa1=7+8 cfa2=6+16
  drivers/iio/adc/vf610_adc.o: warning: objtool: vf610_adc_calculate_rates() falls through to next function vf610_adc_sample_set()
  drivers/pwm/pwm-hibvt.o: warning: objtool: hibvt_pwm_get_state() falls through to next function hibvt_pwm_remove()
  drivers/pwm/pwm-mediatek.o: warning: objtool: mtk_pwm_config() falls through to next function mtk_pwm_enable()
  drivers/spi/spi-bcm2835.o: warning: objtool: .text: unexpected end of section
  drivers/spi/spi-bcm2835aux.o: warning: objtool: .text: unexpected end of section
  drivers/watchdog/digicolor_wdt.o: warning: objtool: dc_wdt_get_timeleft() falls through to next function dc_wdt_restart()

When GCC 7 detects a potential divide-by-zero condition, it sometimes
inserts a 'ud2' instruction for the case where the divisor is zero,
instead of letting the hardware trap on the divide instruction.

Objtool doesn't consider 'ud2' to be fatal unless it's annotated with
unreachable().  So it considers the GCC-generated 'ud2' to be non-fatal,
and it tries to follow the control flow past the 'ud2' and gets
confused.

Previously, objtool *did* assume 'ud2' was always a dead end.  That
changed with the following commit:

  d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")

The motivation behind that change was that Peter was planning on using
'ud2' for __WARN(), which is *not* a dead end.  However, it turns out
that some emulators rely on 'ud2' being fatal, so he ended up using
'ud0' instead:

  9a93848fe787 ("x86/debug: Implement __WARN() using UD0")

For GCC 4.5+, it should be safe to go back to the previous assumption
that 'ud2' is fatal, even when it's not annotated with unreachable().

But for pre-4.5 versions of GCC, the unreachable() macro isn't
supported, so such cases of 'ud2' need to be explicitly annotated as
reachable.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 include/linux/compiler-gcc.h    | 16 ------------
 include/linux/compiler.h        | 25 +++++++++++++++++-
 tools/objtool/arch.h            |  5 ++--
 tools/objtool/arch/x86/decode.c | 17 ++++++++----
 tools/objtool/check.c           | 57 +++++++++++++++++++++++++++++++++++++++--
 5 files changed, 94 insertions(+), 26 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 2a34493e4d04..16d41de92ee3 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -128,22 +128,6 @@
 #define __always_unused		__attribute__((unused))
 #define __mode(x)               __attribute__((mode(x)))
 
-#ifdef CONFIG_STACK_VALIDATION
-#define annotate_unreachable() ({					\
-	asm("%c0:\n\t"							\
-	    ".pushsection .discard.unreachable\n\t"			\
-	    ".long %c0b - .\n\t"					\
-	    ".popsection\n\t" : : "i" (__LINE__));			\
-})
-#define ASM_UNREACHABLE							\
-	"999:\n\t"							\
-	".pushsection .discard.unreachable\n\t"				\
-	".long 999b - .\n\t"						\
-	".popsection\n\t"
-#else
-#define annotate_unreachable()
-#endif
-
 /* gcc version specific checks */
 
 #if GCC_VERSION < 30200
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 2d2721756abf..dfaaeec4a32e 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -185,11 +185,34 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 #endif
 
 /* Unreachable code */
+#ifdef CONFIG_STACK_VALIDATION
+#define annotate_reachable() ({						\
+	asm("%c0:\n\t"							\
+	    ".pushsection .discard.reachable\n\t"			\
+	    ".long %c0b - .\n\t"					\
+	    ".popsection\n\t" : : "i" (__LINE__));			\
+})
+#define annotate_unreachable() ({					\
+	asm("%c0:\n\t"							\
+	    ".pushsection .discard.unreachable\n\t"			\
+	    ".long %c0b - .\n\t"					\
+	    ".popsection\n\t" : : "i" (__LINE__));			\
+})
+#define ASM_UNREACHABLE							\
+	"999:\n\t"							\
+	".pushsection .discard.unreachable\n\t"				\
+	".long 999b - .\n\t"						\
+	".popsection\n\t"
+#else
+#define annotate_reachable()
+#define annotate_unreachable()
+#endif
+
 #ifndef ASM_UNREACHABLE
 # define ASM_UNREACHABLE
 #endif
 #ifndef unreachable
-# define unreachable() do { } while (1)
+# define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
 #endif
 
