[PATCH 0/6] x86,objtool: Split UNWIND_HINT_EMPTY in two

[PATCH 0/6] x86,objtool: Split UNWIND_HINT_EMPTY in two

[Josh Poimboeuf]

Based on tip/objtool/core.

Mark reported that the ORC unwinder incorrectly marks an unwind as
reliable when the unwind terminates prematurely in the dark corners of
return_to_handler() due to lack of information about the next frame.

The problem is UNWIND_HINT_EMPTY is used in two different situations:
end-of-stack marker and undefined stack state.

Split it up into UNWIND_HINT_END_OF_STACK and UNWIND_HINT_UNDEFINED.

Josh Poimboeuf (6):
  objtool: Add objtool_types.h
  objtool: Use relative pointers for annotations
  objtool: Change UNWIND_HINT() argument order
  x86,objtool: Introduce ORC_TYPE_*
  x86,objtool: Separate unret validation from unwind hints
  x86,objtool: Split UNWIND_HINT_EMPTY in two

 .../livepatch/reliable-stacktrace.rst         |   2 +-
 MAINTAINERS                                   |   2 +-
 arch/x86/entry/entry_64.S                     |  26 +--
 arch/x86/include/asm/nospec-branch.h          |  14 +-
 arch/x86/include/asm/orc_types.h              |  12 +-
 arch/x86/include/asm/unwind_hints.h           |  18 +-
 arch/x86/kernel/ftrace_64.S                   |   2 +-
 arch/x86/kernel/head_64.S                     |  17 +-
 arch/x86/kernel/relocate_kernel_64.S          |  10 +-
 arch/x86/kernel/unwind_orc.c                  |  27 ++-
 arch/x86/lib/retpoline.S                      |   6 +-
 arch/x86/platform/pvh/head.S                  |   2 +-
 arch/x86/xen/xen-asm.S                        |   4 +-
 arch/x86/xen/xen-head.S                       |   4 +-
 include/linux/objtool.h                       |  81 +++----
 include/linux/objtool_types.h                 |  57 +++++
 scripts/sorttable.h                           |   2 +-
 tools/arch/x86/include/asm/orc_types.h        |  12 +-
 tools/include/linux/objtool.h                 | 200 ------------------
 tools/include/linux/objtool_types.h           |  57 +++++
 tools/objtool/check.c                         |  69 ++++--
 tools/objtool/include/objtool/check.h         |   4 +-
 tools/objtool/orc_dump.c                      |  15 +-
 tools/objtool/orc_gen.c                       |  43 ++--
 tools/objtool/sync-check.sh                   |   2 +-
 25 files changed, 314 insertions(+), 374 deletions(-)
 create mode 100644 include/linux/objtool_types.h
 delete mode 100644 tools/include/linux/objtool.h
 create mode 100644 tools/include/linux/objtool_types.h

-- 
2.39.1

[PATCH 1/6] objtool: Add objtool_types.h

[Josh Poimboeuf]

Reduce the amount of header sync churn by splitting the shared objtool.h
types into a new file.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 MAINTAINERS                         |   2 +-
 include/linux/objtool.h             |  42 +-----
 include/linux/objtool_types.h       |  48 +++++++
 tools/include/linux/objtool.h       | 200 ----------------------------
 tools/include/linux/objtool_types.h |  48 +++++++
 tools/objtool/check.c               |   2 +-
 tools/objtool/orc_dump.c            |   2 +-
 tools/objtool/orc_gen.c             |   2 +-
 tools/objtool/sync-check.sh         |   2 +-
 9 files changed, 102 insertions(+), 246 deletions(-)
 create mode 100644 include/linux/objtool_types.h
 delete mode 100644 tools/include/linux/objtool.h
 create mode 100644 tools/include/linux/objtool_types.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 2368a813e7ae..0873a33c3af9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14988,8 +14988,8 @@ OBJTOOL
 M:	Josh Poimboeuf <jpoimboe@kernel.org>
 M:	Peter Zijlstra <peterz@infradead.org>
 S:	Supported
+F:	include/linux/objtool*.h
 F:	tools/objtool/
-F:	include/linux/objtool.h
 
 OCELOT ETHERNET SWITCH DRIVER
 M:	Vladimir Oltean <vladimir.oltean@nxp.com>
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 9ac3df3fccf0..8375792acfc0 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -2,47 +2,7 @@
 #ifndef _LINUX_OBJTOOL_H
 #define _LINUX_OBJTOOL_H
 
-#ifndef __ASSEMBLY__
-
-#include <linux/types.h>
-
-/*
- * This struct is used by asm and inline asm code to manually annotate the
- * location of registers on the stack.
- */
-struct unwind_hint {
-	u32		ip;
-	s16		sp_offset;
-	u8		sp_reg;
-	u8		type;
-	u8		signal;
-	u8		end;
-};
-#endif
-
-/*
- * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
- * (the caller's SP right before it made the call).  Used for all callable
- * functions, i.e. all C code and all callable asm functions.
- *
- * UNWIND_HINT_TYPE_REGS: Used in entry code to indicate that sp_reg+sp_offset
- * points to a fully populated pt_regs from a syscall, interrupt, or exception.
- *
- * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
- * sp_reg+sp_offset points to the iret return frame.
- *
- * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
- * Useful for code which doesn't have an ELF function annotation.
- *
- * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
- */
-#define UNWIND_HINT_TYPE_CALL		0
-#define UNWIND_HINT_TYPE_REGS		1
-#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
-#define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_ENTRY		4
-#define UNWIND_HINT_TYPE_SAVE		5
-#define UNWIND_HINT_TYPE_RESTORE	6
+#include <linux/objtool_types.h>
 
