[PATCH v3 4/8] objtool: Move jump table heuristics to a x86 specific source file

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@xxxxxxxxxx>

In preparation for implementing support for the use of compiler emitted
jump table annotations, move the existing code out of the generic
sources. This will permit a clean separation between the two approaches,
where the old one will not be wired up for architectures other than x86.

Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 tools/objtool/arch/loongarch/special.c  |   7 --
 tools/objtool/arch/powerpc/special.c    |   7 --
 tools/objtool/arch/x86/special.c        | 114 +++++++++++++++++++-
 tools/objtool/check.c                   | 112 +------------------
 tools/objtool/include/objtool/special.h |   9 +-
 5 files changed, 122 insertions(+), 127 deletions(-)

diff --git a/tools/objtool/arch/loongarch/special.c b/tools/objtool/arch/loongarch/special.c
index 87230ed570fd..acf3a391a2f9 100644
--- a/tools/objtool/arch/loongarch/special.c
+++ b/tools/objtool/arch/loongarch/special.c
@@ -7,10 +7,3 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
 {
 	return false;
 }
-
-struct reloc *arch_find_switch_table(struct objtool_file *file,
-				     struct instruction *insn,
-				     unsigned long *table_size)
-{
-	return NULL;
-}
diff --git a/tools/objtool/arch/powerpc/special.c b/tools/objtool/arch/powerpc/special.c
index 51610689abf7..3a108437cfa6 100644
--- a/tools/objtool/arch/powerpc/special.c
+++ b/tools/objtool/arch/powerpc/special.c
@@ -11,10 +11,3 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
 {
 	exit(-1);
 }
-
-struct reloc *arch_find_switch_table(struct objtool_file *file,
-				     struct instruction *insn,
-				     unsigned long *table_size)
-{
-	exit(-1);
-}
diff --git a/tools/objtool/arch/x86/special.c b/tools/objtool/arch/x86/special.c
index f8fb67636384..cd964b85e2b1 100644
--- a/tools/objtool/arch/x86/special.c
+++ b/tools/objtool/arch/x86/special.c
@@ -108,9 +108,9 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
  *
  *    NOTE: MITIGATION_RETPOLINE made it harder still to decode dynamic jumps.
  */
-struct reloc *arch_find_switch_table(struct objtool_file *file,
-				     struct instruction *insn,
-				     unsigned long *table_size)
+static struct reloc *find_switch_table(struct objtool_file *file,
+				       struct instruction *insn,
+				       unsigned long *table_size)
 {
 	struct reloc  *text_reloc, *rodata_reloc;
 	struct section *table_sec;
@@ -154,3 +154,111 @@ struct reloc *arch_find_switch_table(struct objtool_file *file,
 	*table_size = 0;
 	return rodata_reloc;
 }
+
+/*
+ * find_jump_table() - Given a dynamic jump, find the switch jump table
+ * associated with it.
+ */
+static void find_jump_table(struct objtool_file *file,
+			    struct symbol *func,
+			    struct instruction *insn)
+{
+	struct reloc *table_reloc;
+	struct instruction *dest_insn, *orig_insn = insn;
+	unsigned long table_size;
+
+	/*
+	 * Backward search using the @first_jump_src links, these help avoid
+	 * much of the 'in between' code. Which avoids us getting confused by
+	 * it.
+	 */
+	for (;
+	     insn && insn_func(insn) && insn_func(insn)->pfunc == func;
+	     insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
+
+		if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
+			break;
+
+		/* allow small jumps within the range */
+		if (insn->type == INSN_JUMP_UNCONDITIONAL &&
+		    insn->jump_dest &&
+		    (insn->jump_dest->offset <= insn->offset ||
+		     insn->jump_dest->offset > orig_insn->offset))
+		    break;
+
+		table_reloc = find_switch_table(file, insn, &table_size);
+		if (!table_reloc)
+			continue;
+		dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
+		if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
+			continue;
+
+		orig_insn->_jump_table = table_reloc;
+		orig_insn->_jump_table_size = table_size;
+		break;
+	}
+}
+
+/*
+ * First pass: Mark the head of each jump table so that in the next pass,
+ * we know when a given jump table ends and the next one starts.
+ */
+static void mark_func_jump_tables(struct objtool_file *file,
+				    struct symbol *func)
+{
+	struct instruction *insn, *last = NULL;
+
+	func_for_each_insn(file, func, insn) {
+		if (!last)
+			last = insn;
+
+		/*
+		 * Store back-pointers for unconditional forward jumps such
+		 * that find_jump_table() can back-track using those and
+		 * avoid some potentially confusing code.
+		 */
+		if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
+		    insn->offset > last->offset &&
+		    insn->jump_dest->offset > insn->offset &&
+		    !insn->jump_dest->first_jump_src) {
+
+			insn->jump_dest->first_jump_src = insn;
+			last = insn->jump_dest;
+		}
+
+		if (insn->type == INSN_JUMP_DYNAMIC)
+			find_jump_table(file, func, insn);
+	}
+}
+
+int add_func_jump_tables(struct objtool_file *file,
+			 struct symbol *func)
+{
+	struct instruction *insn, *insn_t1 = NULL, *insn_t2;
+	int ret = 0;
+
+	mark_func_jump_tables(file, func);
+
+	func_for_each_insn(file, func, insn) {
+		if (!insn_jump_table(insn))
+			continue;
+
+		if (!insn_t1) {
+			insn_t1 = insn;
+			continue;
+		}
+
+		insn_t2 = insn;
+
+		ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
+		if (ret)
+			return ret;
+
+		insn_t1 = insn_t2;
+	}
+
+	if (insn_t1)
+		ret = add_jump_table(file, insn_t1, NULL);
+
+	return ret;
+}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index fbb05e973acc..389475dde47c 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2091,8 +2091,8 @@ static int add_special_section_alts(struct objtool_file *file)
 	return ret;
 }
 