 /*
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index 21aeca874edb..b0d7dc3d71b5 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -31,8 +31,9 @@
 #define INSN_RETURN		6
 #define INSN_CONTEXT_SWITCH	7
 #define INSN_STACK		8
-#define INSN_NOP		9
-#define INSN_OTHER		10
+#define INSN_BUG		9
+#define INSN_NOP		10
+#define INSN_OTHER		11
 #define INSN_LAST		INSN_OTHER
 
 enum op_dest_type {
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index a36c2eba64e7..e4b400b67e41 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -382,20 +382,27 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 
 	case 0x0f:
 
-		if (op2 >= 0x80 && op2 <= 0x8f)
+		if (op2 >= 0x80 && op2 <= 0x8f) {
+
 			*type = INSN_JUMP_CONDITIONAL;
-		else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
-			 op2 == 0x35)
+
+		} else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
+			   op2 == 0x35) {
 
 			/* sysenter, sysret */
 			*type = INSN_CONTEXT_SWITCH;
 
-		else if (op2 == 0x0d || op2 == 0x1f)
+		} else if (op2 == 0x0b || op2 == 0xb9) {
+
+			/* ud2 */
+			*type = INSN_BUG;
+
+		} else if (op2 == 0x0d || op2 == 0x1f) {
 
 			/* nopl/nopw */
 			*type = INSN_NOP;
 
-		else if (op2 == 0xa0 || op2 == 0xa8) {
+		} else if (op2 == 0xa0 || op2 == 0xa8) {
 
 			/* push fs/gs */
 			*type = INSN_STACK;
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 3436a942b606..d07bf4a62b45 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -296,7 +296,7 @@ static int decode_instructions(struct objtool_file *file)
 }
 
 /*
- * Find all uses of the unreachable() macro, which are code path dead ends.
+ * Mark "ud2" instructions and manually annotated dead ends.
  */
 static int add_dead_ends(struct objtool_file *file)
 {
@@ -305,9 +305,20 @@ static int add_dead_ends(struct objtool_file *file)
 	struct instruction *insn;
 	bool found;
 
+	/*
+	 * By default, "ud2" is a dead end unless otherwise annotated, because
+	 * GCC 7 inserts it for certain divide-by-zero cases.
+	 */
+	for_each_insn(file, insn)
+		if (insn->type == INSN_BUG)
+			insn->dead_end = true;
+
+	/*
+	 * Check for manually annotated dead ends.
+	 */
 	sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 	if (!sec)
-		return 0;
+		goto reachable;
 
 	list_for_each_entry(rela, &sec->rela_list, list) {
 		if (rela->sym->type != STT_SECTION) {
@@ -340,6 +351,48 @@ static int add_dead_ends(struct objtool_file *file)
 		insn->dead_end = true;
 	}
 
+reachable:
+	/*
+	 * These manually annotated reachable checks are needed for GCC 4.4,
+	 * where the Linux unreachable() macro isn't supported.  In that case
+	 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
+	 * not a dead end.
+	 */
+	sec = find_section_by_name(file->elf, ".rela.discard.reachable");
+	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)
+			insn = list_prev_entry(insn, list);
+		else if (rela->addend == rela->sym->sec->len) {
+			found = false;
+			list_for_each_entry_reverse(insn, &file->insn_list, list) {
+				if (insn->sec == rela->sym->sec) {
+					found = true;
+					break;
+				}
+			}
+
+			if (!found) {
+				WARN("can't find reachable insn at %s+0x%x",
+				     rela->sym->sec->name, rela->addend);
+				return -1;
+			}
+		} else {
+			WARN("can't find reachable insn at %s+0x%x",
+			     rela->sym->sec->name, rela->addend);
+			return -1;
+		}
+
+		insn->dead_end = false;
+	}
+
 	return 0;
 }
 
-- 
2.13.3

[PATCH 2/4] objtool: Skip unreachable warnings for 'alt' instructions

[Josh Poimboeuf]

When a whitelisted function uses one of the ALTERNATIVE macros, it
produces false positive warnings like:

  arch/x86/kvm/vmx.o: warning: objtool: .altinstr_replacement+0x0: unreachable instruction
  arch/x86/kvm/svm.o: warning: objtool: .altinstr_replacement+0x6e: unreachable instruction

