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-rw-r--r--tools/objtool/Makefile3
-rw-r--r--tools/objtool/arch.h5
-rw-r--r--tools/objtool/arch/x86/decode.c111
-rw-r--r--tools/objtool/cfi.h2
-rw-r--r--tools/objtool/check.c219
-rw-r--r--tools/objtool/check.h3
6 files changed, 207 insertions, 136 deletions
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 3a6425fefc43..6976c73e60c4 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -25,7 +25,8 @@ OBJTOOL_IN := $(OBJTOOL)-in.o
all: $(OBJTOOL)
INCLUDES := -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(HOSTARCH)/include/uapi
-CFLAGS += -Wall -Werror $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -fomit-frame-pointer -O2 -g $(INCLUDES)
+WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed
+CFLAGS += -Wall -Werror $(WARNINGS) -fomit-frame-pointer -O2 -g $(INCLUDES)
LDFLAGS += -lelf $(LIBSUBCMD)
# Allow old libelf to be used:
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index 21aeca874edb..b0d7dc3d71b5 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -31,8 +31,9 @@
#define INSN_RETURN 6
#define INSN_CONTEXT_SWITCH 7
#define INSN_STACK 8
-#define INSN_NOP 9
-#define INSN_OTHER 10
+#define INSN_BUG 9
+#define INSN_NOP 10
+#define INSN_OTHER 11
#define INSN_LAST INSN_OTHER
enum op_dest_type {
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 4559a21a8de2..0e8c8ec4fd4e 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -86,8 +86,8 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
struct insn insn;
int x86_64, sign;
unsigned char op1, op2, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0,
- modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0,
- sib = 0;
+ rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0,
+ modrm_reg = 0, sib = 0;
x86_64 = is_x86_64(elf);
if (x86_64 == -1)
@@ -114,6 +114,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
rex = insn.rex_prefix.bytes[0];
rex_w = X86_REX_W(rex) >> 3;
rex_r = X86_REX_R(rex) >> 2;
+ rex_x = X86_REX_X(rex) >> 1;
rex_b = X86_REX_B(rex);
}
@@ -217,6 +218,18 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
op->dest.reg = CFI_BP;
break;
}
+
+ if (rex_w && !rex_b && modrm_mod == 3 && modrm_rm == 4) {
+
+ /* mov reg, %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
/* fallthrough */
case 0x88:
if (!rex_b &&
@@ -269,80 +282,28 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
break;
case 0x8d:
- if (rex == 0x48 && modrm == 0x65) {
+ if (sib == 0x24 && rex_w && !rex_b && !rex_x) {
- /* lea disp(%rbp), %rsp */
+ /* lea disp(%rsp), reg */
*type = INSN_STACK;
op->src.type = OP_SRC_ADD;
- op->src.reg = CFI_BP;
+ op->src.reg = CFI_SP;
op->src.offset = insn.displacement.value;
op->dest.type = OP_DEST_REG;
- op->dest.reg = CFI_SP;
- break;
- }
+ op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
- if (rex == 0x48 && (modrm == 0xa4 || modrm == 0x64) &&
- sib == 0x24) {
+ } else if (rex == 0x48 && modrm == 0x65) {
- /* lea disp(%rsp), %rsp */
+ /* lea disp(%rbp), %rsp */
*type = INSN_STACK;
op->src.type = OP_SRC_ADD;
- op->src.reg = CFI_SP;
+ op->src.reg = CFI_BP;
op->src.offset = insn.displacement.value;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
- break;
- }
-
- if (rex == 0x48 && modrm == 0x2c && sib == 0x24) {
- /* lea (%rsp), %rbp */
- *type = INSN_STACK;
- op->src.type = OP_SRC_REG;
- op->src.reg = CFI_SP;
- op->dest.type = OP_DEST_REG;
- op->dest.reg = CFI_BP;
- break;
- }
-
- if (rex == 0x4c && modrm == 0x54 && sib == 0x24 &&
- insn.displacement.value == 8) {
-
- /*
- * lea 0x8(%rsp), %r10
- *
- * Here r10 is the "drap" pointer, used as a stack
- * pointer helper when the stack gets realigned.
- */
- *type = INSN_STACK;
- op->src.type = OP_SRC_ADD;
- op->src.reg = CFI_SP;
- op->src.offset = 8;
- op->dest.type = OP_DEST_REG;
- op->dest.reg = CFI_R10;
- break;
- }
-
- if (rex == 0x4c && modrm == 0x6c && sib == 0x24 &&
- insn.displacement.value == 16) {
-
- /*
- * lea 0x10(%rsp), %r13
- *
- * Here r13 is the "drap" pointer, used as a stack
- * pointer helper when the stack gets realigned.
