Merge tag 'objtool-core-2020-10-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool updates from Ingo Molnar:
 "Most of the changes are cleanups and reorganization to make the
  objtool code more arch-agnostic. This is in preparation for non-x86
  support.

  Other changes:

   - KASAN fixes

   - Handle unreachable trap after call to noreturn functions better

   - Ignore unreachable fake jumps

   - Misc smaller fixes & cleanups"

* tag 'objtool-core-2020-10-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
  perf build: Allow nested externs to enable BUILD_BUG() usage
  objtool: Allow nested externs to enable BUILD_BUG()
  objtool: Permit __kasan_check_{read,write} under UACCESS
  objtool: Ignore unreachable trap after call to noreturn functions
  objtool: Handle calling non-function symbols in other sections
  objtool: Ignore unreachable fake jumps
  objtool: Remove useless tests before save_reg()
  objtool: Decode unwind hint register depending on architecture
  objtool: Make unwind hint definitions available to other architectures
  objtool: Only include valid definitions depending on source file type
  objtool: Rename frame.h -> objtool.h
  objtool: Refactor jump table code to support other architectures
  objtool: Make relocation in alternative handling arch dependent
  objtool: Abstract alternative special case handling
  objtool: Move macros describing structures to arch-dependent code
  objtool: Make sync-check consider the target architecture
  objtool: Group headers to check in a single list
  objtool: Define 'struct orc_entry' only when needed
  objtool: Skip ORC entry creation for non-text sections
  objtool: Move ORC logic out of check()
  ...

1 files changed, 51 insertions, 179 deletions

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 326ac390168b..c6ab44543c92 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -14,21 +14,19 @@
 #include "warn.h"
 #include "arch_elf.h"
 
+#include <linux/objtool.h>
 #include <linux/hashtable.h>
 #include <linux/kernel.h>
 #include <linux/static_call_types.h>
 
 #define FAKE_JUMP_OFFSET -1
 
-#define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
-
 struct alternative {
 	struct list_head list;
 	struct instruction *insn;
 	bool skip_orig;
 };
 
-const char *objname;
 struct cfi_init_state initial_func_cfi;
 
 struct instruction *find_insn(struct objtool_file *file,
@@ -111,12 +109,6 @@ static struct instruction *prev_insn_same_sym(struct objtool_file *file,
 	for (insn = next_insn_same_sec(file, insn); insn;		\
 	     insn = next_insn_same_sec(file, insn))
 
-static bool is_static_jump(struct instruction *insn)
-{
-	return insn->type == INSN_JUMP_CONDITIONAL ||
-	       insn->type == INSN_JUMP_UNCONDITIONAL;
-}
-
 static bool is_sibling_call(struct instruction *insn)
 {
 	/* An indirect jump is either a sibling call or a jump to a table. */
@@ -591,6 +583,8 @@ static const char *uaccess_safe_builtin[] = {
 	"__asan_store4_noabort",
 	"__asan_store8_noabort",
 	"__asan_store16_noabort",
+	"__kasan_check_read",
+	"__kasan_check_write",
 	/* KASAN in-line */
 	"__asan_report_load_n_noabort",
 	"__asan_report_load1_noabort",
@@ -879,6 +873,17 @@ static void remove_insn_ops(struct instruction *insn)
 	}
 }
 
+static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
+{
+	struct symbol *call_dest;
+
+	call_dest = find_func_by_offset(sec, offset);
+	if (!call_dest)
+		call_dest = find_symbol_by_offset(sec, offset);
+
+	return call_dest;
+}
+
 /*
  * Find the destination instructions for all calls.
  */
@@ -896,9 +901,7 @@ static int add_call_destinations(struct objtool_file *file)
 					       insn->offset, insn->len);
 		if (!reloc) {
 			dest_off = arch_jump_destination(insn);
-			insn->call_dest = find_func_by_offset(insn->sec, dest_off);
-			if (!insn->call_dest)
-				insn->call_dest = find_symbol_by_offset(insn->sec, dest_off);
+			insn->call_dest = find_call_destination(insn->sec, dest_off);
 
 			if (insn->ignore)
 				continue;
@@ -916,8 +919,8 @@ static int add_call_destinations(struct objtool_file *file)
 
