Commit 65ea47dc authored by Julien Thierry's avatar Julien Thierry Committed by Ingo Molnar
Browse files

objtool: Support multiple stack_op per instruction 



Instruction sets can include more or less complex operations which might
not fit the currently defined set of stack_ops.

Combining more than one stack_op provides more flexibility to describe
the behaviour of an instruction. This also reduces the need to define
new stack_ops specific to a single instruction set.

Allow instruction decoders to generate multiple stack_op per
instruction.

Signed-off-by: default avatarJulien Thierry <jthierry@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Reviewed-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200327152847.15294-11-jthierry@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1ee44470

tools/objtool/arch.h

+3 −1
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ struct op_src { 
struct stack_op {

	struct op_dest dest;

	struct op_src src;

	struct list_head list;

};



struct instruction;
@@ -73,7 +74,8 @@ void arch_initial_func_cfi_state(struct cfi_state *state); 
int arch_decode_instruction(struct elf *elf, struct section *sec,

			    unsigned long offset, unsigned int maxlen,

			    unsigned int *len, enum insn_type *type,

			    unsigned long *immediate, struct stack_op *op);

			    unsigned long *immediate,

			    struct list_head *ops_list);



bool arch_callee_saved_reg(unsigned char reg);

tools/objtool/arch/x86/decode.c

+12 −1
Original line number Diff line number Diff line
@@ -80,13 +80,15 @@ unsigned long arch_jump_destination(struct instruction *insn) 
int arch_decode_instruction(struct elf *elf, struct section *sec,

			    unsigned long offset, unsigned int maxlen,

			    unsigned int *len, enum insn_type *type,

			    unsigned long *immediate, struct stack_op *op)

			    unsigned long *immediate,

			    struct list_head *ops_list)

{

	struct insn insn;

	int x86_64, sign;

	unsigned char op1, op2, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0,

		      rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0,

		      modrm_reg = 0, sib = 0;

	struct stack_op *op;



	x86_64 = is_x86_64(elf);

	if (x86_64 == -1)
@@ -127,6 +129,10 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, 
	if (insn.sib.nbytes)

		sib = insn.sib.bytes[0];



	op = calloc(1, sizeof(*op));

	if (!op)

		return -1;



	switch (op1) {



	case 0x1:
@@ -488,6 +494,11 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, 


	*immediate = insn.immediate.nbytes ? insn.immediate.value : 0;



	if (*type == INSN_STACK)

		list_add_tail(&op->list, ops_list);

	else

		free(op);



	return 0;

}

tools/objtool/check.c

+46 −28
Original line number Diff line number Diff line
@@ -260,6 +260,7 @@ static int decode_instructions(struct objtool_file *file) 
			}

			memset(insn, 0, sizeof(*insn));

			INIT_LIST_HEAD(&insn->alts);

			INIT_LIST_HEAD(&insn->stack_ops);

			clear_insn_state(&insn->state);



			insn->sec = sec;
@@ -269,7 +270,7 @@ static int decode_instructions(struct objtool_file *file) 
						      sec->len - offset,

						      &insn->len, &insn->type,

						      &insn->immediate,

						      &insn->stack_op);

						      &insn->stack_ops);

			if (ret)

				goto err;
@@ -754,6 +755,7 @@ static int handle_group_alt(struct objtool_file *file, 
		}

		memset(fake_jump, 0, sizeof(*fake_jump));

		INIT_LIST_HEAD(&fake_jump->alts);

		INIT_LIST_HEAD(&fake_jump->stack_ops);

		clear_insn_state(&fake_jump->state);



		fake_jump->sec = special_alt->new_sec;
@@ -1452,10 +1454,11 @@ static bool has_valid_stack_frame(struct insn_state *state) 
	return false;

}



static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)

static int update_insn_state_regs(struct instruction *insn,

				  struct insn_state *state,

				  struct stack_op *op)

{

	struct cfi_reg *cfa = &state->cfa;

	struct stack_op *op = &insn->stack_op;



	if (cfa->base != CFI_SP)

		return 0;
@@ -1545,9 +1548,9 @@ static void restore_reg(struct insn_state *state, unsigned char reg) 
 *   41 5d			pop    %r13

 *   c3				retq

 */

static int update_insn_state(struct instruction *insn, struct insn_state *state)

static int update_insn_state(struct instruction *insn, struct insn_state *state,

			     struct stack_op *op)

{

	struct stack_op *op = &insn->stack_op;

	struct cfi_reg *cfa = &state->cfa;

	struct cfi_reg *regs = state->regs;
@@ -1561,7 +1564,7 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state) 
	}



	if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)

		return update_insn_state_regs(insn, state);

		return update_insn_state_regs(insn, state, op);



	switch (op->dest.type) {
@@ -1898,6 +1901,42 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state) 
	return 0;

}



static int handle_insn_ops(struct instruction *insn, struct insn_state *state)

{

	struct stack_op *op;



	list_for_each_entry(op, &insn->stack_ops, list) {

		int res;



		res = update_insn_state(insn, state, op);

		if (res)

			return res;



		if (op->dest.type == OP_DEST_PUSHF) {

			if (!state->uaccess_stack) {

				state->uaccess_stack = 1;

			} else if (state->uaccess_stack >> 31) {

				WARN_FUNC("PUSHF stack exhausted",

					  insn->sec, insn->offset);

				return 1;

			}

			state->uaccess_stack <<= 1;

			state->uaccess_stack  |= state->uaccess;

		}



		if (op->src.type == OP_SRC_POPF) {

			if (state->uaccess_stack) {

				state->uaccess = state->uaccess_stack & 1;

				state->uaccess_stack >>= 1;

				if (state->uaccess_stack == 1)

					state->uaccess_stack = 0;

			}

		}

	}



	return 0;

}



static bool insn_state_match(struct instruction *insn, struct insn_state *state)

{

	struct insn_state *state1 = &insn->state, *state2 = state;
@@ -2198,29 +2237,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, 
			return 0;



		case INSN_STACK:

			if (update_insn_state(insn, &state))

				return 1;



			if (insn->stack_op.dest.type == OP_DEST_PUSHF) {

				if (!state.uaccess_stack) {

					state.uaccess_stack = 1;

				} else if (state.uaccess_stack >> 31) {

					WARN_FUNC("PUSHF stack exhausted", sec, insn->offset);

			if (handle_insn_ops(insn, &state))

				return 1;

				}

				state.uaccess_stack <<= 1;

				state.uaccess_stack  |= state.uaccess;

			}



			if (insn->stack_op.src.type == OP_SRC_POPF) {

				if (state.uaccess_stack) {

					state.uaccess = state.uaccess_stack & 1;

					state.uaccess_stack >>= 1;

					if (state.uaccess_stack == 1)

						state.uaccess_stack = 0;

				}

			}



			break;



		case INSN_STAC:

tools/objtool/check.h

+1 −1
Original line number Diff line number Diff line
@@ -42,7 +42,7 @@ struct instruction { 
	struct rela *jump_table;

	struct list_head alts;

	struct symbol *func;

	struct stack_op stack_op;

	struct list_head stack_ops;

	struct insn_state state;

	struct orc_entry orc;

};

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