- */
- *type = INSN_STACK;
- op->src.type = OP_SRC_ADD;
- op->src.reg = CFI_SP;
- op->src.offset = 16;
- op->dest.type = OP_DEST_REG;
- op->dest.reg = CFI_R13;
- break;
- }
-
- if (rex == 0x49 && modrm == 0x62 &&
- insn.displacement.value == -8) {
+ } else if (rex == 0x49 && modrm == 0x62 &&
+ insn.displacement.value == -8) {
/*
* lea -0x8(%r10), %rsp
@@ -356,11 +317,9 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
op->src.offset = -8;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
- break;
- }
- if (rex == 0x49 && modrm == 0x65 &&
- insn.displacement.value == -16) {
+ } else if (rex == 0x49 && modrm == 0x65 &&
+ insn.displacement.value == -16) {
/*
* lea -0x10(%r13), %rsp
@@ -374,7 +333,6 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
op->src.offset = -16;
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
- break;
}
break;
@@ -406,20 +364,27 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
case 0x0f:
- if (op2 >= 0x80 && op2 <= 0x8f)
+ if (op2 >= 0x80 && op2 <= 0x8f) {
+
*type = INSN_JUMP_CONDITIONAL;
- else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
- op2 == 0x35)
+
+ } else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
+ op2 == 0x35) {
/* sysenter, sysret */
*type = INSN_CONTEXT_SWITCH;
- else if (op2 == 0x0d || op2 == 0x1f)
+ } else if (op2 == 0x0b || op2 == 0xb9) {
+
+ /* ud2 */
+ *type = INSN_BUG;
+
+ } else if (op2 == 0x0d || op2 == 0x1f) {
/* nopl/nopw */
*type = INSN_NOP;
- else if (op2 == 0xa0 || op2 == 0xa8) {
+ } else if (op2 == 0xa0 || op2 == 0xa8) {
/* push fs/gs */
*type = INSN_STACK;
diff --git a/tools/objtool/cfi.h b/tools/objtool/cfi.h
index 443ab2c69992..2fe883c665c7 100644
--- a/tools/objtool/cfi.h
+++ b/tools/objtool/cfi.h
@@ -40,7 +40,7 @@
#define CFI_R14 14
#define CFI_R15 15
#define CFI_RA 16
-#define CFI_NUM_REGS 17
+#define CFI_NUM_REGS 17
struct cfi_reg {
int base;
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 3436a942b606..f744617c9946 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -218,9 +218,12 @@ static void clear_insn_state(struct insn_state *state)
memset(state, 0, sizeof(*state));
state->cfa.base = CFI_UNDEFINED;
- for (i = 0; i < CFI_NUM_REGS; i++)
+ for (i = 0; i < CFI_NUM_REGS; i++) {
state->regs[i].base = CFI_UNDEFINED;
+ state->vals[i].base = CFI_UNDEFINED;
+ }
state->drap_reg = CFI_UNDEFINED;
+ state->drap_offset = -1;
}
/*
@@ -296,7 +299,7 @@ static int decode_instructions(struct objtool_file *file)
}
/*
- * Find all uses of the unreachable() macro, which are code path dead ends.
+ * Mark "ud2" instructions and manually annotated dead ends.
*/
static int add_dead_ends(struct objtool_file *file)
{
@@ -305,9 +308,20 @@ static int add_dead_ends(struct objtool_file *file)
struct instruction *insn;
bool found;
+ /*
+ * By default, "ud2" is a dead end unless otherwise annotated, because
+ * GCC 7 inserts it for certain divide-by-zero cases.
+ */
+ for_each_insn(file, insn)
+ if (insn->type == INSN_BUG)
+ insn->dead_end = true;
+
+ /*
+ * Check for manually annotated dead ends.
+ */
sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
if (!sec)
- return 0;
+ goto reachable;
list_for_each_entry(rela, &sec->rela_list, list) {
if (rela->sym->type != STT_SECTION) {
@@ -340,6 +354,48 @@ static int add_dead_ends(struct objtool_file *file)
insn->dead_end = true;
}
+reachable:
+ /*
+ * These manually annotated reachable checks are needed for GCC 4.4,
+ * where the Linux unreachable() macro isn't supported. In that case
+ * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
+ * not a dead end.