There's no easy way to whitelist alternative instructions, so instead
just skip any 'unreachable' warnings associated with them.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/check.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index d07bf4a62b45..4f0c4aea8f6f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1746,8 +1746,13 @@ static bool ignore_unreachable_insn(struct instruction *insn)
 	/*
 	 * Ignore any unused exceptions.  This can happen when a whitelisted
 	 * function has an exception table entry.
+	 *
+	 * Also ignore alternative replacement instructions.  This can happen
+	 * when a whitelisted function uses one of the ALTERNATIVE macros.
 	 */
-	if (!strcmp(insn->sec->name, ".fixup"))
+	if (!strcmp(insn->sec->name, ".fixup") ||
+	    !strcmp(insn->sec->name, ".altinstr_replacement") ||
+	    !strcmp(insn->sec->name, ".altinstr_aux"))
 		return true;
 
 	/*
-- 
2.13.3

[PATCH 3/4] objtool: Fix '-mtune=atom' decoding support in objtool 2.0

[Josh Poimboeuf]

With '-mtune=atom', which is enabled with CONFIG_MATOM=y, GCC uses some
unusual instructions for setting up the stack.

Instead of:

  mov %rsp, %rbp

it does:

  lea (%rsp), %rbp

And instead of:

  add imm, %rsp

it does:

  lea disp(%rsp), %rsp

Add support for these instructions to the objtool decoder.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Fixes: baa41469a7b9 ("objtool: Implement stack validation 2.0")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/arch/x86/decode.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index e4b400b67e41..7841e5d31973 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -271,7 +271,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 	case 0x8d:
 		if (rex == 0x48 && modrm == 0x65) {
 
-			/* lea -disp(%rbp), %rsp */
+			/* lea disp(%rbp), %rsp */
 			*type = INSN_STACK;
 			op->src.type = OP_SRC_ADD;
 			op->src.reg = CFI_BP;
@@ -281,6 +281,30 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 			break;
 		}
 
+		if (rex == 0x48 && (modrm == 0xa4 || modrm == 0x64) &&
+		    sib == 0x24) {
+
+			/* lea disp(%rsp), %rsp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_ADD;
+			op->src.reg = CFI_SP;
+			op->src.offset = insn.displacement.value;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_SP;
+			break;
+		}
+
+		if (rex == 0x48 && modrm == 0x2c && sib == 0x24) {
+
+			/* lea (%rsp), %rbp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_REG;
+			op->src.reg = CFI_SP;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_BP;
+			break;
+		}
+
 		if (rex == 0x4c && modrm == 0x54 && sib == 0x24 &&
 		    insn.displacement.value == 8) {
 
-- 
2.13.3

[PATCH 4/4] objtool: Disable GCC '-Wpacked' warnings

[Josh Poimboeuf]

Objtool is failing to build with GCC 4.4.7 due to the following
warnings:

  cc1: warnings being treated as errors
  In file included from orc.h:21,
                   from orc_gen.c:21:
  orc_types.h:86: error: packed attribute is unnecessary for ‘sp_offset’
  orc_types.h:87: error: packed attribute is unnecessary for ‘bp_offset’
  orc_types.h:88: error: packed attribute is unnecessary for ‘sp_reg’

I suspect those warnings are a GCC bug.  But -Wpacked isn't very useful
anyway, so just disable it.

Fixes: 627fce14809b ("objtool: Add ORC unwind table generation")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 3a6425fefc43..6976c73e60c4 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -25,7 +25,8 @@ OBJTOOL_IN := $(OBJTOOL)-in.o
 all: $(OBJTOOL)
 
 INCLUDES := -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(HOSTARCH)/include/uapi
-CFLAGS   += -Wall -Werror $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -fomit-frame-pointer -O2 -g $(INCLUDES)
+WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed
+CFLAGS   += -Wall -Werror $(WARNINGS) -fomit-frame-pointer -O2 -g $(INCLUDES)
 LDFLAGS  += -lelf $(LIBSUBCMD)
 
 # Allow old libelf to be used:
-- 
2.13.3

[tip:x86/asm] objtool: Assume unannotated UD2 instructions are dead ends

[tip-bot for Josh Poimboeuf]

