Re: [RFC][PATCH 4/5] objtool: Enable compilation of objtool for all architectures

From: Julien Thierry
Date: Tue May 12 2020 - 13:05:07 EST

Hi Matt,

On 5/11/20 6:35 PM, Matt Helsley wrote:
objtool currently only compiles for x86 architectures. This is
fine as it presently does not support tooling for other
architectures. However, we would like to be able to convert other
kernel tools to run as objtool sub commands because they too
process ELF object files. This will allow us to convert tools
such as recordmcount to use objtool's ELF code.

Since much of recordmcount's ELF code is copy-paste code to/from
a variety of other kernel tools (look at modpost for example) this
means that if we can convert recordmcount we can convert more.

We define a "missing" architecture which contains weak definitions
for tools that do not exist on all architectures. In this case the
"check" and "orc" tools do not exist on all architectures.

To test building for other architectures ($arch below):

cd tools/objtool/arch
ln -s missing $arch
make O=build-$arch ARCH=$arch tools/objtool


Since the stuff under arch/missing is only weak symbols to make up for missing subcmd implementations, can we put everything in a file subcmd_defaults.c (name up for debate!) that would be always be compiled an linked. And some SUBCMD_XXX is set to "y", the corresponding object file gets compiled and overrides the weak symbols from subcmd_defaults.c .

This uses the weak, no-op definitions of the "check" and "orc"
commands for the newly-supported architecture. Presently these
exit with 127 to indicate that the subcommands are missing.
Subsequent patches can then be made to determine if the weak
definitions are used and explicitly report a missing command,
and even to list which subcommands are supported (perhaps if
no subcommand is specified it can list the supported subcommands).

objtool is not currently wired in to KConfig to be built for other
architectures because it's not needed for those architectures and
there are no commands it supports other than those for x86.

This commit allows us to demonstrate the pattern of adding
architecture support and isolates moving the various files from
adding support for more objtool subcommands.

Signed-off-by: Matt Helsley <mhelsley@xxxxxxxxxx>
---
tools/objtool/Build | 9 +++---
tools/objtool/Makefile | 11 ++++++-
tools/objtool/arch.h | 40 ++++++++++++++++++++++++++
tools/objtool/arch/missing/Build | 3 ++
tools/objtool/arch/missing/check.c | 14 +++++++++
tools/objtool/arch/missing/orc_dump.c | 11 +++++++
tools/objtool/arch/missing/orc_gen.c | 16 +++++++++++
tools/objtool/arch/x86/Build | 1 +
tools/objtool/{ => arch/x86}/special.c | 4 +--
tools/objtool/{ => arch/x86}/special.h | 2 +-
tools/objtool/builtin-orc.c | 2 +-
tools/objtool/check.c | 5 ++--
tools/objtool/check.h | 37 ------------------------
tools/objtool/objtool.h | 2 +-
tools/objtool/orc.h | 2 --
tools/objtool/orc_dump.c | 1 +
tools/objtool/orc_gen.c | 3 ++
17 files changed, 112 insertions(+), 51 deletions(-)
create mode 100644 tools/objtool/arch/missing/Build
create mode 100644 tools/objtool/arch/missing/check.c
create mode 100644 tools/objtool/arch/missing/orc_dump.c
create mode 100644 tools/objtool/arch/missing/orc_gen.c
rename tools/objtool/{ => arch/x86}/special.c (98%)
rename tools/objtool/{ => arch/x86}/special.h (95%)

diff --git a/tools/objtool/Build b/tools/objtool/Build
index 66f44f5cd2a6..fb6e6faf6f10 100644
--- a/tools/objtool/Build
+++ b/tools/objtool/Build
@@ -1,11 +1,12 @@
objtool-y += arch/$(SRCARCH)/
+
+objtool-$(SUBCMD_CHECK) += check.o
+objtool-$(SUBCMD_ORC) += orc_gen.o
+objtool-$(SUBCMD_ORC) += orc_dump.o
+
objtool-y += builtin-check.o
objtool-y += builtin-orc.o
-objtool-y += check.o
-objtool-y += orc_gen.o
-objtool-y += orc_dump.o
objtool-y += elf.o
-objtool-y += special.o

I'm not convinced by the moving of special under arch/x86 and I didn't understand it at first.

I guess you did it because it is only used by the check subcmd, which is currently only implemented by x86. Is that the reason?

