Commit b490f453 authored by Miroslav Benes's avatar Miroslav Benes Committed by Peter Zijlstra
Browse files

objtool: Move the IRET hack into the arch decoder 



Quoting Julien:

  "And the other suggestion is my other email was that you don't even
  need to add INSN_EXCEPTION_RETURN. You can keep IRET as
  INSN_CONTEXT_SWITCH by default and x86 decoder lookups the symbol
  conaining an iret. If it's a function symbol, it can just set the type
  to INSN_OTHER so that it caries on to the next instruction after
  having handled the stack_op."

Suggested-by: default avatarJulien Thierry <jthierry@redhat.com>
Signed-off-by: default avatarMiroslav Benes <mbenes@suse.cz>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200428191659.913283807@infradead.org
parent b09fb65e

tools/objtool/arch.h

+0 −1
Original line number Diff line number Diff line
@@ -19,7 +19,6 @@ enum insn_type { 
	INSN_CALL,

	INSN_CALL_DYNAMIC,

	INSN_RETURN,

	INSN_EXCEPTION_RETURN,

	INSN_CONTEXT_SWITCH,

	INSN_BUG,

	INSN_NOP,

tools/objtool/arch/x86/decode.c

+18 −10
Original line number Diff line number Diff line
@@ -94,6 +94,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec, 
		      rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0,

		      modrm_reg = 0, sib = 0;

	struct stack_op *op = NULL;

	struct symbol *sym;



	x86_64 = is_x86_64(elf);

	if (x86_64 == -1)
@@ -469,8 +470,12 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec, 
		break;



	case 0xcf: /* iret */

		*type = INSN_EXCEPTION_RETURN;



		/*

		 * Handle sync_core(), which has an IRET to self.

		 * All other IRET are in STT_NONE entry code.

		 */

		sym = find_symbol_containing(sec, offset);

		if (sym && sym->type == STT_FUNC) {

			ADD_OP(op) {

				/* add $40, %rsp */

				op->src.type = OP_SRC_ADD;
@@ -480,6 +485,9 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec, 
				op->dest.reg = CFI_SP;

			}

			break;

		}



		/* fallthrough */



	case 0xca: /* retf */

	case 0xcb: /* retf */

tools/objtool/check.c

+0 −11
Original line number Diff line number Diff line
@@ -2320,17 +2320,6 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, 


			break;



		case INSN_EXCEPTION_RETURN:

			/*

			 * This handles x86's sync_core() case, where we use an

			 * IRET to self. All 'normal' IRET instructions are in

			 * STT_NOTYPE entry symbols.

			 */

			if (func)

				break;



			return 0;



		case INSN_CONTEXT_SWITCH:

			if (func && (!next_insn || !next_insn->hint)) {

				WARN_FUNC("unsupported instruction in callable function",

tools/objtool/elf.c

+2 −2
Original line number Diff line number Diff line
@@ -61,7 +61,7 @@ static void rb_add(struct rb_root *tree, struct rb_node *node, 
	rb_insert_color(node, tree);

}



static struct rb_node *rb_find_first(struct rb_root *tree, const void *key,

static struct rb_node *rb_find_first(const struct rb_root *tree, const void *key,

			       int (*cmp)(const void *key, const struct rb_node *))

{

	struct rb_node *node = tree->rb_node;
@@ -189,7 +189,7 @@ struct symbol *find_func_by_offset(struct section *sec, unsigned long offset) 
	return NULL;

}



struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)

struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset)

{

	struct rb_node *node;

tools/objtool/elf.h

+1 −1
Original line number Diff line number Diff line
@@ -124,7 +124,7 @@ struct section *find_section_by_name(const struct elf *elf, const char *name); 
struct symbol *find_func_by_offset(struct section *sec, unsigned long offset);

struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);

struct symbol *find_symbol_by_name(const struct elf *elf, const char *name);

struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);

struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset);

struct rela *find_rela_by_dest(const struct elf *elf, struct section *sec, unsigned long offset);

struct rela *find_rela_by_dest_range(const struct elf *elf, struct section *sec,

				     unsigned long offset, unsigned int len);

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