Commit-ID:  649ea4d5a624f061a111b1f1cb0e47cfdc3ac21b
Gitweb:     http://git.kernel.org/tip/649ea4d5a624f061a111b1f1cb0e47cfdc3ac21b
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Thu, 27 Jul 2017 15:56:53 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 28 Jul 2017 08:33:32 +0200

objtool: Assume unannotated UD2 instructions are dead ends

Arnd reported some false positive warnings with GCC 7:

  drivers/hid/wacom_wac.o: warning: objtool: wacom_bpt3_touch()+0x2a5: stack state mismatch: cfa1=7+8 cfa2=6+16
  drivers/iio/adc/vf610_adc.o: warning: objtool: vf610_adc_calculate_rates() falls through to next function vf610_adc_sample_set()
  drivers/pwm/pwm-hibvt.o: warning: objtool: hibvt_pwm_get_state() falls through to next function hibvt_pwm_remove()
  drivers/pwm/pwm-mediatek.o: warning: objtool: mtk_pwm_config() falls through to next function mtk_pwm_enable()
  drivers/spi/spi-bcm2835.o: warning: objtool: .text: unexpected end of section
  drivers/spi/spi-bcm2835aux.o: warning: objtool: .text: unexpected end of section
  drivers/watchdog/digicolor_wdt.o: warning: objtool: dc_wdt_get_timeleft() falls through to next function dc_wdt_restart()

When GCC 7 detects a potential divide-by-zero condition, it sometimes
inserts a UD2 instruction for the case where the divisor is zero,
instead of letting the hardware trap on the divide instruction.

Objtool doesn't consider UD2 to be fatal unless it's annotated with
unreachable().  So it considers the GCC-generated UD2 to be non-fatal,
and it tries to follow the control flow past the UD2 and gets
confused.

Previously, objtool *did* assume UD2 was always a dead end.  That
changed with the following commit:

  d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")

The motivation behind that change was that Peter was planning on using
UD2 for __WARN(), which is *not* a dead end.  However, it turns out
that some emulators rely on UD2 being fatal, so he ended up using
'ud0' instead:

  9a93848fe787 ("x86/debug: Implement __WARN() using UD0")

For GCC 4.5+, it should be safe to go back to the previous assumption
that UD2 is fatal, even when it's not annotated with unreachable().

But for pre-4.5 versions of GCC, the unreachable() macro isn't
supported, so such cases of UD2 need to be explicitly annotated as
reachable.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
Link: http://lkml.kernel.org/r/e57fa9dfede25f79487da8126ee9cdf7b856db65.1501188854.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/compiler-gcc.h    | 16 ------------
 include/linux/compiler.h        | 25 +++++++++++++++++-
 tools/objtool/arch.h            |  5 ++--
 tools/objtool/arch/x86/decode.c | 17 ++++++++----
 tools/objtool/check.c           | 57 +++++++++++++++++++++++++++++++++++++++--
 5 files changed, 94 insertions(+), 26 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 17cbe3c..dd4b4c5 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -128,22 +128,6 @@
 #define __always_unused		__attribute__((unused))
 #define __mode(x)               __attribute__((mode(x)))
 
-#ifdef CONFIG_STACK_VALIDATION
-#define annotate_unreachable() ({					\
-	asm("%c0:\n\t"							\
-	    ".pushsection .discard.unreachable\n\t"			\
-	    ".long %c0b - .\n\t"					\
-	    ".popsection\n\t" : : "i" (__LINE__));			\
-})
-#define ASM_UNREACHABLE							\
-	"999:\n\t"							\
-	".pushsection .discard.unreachable\n\t"				\
-	".long 999b - .\n\t"						\
-	".popsection\n\t"
-#else
-#define annotate_unreachable()
-#endif
-
 /* gcc version specific checks */
 
 #if GCC_VERSION < 30200
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 641f591..70f070d 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -185,11 +185,34 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 #endif
 