 		} else if (reloc->sym->type == STT_SECTION) {
 			dest_off = arch_dest_reloc_offset(reloc->addend);
-			insn->call_dest = find_func_by_offset(reloc->sym->sec,
-							      dest_off);
+			insn->call_dest = find_call_destination(reloc->sym->sec,
+								dest_off);
 			if (!insn->call_dest) {
 				WARN_FUNC("can't find call dest symbol at %s+0x%lx",
 					  insn->sec, insn->offset,
@@ -1029,6 +1032,8 @@ static int handle_group_alt(struct objtool_file *file,
 	alt_group = alt_group_next_index++;
 	insn = *new_insn;
 	sec_for_each_insn_from(file, insn) {
+		struct reloc *alt_reloc;
+
 		if (insn->offset >= special_alt->new_off + special_alt->new_len)
 			break;
 
@@ -1045,14 +1050,11 @@ static int handle_group_alt(struct objtool_file *file,
 		 * .altinstr_replacement section, unless the arch's
 		 * alternatives code can adjust the relative offsets
 		 * accordingly.
-		 *
-		 * The x86 alternatives code adjusts the offsets only when it
-		 * encounters a branch instruction at the very beginning of the
-		 * replacement group.
 		 */
-		if ((insn->offset != special_alt->new_off ||
-		    (insn->type != INSN_CALL && !is_static_jump(insn))) &&
-		    find_reloc_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {
+		alt_reloc = find_reloc_by_dest_range(file->elf, insn->sec,
+						   insn->offset, insn->len);
+		if (alt_reloc &&
+		    !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
 
 			WARN_FUNC("unsupported relocation in alternatives section",
 				  insn->sec, insn->offset);
@@ -1254,56 +1256,15 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 }
 
 /*
- * find_jump_table() - Given a dynamic jump, find the switch jump table in
- * .rodata associated with it.
- *
- * There are 3 basic patterns:
- *
- * 1. jmpq *[rodata addr](,%reg,8)
- *
- *    This is the most common case by far.  It jumps to an address in a simple
- *    jump table which is stored in .rodata.
- *
- * 2. jmpq *[rodata addr](%rip)
- *
- *    This is caused by a rare GCC quirk, currently only seen in three driver
- *    functions in the kernel, only with certain obscure non-distro configs.
- *
- *    As part of an optimization, GCC makes a copy of an existing switch jump
- *    table, modifies it, and then hard-codes the jump (albeit with an indirect
- *    jump) to use a single entry in the table.  The rest of the jump table and
- *    some of its jump targets remain as dead code.
- *
- *    In such a case we can just crudely ignore all unreachable instruction
- *    warnings for the entire object file.  Ideally we would just ignore them
- *    for the function, but that would require redesigning the code quite a
- *    bit.  And honestly that's just not worth doing: unreachable instruction
- *    warnings are of questionable value anyway, and this is such a rare issue.
- *
- * 3. mov [rodata addr],%reg1
- *    ... some instructions ...
- *    jmpq *(%reg1,%reg2,8)
- *
- *    This is a fairly uncommon pattern which is new for GCC 6.  As of this
- *    writing, there are 11 occurrences of it in the allmodconfig kernel.
- *
- *    As of GCC 7 there are quite a few more of these and the 'in between' code
- *    is significant. Esp. with KASAN enabled some of the code between the mov
- *    and jmpq uses .rodata itself, which can confuse things.
- *
- *    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.
+ * find_jump_table() - Given a dynamic jump, find the switch jump table
+ * associated with it.
  */
 static struct reloc *find_jump_table(struct objtool_file *file,
 				      struct symbol *func,
 				      struct instruction *insn)
 {
-	struct reloc *text_reloc, *table_reloc;
+	struct reloc *table_reloc;
 	struct instruction *dest_insn, *orig_insn = insn;
-	struct section *table_sec;
-	unsigned long table_offset;
 
 	/*
 	 * Backward search using the @first_jump_src links, these help avoid
@@ -1324,52 +1285,13 @@ static struct reloc *find_jump_table(struct objtool_file *file,
 		     insn->jump_dest->offset > orig_insn->offset))
 		    break;
 
