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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Josh Poimboeuf <jpoimboe@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Borislav Petkov <bp@suse.de>,
        Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Subject: [PATCH 5.18 46/61] objtool: Re-add UNWIND_HINT_{SAVE_RESTORE}
Date:   Tue, 12 Jul 2022 20:39:43 +0200
Message-Id: <20220712183238.788053078@linuxfoundation.org>
In-Reply-To: <20220712183236.931648980@linuxfoundation.org>
References: <20220712183236.931648980@linuxfoundation.org>
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From: Josh Poimboeuf <jpoimboe@kernel.org>

commit 8faea26e611189e933ea2281975ff4dc7c1106b6 upstream.

Commit

  c536ed2fffd5 ("objtool: Remove SAVE/RESTORE hints")

removed the save/restore unwind hints because they were no longer
needed. Now they're going to be needed again so re-add them.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/include/asm/unwind_hints.h   |   12 ++++++++--
 include/linux/objtool.h               |    6 +++--
 tools/include/linux/objtool.h         |    6 +++--
 tools/objtool/check.c                 |   40 ++++++++++++++++++++++++++++++++++
 tools/objtool/include/objtool/check.h |   19 ++++++++--------
 5 files changed, 68 insertions(+), 15 deletions(-)

--- a/arch/x86/include/asm/unwind_hints.h
+++ b/arch/x86/include/asm/unwind_hints.h
@@ -8,11 +8,11 @@
 #ifdef __ASSEMBLY__
 
 .macro UNWIND_HINT_EMPTY
-	UNWIND_HINT sp_reg=ORC_REG_UNDEFINED type=UNWIND_HINT_TYPE_CALL end=1
+	UNWIND_HINT type=UNWIND_HINT_TYPE_CALL end=1
 .endm
 
 .macro UNWIND_HINT_ENTRY
-	UNWIND_HINT sp_reg=ORC_REG_UNDEFINED type=UNWIND_HINT_TYPE_ENTRY end=1
+	UNWIND_HINT type=UNWIND_HINT_TYPE_ENTRY end=1
 .endm
 
 .macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 partial=0
@@ -56,6 +56,14 @@
 	UNWIND_HINT sp_reg=ORC_REG_SP sp_offset=8 type=UNWIND_HINT_TYPE_FUNC
 .endm
 
+.macro UNWIND_HINT_SAVE
+	UNWIND_HINT type=UNWIND_HINT_TYPE_SAVE
+.endm
+
+.macro UNWIND_HINT_RESTORE
+	UNWIND_HINT type=UNWIND_HINT_TYPE_RESTORE
+.endm
+
 #else
 
 #define UNWIND_HINT_FUNC \
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -40,6 +40,8 @@ struct unwind_hint {
 #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_STACK_VALIDATION
 
@@ -125,7 +127,7 @@ struct unwind_hint {
  * the debuginfo as necessary.  It will also warn if it sees any
  * inconsistencies.
  */
-.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 end=0
 .Lunwind_hint_ip_\@:
 	.pushsection .discard.unwind_hints
 		/* struct unwind_hint */
@@ -178,7 +180,7 @@ struct unwind_hint {
 #define ASM_REACHABLE
 #else
 #define ANNOTATE_INTRA_FUNCTION_CALL
-.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 end=0
 .endm
 .macro STACK_FRAME_NON_STANDARD func:req
 .endm
--- a/tools/include/linux/objtool.h
+++ b/tools/include/linux/objtool.h
@@ -40,6 +40,8 @@ struct unwind_hint {
 #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_STACK_VALIDATION
 
@@ -125,7 +127,7 @@ struct unwind_hint {
  * the debuginfo as necessary.  It will also warn if it sees any
  * inconsistencies.
  */
-.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 end=0
 .Lunwind_hint_ip_\@:
 	.pushsection .discard.unwind_hints
 		/* struct unwind_hint */
@@ -178,7 +180,7 @@ struct unwind_hint {
 #define ASM_REACHABLE
 #else
 #define ANNOTATE_INTRA_FUNCTION_CALL
-.macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 end=0
 .endm
 .macro STACK_FRAME_NON_STANDARD func:req
 .endm
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2031,6 +2031,17 @@ static int read_unwind_hints(struct objt
 
 		insn->hint = true;
 
+		if (hint->type == UNWIND_HINT_TYPE_SAVE) {
+			insn->hint = false;
+			insn->save = true;
+			continue;
+		}
+
+		if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
+			insn->restore = true;
+			continue;
+		}
+
 		if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
 			struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
 
@@ -3436,6 +3447,35 @@ static int validate_branch(struct objtoo
 			state.instr += insn->instr;
 
 		if (insn->hint) {
+			if (insn->restore) {
+				struct instruction *save_insn, *i;
+
+				i = insn;
+				save_insn = NULL;
+
+				sym_for_each_insn_continue_reverse(file, func, i) {
+					if (i->save) {
+						save_insn = i;
+						break;
+					}
+				}
+
+				if (!save_insn) {
+					WARN_FUNC("no corresponding CFI save for CFI restore",
+						  sec, insn->offset);
+					return 1;
+				}
+
+				if (!save_insn->visited) {
+					WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
+						  sec, insn->offset);
+					return 1;
+				}
+
+				insn->cfi = save_insn->cfi;
+				nr_cfi_reused++;
+			}
+
 			state.cfi = *insn->cfi;
 		} else {
 			/* XXX track if we actually changed state.cfi */
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -46,18 +46,19 @@ struct instruction {
 	enum insn_type type;
 	unsigned long immediate;
 
-	u8 dead_end	: 1,
-	   ignore	: 1,
-	   ignore_alts	: 1,
-	   hint		: 1,
-	   retpoline_safe : 1,
-	   noendbr	: 1,
-	   entry	: 1;
-		/* 1 bit hole */
+	u16 dead_end		: 1,
+	   ignore		: 1,
+	   ignore_alts		: 1,
+	   hint			: 1,
+	   save			: 1,
+	   restore		: 1,
+	   retpoline_safe	: 1,
+	   noendbr		: 1,
+	   entry		: 1;
+		/* 7 bit hole */
 
 	s8 instr;
 	u8 visited;
-	/* u8 hole */
 
 	struct alt_group *alt_group;
 	struct symbol *call_dest;