 /* Unreachable code */
+#ifdef CONFIG_STACK_VALIDATION
+#define annotate_reachable() ({						\
+	asm("%c0:\n\t"							\
+	    ".pushsection .discard.reachable\n\t"			\
+	    ".long %c0b - .\n\t"					\
+	    ".popsection\n\t" : : "i" (__LINE__));			\
+})
+#define annotate_unreachable() ({					\
+	asm("%c0:\n\t"							\
+	    ".pushsection .discard.unreachable\n\t"			\
+	    ".long %c0b - .\n\t"					\
+	    ".popsection\n\t" : : "i" (__LINE__));			\
+})
+#define ASM_UNREACHABLE							\
+	"999:\n\t"							\
+	".pushsection .discard.unreachable\n\t"				\
+	".long 999b - .\n\t"						\
+	".popsection\n\t"
+#else
+#define annotate_reachable()
+#define annotate_unreachable()
+#endif
+
 #ifndef ASM_UNREACHABLE
 # define ASM_UNREACHABLE
 #endif
 #ifndef unreachable
-# define unreachable() do { } while (1)
+# define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
 #endif
 
 /*
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index 21aeca8..b0d7dc3 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -31,8 +31,9 @@
 #define INSN_RETURN		6
 #define INSN_CONTEXT_SWITCH	7
 #define INSN_STACK		8
-#define INSN_NOP		9
-#define INSN_OTHER		10
+#define INSN_BUG		9
+#define INSN_NOP		10
+#define INSN_OTHER		11
 #define INSN_LAST		INSN_OTHER
 
 enum op_dest_type {
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index a36c2eb..e4b400b 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -382,20 +382,27 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 
 	case 0x0f:
 
-		if (op2 >= 0x80 && op2 <= 0x8f)
+		if (op2 >= 0x80 && op2 <= 0x8f) {
+
 			*type = INSN_JUMP_CONDITIONAL;
-		else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
-			 op2 == 0x35)
+
+		} else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
+			   op2 == 0x35) {
 
 			/* sysenter, sysret */
 			*type = INSN_CONTEXT_SWITCH;
 
-		else if (op2 == 0x0d || op2 == 0x1f)
+		} else if (op2 == 0x0b || op2 == 0xb9) {
+
+			/* ud2 */
+			*type = INSN_BUG;
+
+		} else if (op2 == 0x0d || op2 == 0x1f) {
 
 			/* nopl/nopw */
 			*type = INSN_NOP;
 
-		else if (op2 == 0xa0 || op2 == 0xa8) {
+		} else if (op2 == 0xa0 || op2 == 0xa8) {
 
 			/* push fs/gs */
 			*type = INSN_STACK;
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 3436a942..d07bf4a 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -296,7 +296,7 @@ static int decode_instructions(struct objtool_file *file)
 }
 
 /*
- * Find all uses of the unreachable() macro, which are code path dead ends.
+ * Mark "ud2" instructions and manually annotated dead ends.
  */
 static int add_dead_ends(struct objtool_file *file)
 {
@@ -305,9 +305,20 @@ static int add_dead_ends(struct objtool_file *file)
 	struct instruction *insn;
 	bool found;
 
+	/*
+	 * By default, "ud2" is a dead end unless otherwise annotated, because
+	 * GCC 7 inserts it for certain divide-by-zero cases.
+	 */
+	for_each_insn(file, insn)
+		if (insn->type == INSN_BUG)
+			insn->dead_end = true;
+
+	/*
+	 * Check for manually annotated dead ends.
+	 */
 	sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 	if (!sec)
-		return 0;
+		goto reachable;
 
 	list_for_each_entry(rela, &sec->rela_list, list) {
 		if (rela->sym->type != STT_SECTION) {
@@ -340,6 +351,48 @@ static int add_dead_ends(struct objtool_file *file)
 		insn->dead_end = true;
 	}
 
+reachable:
+	/*
+	 * These manually annotated reachable checks are needed for GCC 4.4,
+	 * where the Linux unreachable() macro isn't supported.  In that case
+	 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
+	 * not a dead end.
+	 */
+	sec = find_section_by_name(file->elf, ".rela.discard.reachable");
+	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)
+			insn = list_prev_entry(insn, list);
+		else if (rela->addend == rela->sym->sec->len) {
+			found = false;
+			list_for_each_entry_reverse(insn, &file->insn_list, list) {
+				if (insn->sec == rela->sym->sec) {
+					found = true;
+					break;
+				}
+			}
+
+			if (!found) {
+				WARN("can't find reachable insn at %s+0x%x",
+				     rela->sym->sec->name, rela->addend);
+				return -1;
+			}
+		} else {
+			WARN("can't find reachable insn at %s+0x%x",
+			     rela->sym->sec->name, rela->addend);
+			return -1;
+		}
+
+		insn->dead_end = false;
+	}
+
 	return 0;
 }
 