-		/* 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 ||
-		    !text_reloc->sym->sec->rodata)
-			continue;
-
-		table_offset = text_reloc->addend;
-		table_sec = text_reloc->sym->sec;
-
-		if (text_reloc->type == R_X86_64_PC32)
-			table_offset += 4;
-
-		/*
-		 * Make sure the .rodata address isn't associated with a
-		 * symbol.  GCC jump tables are anonymous data.
-		 *
-		 * Also support C jump tables which are in the same format as
-		 * switch jump tables.  For objtool to recognize them, they
-		 * need to be placed in the C_JUMP_TABLE_SECTION section.  They
-		 * have symbols associated with them.
-		 */
-		if (find_symbol_containing(table_sec, table_offset) &&
-		    strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
-			continue;
-
-		/*
-		 * Each table entry has a reloc associated with it.  The reloc
-		 * should reference text in the same function as the original
-		 * instruction.
-		 */
-		table_reloc = find_reloc_by_dest(file->elf, table_sec, table_offset);
+		table_reloc = arch_find_switch_table(file, insn);
 		if (!table_reloc)
 			continue;
 		dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
 		if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
 			continue;
 
-		/*
-		 * Use of RIP-relative switch jumps is quite rare, and
-		 * indicates a rare GCC quirk/bug which can leave dead code
-		 * behind.
-		 */
-		if (text_reloc->type == R_X86_64_PC32)
-			file->ignore_unreachables = true;
-
 		return table_reloc;
 	}
 
@@ -1512,32 +1434,7 @@ static int read_unwind_hints(struct objtool_file *file)
 
 		insn->hint = true;
 
-		switch (hint->sp_reg) {
-		case ORC_REG_UNDEFINED:
-			cfa->base = CFI_UNDEFINED;
-			break;
-		case ORC_REG_SP:
-			cfa->base = CFI_SP;
-			break;
-		case ORC_REG_BP:
-			cfa->base = CFI_BP;
-			break;
-		case ORC_REG_SP_INDIRECT:
-			cfa->base = CFI_SP_INDIRECT;
-			break;
-		case ORC_REG_R10:
-			cfa->base = CFI_R10;
-			break;
-		case ORC_REG_R13:
-			cfa->base = CFI_R13;
-			break;
-		case ORC_REG_DI:
-			cfa->base = CFI_DI;
-			break;
-		case ORC_REG_DX:
-			cfa->base = CFI_DX;
-			break;
-		default:
+		if (arch_decode_hint_reg(insn, hint->sp_reg)) {
 			WARN_FUNC("unsupported unwind_hint sp base reg %d",
 				  insn->sec, insn->offset, hint->sp_reg);
 			return -1;
@@ -1951,7 +1848,8 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
 		return 0;
 	}
 
-	if (cfi->type == ORC_TYPE_REGS || cfi->type == ORC_TYPE_REGS_IRET)
+	if (cfi->type == UNWIND_HINT_TYPE_REGS ||
+	    cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
 		return update_cfi_state_regs(insn, cfi, op);
 
 	switch (op->dest.type) {
@@ -2199,7 +2097,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
 				/* drap: push %rbp */
 				cfi->stack_size = 0;
 
-			} else if (regs[op->src.reg].base == CFI_UNDEFINED) {
+			} else {
 
 				/* drap: push %reg */
 				save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
@@ -2228,9 +2126,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
 
 				/* save drap offset so we know when to restore it */
 				cfi->drap_offset = op->dest.offset;
-			}
-
-			else if (regs[op->src.reg].base == CFI_UNDEFINED) {
+			} else {
 
 				/* drap: mov reg, disp(%rbp) */
 				save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
@@ -2800,9 +2696,10 @@ static bool is_ubsan_insn(struct instruction *insn)
 			"__ubsan_handle_builtin_unreachable"));
 }
 