 #ifdef CONFIG_OBJTOOL
 
diff --git a/include/linux/objtool_types.h b/include/linux/objtool_types.h
new file mode 100644
index 000000000000..8513537a30ed
--- /dev/null
+++ b/include/linux/objtool_types.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_OBJTOOL_TYPES_H
+#define _LINUX_OBJTOOL_TYPES_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+
+/*
+ * This struct is used by asm and inline asm code to manually annotate the
+ * location of registers on the stack.
+ */
+struct unwind_hint {
+	u32		ip;
+	s16		sp_offset;
+	u8		sp_reg;
+	u8		type;
+	u8		signal;
+	u8		end;
+};
+
+#endif /* __ASSEMBLY__ */
+
+/*
+ * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
+ * (the caller's SP right before it made the call).  Used for all callable
+ * functions, i.e. all C code and all callable asm functions.
+ *
+ * UNWIND_HINT_TYPE_REGS: Used in entry code to indicate that sp_reg+sp_offset
+ * points to a fully populated pt_regs from a syscall, interrupt, or exception.
+ *
+ * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
+ * sp_reg+sp_offset points to the iret return frame.
+ *
+ * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
+ * Useful for code which doesn't have an ELF function annotation.
+ *
+ * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
+ */
+#define UNWIND_HINT_TYPE_CALL		0
+#define UNWIND_HINT_TYPE_REGS		1
+#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+#define UNWIND_HINT_TYPE_FUNC		3
+#define UNWIND_HINT_TYPE_ENTRY		4
+#define UNWIND_HINT_TYPE_SAVE		5
+#define UNWIND_HINT_TYPE_RESTORE	6
+
+#endif /* _LINUX_OBJTOOL_TYPES_H */
diff --git a/tools/include/linux/objtool.h b/tools/include/linux/objtool.h
deleted file mode 100644
index 9ac3df3fccf0..000000000000
--- a/tools/include/linux/objtool.h
+++ /dev/null
@@ -1,200 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _LINUX_OBJTOOL_H
-#define _LINUX_OBJTOOL_H
-
-#ifndef __ASSEMBLY__
-
-#include <linux/types.h>
-
-/*
- * This struct is used by asm and inline asm code to manually annotate the
- * location of registers on the stack.
- */
-struct unwind_hint {
-	u32		ip;
-	s16		sp_offset;
-	u8		sp_reg;
-	u8		type;
-	u8		signal;
-	u8		end;
-};
-#endif
-
-/*
- * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
- * (the caller's SP right before it made the call).  Used for all callable
- * functions, i.e. all C code and all callable asm functions.
- *
- * UNWIND_HINT_TYPE_REGS: Used in entry code to indicate that sp_reg+sp_offset
- * points to a fully populated pt_regs from a syscall, interrupt, or exception.
- *
- * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
- * sp_reg+sp_offset points to the iret return frame.
- *
- * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
- * Useful for code which doesn't have an ELF function annotation.
- *
- * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
- */
-#define UNWIND_HINT_TYPE_CALL		0
-#define UNWIND_HINT_TYPE_REGS		1
-#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
-#define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_ENTRY		4
-#define UNWIND_HINT_TYPE_SAVE		5
-#define UNWIND_HINT_TYPE_RESTORE	6
-
-#ifdef CONFIG_OBJTOOL
-
-#include <asm/asm.h>
-
-#ifndef __ASSEMBLY__
-
-#define UNWIND_HINT(sp_reg, sp_offset, type, signal, end)	\
-	"987: \n\t"						\
-	".pushsection .discard.unwind_hints\n\t"		\
-	/* struct unwind_hint */				\
-	".long 987b - .\n\t"					\
-	".short " __stringify(sp_offset) "\n\t"			\
-	".byte " __stringify(sp_reg) "\n\t"			\
-	".byte " __stringify(type) "\n\t"			\
-	".byte " __stringify(signal) "\n\t"			\
-	".byte " __stringify(end) "\n\t"			\
-	".balign 4 \n\t"					\
-	".popsection\n\t"
-
-/*
- * This macro marks the given function's stack frame as "non-standard", which
- * tells objtool to ignore the function when doing stack metadata validation.
- * It should only be used in special cases where you're 100% sure it won't
- * affect the reliability of frame pointers and kernel stack traces.
- *
- * For more information, see tools/objtool/Documentation/objtool.txt.
- */
-#define STACK_FRAME_NON_STANDARD(func) \
-	static void __used __section(".discard.func_stack_frame_non_standard") \
-		*__func_stack_frame_non_standard_##func = func
-
-/*
- * STACK_FRAME_NON_STANDARD_FP() is a frame-pointer-specific function ignore
- * for the case where a function is intentionally missing frame pointer setup,
- * but otherwise needs objtool/ORC coverage when frame pointers are disabled.
- */
-#ifdef CONFIG_FRAME_POINTER
-#define STACK_FRAME_NON_STANDARD_FP(func) STACK_FRAME_NON_STANDARD(func)
-#else
-#define STACK_FRAME_NON_STANDARD_FP(func)
-#endif
-
-#define ANNOTATE_NOENDBR					\
-	"986: \n\t"						\
-	".pushsection .discard.noendbr\n\t"			\
-	_ASM_PTR " 986b\n\t"					\
-	".popsection\n\t"
-
-#define ASM_REACHABLE							\
-	"998:\n\t"							\
-	".pushsection .discard.reachable\n\t"				\
-	".long 998b - .\n\t"						\
-	".popsection\n\t"
-
-#else /* __ASSEMBLY__ */
-
-/*
- * This macro indicates that the following intra-function call is valid.
- * Any non-annotated intra-function call will cause objtool to issue a warning.
- */
-#define ANNOTATE_INTRA_FUNCTION_CALL				\
-	999:							\
-	.pushsection .discard.intra_function_calls;		\
-	.long 999b;						\
-	.popsection;
-
-/*
- * In asm, there are two kinds of code: normal C-type callable functions and
- * the rest.  The normal callable functions can be called by other code, and
- * don't do anything unusual with the stack.  Such normal callable functions
- * are annotated with the ENTRY/ENDPROC macros.  Most asm code falls in this
- * category.  In this case, no special debugging annotations are needed because
- * objtool can automatically generate the ORC data for the ORC unwinder to read
- * at runtime.
- *
- * Anything which doesn't fall into the above category, such as syscall and
- * interrupt handlers, tends to not be called directly by other functions, and
- * often does unusual non-C-function-type things with the stack pointer.  Such
- * code needs to be annotated such that objtool can understand it.  The
- * following CFI hint macros are for this type of code.
- *
- * These macros provide hints to objtool about the state of the stack at each
- * instruction.  Objtool starts from the hints and follows the code flow,
- * making automatic CFI adjustments when it sees pushes and pops, filling out
- * the debuginfo as necessary.  It will also warn if it sees any
- * inconsistencies.
- */
-.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
-.Lunwind_hint_ip_\@:
-	.pushsection .discard.unwind_hints
-		/* struct unwind_hint */
-		.long .Lunwind_hint_ip_\@ - .
-		.short \sp_offset
-		.byte \sp_reg
-		.byte \type
-		.byte \signal
-		.byte \end
-		.balign 4
-	.popsection
-.endm
-
-.macro STACK_FRAME_NON_STANDARD func:req
-	.pushsection .discard.func_stack_frame_non_standard, "aw"
-	_ASM_PTR \func
-	.popsection
-.endm
-
-.macro STACK_FRAME_NON_STANDARD_FP func:req
-#ifdef CONFIG_FRAME_POINTER
-	STACK_FRAME_NON_STANDARD \func
-#endif
-.endm
-
-.macro ANNOTATE_NOENDBR
-.Lhere_\@:
-	.pushsection .discard.noendbr
-	.quad	.Lhere_\@
-	.popsection
-.endm
-
-.macro REACHABLE
-.Lhere_\@:
-	.pushsection .discard.reachable
-	.long	.Lhere_\@ - .
-	.popsection
-.endm
-
-#endif /* __ASSEMBLY__ */
-
-#else /* !CONFIG_OBJTOOL */
-
-#ifndef __ASSEMBLY__
-
-#define UNWIND_HINT(sp_reg, sp_offset, type, signal, end) \
-	"\n\t"
-#define STACK_FRAME_NON_STANDARD(func)
-#define STACK_FRAME_NON_STANDARD_FP(func)
-#define ANNOTATE_NOENDBR
-#define ASM_REACHABLE
-#else
-#define ANNOTATE_INTRA_FUNCTION_CALL
-.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
-.endm
-.macro STACK_FRAME_NON_STANDARD func:req
-.endm
-.macro ANNOTATE_NOENDBR
-.endm
-.macro REACHABLE
-.endm
-#endif
-
-#endif /* CONFIG_OBJTOOL */
-
-#endif /* _LINUX_OBJTOOL_H */
diff --git a/tools/include/linux/objtool_types.h b/tools/include/linux/objtool_types.h
new file mode 100644
index 000000000000..8513537a30ed
--- /dev/null
+++ b/tools/include/linux/objtool_types.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_OBJTOOL_TYPES_H
+#define _LINUX_OBJTOOL_TYPES_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+
+/*
+ * This struct is used by asm and inline asm code to manually annotate the
+ * location of registers on the stack.
+ */
+struct unwind_hint {
+	u32		ip;
+	s16		sp_offset;
+	u8		sp_reg;
+	u8		type;
+	u8		signal;
+	u8		end;
+};
+
+#endif /* __ASSEMBLY__ */
+
+/*
+ * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
+ * (the caller's SP right before it made the call).  Used for all callable
+ * functions, i.e. all C code and all callable asm functions.
+ *
+ * UNWIND_HINT_TYPE_REGS: Used in entry code to indicate that sp_reg+sp_offset
+ * points to a fully populated pt_regs from a syscall, interrupt, or exception.
+ *
+ * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
+ * sp_reg+sp_offset points to the iret return frame.
+ *
+ * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
+ * Useful for code which doesn't have an ELF function annotation.
+ *
+ * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
+ */
+#define UNWIND_HINT_TYPE_CALL		0
+#define UNWIND_HINT_TYPE_REGS		1
+#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+#define UNWIND_HINT_TYPE_FUNC		3
+#define UNWIND_HINT_TYPE_ENTRY		4
+#define UNWIND_HINT_TYPE_SAVE		5
+#define UNWIND_HINT_TYPE_RESTORE	6
+
+#endif /* _LINUX_OBJTOOL_TYPES_H */
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5822de376d9a..3d4b650d3284 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -17,7 +17,7 @@
 #include <objtool/warn.h>
 #include <objtool/endianness.h>
 
-#include <linux/objtool.h>
+#include <linux/objtool_types.h>
 #include <linux/hashtable.h>
 #include <linux/kernel.h>
 #include <linux/static_call_types.h>
diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index 2d8ebdcd1db3..9f6c528c26f2 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -4,7 +4,7 @@
  */
 
 #include <unistd.h>
-#include <linux/objtool.h>
+#include <linux/objtool_types.h>
 #include <asm/orc_types.h>
 #include <objtool/objtool.h>
 #include <objtool/warn.h>
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index 57a4527d5988..f49630a21e0f 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -6,7 +6,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include <linux/objtool.h>
+#include <linux/objtool_types.h>
 #include <asm/orc_types.h>
 
 #include <objtool/check.h>
diff --git a/tools/objtool/sync-check.sh b/tools/objtool/sync-check.sh
index 105a291ff8e7..81d120d05442 100755
--- a/tools/objtool/sync-check.sh
+++ b/tools/objtool/sync-check.sh
@@ -6,7 +6,7 @@ if [ -z "$SRCARCH" ]; then
 	exit 1
 fi
 