+ */
+ sec = find_section_by_name(file->elf, ".rela.discard.reachable");
+ if (!sec)
+ return 0;
+
+ list_for_each_entry(rela, &sec->rela_list, list) {
+ if (rela->sym->type != STT_SECTION) {
+ WARN("unexpected relocation symbol type in %s", sec->name);
+ return -1;
+ }
+ insn = find_insn(file, rela->sym->sec, rela->addend);
+ if (insn)
+ insn = list_prev_entry(insn, list);
+ else if (rela->addend == rela->sym->sec->len) {
+ found = false;
+ list_for_each_entry_reverse(insn, &file->insn_list, list) {
+ if (insn->sec == rela->sym->sec) {
+ found = true;
+ break;
+ }
+ }
+
+ if (!found) {
+ WARN("can't find reachable insn at %s+0x%x",
+ rela->sym->sec->name, rela->addend);
+ return -1;
+ }
+ } else {
+ WARN("can't find reachable insn at %s+0x%x",
+ rela->sym->sec->name, rela->addend);
+ return -1;
+ }
+
+ insn->dead_end = false;
+ }
+
return 0;
}
@@ -1057,8 +1113,7 @@ static int update_insn_state_regs(struct instruction *insn, struct insn_state *s
static void save_reg(struct insn_state *state, unsigned char reg, int base,
int offset)
{
- if ((arch_callee_saved_reg(reg) ||
- (state->drap && reg == state->drap_reg)) &&
+ if (arch_callee_saved_reg(reg) &&
state->regs[reg].base == CFI_UNDEFINED) {
state->regs[reg].base = base;
state->regs[reg].offset = offset;
@@ -1148,24 +1203,47 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
switch (op->src.type) {
case OP_SRC_REG:
- if (cfa->base == op->src.reg && cfa->base == CFI_SP &&
- op->dest.reg == CFI_BP && regs[CFI_BP].base == CFI_CFA &&
- regs[CFI_BP].offset == -cfa->offset) {
-
- /* mov %rsp, %rbp */
- cfa->base = op->dest.reg;
- state->bp_scratch = false;
- } else if (state->drap) {
-
- /* drap: mov %rsp, %rbp */
- regs[CFI_BP].base = CFI_BP;
- regs[CFI_BP].offset = -state->stack_size;
- state->bp_scratch = false;
- } else if (!no_fp) {
-
- WARN_FUNC("unknown stack-related register move",
- insn->sec, insn->offset);
- return -1;
+ if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP) {
+
+ if (cfa->base == CFI_SP &&
+ regs[CFI_BP].base == CFI_CFA &&
+ regs[CFI_BP].offset == -cfa->offset) {
+
+ /* mov %rsp, %rbp */
+ cfa->base = op->dest.reg;
+ state->bp_scratch = false;
+ }
+
+ else if (state->drap) {
+
+ /* drap: mov %rsp, %rbp */
+ regs[CFI_BP].base = CFI_BP;
+ regs[CFI_BP].offset = -state->stack_size;
+ state->bp_scratch = false;
+ }
+ }
+
+ else if (op->dest.reg == cfa->base) {
+
+ /* mov %reg, %rsp */
+ if (cfa->base == CFI_SP &&
+ state->vals[op->src.reg].base == CFI_CFA) {
+
+ /*
+ * This is needed for the rare case
+ * where GCC does something dumb like:
+ *
+ * lea 0x8(%rsp), %rcx
+ * ...
+ * mov %rcx, %rsp
+ */
+ cfa->offset = -state->vals[op->src.reg].offset;
+ state->stack_size = cfa->offset;
+
+ } else {
+ cfa->base = CFI_UNDEFINED;
+ cfa->offset = 0;
+ }
}
break;
@@ -1187,11 +1265,25 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
break;
}
- if (op->dest.reg != CFI_BP && op->src.reg == CFI_SP &&
- cfa->base == CFI_SP) {
+ if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
/* drap: lea disp(%rsp), %drap */
state->drap_reg = op->dest.reg;
+
+ /*
+ * lea disp(%rsp), %reg
+ *
+ * This is needed for the rare case where GCC
+ * does something dumb like:
+ *
+ * lea 0x8(%rsp), %rcx
+ * ...
