objtool: Implement stack validation 2.0

This is a major rewrite of objtool.  Instead of only tracking frame
pointer changes, it now tracks all stack-related operations, including
all register saves/restores.

In addition to making stack validation more robust, this also paves the
way for undwarf generation.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/678bd94c0566c6129bcc376cddb259c4c5633004.1498659915.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

tools/objtool/Makefile

@@ -25,7 +25,7 @@ OBJTOOL_IN := $(OBJTOOL)-in.o
 all: $(OBJTOOL)
 
 INCLUDES := -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(HOSTARCH)/include/uapi
-CFLAGS   += -Wall -Werror $(EXTRA_WARNINGS) -fomit-frame-pointer -O2 -g $(INCLUDES)
+CFLAGS   += -Wall -Werror $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -fomit-frame-pointer -O2 -g $(INCLUDES)
 LDFLAGS  += -lelf $(LIBSUBCMD)
 
 # Allow old libelf to be used:

tools/objtool/arch.h

@@ -19,25 +19,63 @@
 #define _ARCH_H
 
 #include <stdbool.h>
+#include <linux/list.h>
 #include "elf.h"
+#include "cfi.h"
 
-#define INSN_FP_SAVE		1
-#define INSN_FP_SETUP		2
-#define INSN_FP_RESTORE		3
-#define INSN_JUMP_CONDITIONAL	4
-#define INSN_JUMP_UNCONDITIONAL	5
-#define INSN_JUMP_DYNAMIC	6
-#define INSN_CALL		7
-#define INSN_CALL_DYNAMIC	8
-#define INSN_RETURN		9
-#define INSN_CONTEXT_SWITCH	10
-#define INSN_NOP		11
-#define INSN_OTHER		12
+#define INSN_JUMP_CONDITIONAL	1
+#define INSN_JUMP_UNCONDITIONAL	2
+#define INSN_JUMP_DYNAMIC	3
+#define INSN_CALL		4
+#define INSN_CALL_DYNAMIC	5
+#define INSN_RETURN		6
+#define INSN_CONTEXT_SWITCH	7
+#define INSN_STACK		8
+#define INSN_NOP		9
+#define INSN_OTHER		10
 #define INSN_LAST		INSN_OTHER
 
+enum op_dest_type {
+	OP_DEST_REG,
+	OP_DEST_REG_INDIRECT,
+	OP_DEST_MEM,
+	OP_DEST_PUSH,
+	OP_DEST_LEAVE,
+};
+
+struct op_dest {
+	enum op_dest_type type;
+	unsigned char reg;
+	int offset;
+};
+
+enum op_src_type {
+	OP_SRC_REG,
+	OP_SRC_REG_INDIRECT,
+	OP_SRC_CONST,
+	OP_SRC_POP,
+	OP_SRC_ADD,
+	OP_SRC_AND,
+};
+
+struct op_src {
+	enum op_src_type type;
+	unsigned char reg;
+	int offset;
+};
+
+struct stack_op {
+	struct op_dest dest;
+	struct op_src src;
+};
+
+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, unsigned char *type,
-			    unsigned long *displacement);
+			    unsigned long *immediate, struct stack_op *op);
+
+bool arch_callee_saved_reg(unsigned char reg);
 
 #endif /* _ARCH_H */

tools/objtool/cfi.h

+/*
+ * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _OBJTOOL_CFI_H
+#define _OBJTOOL_CFI_H
+
+#define CFI_UNDEFINED		-1
+#define CFI_CFA			-2
+#define CFI_SP_INDIRECT		-3
+#define CFI_BP_INDIRECT		-4
+
+#define CFI_AX			0
+#define CFI_DX			1
+#define CFI_CX			2
+#define CFI_BX			3
+#define CFI_SI			4
+#define CFI_DI			5
+#define CFI_BP			6
+#define CFI_SP			7
+#define CFI_R8			8
+#define CFI_R9			9
+#define CFI_R10			10
+#define CFI_R11			11
+#define CFI_R12			12
+#define CFI_R13			13
+#define CFI_R14			14
+#define CFI_R15			15
+#define CFI_RA			16
+#define CFI_NUM_REGS	17
+
+struct cfi_reg {
+	int base;
+	int offset;
+};
+
+struct cfi_state {
+	struct cfi_reg cfa;
+	struct cfi_reg regs[CFI_NUM_REGS];
+};
+
+#endif /* _OBJTOOL_CFI_H */

tools/objtool/check.h

@@ -20,22 +20,34 @@
 
 #include <stdbool.h>
 #include "elf.h"
+#include "cfi.h"
 #include "arch.h"
 #include <linux/hashtable.h>
 