I feel that the proper way to do it would be to leave special.c/h where they are and have "objtool-$(SUBCMD_CHECK) += special.o". Unless there was some other motivation for it.

objtool-y += objtool.o
objtool-y += libstring.o
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index f591c4d1b6fe..8aac9e133188 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -45,7 +45,16 @@ elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(CC) $(CFLAGS) -x c -E -
CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)
AWK = awk
-export srctree OUTPUT CFLAGS SRCARCH AWK
+
+ifeq ($(SRCARCH),x86)
+ SUBCMD_CHECK := y
+ SUBCMD_ORC := y
+else
+ SUBCMD_CHECK := n
+ SUBCMD_ORC := n
+endif
+

Nit: Can we default all SUBCMD_* variables to 'n' outside a branch and then individual arches override the relevant variables to 'y' in their "ifeq ($SRCARCH, <arch>)" branch?

+export srctree OUTPUT CFLAGS SRCARCH AWK SUBCMD_CHECK SUBCMD_ORC
include $(srctree)/tools/build/Makefile.include
$(OBJTOOL_IN): fixdep FORCE
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index ced3765c4f44..4ec9686f4898 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -11,6 +11,9 @@
#include "elf.h"
#include "cfi.h"
+#include <asm/orc_types.h>
+#include "orc.h"
+
enum insn_type {
INSN_JUMP_CONDITIONAL,
INSN_JUMP_UNCONDITIONAL,
@@ -66,6 +69,43 @@ struct stack_op {
struct op_src src;
};
+struct insn_state {
+ struct cfi_reg cfa;
+ struct cfi_reg regs[CFI_NUM_REGS];
+ int stack_size;
+ unsigned char type;
+ bool bp_scratch;
+ bool drap, end, uaccess, df;
+ bool noinstr;
+ s8 instr;
+ unsigned int uaccess_stack;
+ int drap_reg, drap_offset;
+ struct cfi_reg vals[CFI_NUM_REGS];
+};
+
+struct instruction {
+ struct list_head list;
+ struct hlist_node hash;
+ struct section *sec;
+ unsigned long offset;
+ unsigned int len;
+ enum insn_type type;
+ unsigned long immediate;
+ bool alt_group, dead_end, ignore, hint, save, restore, ignore_alts;
+ bool retpoline_safe;
+ s8 instr;
+ u8 visited;
+ struct symbol *call_dest;
+ struct instruction *jump_dest;
+ struct instruction *first_jump_src;
+ struct rela *jump_table;
+ struct list_head alts;
+ struct symbol *func;
+ struct stack_op stack_op;
+ struct insn_state state;
+ struct orc_entry orc;
+};
+
void arch_initial_func_cfi_state(struct cfi_state *state);
int arch_decode_instruction(struct elf *elf, struct section *sec,
diff --git a/tools/objtool/arch/missing/Build b/tools/objtool/arch/missing/Build
new file mode 100644
index 000000000000..a2478db59484
--- /dev/null
+++ b/tools/objtool/arch/missing/Build
@@ -0,0 +1,3 @@
+objtool-y += check.o
+objtool-y += orc_gen.o
+objtool-y += orc_dump.o
diff --git a/tools/objtool/arch/missing/check.c b/tools/objtool/arch/missing/check.c
new file mode 100644
index 000000000000..5eac14c8c6a5
--- /dev/null
+++ b/tools/objtool/arch/missing/check.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2020 Matt Helsley <mhelsley@xxxxxxxxxx>
+ */
+
+#include <stdbool.h>
+#include "../../check.h"
+
+const char *objname;
+
+int __attribute__ ((weak)) check(const char *_objname, bool orc)
+{
+ return 127;
+}
diff --git a/tools/objtool/arch/missing/orc_dump.c b/tools/objtool/arch/missing/orc_dump.c
new file mode 100644
index 000000000000..f7ebb3a2ce9e
--- /dev/null
+++ b/tools/objtool/arch/missing/orc_dump.c
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
+ */
+
+#include "../../orc.h"
+
+int __attribute__ ((weak)) orc_dump(const char *_objname)
+{
+ return 127;
+}
diff --git a/tools/objtool/arch/missing/orc_gen.c b/tools/objtool/arch/missing/orc_gen.c
new file mode 100644
index 000000000000..4bf62ddf58a4
--- /dev/null
+++ b/tools/objtool/arch/missing/orc_gen.c
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
+ */
+
+#include "../../orc.h"
+
+int __attribute__ ((weak)) create_orc(struct objtool_file *file)
+{
+ return 127;
+}
+
+int __attribute__ ((weak)) create_orc_sections(struct objtool_file *file)
+{
+ return 127;
+}
diff --git a/tools/objtool/arch/x86/Build b/tools/objtool/arch/x86/Build
index 7c5004008e97..de01c67dea14 100644
--- a/tools/objtool/arch/x86/Build
+++ b/tools/objtool/arch/x86/Build
@@ -1,4 +1,5 @@