+ * mov %rcx, %rsp
+ */
+ state->vals[op->dest.reg].base = CFI_CFA;
+ state->vals[op->dest.reg].offset = \
+ -state->stack_size + op->src.offset;
+
break;
}
@@ -1228,7 +1320,6 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
cfa->base = state->drap_reg;
cfa->offset = state->stack_size = 0;
state->drap = true;
-
}
/*
@@ -1246,17 +1337,19 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
cfa->base = CFI_SP;
}
- if (regs[op->dest.reg].offset == -state->stack_size) {
+ if (state->drap && cfa->base == CFI_BP_INDIRECT &&
+ op->dest.type == OP_DEST_REG &&
+ op->dest.reg == state->drap_reg &&
+ state->drap_offset == -state->stack_size) {
- if (state->drap && cfa->base == CFI_BP_INDIRECT &&
- op->dest.type == OP_DEST_REG &&
- op->dest.reg == state->drap_reg) {
+ /* drap: pop %drap */
+ cfa->base = state->drap_reg;
+ cfa->offset = 0;
+ state->drap_offset = -1;
- /* drap: pop %drap */
- cfa->base = state->drap_reg;
- cfa->offset = 0;
- }
+ } else if (regs[op->dest.reg].offset == -state->stack_size) {
+ /* pop %reg */
restore_reg(state, op->dest.reg);
}
@@ -1268,14 +1361,18 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
case OP_SRC_REG_INDIRECT:
if (state->drap && op->src.reg == CFI_BP &&
+ op->src.offset == state->drap_offset) {
+
+ /* drap: mov disp(%rbp), %drap */
+ cfa->base = state->drap_reg;
+ cfa->offset = 0;
+ state->drap_offset = -1;
+ }
+
+ if (state->drap && op->src.reg == CFI_BP &&
op->src.offset == regs[op->dest.reg].offset) {
/* drap: mov disp(%rbp), %reg */
- if (op->dest.reg == state->drap_reg) {
- cfa->base = state->drap_reg;
- cfa->offset = 0;
- }
-
restore_reg(state, op->dest.reg);
} else if (op->src.reg == cfa->base &&
@@ -1311,8 +1408,8 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
cfa->base = CFI_BP_INDIRECT;
cfa->offset = -state->stack_size;
- /* save drap so we know when to undefine it */
- save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
+ /* save drap so we know when to restore it */
+ state->drap_offset = -state->stack_size;
} else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
@@ -1346,8 +1443,8 @@ static int update_insn_state(struct instruction *insn, struct insn_state *state)
cfa->base = CFI_BP_INDIRECT;
cfa->offset = op->dest.offset;
- /* save drap so we know when to undefine it */
- save_reg(state, op->src.reg, CFI_CFA, op->dest.offset);
+ /* save drap offset so we know when to restore it */
+ state->drap_offset = op->dest.offset;
}
else if (regs[op->src.reg].base == CFI_UNDEFINED) {
@@ -1438,11 +1535,12 @@ static bool insn_state_match(struct instruction *insn, struct insn_state *state)
insn->sec, insn->offset, state1->type, state2->type);
} else if (state1->drap != state2->drap ||
- (state1->drap && state1->drap_reg != state2->drap_reg)) {
- WARN_FUNC("stack state mismatch: drap1=%d(%d) drap2=%d(%d)",
+ (state1->drap && state1->drap_reg != state2->drap_reg) ||
+ (state1->drap && state1->drap_offset != state2->drap_offset)) {
+ WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
insn->sec, insn->offset,
- state1->drap, state1->drap_reg,
- state2->drap, state2->drap_reg);
+ state1->drap, state1->drap_reg, state1->drap_offset,
+ state2->drap, state2->drap_reg, state2->drap_offset);
} else
return true;
@@ -1471,26 +1569,26 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
if (insn->alt_group && list_empty(&insn->alts)) {
WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
sec, insn->offset);
- return -1;
+ return 1;
}
while (1) {
next_insn = next_insn_same_sec(file, insn);
- if (file->c_file && insn->func) {
- if (func && func != insn->func) {
- WARN("%s() falls through to next function %s()",
- func->name, insn->func->name);
- return 1;
- }
+
+ if (file->c_file && func && insn->func && func != insn->func) {
+ WARN("%s() falls through to next function %s()",
+ func->name, insn->func->name);
+ return 1;
}
- func = insn->func;
+ if (insn->func)
+ func = insn->func;
if (func && insn->ignore) {
WARN_FUNC("BUG: why am I validating an ignored function?",
sec, insn->offset);
- return -1;
+ return 1;
}
if (insn->visited) {
@@ -1628,7 +1726,7 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
case INSN_STACK:
if (update_insn_state(insn, &state))
- return -1;
+ return 1;
break;
@@ -1693,8 +1791,13 @@ static bool ignore_unreachable_insn(struct instruction *insn)
/*
* Ignore any unused exceptions. This can happen when a whitelisted
* function has an exception table entry.
+ *
+ * Also ignore alternative replacement instructions. This can happen
+ * when a whitelisted function uses one of the ALTERNATIVE macros.
*/
- if (!strcmp(insn->sec->name, ".fixup"))
+ if (!strcmp(insn->sec->name, ".fixup") ||
+ !strcmp(insn->sec->name, ".altinstr_replacement") ||
+ !strcmp(insn->sec->name, ".altinstr_aux"))
return true;
/*
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index c9af11f0c8af..47d9ea70a83d 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -32,7 +32,8 @@ struct insn_state {
unsigned char type;
bool bp_scratch;
bool drap;
- int drap_reg;
+ int drap_reg, drap_offset;
+ struct cfi_reg vals[CFI_NUM_REGS];
};
struct instruction {
generated by cgit (git 2.34.1) at 2024-05-27 18:31:36 +0000