-FILES="include/linux/objtool.h"
+FILES="include/linux/objtool_types.h"
 
 if [ "$SRCARCH" = "x86" ]; then
 FILES="$FILES
-- 
2.39.1

[PATCH 2/6] objtool: Use relative pointers for annotations

[Josh Poimboeuf]

They produce the needed relocations while using half the space.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/nospec-branch.h |  6 +++---
 include/linux/objtool.h              | 12 ++++++------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 3ef70e54a858..78ed1546b775 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -194,9 +194,9 @@
  * builds.
  */
 .macro ANNOTATE_RETPOLINE_SAFE
-	.Lannotate_\@:
+.Lhere_\@:
 	.pushsection .discard.retpoline_safe
-	_ASM_PTR .Lannotate_\@
+	.long .Lhere_\@ - .
 	.popsection
 .endm
 
@@ -318,7 +318,7 @@
 #define ANNOTATE_RETPOLINE_SAFE					\
 	"999:\n\t"						\
 	".pushsection .discard.retpoline_safe\n\t"		\
-	_ASM_PTR " 999b\n\t"					\
+	".long 999b - .\n\t"					\
 	".popsection\n\t"
 
 typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE];
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 8375792acfc0..2b0258d273fc 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -49,7 +49,7 @@
 #define ANNOTATE_NOENDBR					\
 	"986: \n\t"						\
 	".pushsection .discard.noendbr\n\t"			\
-	_ASM_PTR " 986b\n\t"					\
+	".long 986b - .\n\t"					\
 	".popsection\n\t"
 
 #define ASM_REACHABLE							\
@@ -67,7 +67,7 @@
 #define ANNOTATE_INTRA_FUNCTION_CALL				\
 	999:							\
 	.pushsection .discard.intra_function_calls;		\
-	.long 999b;						\
+	.long 999b - .;						\
 	.popsection;
 
 /*
@@ -92,10 +92,10 @@
  * inconsistencies.
  */
 .macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
-.Lunwind_hint_ip_\@:
+.Lhere_\@:
 	.pushsection .discard.unwind_hints
 		/* struct unwind_hint */
-		.long .Lunwind_hint_ip_\@ - .
+		.long .Lhere_\@ - .
 		.short \sp_offset
 		.byte \sp_reg
 		.byte \type
@@ -107,7 +107,7 @@
 
 .macro STACK_FRAME_NON_STANDARD func:req
 	.pushsection .discard.func_stack_frame_non_standard, "aw"
-	_ASM_PTR \func
+	.long \func - .
 	.popsection
 .endm
 
@@ -120,7 +120,7 @@
 .macro ANNOTATE_NOENDBR
 .Lhere_\@:
 	.pushsection .discard.noendbr
-	.quad	.Lhere_\@
+	.long	.Lhere_\@ - .
 	.popsection
 .endm
 
-- 
2.39.1

[PATCH 3/6] objtool: Change UNWIND_HINT() argument order

[Josh Poimboeuf]

The most important argument is 'type', make that one first.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/unwind_hints.h | 2 +-
 include/linux/objtool.h             | 5 ++---
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h
index e7c71750b309..97b392217c0f 100644
--- a/arch/x86/include/asm/unwind_hints.h
+++ b/arch/x86/include/asm/unwind_hints.h
@@ -67,7 +67,7 @@
 #else
 
 #define UNWIND_HINT_FUNC \
-	UNWIND_HINT(ORC_REG_SP, 8, UNWIND_HINT_TYPE_FUNC, 0, 0)
+	UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0, 0)
 
 #endif /* __ASSEMBLY__ */
 
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 2b0258d273fc..725d7f0b6748 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -10,7 +10,7 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(sp_reg, sp_offset, type, signal, end)	\
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end)	\
 	"987: \n\t"						\
 	".pushsection .discard.unwind_hints\n\t"		\
 	/* struct unwind_hint */				\
@@ -137,8 +137,7 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(sp_reg, sp_offset, type, signal, end) \
-	"\n\t"
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end) "\n\t"
 #define STACK_FRAME_NON_STANDARD(func)
 #define STACK_FRAME_NON_STANDARD_FP(func)
 #define ANNOTATE_NOENDBR
-- 
2.39.1

[PATCH 4/6] x86,objtool: Introduce ORC_TYPE_*

[Josh Poimboeuf]

Unwind hints and ORC entry types are two distinct things.  Separate them
out more explicitly.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/orc_types.h       |  4 ++++
 arch/x86/kernel/unwind_orc.c           | 12 ++++++------
 include/linux/objtool_types.h          |  1 +
 tools/arch/x86/include/asm/orc_types.h |  4 ++++
 tools/include/linux/objtool_types.h    |  1 +
 tools/objtool/orc_dump.c               |  7 +++----
 tools/objtool/orc_gen.c                | 19 +++++++++++++++++--
 7 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
index 1343a62106de..b4d4ec78589e 100644
--- a/arch/x86/include/asm/orc_types.h
+++ b/arch/x86/include/asm/orc_types.h
@@ -39,6 +39,10 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
+#define ORC_TYPE_CALL			0
+#define ORC_TYPE_REGS			1
+#define ORC_TYPE_REGS_PARTIAL		2
+
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>
 
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 37307b40f8da..8348ac581de3 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -133,7 +133,7 @@ static struct orc_entry null_orc_entry = {
 	.sp_offset = sizeof(long),
 	.sp_reg = ORC_REG_SP,
 	.bp_reg = ORC_REG_UNDEFINED,
-	.type = UNWIND_HINT_TYPE_CALL
+	.type = ORC_TYPE_CALL
 };
 
 #ifdef CONFIG_CALL_THUNKS
@@ -153,7 +153,7 @@ static struct orc_entry *orc_callthunk_find(unsigned long ip)
 
 /* Fake frame pointer entry -- used as a fallback for generated code */
 static struct orc_entry orc_fp_entry = {
-	.type		= UNWIND_HINT_TYPE_CALL,
+	.type		= ORC_TYPE_CALL,
 	.sp_reg		= ORC_REG_BP,
 	.sp_offset	= 16,
 	.bp_reg		= ORC_REG_PREV_SP,
@@ -554,7 +554,7 @@ bool unwind_next_frame(struct unwind_state *state)
 
 	/* Find IP, SP and possibly regs: */
 	switch (orc->type) {
-	case UNWIND_HINT_TYPE_CALL:
+	case ORC_TYPE_CALL:
 		ip_p = sp - sizeof(long);
 
 		if (!deref_stack_reg(state, ip_p, &state->ip))
@@ -567,7 +567,7 @@ bool unwind_next_frame(struct unwind_state *state)
 		state->prev_regs = NULL;
 		break;
 
-	case UNWIND_HINT_TYPE_REGS:
+	case ORC_TYPE_REGS:
 		if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
 			orc_warn_current("can't access registers at %pB\n",
 					 (void *)orig_ip);
@@ -590,13 +590,13 @@ bool unwind_next_frame(struct unwind_state *state)
 		state->full_regs = true;
 		break;
 
-	case UNWIND_HINT_TYPE_REGS_PARTIAL:
+	case ORC_TYPE_REGS_PARTIAL:
 		if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
 			orc_warn_current("can't access iret registers at %pB\n",
 					 (void *)orig_ip);
 			goto err;
 		}
-		/* See UNWIND_HINT_TYPE_REGS case comment. */
+		/* See ORC_TYPE_REGS case comment. */
 		state->ip = unwind_recover_rethook(state, state->ip,
 				(unsigned long *)(state->sp - sizeof(long)));
 
diff --git a/include/linux/objtool_types.h b/include/linux/objtool_types.h
index 8513537a30ed..9a83468c0039 100644
--- a/include/linux/objtool_types.h
+++ b/include/linux/objtool_types.h
@@ -40,6 +40,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_CALL		0
 #define UNWIND_HINT_TYPE_REGS		1
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+/* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
 #define UNWIND_HINT_TYPE_ENTRY		4
 #define UNWIND_HINT_TYPE_SAVE		5
diff --git a/tools/arch/x86/include/asm/orc_types.h b/tools/arch/x86/include/asm/orc_types.h
index 1343a62106de..b4d4ec78589e 100644
--- a/tools/arch/x86/include/asm/orc_types.h
+++ b/tools/arch/x86/include/asm/orc_types.h
@@ -39,6 +39,10 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
+#define ORC_TYPE_CALL			0
+#define ORC_TYPE_REGS			1
+#define ORC_TYPE_REGS_PARTIAL		2
+
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>
 
diff --git a/tools/include/linux/objtool_types.h b/tools/include/linux/objtool_types.h
index 8513537a30ed..9a83468c0039 100644
--- a/tools/include/linux/objtool_types.h
+++ b/tools/include/linux/objtool_types.h
@@ -40,6 +40,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_CALL		0
 #define UNWIND_HINT_TYPE_REGS		1
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+/* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
 #define UNWIND_HINT_TYPE_ENTRY		4
 #define UNWIND_HINT_TYPE_SAVE		5
diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index 9f6c528c26f2..97ecbb8b9034 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -4,7 +4,6 @@
  */
 