+struct insn_state {
+	struct cfi_reg cfa;
+	struct cfi_reg regs[CFI_NUM_REGS];
+	int stack_size;
+	bool bp_scratch;
+	bool drap;
+	int drap_reg;
+};
+
 struct instruction {
 	struct list_head list;
 	struct hlist_node hash;
 	struct section *sec;
 	unsigned long offset;
-	unsigned int len, state;
+	unsigned int len;
 	unsigned char type;
 	unsigned long immediate;
-	bool alt_group, visited, dead_end;
+	bool alt_group, visited, dead_end, ignore;
 	struct symbol *call_dest;
 	struct instruction *jump_dest;
 	struct list_head alts;
 	struct symbol *func;
+	struct stack_op stack_op;
+	struct insn_state state;
 };
 
 struct objtool_file {
@@ -48,4 +60,7 @@ struct objtool_file {
 
 int check(const char *objname, bool nofp);
 
+#define for_each_insn(file, insn)					\
+	list_for_each_entry(insn, &file->insn_list, list)
+
 #endif /* _CHECK_H */

tools/objtool/elf.c

@@ -37,6 +37,9 @@
 #define ELF_C_READ_MMAP ELF_C_READ
 #endif
 
+#define WARN_ELF(format, ...)					\
+	WARN(format ": %s", ##__VA_ARGS__, elf_errmsg(-1))
+
 struct section *find_section_by_name(struct elf *elf, const char *name)
 {
 	struct section *sec;
@@ -139,12 +142,12 @@ static int read_sections(struct elf *elf)
 	int i;
 
 	if (elf_getshdrnum(elf->elf, &sections_nr)) {
-		perror("elf_getshdrnum");
+		WARN_ELF("elf_getshdrnum");
 		return -1;
 	}
 
 	if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
-		perror("elf_getshdrstrndx");
+		WARN_ELF("elf_getshdrstrndx");
 		return -1;
 	}
 
@@ -165,37 +168,36 @@ static int read_sections(struct elf *elf)
 
 		s = elf_getscn(elf->elf, i);
 		if (!s) {
-			perror("elf_getscn");
+			WARN_ELF("elf_getscn");
 			return -1;
 		}
 
 		sec->idx = elf_ndxscn(s);
 
 		if (!gelf_getshdr(s, &sec->sh)) {
-			perror("gelf_getshdr");
+			WARN_ELF("gelf_getshdr");
 			return -1;
 		}
 
 		sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
 		if (!sec->name) {
-			perror("elf_strptr");
+			WARN_ELF("elf_strptr");
 			return -1;
 		}
 
-		sec->elf_data = elf_getdata(s, NULL);
-		if (!sec->elf_data) {
-			perror("elf_getdata");
+		sec->data = elf_getdata(s, NULL);
+		if (!sec->data) {
+			WARN_ELF("elf_getdata");
 			return -1;
 		}
 
-		if (sec->elf_data->d_off != 0 ||
-		    sec->elf_data->d_size != sec->sh.sh_size) {
+		if (sec->data->d_off != 0 ||
+		    sec->data->d_size != sec->sh.sh_size) {
 			WARN("unexpected data attributes for %s", sec->name);
 			return -1;
 		}
 
-		sec->data = (unsigned long)sec->elf_data->d_buf;
-		sec->len = sec->elf_data->d_size;
+		sec->len = sec->data->d_size;
 	}
 
 	/* sanity check, one more call to elf_nextscn() should return NULL */
@@ -232,15 +234,15 @@ static int read_symbols(struct elf *elf)
 
 		sym->idx = i;
 