objtool-y += decode.o
+objtool-y += special.o
inat_tables_script = ../arch/x86/tools/gen-insn-attr-x86.awk
inat_tables_maps = ../arch/x86/lib/x86-opcode-map.txt
diff --git a/tools/objtool/special.c b/tools/objtool/arch/x86/special.c
similarity index 98%
rename from tools/objtool/special.c
rename to tools/objtool/arch/x86/special.c
index e74e0189de22..677b6efe1446 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/arch/x86/special.c
@@ -11,9 +11,9 @@
#include <stdlib.h>
#include <string.h>
-#include "builtin.h"
+#include "../../builtin.h"
#include "special.h"
-#include "warn.h"
+#include "../../warn.h"
#define EX_ENTRY_SIZE 12
#define EX_ORIG_OFFSET 0
diff --git a/tools/objtool/special.h b/tools/objtool/arch/x86/special.h
similarity index 95%
rename from tools/objtool/special.h
rename to tools/objtool/arch/x86/special.h
index 35061530e46e..beba41950725 100644
--- a/tools/objtool/special.h
+++ b/tools/objtool/arch/x86/special.h
@@ -7,7 +7,7 @@
#define _SPECIAL_H
#include <stdbool.h>
-#include "elf.h"
+#include "../../elf.h"
struct special_alt {
struct list_head list;
diff --git a/tools/objtool/builtin-orc.c b/tools/objtool/builtin-orc.c
index 5f7cc6157edd..e6e54ae4ab75 100644
--- a/tools/objtool/builtin-orc.c
+++ b/tools/objtool/builtin-orc.c
@@ -15,7 +15,7 @@
#include <string.h>
#include "builtin.h"
#include "check.h"
-
+#include "orc.h"
static const char *orc_usage[] = {
"objtool orc generate [<options>] file.o",
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4b170fd08a28..d8a10961fe2c 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -7,10 +7,11 @@
#include <stdlib.h>
#include "builtin.h"
+#include "cfi.h"
+#include "arch.h"
#include "check.h"
#include "elf.h"
-#include "special.h"
-#include "arch.h"
+#include "arch/x86/special.h"
#include "warn.h"
#include <linux/hashtable.h>
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index ec6ff7f0970c..4d34bfc84dc7 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -8,43 +8,6 @@
#include <stdbool.h>
#include "objtool.h"
-#include "cfi.h"
-#include "arch.h"
-#include "orc.h"
-
-struct insn_state {
- struct cfi_reg cfa;
- struct cfi_reg regs[CFI_NUM_REGS];
- int stack_size;
- unsigned char type;
- bool bp_scratch;
- bool drap, end, uaccess, df;
- unsigned int uaccess_stack;
- int drap_reg, drap_offset;
- struct cfi_reg vals[CFI_NUM_REGS];
-};
-
-struct instruction {
- struct list_head list;
- struct hlist_node hash;
- struct section *sec;
- unsigned long offset;
- unsigned int len;
- enum insn_type type;
- unsigned long immediate;
- bool alt_group, dead_end, ignore, hint, save, restore, ignore_alts;
- bool retpoline_safe;
- u8 visited;
- struct symbol *call_dest;
- struct instruction *jump_dest;
- struct instruction *first_jump_src;
- struct rela *jump_table;
- struct list_head alts;
- struct symbol *func;
- struct stack_op stack_op;
- struct insn_state state;
- struct orc_entry orc;
-};
int check(const char *objname, bool orc);
diff --git a/tools/objtool/objtool.h b/tools/objtool/objtool.h
index afa52fe6f644..5ff352083056 100644
--- a/tools/objtool/objtool.h
+++ b/tools/objtool/objtool.h
@@ -17,4 +17,4 @@ struct objtool_file {
DECLARE_HASHTABLE(insn_hash, 20);
bool ignore_unreachables, c_file, hints, rodata;
};
-#endif
+#endif /* _OBJTOOL_H */
diff --git a/tools/objtool/orc.h b/tools/objtool/orc.h
index ee2832221e62..c67f451d7610 100644
--- a/tools/objtool/orc.h
+++ b/tools/objtool/orc.h
@@ -6,8 +6,6 @@
#ifndef _ORC_H
#define _ORC_H
-#include <asm/orc_types.h>
-
struct objtool_file;
int create_orc(struct objtool_file *file);
diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index ba4cbb1cdd63..73c8beb6e402 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -4,6 +4,7 @@
*/
#include <unistd.h>
+#include <asm/orc_types.h>
#include "orc.h"
#include "warn.h"
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index 4c0dabd28000..7693f7f31293 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -5,8 +5,11 @@
#include <stdlib.h>
#include <string.h>
+#include <asm/orc_types.h>
#include "orc.h"
+#include "cfi.h"
+#include "arch.h"
#include "check.h"
#include "warn.h"


--
Julien Thierry