 #include <unistd.h>
-#include <linux/objtool_types.h>
 #include <asm/orc_types.h>
 #include <objtool/objtool.h>
 #include <objtool/warn.h>
@@ -39,11 +38,11 @@ static const char *reg_name(unsigned int reg)
 static const char *orc_type_name(unsigned int type)
 {
 	switch (type) {
-	case UNWIND_HINT_TYPE_CALL:
+	case ORC_TYPE_CALL:
 		return "call";
-	case UNWIND_HINT_TYPE_REGS:
+	case ORC_TYPE_REGS:
 		return "regs";
-	case UNWIND_HINT_TYPE_REGS_PARTIAL:
+	case ORC_TYPE_REGS_PARTIAL:
 		return "regs (partial)";
 	default:
 		return "?";
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index f49630a21e0f..e85bbb996f6c 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -26,6 +26,22 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 		return 0;
 	}
 
+	switch (cfi->type) {
+	case UNWIND_HINT_TYPE_CALL:
+		orc->type = ORC_TYPE_CALL;
+		break;
+	case UNWIND_HINT_TYPE_REGS:
+		orc->type = ORC_TYPE_REGS;
+		break;
+	case UNWIND_HINT_TYPE_REGS_PARTIAL:
+		orc->type = ORC_TYPE_REGS_PARTIAL;
+		break;
+	default:
+		WARN_FUNC("unknown unwind hint type %d",
+			  insn->sec, insn->offset, cfi->type);
+		return -1;
+	}
+
 	orc->end = cfi->end;
 	orc->signal = cfi->signal;
 
@@ -83,7 +99,6 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 
 	orc->sp_offset = cfi->cfa.offset;
 	orc->bp_offset = bp->offset;
-	orc->type = cfi->type;
 
 	return 0;
 }
@@ -151,7 +166,7 @@ int orc_create(struct objtool_file *file)
 	struct orc_entry null = {
 		.sp_reg  = ORC_REG_UNDEFINED,
 		.bp_reg  = ORC_REG_UNDEFINED,
-		.type    = UNWIND_HINT_TYPE_CALL,
+		.type    = ORC_TYPE_CALL,
 	};
 
 	/* Build a deduplicated list of ORC entries: */
-- 
2.39.1

[PATCH 5/6] x86,objtool: Separate unret validation from unwind hints

[Josh Poimboeuf]

The ENTRY unwind hint type is serving double duty as both an empty
unwind hint and an unret validation annotation.

Unret validation is unrelated to unwinding. Separate it out into its own
annotation.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/entry/entry_64.S             | 14 +++---
 arch/x86/include/asm/nospec-branch.h  |  8 ++--
 arch/x86/include/asm/unwind_hints.h   |  8 +++-
 arch/x86/kernel/head_64.S             |  5 ---
 include/linux/objtool.h               | 16 +++++++
 include/linux/objtool_types.h         |  5 +--
 tools/include/linux/objtool_types.h   |  5 +--
 tools/objtool/check.c                 | 65 ++++++++++++++++++---------
 tools/objtool/include/objtool/check.h |  4 +-
 9 files changed, 85 insertions(+), 45 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index eccc3431e515..5b93eb7db0ab 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -388,9 +388,9 @@ SYM_CODE_START(\asmsym)
 
 	.if \vector == X86_TRAP_BP
 		/* #BP advances %rip to the next instruction */
-		UNWIND_HINT_IRET_REGS offset=\has_error_code*8 signal=0
+		UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8 signal=0
 	.else
-		UNWIND_HINT_IRET_REGS offset=\has_error_code*8
+		UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8
 	.endif
 
 	ENDBR
@@ -461,7 +461,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_mce_db vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS
+	UNWIND_HINT_IRET_ENTRY
 	ENDBR
 	ASM_CLAC
 	cld
@@ -518,7 +518,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_vc vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS
+	UNWIND_HINT_IRET_ENTRY
 	ENDBR
 	ASM_CLAC
 	cld
@@ -582,7 +582,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_df vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS offset=8
+	UNWIND_HINT_IRET_ENTRY offset=8
 	ENDBR
 	ASM_CLAC
 	cld
@@ -1107,7 +1107,7 @@ SYM_CODE_START(error_entry)
 	FENCE_SWAPGS_KERNEL_ENTRY
 	CALL_DEPTH_ACCOUNT
 	leaq	8(%rsp), %rax			/* return pt_regs pointer */
-	ANNOTATE_UNRET_END
+	VALIDATE_UNRET_END
 	RET
 
 .Lbstep_iret:
@@ -1153,7 +1153,7 @@ SYM_CODE_END(error_return)
  *	      when PAGE_TABLE_ISOLATION is in use.  Do not clobber.
  */
 SYM_CODE_START(asm_exc_nmi)
-	UNWIND_HINT_IRET_REGS
+	UNWIND_HINT_IRET_ENTRY
 	ENDBR
 
 	/*
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 78ed1546b775..edb2b0cb8efe 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -210,8 +210,8 @@
  * Abuse ANNOTATE_RETPOLINE_SAFE on a NOP to indicate UNRET_END, should
  * eventually turn into it's own annotation.
  */
-.macro ANNOTATE_UNRET_END
-#ifdef CONFIG_DEBUG_ENTRY
+.macro VALIDATE_UNRET_END
+#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
 	ANNOTATE_RETPOLINE_SAFE
 	nop
 #endif
@@ -286,7 +286,7 @@
 .macro UNTRAIN_RET
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
 	defined(CONFIG_CALL_DEPTH_TRACKING)
-	ANNOTATE_UNRET_END
+	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
@@ -297,7 +297,7 @@
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
 	defined(CONFIG_CALL_DEPTH_TRACKING)
-	ANNOTATE_UNRET_END
+	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h
index 97b392217c0f..4c0f28d665eb 100644
--- a/arch/x86/include/asm/unwind_hints.h
+++ b/arch/x86/include/asm/unwind_hints.h
@@ -12,7 +12,8 @@
 .endm
 
 .macro UNWIND_HINT_ENTRY
-	UNWIND_HINT type=UNWIND_HINT_TYPE_ENTRY end=1
+	VALIDATE_UNRET_BEGIN
+	UNWIND_HINT_EMPTY
 .endm
 
 .macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 partial=0 signal=1
@@ -52,6 +53,11 @@
 	UNWIND_HINT_REGS base=\base offset=\offset partial=1 signal=\signal
 .endm
 
+.macro UNWIND_HINT_IRET_ENTRY base=%rsp offset=0 signal=1
+	VALIDATE_UNRET_BEGIN
+	UNWIND_HINT_IRET_REGS base=\base offset=\offset signal=\signal
+.endm
+
 .macro UNWIND_HINT_FUNC
 	UNWIND_HINT sp_reg=ORC_REG_SP sp_offset=8 type=UNWIND_HINT_TYPE_FUNC
 .endm
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 222efd4a09bc..ee3ed15ee1f8 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -390,8 +390,6 @@ SYM_CODE_START_NOALIGN(vc_boot_ghcb)
 	UNWIND_HINT_IRET_REGS offset=8
 	ENDBR
 
-	ANNOTATE_UNRET_END
-
 	/* Build pt_regs */
 	PUSH_AND_CLEAR_REGS
 
@@ -451,7 +449,6 @@ SYM_CODE_END(early_idt_handler_array)
 
 SYM_CODE_START_LOCAL(early_idt_handler_common)
 	UNWIND_HINT_IRET_REGS offset=16
-	ANNOTATE_UNRET_END
 	/*
 	 * The stack is the hardware frame, an error code or zero, and the
 	 * vector number.
@@ -501,8 +498,6 @@ SYM_CODE_START_NOALIGN(vc_no_ghcb)
 	UNWIND_HINT_IRET_REGS offset=8
 	ENDBR
 
-	ANNOTATE_UNRET_END
-
 	/* Build pt_regs */
 	PUSH_AND_CLEAR_REGS
 
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 725d7f0b6748..5aa475118820 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -124,6 +124,22 @@
 	.popsection
 .endm
 
