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Subject[PATCH v2 10/10] objtool: Support multiple stack_op per instruction
Date
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: Julien Thierry <jthierry@redhat.com>
---
tools/objtool/arch.h | 4 +-
tools/objtool/arch/x86/decode.c | 13 +++++-
tools/objtool/check.c | 74 ++++++++++++++++++++-------------
tools/objtool/check.h | 2 +-
4 files changed, 62 insertions(+), 31 deletions(-)

diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index a9a50a25ca66..f9883c431949 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -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);

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 7ce8650cf085..199b4084a13c 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -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;
}

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index dbfd1f5d06f7..30d916dcc2a8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -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;

@@ -757,6 +758,7 @@ 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;
@@ -1459,10 +1461,11 @@ 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;
@@ -1552,9 +1555,9 @@ 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;

@@ -1568,7 +1571,7 @@ 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) {

@@ -1905,6 +1908,42 @@ 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;
@@ -2205,29 +2244,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
return 0;

case INSN_STACK:
- if (update_insn_state(insn, &state))
+ if (handle_insn_ops(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);
- 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:
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index d1b55961474c..1a089fc0bd23 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -43,7 +43,7 @@ struct instruction {
struct list_head alts;
struct symbol *func;
struct symbol *code_sym;
- struct stack_op stack_op;
+ struct list_head stack_ops;
struct insn_state state;
struct orc_entry orc;
};
--
2.21.1
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