-static int add_jump_table(struct objtool_file *file, struct instruction *insn,
-			  struct reloc *next_table)
+int add_jump_table(struct objtool_file *file, struct instruction *insn,
+		   struct reloc *next_table)
 {
 	unsigned long table_size = insn_jump_table_size(insn);
 	struct symbol *pfunc = insn_func(insn)->pfunc;
@@ -2169,111 +2169,10 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 	return 0;
 }
 
-/*
- * find_jump_table() - Given a dynamic jump, find the switch jump table
- * associated with it.
- */
-static void find_jump_table(struct objtool_file *file, struct symbol *func,
-			    struct instruction *insn)
+int __weak add_func_jump_tables(struct objtool_file *file,
+				struct symbol *func)
 {
-	struct reloc *table_reloc;
-	struct instruction *dest_insn, *orig_insn = insn;
-	unsigned long table_size;
-
-	/*
-	 * Backward search using the @first_jump_src links, these help avoid
-	 * much of the 'in between' code. Which avoids us getting confused by
-	 * it.
-	 */
-	for (;
-	     insn && insn_func(insn) && insn_func(insn)->pfunc == func;
-	     insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
-
-		if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
-			break;
-
-		/* allow small jumps within the range */
-		if (insn->type == INSN_JUMP_UNCONDITIONAL &&
-		    insn->jump_dest &&
-		    (insn->jump_dest->offset <= insn->offset ||
-		     insn->jump_dest->offset > orig_insn->offset))
-		    break;
-
-		table_reloc = arch_find_switch_table(file, insn, &table_size);
-		if (!table_reloc)
-			continue;
-		dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
-		if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
-			continue;
-
-		orig_insn->_jump_table = table_reloc;
-		orig_insn->_jump_table_size = table_size;
-		break;
-	}
-}
-
-/*
- * First pass: Mark the head of each jump table so that in the next pass,
- * we know when a given jump table ends and the next one starts.
- */
-static void mark_func_jump_tables(struct objtool_file *file,
-				    struct symbol *func)
-{
-	struct instruction *insn, *last = NULL;
-
-	func_for_each_insn(file, func, insn) {
-		if (!last)
-			last = insn;
-
-		/*
-		 * Store back-pointers for unconditional forward jumps such
-		 * that find_jump_table() can back-track using those and
-		 * avoid some potentially confusing code.
-		 */
-		if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
-		    insn->offset > last->offset &&
-		    insn->jump_dest->offset > insn->offset &&
-		    !insn->jump_dest->first_jump_src) {
-
-			insn->jump_dest->first_jump_src = insn;
-			last = insn->jump_dest;
-		}
-
-		if (insn->type != INSN_JUMP_DYNAMIC)
-			continue;
-
-		find_jump_table(file, func, insn);
-	}
-}
-
-static int add_func_jump_tables(struct objtool_file *file,
-				  struct symbol *func)
-{
-	struct instruction *insn, *insn_t1 = NULL, *insn_t2;
-	int ret = 0;
-
-	func_for_each_insn(file, func, insn) {
-		if (!insn_jump_table(insn))
-			continue;
-
-		if (!insn_t1) {
-			insn_t1 = insn;
-			continue;
-		}
-
-		insn_t2 = insn;
-
-		ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
-		if (ret)
-			return ret;
-
-		insn_t1 = insn_t2;
-	}
-
-	if (insn_t1)
-		ret = add_jump_table(file, insn_t1, NULL);
-
-	return ret;
+	return 0;
 }
 
 /*
@@ -2293,7 +2192,6 @@ static int add_jump_table_alts(struct objtool_file *file)
 		if (func->type != STT_FUNC)
 			continue;
 
-		mark_func_jump_tables(file, func);
 		ret = add_func_jump_tables(file, func);
 		if (ret)
 			return ret;
diff --git a/tools/objtool/include/objtool/special.h b/tools/objtool/include/objtool/special.h
index e7ee7ffccefd..019b511eca6e 100644
--- a/tools/objtool/include/objtool/special.h
+++ b/tools/objtool/include/objtool/special.h
@@ -37,7 +37,10 @@ void arch_handle_alternative(unsigned short feature, struct special_alt *alt);
 bool arch_support_alt_relocation(struct special_alt *special_alt,
 				 struct instruction *insn,
 				 struct reloc *reloc);
-struct reloc *arch_find_switch_table(struct objtool_file *file,
-				     struct instruction *insn,
-				     unsigned long *table_size);
+
+int add_func_jump_tables(struct objtool_file *file, struct symbol *func);
+
+int add_jump_table(struct objtool_file *file, struct instruction *insn,
+		   struct reloc *next_table);
+
 #endif /* _SPECIAL_H */
-- 
2.47.0.rc1.288.g06298d1525-goog