+/*
+ * Use objtool to validate the entry requirement that all code paths do
+ * VALIDATE_UNRET_END before RET.
+ *
+ * NOTE: The macro must be used at the beginning of a global symbol, otherwise
+ * it will be ignored.
+ */
+.macro VALIDATE_UNRET_BEGIN
+#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+.Lhere_\@:
+	.pushsection .discard.validate_unret
+	.long	.Lhere_\@ - .
+	.popsection
+#endif
+.endm
+
 .macro REACHABLE
 .Lhere_\@:
 	.pushsection .discard.reachable
diff --git a/include/linux/objtool_types.h b/include/linux/objtool_types.h
index 9a83468c0039..9787ad0f2ef4 100644
--- a/include/linux/objtool_types.h
+++ b/include/linux/objtool_types.h
@@ -42,8 +42,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
 /* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_ENTRY		4
-#define UNWIND_HINT_TYPE_SAVE		5
-#define UNWIND_HINT_TYPE_RESTORE	6
+#define UNWIND_HINT_TYPE_SAVE		4
+#define UNWIND_HINT_TYPE_RESTORE	5
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
diff --git a/tools/include/linux/objtool_types.h b/tools/include/linux/objtool_types.h
index 9a83468c0039..9787ad0f2ef4 100644
--- a/tools/include/linux/objtool_types.h
+++ b/tools/include/linux/objtool_types.h
@@ -42,8 +42,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
 /* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_ENTRY		4
-#define UNWIND_HINT_TYPE_SAVE		5
-#define UNWIND_HINT_TYPE_RESTORE	6
+#define UNWIND_HINT_TYPE_SAVE		4
+#define UNWIND_HINT_TYPE_RESTORE	5
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 3d4b650d3284..226c2db3df89 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2304,16 +2304,9 @@ static int read_unwind_hints(struct objtool_file *file)
 					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;
@@ -2446,6 +2439,34 @@ static int read_instr_hints(struct objtool_file *file)
 	return 0;
 }
 
+static int read_validate_unret_hints(struct objtool_file *file)
+{
+	struct section *sec;
+	struct instruction *insn;
+	struct reloc *reloc;
+
+	sec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
+	if (!sec)
+		return 0;
+
+	list_for_each_entry(reloc, &sec->reloc_list, list) {
+		if (reloc->sym->type != STT_SECTION) {
+			WARN("unexpected relocation symbol type in %s", sec->name);
+			return -1;
+		}
+
+		insn = find_insn(file, reloc->sym->sec, reloc->addend);
+		if (!insn) {
+			WARN("bad .discard.instr_end entry");
+			return -1;
+		}
+		insn->unret = 1;
+	}
+
+	return 0;
+}
+
+
 static int read_intra_function_calls(struct objtool_file *file)
 {
 	struct instruction *insn;
@@ -2664,6 +2685,10 @@ static int decode_sections(struct objtool_file *file)
 	if (ret)
 		return ret;
 
+	ret = read_validate_unret_hints(file);
+	if (ret)
+		return ret;
+
 	return 0;
 }
 
@@ -3860,10 +3885,10 @@ static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
 /*
  * Validate rethunk entry constraint: must untrain RET before the first RET.
  *
- * Follow every branch (intra-function) and ensure ANNOTATE_UNRET_END comes
+ * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
  * before an actual RET instruction.
  */
-static int validate_entry(struct objtool_file *file, struct instruction *insn)
+static int validate_unret(struct objtool_file *file, struct instruction *insn)
 {
 	struct instruction *next, *dest;
 	int ret, warnings = 0;
@@ -3871,10 +3896,10 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
 	for (;;) {
 		next = next_insn_to_validate(file, insn);
 
-		if (insn->visited & VISITED_ENTRY)
+		if (insn->visited & VISITED_UNRET)
 			return 0;
 
-		insn->visited |= VISITED_ENTRY;
+		insn->visited |= VISITED_UNRET;
 
 		if (!insn->ignore_alts && insn->alts) {
 			struct alternative *alt;
@@ -3884,7 +3909,7 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
 				if (alt->skip_orig)
 					skip_orig = true;
 
-				ret = validate_entry(file, alt->insn);
+				ret = validate_unret(file, alt->insn);
 				if (ret) {
 				        if (opts.backtrace)
 						BT_FUNC("(alt)", insn);
@@ -3912,7 +3937,7 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
 						  insn->sec, insn->offset);
 					return -1;
 				}
-				ret = validate_entry(file, insn->jump_dest);
+				ret = validate_unret(file, insn->jump_dest);
 				if (ret) {
 					if (opts.backtrace) {
 						BT_FUNC("(branch%s)", insn,
@@ -3937,7 +3962,7 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
 				return -1;
 			}
 
-			ret = validate_entry(file, dest);
+			ret = validate_unret(file, dest);
 			if (ret) {
 				if (opts.backtrace)
 					BT_FUNC("(call)", insn);
@@ -3973,19 +3998,19 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
 }
 
 /*
- * Validate that all branches starting at 'insn->entry' encounter UNRET_END
- * before RET.
+ * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
+ * VALIDATE_UNRET_END before RET.
  */
-static int validate_unret(struct objtool_file *file)
+static int validate_unrets(struct objtool_file *file)
 {
 	struct instruction *insn;
 	int ret, warnings = 0;
 
 	for_each_insn(file, insn) {
-		if (!insn->entry)
+		if (!insn->unret)
 			continue;
 
-		ret = validate_entry(file, insn);
+		ret = validate_unret(file, insn);
 		if (ret < 0) {
 			WARN_FUNC("Failed UNRET validation", insn->sec, insn->offset);
 			return ret;
@@ -4604,7 +4629,7 @@ int check(struct objtool_file *file)
 		 * Must be after validate_branch() and friends, it plays
 		 * further games with insn->visited.
 		 */
-		ret = validate_unret(file);
+		ret = validate_unrets(file);
 		if (ret < 0)
 			return ret;
 		warnings += ret;
diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index 3e7c7004f7df..daa46f1f0965 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -61,7 +61,7 @@ struct instruction {
 	    restore		: 1,
 	    retpoline_safe	: 1,
 	    noendbr		: 1,
-	    entry		: 1,
+	    unret		: 1,
 	    visited		: 4,
 	    no_reloc		: 1;
 		/* 10 bit hole */
@@ -92,7 +92,7 @@ static inline struct symbol *insn_func(struct instruction *insn)
 #define VISITED_BRANCH		0x01
 #define VISITED_BRANCH_UACCESS	0x02
 #define VISITED_BRANCH_MASK	0x03
-#define VISITED_ENTRY		0x04
+#define VISITED_UNRET		0x04
 
 static inline bool is_static_jump(struct instruction *insn)
 {
-- 
2.39.1

[PATCH 6/6] x86,objtool: Split UNWIND_HINT_EMPTY in two

[Josh Poimboeuf]

Mark reported that the ORC unwinder incorrectly marks an unwind as
reliable when the unwind terminates prematurely in the dark corners of
return_to_handler() due to lack of information about the next frame.

The problem is UNWIND_HINT_EMPTY is used in two different situations:

  1) The end of the kernel stack unwind before hitting user entry, boot
     code, or fork entry

  2) A blind spot in ORC coverage where the unwinder has to bail due to
     lack of information about the next frame

The ORC unwinder has no way to tell the difference between the two.
When it encounters an undefined stack state with 'end=1', it blindly
marks the stack reliable, which can break the livepatch consistency
model.

Fix it by splitting UNWIND_HINT_EMPTY into UNWIND_HINT_UNDEFINED and
UNWIND_HINT_END_OF_STACK.

Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 .../livepatch/reliable-stacktrace.rst         |  2 +-
 arch/x86/entry/entry_64.S                     | 12 ++++-----
 arch/x86/include/asm/orc_types.h              | 14 +++++-----
 arch/x86/include/asm/unwind_hints.h           | 12 ++++++---
 arch/x86/kernel/ftrace_64.S                   |  2 +-
 arch/x86/kernel/head_64.S                     | 12 ++++-----
 arch/x86/kernel/relocate_kernel_64.S          | 10 +++----
 arch/x86/kernel/unwind_orc.c                  | 15 +++++------
 arch/x86/lib/retpoline.S                      |  6 ++---
 arch/x86/platform/pvh/head.S                  |  2 +-
 arch/x86/xen/xen-asm.S                        |  4 +--
 arch/x86/xen/xen-head.S                       |  4 +--
 include/linux/objtool.h                       | 10 +++----
 include/linux/objtool_types.h                 | 27 ++++++++++++-------
 scripts/sorttable.h                           |  2 +-
 tools/arch/x86/include/asm/orc_types.h        | 14 +++++-----
 tools/include/linux/objtool_types.h           | 27 ++++++++++++-------
 tools/objtool/check.c                         |  2 +-
 tools/objtool/orc_dump.c                      |  8 ++++--
 tools/objtool/orc_gen.c                       | 26 +++++++++---------
 20 files changed, 116 insertions(+), 95 deletions(-)

diff --git a/Documentation/livepatch/reliable-stacktrace.rst b/Documentation/livepatch/reliable-stacktrace.rst
index 67459d2ca2af..d56bb706172f 100644
--- a/Documentation/livepatch/reliable-stacktrace.rst
+++ b/Documentation/livepatch/reliable-stacktrace.rst
@@ -183,7 +183,7 @@ trampoline or return trampoline. For example, considering the x86_64
 .. code-block:: none
 
    SYM_CODE_START(return_to_handler)
-           UNWIND_HINT_EMPTY
+           UNWIND_HINT_UNDEFINED
            subq  $24, %rsp
 
            /* Save the return values */
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 5b93eb7db0ab..45e135be2a9f 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -205,7 +205,7 @@ syscall_return_via_sysret:
 	 */
 	movq	%rsp, %rdi
 	movq	PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 
 	pushq	RSP-RDI(%rdi)	/* RSP */
 	pushq	(%rdi)		/* RDI */
@@ -286,7 +286,7 @@ SYM_FUNC_END(__switch_to_asm)
 .pushsection .text, "ax"
 	__FUNC_ALIGN
 SYM_CODE_START_NOALIGN(ret_from_fork)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR // copy_thread
 	CALL_DEPTH_ACCOUNT
 	movq	%rax, %rdi
@@ -303,7 +303,7 @@ SYM_CODE_START_NOALIGN(ret_from_fork)
 
 1:
 	/* kernel thread */
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	movq	%r12, %rdi
 	CALL_NOSPEC rbx
 	/*
@@ -643,7 +643,7 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL)
 	 */
 	movq	%rsp, %rdi
 	movq	PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 
 	/* Copy the IRET frame to the trampoline stack. */
 	pushq	6*8(%rdi)	/* SS */
@@ -869,7 +869,7 @@ SYM_CODE_END(exc_xen_hypervisor_callback)
  */
 	__FUNC_ALIGN
 SYM_CODE_START_NOALIGN(xen_failsafe_callback)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ENDBR
 	movl	%ds, %ecx
 	cmpw	%cx, 0x10(%rsp)
@@ -1520,7 +1520,7 @@ SYM_CODE_END(asm_exc_nmi)
  * MSRs to fully disable 32-bit SYSCALL.
  */
 SYM_CODE_START(ignore_sysret)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ENDBR
 	mov	$-ENOSYS, %eax
 	sysretl
diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
index b4d4ec78589e..46d7e06763c9 100644
--- a/arch/x86/include/asm/orc_types.h
+++ b/arch/x86/include/asm/orc_types.h
@@ -39,9 +39,11 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
-#define ORC_TYPE_CALL			0
-#define ORC_TYPE_REGS			1
-#define ORC_TYPE_REGS_PARTIAL		2
+#define ORC_TYPE_UNDEFINED		0
+#define ORC_TYPE_END_OF_STACK		1
+#define ORC_TYPE_CALL			2
+#define ORC_TYPE_REGS			3
+#define ORC_TYPE_REGS_PARTIAL		4
 
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>
@@ -60,16 +62,14 @@ struct orc_entry {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	unsigned	sp_reg:4;
 	unsigned	bp_reg:4;
-	unsigned	type:2;
+	unsigned	type:3;
 	unsigned	signal:1;
-	unsigned	end:1;
 #elif defined(__BIG_ENDIAN_BITFIELD)
 	unsigned	bp_reg:4;
 	unsigned	sp_reg:4;
 	unsigned	unused:4;
-	unsigned	end:1;
 	unsigned	signal:1;
-	unsigned	type:2;
+	unsigned	type:3;
 #endif
 } __packed;
 
diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h
index 4c0f28d665eb..01cb9692b160 100644
--- a/arch/x86/include/asm/unwind_hints.h
+++ b/arch/x86/include/asm/unwind_hints.h
@@ -7,13 +7,17 @@
 
 #ifdef __ASSEMBLY__
 
-.macro UNWIND_HINT_EMPTY
-	UNWIND_HINT type=UNWIND_HINT_TYPE_CALL end=1
+.macro UNWIND_HINT_END_OF_STACK
+	UNWIND_HINT type=UNWIND_HINT_TYPE_END_OF_STACK
+.endm
+
+.macro UNWIND_HINT_UNDEFINED
+	UNWIND_HINT type=UNWIND_HINT_TYPE_UNDEFINED
 .endm
 
 .macro UNWIND_HINT_ENTRY
 	VALIDATE_UNRET_BEGIN
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 .endm
 
 .macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 partial=0 signal=1
@@ -73,7 +77,7 @@
 #else
 
 #define UNWIND_HINT_FUNC \
-	UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0, 0)
+	UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0)
 
 #endif /* __ASSEMBLY__ */
 
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index 1265ad519249..0387732e9c3f 100644
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -340,7 +340,7 @@ STACK_FRAME_NON_STANDARD_FP(__fentry__)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 SYM_CODE_START(return_to_handler)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	subq  $16, %rsp
 
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index ee3ed15ee1f8..8d8d25c64827 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -42,7 +42,7 @@ L3_START_KERNEL = pud_index(__START_KERNEL_map)
 	__HEAD
 	.code64
 SYM_CODE_START_NOALIGN(startup_64)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	/*
 	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
 	 * and someone has loaded an identity mapped page table
@@ -105,7 +105,7 @@ SYM_CODE_START_NOALIGN(startup_64)
 	lretq
 
 .Lon_kernel_cs:
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 
 	/* Sanitize CPU configuration */
 	call verify_cpu
@@ -127,7 +127,7 @@ SYM_CODE_START_NOALIGN(startup_64)
 SYM_CODE_END(startup_64)
 
 SYM_CODE_START(secondary_startup_64)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 	/*
 	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
@@ -156,7 +156,7 @@ SYM_CODE_START(secondary_startup_64)
 	 * verify_cpu() above to make sure NX is enabled.
 	 */
 SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 
 	/*
@@ -238,7 +238,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
 	ANNOTATE_RETPOLINE_SAFE
 	jmp	*%rax
 1:
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR // above
 
 	/*
@@ -371,7 +371,7 @@ SYM_CODE_END(secondary_startup_64)
  */
 SYM_CODE_START(start_cpu0)
 	ANNOTATE_NOENDBR
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	movq	initial_stack(%rip), %rsp
 	jmp	.Ljump_to_C_code
 SYM_CODE_END(start_cpu0)
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 4a73351f87f8..56cab1bb25f5 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -43,7 +43,7 @@
 	.code64
 SYM_CODE_START_NOALIGN(relocate_range)
 SYM_CODE_START_NOALIGN(relocate_kernel)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 	/*
 	 * %rdi indirection_page
@@ -113,7 +113,7 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
 SYM_CODE_END(relocate_kernel)
 
 SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	/* set return address to 0 if not preserving context */
 	pushq	$0
 	/* store the start address on the stack */
@@ -231,7 +231,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 SYM_CODE_END(identity_mapped)
 
 SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR // RET target, above
 	movq	RSP(%r8), %rsp
 	movq	CR4(%r8), %rax
@@ -256,8 +256,8 @@ SYM_CODE_END(virtual_mapped)
 
 	/* Do the copies */
 SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
-	UNWIND_HINT_EMPTY
-	movq	%rdi, %rcx 	/* Put the page_list in %rcx */
+	UNWIND_HINT_END_OF_STACK
+	movq	%rdi, %rcx	/* Put the page_list in %rcx */
 	xorl	%edi, %edi
 	xorl	%esi, %esi
 	jmp	1f
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 8348ac581de3..3ac50b7298d1 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -158,7 +158,6 @@ static struct orc_entry orc_fp_entry = {
 	.sp_offset	= 16,
 	.bp_reg		= ORC_REG_PREV_SP,
 	.bp_offset	= -16,
-	.end		= 0,
 };
 
 static struct orc_entry *orc_find(unsigned long ip)
@@ -250,13 +249,13 @@ static int orc_sort_cmp(const void *_a, const void *_b)
 		return -1;
 