-static bool ignore_unreachable_insn(struct instruction *insn)
+static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
 {
 	int i;
+	struct instruction *prev_insn;
 
 	if (insn->ignore || insn->type == INSN_NOP)
 		return true;
@@ -2819,6 +2716,9 @@ static bool ignore_unreachable_insn(struct instruction *insn)
 	    !strcmp(insn->sec->name, ".altinstr_aux"))
 		return true;
 
+	if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->offset == FAKE_JUMP_OFFSET)
+		return true;
+
 	if (!insn->func)
 		return false;
 
@@ -2827,8 +2727,11 @@ static bool ignore_unreachable_insn(struct instruction *insn)
 	 * __builtin_unreachable().  The BUG() macro has an unreachable() after
 	 * the UD2, which causes GCC's undefined trap logic to emit another UD2
 	 * (or occasionally a JMP to UD2).
+	 *
+	 * It may also insert a UD2 after calling a __noreturn function.
 	 */
-	if (list_prev_entry(insn, list)->dead_end &&
+	prev_insn = list_prev_entry(insn, list);
+	if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
 	    (insn->type == INSN_BUG ||
 	     (insn->type == INSN_JUMP_UNCONDITIONAL &&
 	      insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
@@ -2955,7 +2858,7 @@ static int validate_reachable_instructions(struct objtool_file *file)
 		return 0;
 
 	for_each_insn(file, insn) {
-		if (insn->visited || ignore_unreachable_insn(insn))
+		if (insn->visited || ignore_unreachable_insn(file, insn))
 			continue;
 
 		WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
@@ -2965,37 +2868,22 @@ static int validate_reachable_instructions(struct objtool_file *file)
 	return 0;
 }
 
-static struct objtool_file file;
-
-int check(const char *_objname, bool orc)
+int check(struct objtool_file *file)
 {
 	int ret, warnings = 0;
 
-	objname = _objname;
-
-	file.elf = elf_open_read(objname, O_RDWR);
-	if (!file.elf)
-		return 1;
-
-	INIT_LIST_HEAD(&file.insn_list);
-	hash_init(file.insn_hash);
-	INIT_LIST_HEAD(&file.static_call_list);
-	file.c_file = !vmlinux && find_section_by_name(file.elf, ".comment");
-	file.ignore_unreachables = no_unreachable;
-	file.hints = false;
-
 	arch_initial_func_cfi_state(&initial_func_cfi);
 
-	ret = decode_sections(&file);
+	ret = decode_sections(file);
 	if (ret < 0)
 		goto out;
 	warnings += ret;
 
-	if (list_empty(&file.insn_list))
+	if (list_empty(&file->insn_list))
 		goto out;
 
 	if (vmlinux && !validate_dup) {
-		ret = validate_vmlinux_functions(&file);
+		ret = validate_vmlinux_functions(file);
 		if (ret < 0)
 			goto out;
 
@@ -3004,50 +2892,34 @@ int check(const char *_objname, bool orc)
 	}
 
 	if (retpoline) {
-		ret = validate_retpoline(&file);
+		ret = validate_retpoline(file);
 		if (ret < 0)
 			return ret;
 		warnings += ret;
 	}
 
-	ret = validate_functions(&file);
+	ret = validate_functions(file);
 	if (ret < 0)
 		goto out;
 	warnings += ret;
 
-	ret = validate_unwind_hints(&file, NULL);
+	ret = validate_unwind_hints(file, NULL);
 	if (ret < 0)
 		goto out;
 	warnings += ret;
 
 	if (!warnings) {
-		ret = validate_reachable_instructions(&file);
+		ret = validate_reachable_instructions(file);
 		if (ret < 0)
 			goto out;
 		warnings += ret;
 	}
 
-	ret = create_static_call_sections(&file);
+	ret = create_static_call_sections(file);
 	if (ret < 0)
 		goto out;
 	warnings += ret;
 
-	if (orc) {
-		ret = create_orc(&file);
-		if (ret < 0)
-			goto out;
-
-		ret = create_orc_sections(&file);
-		if (ret < 0)
-			goto out;
-	}
-
-	if (file.elf->changed) {
-		ret = elf_write(file.elf);
-		if (ret < 0)
-			goto out;
-	}
-
 out:
 	if (ret < 0) {
 		/*