-		if (!gelf_getsym(symtab->elf_data, i, &sym->sym)) {
-			perror("gelf_getsym");
+		if (!gelf_getsym(symtab->data, i, &sym->sym)) {
+			WARN_ELF("gelf_getsym");
 			goto err;
 		}
 
 		sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
 				       sym->sym.st_name);
 		if (!sym->name) {
-			perror("elf_strptr");
+			WARN_ELF("elf_strptr");
 			goto err;
 		}
 
@@ -322,8 +324,8 @@ static int read_relas(struct elf *elf)
 			}
 			memset(rela, 0, sizeof(*rela));
 
-			if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {
-				perror("gelf_getrela");
+			if (!gelf_getrela(sec->data, i, &rela->rela)) {
+				WARN_ELF("gelf_getrela");
 				return -1;
 			}
 
@@ -362,12 +364,6 @@ struct elf *elf_open(const char *name)
 
 	INIT_LIST_HEAD(&elf->sections);
 
-	elf->name = strdup(name);
-	if (!elf->name) {
-		perror("strdup");
-		goto err;
-	}
-
 	elf->fd = open(name, O_RDONLY);
 	if (elf->fd == -1) {
 		perror("open");
@@ -376,12 +372,12 @@ struct elf *elf_open(const char *name)
 
 	elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
 	if (!elf->elf) {
-		perror("elf_begin");
+		WARN_ELF("elf_begin");
 		goto err;
 	}
 
 	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
-		perror("gelf_getehdr");
+		WARN_ELF("gelf_getehdr");
 		goto err;
 	}
 
@@ -407,6 +403,12 @@ void elf_close(struct elf *elf)
 	struct symbol *sym, *tmpsym;
 	struct rela *rela, *tmprela;
 
+	if (elf->elf)
+		elf_end(elf->elf);
+
+	if (elf->fd > 0)
+		close(elf->fd);
+
 	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
 		list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
 			list_del(&sym->list);
@@ -421,11 +423,6 @@ void elf_close(struct elf *elf)
 		list_del(&sec->list);
 		free(sec);
 	}
-	if (elf->name)
-		free(elf->name);
-	if (elf->fd > 0)
-		close(elf->fd);
-	if (elf->elf)
-		elf_end(elf->elf);
+
 	free(elf);
 }

tools/objtool/elf.h

@@ -37,10 +37,9 @@ struct section {
 	DECLARE_HASHTABLE(rela_hash, 16);
 	struct section *base, *rela;
 	struct symbol *sym;
-	Elf_Data *elf_data;
+	Elf_Data *data;
 	char *name;
 	int idx;
-	unsigned long data;
 	unsigned int len;
 };
 
@@ -86,6 +85,7 @@ struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
 struct symbol *find_containing_func(struct section *sec, unsigned long offset);
 void elf_close(struct elf *elf);
 
-
+#define for_each_sec(file, sec)						\
+	list_for_each_entry(sec, &file->elf->sections, list)
 
 #endif /* _OBJTOOL_ELF_H */

tools/objtool/special.c

@@ -91,16 +91,16 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
 	alt->jump_or_nop = entry->jump_or_nop;
 
 	if (alt->group) {
-		alt->orig_len = *(unsigned char *)(sec->data + offset +
+		alt->orig_len = *(unsigned char *)(sec->data->d_buf + offset +
 						   entry->orig_len);
-		alt->new_len = *(unsigned char *)(sec->data + offset +
+		alt->new_len = *(unsigned char *)(sec->data->d_buf + offset +
 						  entry->new_len);
 	}
 
 	if (entry->feature) {
 		unsigned short feature;
 
-		feature = *(unsigned short *)(sec->data + offset +
+		feature = *(unsigned short *)(sec->data->d_buf + offset +
 					      entry->feature);
 
 		/*

tools/objtool/warn.h

@@ -18,6 +18,13 @@
 #ifndef _WARN_H
 #define _WARN_H
 
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include "elf.h"
+
 extern const char *objname;
 
 static inline char *offstr(struct section *sec, unsigned long offset)
@@ -57,4 +64,7 @@ static inline char *offstr(struct section *sec, unsigned long offset)
 	free(_str);					\
 })
 
+#define WARN_ELF(format, ...)				\
+	WARN(format ": %s", ##__VA_ARGS__, elf_errmsg(-1))
+
 #endif /* _WARN_H */