 	/*
-	 * The "weak" section terminator entries need to always be on the left
+	 * The "weak" section terminator entries need to always be first
 	 * to ensure the lookup code skips them in favor of real entries.
 	 * These terminator entries exist to handle any gaps created by
 	 * whitelisted .o files which didn't get objtool generation.
 	 */
 	orc_a = cur_orc_table + (a - cur_orc_ip_table);
-	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
+	return orc_a->type == ORC_TYPE_UNDEFINED ? -1 : 1;
 }
 
 void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
@@ -474,14 +473,12 @@ bool unwind_next_frame(struct unwind_state *state)
 		 */
 		orc = &orc_fp_entry;
 		state->error = true;
-	}
-
-	/* End-of-stack check for kernel threads: */
-	if (orc->sp_reg == ORC_REG_UNDEFINED) {
-		if (!orc->end)
+	} else {
+		if (orc->type == ORC_TYPE_UNDEFINED)
 			goto err;
 
-		goto the_end;
+		if (orc->type == ORC_TYPE_END_OF_STACK)
+			goto the_end;
 	}
 
 	state->signal = orc->signal;
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 5f61c65322be..27ef53fab6bd 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -33,7 +33,7 @@
 
 	.align RETPOLINE_THUNK_SIZE
 SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 
 	ALTERNATIVE_2 __stringify(RETPOLINE \reg), \
@@ -75,7 +75,7 @@ SYM_CODE_END(__x86_indirect_thunk_array)
 	.align RETPOLINE_THUNK_SIZE
 
 SYM_INNER_LABEL(__x86_indirect_call_thunk_\reg, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 
 	CALL_DEPTH_ACCOUNT
@@ -103,7 +103,7 @@ SYM_CODE_END(__x86_indirect_call_thunk_array)
 	.align RETPOLINE_THUNK_SIZE
 
 SYM_INNER_LABEL(__x86_indirect_jump_thunk_\reg, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	POLINE \reg
 	ANNOTATE_UNRET_SAFE
diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index 7fe564eaf228..c4365a05ab83 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -50,7 +50,7 @@
 #define PVH_DS_SEL		(PVH_GDT_ENTRY_DS * 8)
 
 SYM_CODE_START_LOCAL(pvh_start_xen)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	cld
 
 	lgdt (_pa(gdt))
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index 4a184f6e4e4d..08f1ceb9eb81 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -165,7 +165,7 @@ xen_pv_trap asm_exc_xen_hypervisor_callback
 SYM_CODE_START(xen_early_idt_handler_array)
 	i = 0
 	.rept NUM_EXCEPTION_VECTORS
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ENDBR
 	pop %rcx
 	pop %r11
@@ -193,7 +193,7 @@ hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
  * rsp->rax		}
  */
 SYM_CODE_START(xen_iret)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	pushq $0
 	jmp hypercall_iret
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index e36ea4268bd2..6eafdd17c242 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -45,7 +45,7 @@ SYM_CODE_END(hypercall_page)
 #ifdef CONFIG_XEN_PV
 	__INIT
 SYM_CODE_START(startup_xen)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 	cld
 
@@ -71,7 +71,7 @@ SYM_CODE_END(startup_xen)
 #ifdef CONFIG_XEN_PV_SMP
 .pushsection .text
 SYM_CODE_START(asm_cpu_bringup_and_idle)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ENDBR
 
 	call cpu_bringup_and_idle
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 5aa475118820..03f82c2c2ebf 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -10,7 +10,7 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end)	\
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal)	\
 	"987: \n\t"						\
 	".pushsection .discard.unwind_hints\n\t"		\
 	/* struct unwind_hint */				\
@@ -19,7 +19,6 @@
 	".byte " __stringify(sp_reg) "\n\t"			\
 	".byte " __stringify(type) "\n\t"			\
 	".byte " __stringify(signal) "\n\t"			\
-	".byte " __stringify(end) "\n\t"			\
 	".balign 4 \n\t"					\
 	".popsection\n\t"
 
@@ -91,7 +90,7 @@
  * the debuginfo as necessary.  It will also warn if it sees any
  * inconsistencies.
  */
-.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
 .Lhere_\@:
 	.pushsection .discard.unwind_hints
 		/* struct unwind_hint */
@@ -100,7 +99,6 @@
 		.byte \sp_reg
 		.byte \type
 		.byte \signal
-		.byte \end
 		.balign 4
 	.popsection
 .endm
@@ -153,14 +151,14 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end) "\n\t"
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal) "\n\t"
 #define STACK_FRAME_NON_STANDARD(func)
 #define STACK_FRAME_NON_STANDARD_FP(func)
 #define ANNOTATE_NOENDBR
 #define ASM_REACHABLE
 #else
 #define ANNOTATE_INTRA_FUNCTION_CALL
-.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
 .endm
 .macro STACK_FRAME_NON_STANDARD func:req
 .endm
diff --git a/include/linux/objtool_types.h b/include/linux/objtool_types.h
index 9787ad0f2ef4..453a4f4ef39d 100644
--- a/include/linux/objtool_types.h
+++ b/include/linux/objtool_types.h
@@ -16,12 +16,18 @@ struct unwind_hint {
 	u8		sp_reg;
 	u8		type;
 	u8		signal;
-	u8		end;
 };
 
 #endif /* __ASSEMBLY__ */
 
 /*
+ * UNWIND_HINT_TYPE_UNDEFINED: A blind spot in ORC coverage which can result in
+ * a truncated and unreliable stack unwind.
+ *
+ * UNWIND_HINT_TYPE_END_OF_STACK: The end of the kernel stack unwind before
+ * hitting user entry, boot code, or fork entry (when there are no pt_regs
+ * available).
+ *
  * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
  * (the caller's SP right before it made the call).  Used for all callable
  * functions, i.e. all C code and all callable asm functions.
@@ -32,17 +38,20 @@ struct unwind_hint {
  * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
  * sp_reg+sp_offset points to the iret return frame.
  *
- * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
+ * UNWIND_HINT_TYPE_FUNC: Generate the unwind metadata of a callable function.
  * Useful for code which doesn't have an ELF function annotation.
  *
- * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
+ * UNWIND_HINT_TYPE_{SAVE,RESTORE}: Save the unwind metadata at a certain
+ * location so that it can be restored later.
  */
-#define UNWIND_HINT_TYPE_CALL		0
-#define UNWIND_HINT_TYPE_REGS		1
-#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+#define UNWIND_HINT_TYPE_UNDEFINED	0
+#define UNWIND_HINT_TYPE_END_OF_STACK	1
+#define UNWIND_HINT_TYPE_CALL		2
+#define UNWIND_HINT_TYPE_REGS		3
+#define UNWIND_HINT_TYPE_REGS_PARTIAL	4
 /* The below hint types don't have corresponding ORC types */
-#define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_SAVE		4
-#define UNWIND_HINT_TYPE_RESTORE	5
+#define UNWIND_HINT_TYPE_FUNC		5
+#define UNWIND_HINT_TYPE_SAVE		6
+#define UNWIND_HINT_TYPE_RESTORE	7
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
diff --git a/scripts/sorttable.h b/scripts/sorttable.h
index deb7c1d3e979..7bd0184380d3 100644
--- a/scripts/sorttable.h
+++ b/scripts/sorttable.h
@@ -128,7 +128,7 @@ static int orc_sort_cmp(const void *_a, const void *_b)
 	 * whitelisted .o files which didn't get objtool generation.
 	 */
 	orc_a = g_orc_table + (a - g_orc_ip_table);
-	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
+	return orc_a->type == ORC_TYPE_UNDEFINED ? -1 : 1;
 }
 
 static void *sort_orctable(void *arg)
diff --git a/tools/arch/x86/include/asm/orc_types.h b/tools/arch/x86/include/asm/orc_types.h
index b4d4ec78589e..46d7e06763c9 100644
--- a/tools/arch/x86/include/asm/orc_types.h
+++ b/tools/arch/x86/include/asm/orc_types.h
@@ -39,9 +39,11 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
-#define ORC_TYPE_CALL			0
-#define ORC_TYPE_REGS			1
-#define ORC_TYPE_REGS_PARTIAL		2
+#define ORC_TYPE_UNDEFINED		0
+#define ORC_TYPE_END_OF_STACK		1
+#define ORC_TYPE_CALL			2
+#define ORC_TYPE_REGS			3
+#define ORC_TYPE_REGS_PARTIAL		4
 