[tip:x86/asm] objtool: Skip unreachable warnings for 'alt' instructions

[tip-bot for Josh Poimboeuf]

Commit-ID:  0e2bb2bc14b3df754b0a86e87cd8923df0701a1b
Gitweb:     http://git.kernel.org/tip/0e2bb2bc14b3df754b0a86e87cd8923df0701a1b
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Thu, 27 Jul 2017 15:56:54 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 28 Jul 2017 08:33:32 +0200

objtool: Skip unreachable warnings for 'alt' instructions

When a whitelisted function uses one of the ALTERNATIVE macros, it
produces false positive warnings like:

  arch/x86/kvm/vmx.o: warning: objtool: .altinstr_replacement+0x0: unreachable instruction
  arch/x86/kvm/svm.o: warning: objtool: .altinstr_replacement+0x6e: unreachable instruction

There's no easy way to whitelist alternative instructions, so instead
just skip any 'unreachable' warnings associated with them.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a5d0a8c60155f03b36a31fac871e12cf75f35fd0.1501188854.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/objtool/check.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index d07bf4a..4f0c4ae 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1746,8 +1746,13 @@ static bool ignore_unreachable_insn(struct instruction *insn)
 	/*
 	 * Ignore any unused exceptions.  This can happen when a whitelisted
 	 * function has an exception table entry.
+	 *
+	 * Also ignore alternative replacement instructions.  This can happen
+	 * when a whitelisted function uses one of the ALTERNATIVE macros.
 	 */
-	if (!strcmp(insn->sec->name, ".fixup"))
+	if (!strcmp(insn->sec->name, ".fixup") ||
+	    !strcmp(insn->sec->name, ".altinstr_replacement") ||
+	    !strcmp(insn->sec->name, ".altinstr_aux"))
 		return true;
 
 	/*

[tip:x86/asm] objtool: Fix '-mtune=atom' decoding support in objtool 2.0

[tip-bot for Josh Poimboeuf]

Commit-ID:  5b8de48e82ba322483c925ce33f193e28e59a5fd
Gitweb:     http://git.kernel.org/tip/5b8de48e82ba322483c925ce33f193e28e59a5fd
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Thu, 27 Jul 2017 15:56:55 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 28 Jul 2017 08:33:32 +0200

objtool: Fix '-mtune=atom' decoding support in objtool 2.0

With '-mtune=atom', which is enabled with CONFIG_MATOM=y, GCC uses some
unusual instructions for setting up the stack.

Instead of:

  mov %rsp, %rbp

it does:

  lea (%rsp), %rbp

And instead of:

  add imm, %rsp

it does:

  lea disp(%rsp), %rsp

Add support for these instructions to the objtool decoder.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: baa41469a7b9 ("objtool: Implement stack validation 2.0")
Link: http://lkml.kernel.org/r/4ea1db896e821226efe1f8e09f270771bde47e65.1501188854.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/objtool/arch/x86/decode.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index e4b400b..7841e5d 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -271,7 +271,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 	case 0x8d:
 		if (rex == 0x48 && modrm == 0x65) {
 
-			/* lea -disp(%rbp), %rsp */
+			/* lea disp(%rbp), %rsp */
 			*type = INSN_STACK;
 			op->src.type = OP_SRC_ADD;
 			op->src.reg = CFI_BP;
@@ -281,6 +281,30 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 			break;
 		}
 
+		if (rex == 0x48 && (modrm == 0xa4 || modrm == 0x64) &&
+		    sib == 0x24) {
+
+			/* lea disp(%rsp), %rsp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_ADD;
+			op->src.reg = CFI_SP;
+			op->src.offset = insn.displacement.value;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_SP;
+			break;
+		}
+
+		if (rex == 0x48 && modrm == 0x2c && sib == 0x24) {
+
+			/* lea (%rsp), %rbp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_REG;
+			op->src.reg = CFI_SP;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_BP;
+			break;
+		}
+
 		if (rex == 0x4c && modrm == 0x54 && sib == 0x24 &&
 		    insn.displacement.value == 8) {
 

