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Subject[PATCH 19/20] objtool: uaccess PUSHF/POPF support
Add PUSHF / POPF state.uaccess restore logic.

XXX: should possibly be merged with the previous patch such that KASAN
doesn't explode in between. Split for review.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
tools/objtool/arch.h | 2 ++
tools/objtool/arch/x86/decode.c | 4 ++--
tools/objtool/check.c | 30 ++++++++++++++++++++++++++----
tools/objtool/check.h | 1 +
4 files changed, 31 insertions(+), 6 deletions(-)

--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -43,6 +43,7 @@ enum op_dest_type {
OP_DEST_REG_INDIRECT,
OP_DEST_MEM,
OP_DEST_PUSH,
+ OP_DEST_PUSHF,
OP_DEST_LEAVE,
};

@@ -57,6 +58,7 @@ enum op_src_type {
OP_SRC_REG_INDIRECT,
OP_SRC_CONST,
OP_SRC_POP,
+ OP_SRC_POPF,
OP_SRC_ADD,
OP_SRC_AND,
};
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -357,13 +357,13 @@ int arch_decode_instruction(struct elf *
/* pushf */
*type = INSN_STACK;
op->src.type = OP_SRC_CONST;
- op->dest.type = OP_DEST_PUSH;
+ op->dest.type = OP_DEST_PUSHF;
break;

case 0x9d:
/* popf */
*type = INSN_STACK;
- op->src.type = OP_SRC_POP;
+ op->src.type = OP_SRC_POPF;
op->dest.type = OP_DEST_MEM;
break;

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1392,11 +1392,11 @@ static int update_insn_state_regs(struct
return 0;

/* push */
- if (op->dest.type == OP_DEST_PUSH)
+ if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
cfa->offset += 8;

/* pop */
- if (op->src.type == OP_SRC_POP)
+ if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
cfa->offset -= 8;

/* add immediate to sp */
@@ -1653,6 +1653,7 @@ static int update_insn_state(struct inst
break;

case OP_SRC_POP:
+ case OP_SRC_POPF:
if (!state->drap && op->dest.type == OP_DEST_REG &&
op->dest.reg == cfa->base) {

@@ -1717,6 +1718,7 @@ static int update_insn_state(struct inst
break;

case OP_DEST_PUSH:
+ case OP_DEST_PUSHF:
state->stack_size += 8;
if (cfa->base == CFI_SP)
cfa->offset += 8;
@@ -1807,7 +1809,7 @@ static int update_insn_state(struct inst
break;

case OP_DEST_MEM:
- if (op->src.type != OP_SRC_POP) {
+ if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
WARN_FUNC("unknown stack-related memory operation",
insn->sec, insn->offset);
return -1;
@@ -2109,6 +2111,26 @@ static int validate_branch(struct objtoo
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);
+ 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:
@@ -2126,7 +2148,7 @@ static int validate_branch(struct objtoo
return 1;
}

- if (func_uaccess_safe(func)) {
+ if (func_uaccess_safe(func) && !state.uaccess_stack) {
WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
return 1;
}
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -32,6 +32,7 @@ struct insn_state {
unsigned char type;
bool bp_scratch;
bool drap, end, uaccess;
+ unsigned int uaccess_stack;
int drap_reg, drap_offset;
struct cfi_reg vals[CFI_NUM_REGS];
};

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