1 files changed, 41 insertions, 34 deletions

diff --git a/tools/objtool/arch/x86/special.c b/tools/objtool/arch/x86/special.c
index 29e949579ede..e817a3fff449 100644
--- a/tools/objtool/arch/x86/special.c
+++ b/tools/objtool/arch/x86/special.c
@@ -3,39 +3,36 @@
 
 #include <objtool/special.h>
 #include <objtool/builtin.h>
+#include <objtool/warn.h>
+#include <asm/cpufeatures.h>
 
-#define X86_FEATURE_POPCNT (4 * 32 + 23)
-#define X86_FEATURE_SMAP   (9 * 32 + 20)
+/* cpu feature name array generated from cpufeatures.h */
+#include "cpu-feature-names.c"
 
-void arch_handle_alternative(unsigned short feature, struct special_alt *alt)
+void arch_handle_alternative(struct special_alt *alt)
 {
-	switch (feature) {
-	case X86_FEATURE_SMAP:
-		/*
-		 * If UACCESS validation is enabled; force that alternative;
-		 * otherwise force it the other way.
-		 *
-		 * What we want to avoid is having both the original and the
-		 * alternative code flow at the same time, in that case we can
-		 * find paths that see the STAC but take the NOP instead of
-		 * CLAC and the other way around.
-		 */
-		if (opts.uaccess)
-			alt->skip_orig = true;
-		else
-			alt->skip_alt = true;
-		break;
-	case X86_FEATURE_POPCNT:
-		/*
-		 * It has been requested that we don't validate the !POPCNT
-		 * feature path which is a "very very small percentage of
-		 * machines".
-		 */
-		alt->skip_orig = true;
-		break;
-	default:
-		break;
-	}
+	static struct special_alt *group, *prev;
+
+	/*
+	 * Recompute orig_len for nested ALTERNATIVE()s.
+	 */
+	if (group && group->orig_sec == alt->orig_sec &&
+	             group->orig_off == alt->orig_off) {
+
+		struct special_alt *iter = group;
+		for (;;) {
+			unsigned int len = max(iter->orig_len, alt->orig_len);
+			iter->orig_len = alt->orig_len = len;
+
+			if (iter == prev)
+				break;
+
+			iter = list_next_entry(iter, list);
+		}
+
+	} else group = alt;
+
+	prev = alt;
 }
 
 bool arch_support_alt_relocation(struct special_alt *special_alt,
@@ -83,10 +80,11 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
  *    TODO: Once we have DWARF CFI and smarter instruction decoding logic,
  *    ensure the same register is used in the mov and jump instructions.
  *
- *    NOTE: RETPOLINE made it harder still to decode dynamic jumps.
+ *    NOTE: MITIGATION_RETPOLINE made it harder still to decode dynamic jumps.
  */
 struct reloc *arch_find_switch_table(struct objtool_file *file,
-				    struct instruction *insn)
+				     struct instruction *insn,
+				     unsigned long *table_size)
 {
 	struct reloc  *text_reloc, *rodata_reloc;
 	struct section *table_sec;
@@ -95,7 +93,7 @@ struct reloc *arch_find_switch_table(struct objtool_file *file,
 	/* look for a relocation which references .rodata */
 	text_reloc = find_reloc_by_dest_range(file->elf, insn->sec,
 					      insn->offset, insn->len);
-	if (!text_reloc || text_reloc->sym->type != STT_SECTION ||
+	if (!text_reloc || !is_sec_sym(text_reloc->sym) ||
 	    !text_reloc->sym->sec->rodata)
 		return NULL;
 
@@ -132,8 +130,17 @@ struct reloc *arch_find_switch_table(struct objtool_file *file,
 	 * indicates a rare GCC quirk/bug which can leave dead
 	 * code behind.
 	 */
-	if (reloc_type(text_reloc) == R_X86_64_PC32)
+	if (!file->ignore_unreachables && reloc_type(text_reloc) == R_X86_64_PC32) {
+		WARN_INSN(insn, "ignoring unreachables due to jump table quirk");
 		file->ignore_unreachables = true;
+	}
 
+	*table_size = 0;
 	return rodata_reloc;
 }
+
+const char *arch_cpu_feature_name(int feature_number)
+{
+	return (feature_number < ARRAY_SIZE(cpu_feature_names)) ?
+		cpu_feature_names[feature_number] : NULL;
+}