[tip:x86/asm] objtool: Disable GCC '-Wpacked' warnings

[tip-bot for Josh Poimboeuf]

Commit-ID:  21ec3bf6aeb4033210747837421e63286ba32646
Gitweb:     http://git.kernel.org/tip/21ec3bf6aeb4033210747837421e63286ba32646
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Thu, 27 Jul 2017 15:56:56 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 28 Jul 2017 08:33:32 +0200

objtool: Disable GCC '-Wpacked' warnings

Objtool is failing to build with GCC 4.4.7 due to the following
warnings:

  cc1: warnings being treated as errors
  In file included from orc.h:21,
                   from orc_gen.c:21:
  orc_types.h:86: error: packed attribute is unnecessary for ‘sp_offset’
  orc_types.h:87: error: packed attribute is unnecessary for ‘bp_offset’
  orc_types.h:88: error: packed attribute is unnecessary for ‘sp_reg’

I suspect those warnings are a GCC bug.  But -Wpacked isn't very useful
anyway, so just disable it.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 627fce14809b ("objtool: Add ORC unwind table generation")
Link: http://lkml.kernel.org/r/76d85d7b5a87566465095c500bce222ff5d7b146.1501188854.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/objtool/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 3a6425f..6976c73 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -25,7 +25,8 @@ OBJTOOL_IN := $(OBJTOOL)-in.o
 all: $(OBJTOOL)
 
 INCLUDES := -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(HOSTARCH)/include/uapi
-CFLAGS   += -Wall -Werror $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -fomit-frame-pointer -O2 -g $(INCLUDES)
+WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed
+CFLAGS   += -Wall -Werror $(WARNINGS) -fomit-frame-pointer -O2 -g $(INCLUDES)
 LDFLAGS  += -lelf $(LIBSUBCMD)
 
 # Allow old libelf to be used:

[tip:x86/urgent] objtool: Fix '-mtune=atom' decoding support in objtool 2.0

[tip-bot for Josh Poimboeuf]

Commit-ID:  deecd4d71b12626db48544faa66bb897e2cafd07
Gitweb:     http://git.kernel.org/tip/deecd4d71b12626db48544faa66bb897e2cafd07
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Thu, 27 Jul 2017 15:56:55 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 21 Aug 2017 16:07:27 +0200

objtool: Fix '-mtune=atom' decoding support in objtool 2.0

With '-mtune=atom', which is enabled with CONFIG_MATOM=y, GCC uses some
unusual instructions for setting up the stack.

Instead of:

  mov %rsp, %rbp

it does:

  lea (%rsp), %rbp

And instead of:

  add imm, %rsp

it does:

  lea disp(%rsp), %rsp

Add support for these instructions to the objtool decoder.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: baa41469a7b9 ("objtool: Implement stack validation 2.0")
Link: http://lkml.kernel.org/r/4ea1db896e821226efe1f8e09f270771bde47e65.1501188854.git.jpoimboe@redhat.com
[ This is a cherry-picked version of upcoming commit 5b8de48e82ba. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 tools/objtool/arch/x86/decode.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index a36c2eb..4559a21a 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -271,7 +271,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 	case 0x8d:
 		if (rex == 0x48 && modrm == 0x65) {
 
-			/* lea -disp(%rbp), %rsp */
+			/* lea disp(%rbp), %rsp */
 			*type = INSN_STACK;
 			op->src.type = OP_SRC_ADD;
 			op->src.reg = CFI_BP;
@@ -281,6 +281,30 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 			break;
 		}
 
+		if (rex == 0x48 && (modrm == 0xa4 || modrm == 0x64) &&
+		    sib == 0x24) {
+
+			/* lea disp(%rsp), %rsp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_ADD;
+			op->src.reg = CFI_SP;
+			op->src.offset = insn.displacement.value;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_SP;
+			break;
+		}
+
+		if (rex == 0x48 && modrm == 0x2c && sib == 0x24) {
+
+			/* lea (%rsp), %rbp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_REG;
+			op->src.reg = CFI_SP;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_BP;
+			break;
+		}
+
 		if (rex == 0x4c && modrm == 0x54 && sib == 0x24 &&
 		    insn.displacement.value == 8) {