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>
@@ -60,16 +62,14 @@ struct orc_entry {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	unsigned	sp_reg:4;
 	unsigned	bp_reg:4;
-	unsigned	type:2;
+	unsigned	type:3;
 	unsigned	signal:1;
-	unsigned	end:1;
 #elif defined(__BIG_ENDIAN_BITFIELD)
 	unsigned	bp_reg:4;
 	unsigned	sp_reg:4;
 	unsigned	unused:4;
-	unsigned	end:1;
 	unsigned	signal:1;
-	unsigned	type:2;
+	unsigned	type:3;
 #endif
 } __packed;
 
diff --git a/tools/include/linux/objtool_types.h b/tools/include/linux/objtool_types.h
index 9787ad0f2ef4..453a4f4ef39d 100644
--- a/tools/include/linux/objtool_types.h
+++ b/tools/include/linux/objtool_types.h
@@ -16,12 +16,18 @@ struct unwind_hint {
 	u8		sp_reg;
 	u8		type;
 	u8		signal;
-	u8		end;
 };
 
 #endif /* __ASSEMBLY__ */
 
 /*
+ * UNWIND_HINT_TYPE_UNDEFINED: A blind spot in ORC coverage which can result in
+ * a truncated and unreliable stack unwind.
+ *
+ * UNWIND_HINT_TYPE_END_OF_STACK: The end of the kernel stack unwind before
+ * hitting user entry, boot code, or fork entry (when there are no pt_regs
+ * available).
+ *
  * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
  * (the caller's SP right before it made the call).  Used for all callable
  * functions, i.e. all C code and all callable asm functions.
@@ -32,17 +38,20 @@ struct unwind_hint {
  * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
  * sp_reg+sp_offset points to the iret return frame.
  *
- * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
+ * UNWIND_HINT_TYPE_FUNC: Generate the unwind metadata of a callable function.
  * Useful for code which doesn't have an ELF function annotation.
  *
- * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
+ * UNWIND_HINT_TYPE_{SAVE,RESTORE}: Save the unwind metadata at a certain
+ * location so that it can be restored later.
  */
-#define UNWIND_HINT_TYPE_CALL		0
-#define UNWIND_HINT_TYPE_REGS		1
-#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+#define UNWIND_HINT_TYPE_UNDEFINED	0
+#define UNWIND_HINT_TYPE_END_OF_STACK	1
+#define UNWIND_HINT_TYPE_CALL		2
+#define UNWIND_HINT_TYPE_REGS		3
+#define UNWIND_HINT_TYPE_REGS_PARTIAL	4
 /* The below hint types don't have corresponding ORC types */
-#define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_SAVE		4
-#define UNWIND_HINT_TYPE_RESTORE	5
+#define UNWIND_HINT_TYPE_FUNC		5
+#define UNWIND_HINT_TYPE_SAVE		6
+#define UNWIND_HINT_TYPE_RESTORE	7
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 226c2db3df89..d04711d4b2cd 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2240,6 +2240,7 @@ static void set_func_state(struct cfi_state *state)
 	memcpy(&state->regs, &initial_func_cfi.regs,
 	       CFI_NUM_REGS * sizeof(struct cfi_reg));
 	state->stack_size = initial_func_cfi.cfa.offset;
+	state->type = UNWIND_HINT_TYPE_CALL;
 }
 
 static int read_unwind_hints(struct objtool_file *file)
@@ -2324,7 +2325,6 @@ static int read_unwind_hints(struct objtool_file *file)
 		cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
 		cfi.type = hint->type;
 		cfi.signal = hint->signal;
-		cfi.end = hint->end;
 
 		insn->cfi = cfi_hash_find_or_add(&cfi);
 	}
diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index 97ecbb8b9034..0e183bb1c720 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -38,6 +38,10 @@ static const char *reg_name(unsigned int reg)
 static const char *orc_type_name(unsigned int type)
 {
 	switch (type) {
+	case ORC_TYPE_UNDEFINED:
+		return "(und)";
+	case ORC_TYPE_END_OF_STACK:
+		return "end";
 	case ORC_TYPE_CALL:
 		return "call";
 	case ORC_TYPE_REGS:
@@ -201,6 +205,7 @@ int orc_dump(const char *_objname)
 			printf("%llx:", (unsigned long long)(orc_ip_addr + (i * sizeof(int)) + orc_ip[i]));
 		}
 
+		printf("type:%s", orc_type_name(orc[i].type));
 
 		printf(" sp:");
 
@@ -210,8 +215,7 @@ int orc_dump(const char *_objname)
 
 		print_reg(orc[i].bp_reg, bswap_if_needed(&dummy_elf, orc[i].bp_offset));
 
-		printf(" type:%s signal:%d end:%d\n",
-		       orc_type_name(orc[i].type), orc[i].signal, orc[i].end);
+		printf(" signal:%d\n", orc[i].signal);
 	}
 
 	elf_end(elf);
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index e85bbb996f6c..b327f9ccfe73 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -21,12 +21,22 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 	memset(orc, 0, sizeof(*orc));
 
 	if (!cfi) {
-		orc->end = 0;
-		orc->sp_reg = ORC_REG_UNDEFINED;
+		/*
+		 * This is usually either unreachable nops/traps (which don't
+		 * trigger unreachable instruction warnings), or
+		 * STACK_FRAME_NON_STANDARD functions.
+		 */
+		orc->type = ORC_TYPE_UNDEFINED;
 		return 0;
 	}
 
 	switch (cfi->type) {
+	case UNWIND_HINT_TYPE_UNDEFINED:
+		orc->type = ORC_TYPE_UNDEFINED;
+		return 0;
+	case UNWIND_HINT_TYPE_END_OF_STACK:
+		orc->type = ORC_TYPE_END_OF_STACK;
+		return 0;
 	case UNWIND_HINT_TYPE_CALL:
 		orc->type = ORC_TYPE_CALL;
 		break;
@@ -42,14 +52,8 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 		return -1;
 	}
 
-	orc->end = cfi->end;
 	orc->signal = cfi->signal;
 
-	if (cfi->cfa.base == CFI_UNDEFINED) {
-		orc->sp_reg = ORC_REG_UNDEFINED;
-		return 0;
-	}
-
 	switch (cfi->cfa.base) {
 	case CFI_SP:
 		orc->sp_reg = ORC_REG_SP;
@@ -163,11 +167,7 @@ int orc_create(struct objtool_file *file)
 	struct orc_list_entry *entry;
 	struct list_head orc_list;
 
-	struct orc_entry null = {
-		.sp_reg  = ORC_REG_UNDEFINED,
-		.bp_reg  = ORC_REG_UNDEFINED,
-		.type    = ORC_TYPE_CALL,
-	};
+	struct orc_entry null = { .type = ORC_TYPE_UNDEFINED };
 
 	/* Build a deduplicated list of ORC entries: */
 	INIT_LIST_HEAD(&orc_list);
-- 
2.39.1

Re: [PATCH 6/6] x86,objtool: Split UNWIND_HINT_EMPTY in two

[Steven Rostedt]

On Wed,  1 Mar 2023 07:13:12 -0800
Josh Poimboeuf <jpoimboe@kernel.org> wrote:

> diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
> index 1265ad519249..0387732e9c3f 100644
> --- a/arch/x86/kernel/ftrace_64.S
> +++ b/arch/x86/kernel/ftrace_64.S
> @@ -340,7 +340,7 @@ STACK_FRAME_NON_STANDARD_FP(__fentry__)
>  
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>  SYM_CODE_START(return_to_handler)
> -	UNWIND_HINT_EMPTY
> +	UNWIND_HINT_UNDEFINED
>  	ANNOTATE_NOENDBR
>  	subq  $16, %rsp
>  

Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>

-- Steve

Re: [PATCH 0/6] x86,objtool: Split UNWIND_HINT_EMPTY in two

[Peter Zijlstra]

On Wed, Mar 01, 2023 at 07:13:06AM -0800, Josh Poimboeuf wrote:
> Based on tip/objtool/core.
> 
> Mark reported that the ORC unwinder incorrectly marks an unwind as
> reliable when the unwind terminates prematurely in the dark corners of
> return_to_handler() due to lack of information about the next frame.
> 
> The problem is UNWIND_HINT_EMPTY is used in two different situations:
> end-of-stack marker and undefined stack state.
> 
> Split it up into UNWIND_HINT_END_OF_STACK and UNWIND_HINT_UNDEFINED.
> 
> Josh Poimboeuf (6):
>   objtool: Add objtool_types.h
>   objtool: Use relative pointers for annotations
>   objtool: Change UNWIND_HINT() argument order
>   x86,objtool: Introduce ORC_TYPE_*
>   x86,objtool: Separate unret validation from unwind hints
>   x86,objtool: Split UNWIND_HINT_EMPTY in two

Quite a bit of churn, but the end result does seem cleaner.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>