Date: Mon, 17 Jun 2024 17:58:20 +0000
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Masahiro Yamada <masahiroy@...nel.org>, Luis Chamberlain <mcgrof@...nel.org>, 
	Miguel Ojeda <ojeda@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Matthew Maurer <mmaurer@...gle.com>, Alex Gaynor <alex.gaynor@...il.com>, 
	Wedson Almeida Filho <wedsonaf@...il.com>, Gary Guo <gary@...yguo.net>, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH 01/15] tools: Add gendwarfksyms

Add a basic DWARF parser, which uses libdw to traverse the debugging
information in an object file and looks for functions and variables.
In follow-up patches, this will be expanded to produce symbol versions
for CONFIG_MODVERSIONS from DWARF. This tool is needed mainly for Rust
kernel module compatibility.

Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
---
 tools/Makefile                      |  11 +--
 tools/gendwarfksyms/Build           |   2 +
 tools/gendwarfksyms/Makefile        |  49 +++++++++++
 tools/gendwarfksyms/gendwarfksyms.c | 128 ++++++++++++++++++++++++++++
 tools/gendwarfksyms/gendwarfksyms.h |  71 +++++++++++++++
 tools/gendwarfksyms/types.c         |  87 +++++++++++++++++++
 6 files changed, 343 insertions(+), 5 deletions(-)
 create mode 100644 tools/gendwarfksyms/Build
 create mode 100644 tools/gendwarfksyms/Makefile
 create mode 100644 tools/gendwarfksyms/gendwarfksyms.c
 create mode 100644 tools/gendwarfksyms/gendwarfksyms.h
 create mode 100644 tools/gendwarfksyms/types.c

diff --git a/tools/Makefile b/tools/Makefile
index 276f5d0d53a4..60806ff753b7 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -17,6 +17,7 @@ help:
 	@echo '  firewire               - the userspace part of nosy, an IEEE-1394 traffic sniffer'
 	@echo '  firmware               - Firmware tools'
 	@echo '  freefall               - laptop accelerometer program for disk protection'
+	@echo '  gendwarfksyms          - generates symbol versions from DWARF'
 	@echo '  gpio                   - GPIO tools'
 	@echo '  hv                     - tools used when in Hyper-V clients'
 	@echo '  iio                    - IIO tools'
@@ -68,7 +69,7 @@ acpi: FORCE
 cpupower: FORCE
 	$(call descend,power/$@)
 
-counter firewire hv guest bootconfig spi usb virtio mm bpf iio gpio objtool leds wmi pci firmware debugging tracing: FORCE
+counter firewire hv guest bootconfig spi usb virtio mm bpf iio gendwarfksyms gpio objtool leds wmi pci firmware debugging tracing: FORCE
 	$(call descend,$@)
 
 bpf/%: FORCE
@@ -154,8 +155,8 @@ freefall_install:
 kvm_stat_install:
 	$(call descend,kvm/$(@:_install=),install)
 
-install: acpi_install counter_install cpupower_install gpio_install \
-		hv_install firewire_install iio_install \
+install: acpi_install counter_install cpupower_install gendwarfksyms_install \
+		gpio_install hv_install firewire_install iio_install \
 		perf_install selftests_install turbostat_install usb_install \
 		virtio_install mm_install bpf_install x86_energy_perf_policy_install \
 		tmon_install freefall_install objtool_install kvm_stat_install \
@@ -168,7 +169,7 @@ acpi_clean:
 cpupower_clean:
 	$(call descend,power/cpupower,clean)
 
-counter_clean hv_clean firewire_clean bootconfig_clean spi_clean usb_clean virtio_clean mm_clean wmi_clean bpf_clean iio_clean gpio_clean objtool_clean leds_clean pci_clean firmware_clean debugging_clean tracing_clean:
+counter_clean hv_clean firewire_clean bootconfig_clean spi_clean usb_clean virtio_clean mm_clean wmi_clean bpf_clean iio_clean gendwarfksyms_clean gpio_clean objtool_clean leds_clean pci_clean firmware_clean debugging_clean tracing_clean:
 	$(call descend,$(@:_clean=),clean)
 
 libapi_clean:
@@ -211,7 +212,7 @@ build_clean:
 clean: acpi_clean counter_clean cpupower_clean hv_clean firewire_clean \
 		perf_clean selftests_clean turbostat_clean bootconfig_clean spi_clean usb_clean virtio_clean \
 		mm_clean bpf_clean iio_clean x86_energy_perf_policy_clean tmon_clean \
-		freefall_clean build_clean libbpf_clean libsubcmd_clean \
+		freefall_clean build_clean libbpf_clean libsubcmd_clean gendwarfksyms_clean \
 		gpio_clean objtool_clean leds_clean wmi_clean pci_clean firmware_clean debugging_clean \
 		intel-speed-select_clean tracing_clean thermal_clean thermometer_clean thermal-engine_clean
 
diff --git a/tools/gendwarfksyms/Build b/tools/gendwarfksyms/Build
new file mode 100644
index 000000000000..805591b6df80
--- /dev/null
+++ b/tools/gendwarfksyms/Build
@@ -0,0 +1,2 @@
+gendwarfksyms-y += gendwarfksyms.o
+gendwarfksyms-y += types.o
diff --git a/tools/gendwarfksyms/Makefile b/tools/gendwarfksyms/Makefile
new file mode 100644
index 000000000000..1138ebd8bd0f
--- /dev/null
+++ b/tools/gendwarfksyms/Makefile
@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: GPL-2.0
+include ../scripts/Makefile.include
+include ../scripts/Makefile.arch
+
+ifeq ($(srctree),)
+srctree := $(patsubst %/,%,$(dir $(CURDIR)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+endif
+
+GENDWARFKSYMS    := $(OUTPUT)gendwarfksyms
+GENDWARFKSYMS_IN := $(GENDWARFKSYMS)-in.o
+
+LIBDW_FLAGS := $(shell $(HOSTPKG_CONFIG) libdw --cflags 2>/dev/null)
+LIBDW_LIBS  := $(shell $(HOSTPKG_CONFIG) libdw --libs 2>/dev/null || echo -ldw -lelf)
+
+all: $(GENDWARFKSYMS)
+
+INCLUDES := -I$(srctree)/tools/include
+
+WARNINGS := -Wall -Wno-unused-value
+GENDWARFKSYMS_CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBDW_FLAGS)
+GENDWARFKSYMS_LDFLAGS := $(LIBDW_LIBS) $(KBUILD_HOSTLDFLAGS)
+
+# Always want host compilation.
+HOST_OVERRIDES := CC="$(HOSTCC)" LD="$(HOSTLD)" AR="$(HOSTAR)"
+
+ifeq ($(V),1)
+  Q =
+else
+  Q = @
+endif
+
+export srctree OUTPUT
+include $(srctree)/tools/build/Makefile.include
+
+$(GENDWARFKSYMS_IN): FORCE
+	$(Q)$(MAKE) $(build)=gendwarfksyms $(HOST_OVERRIDES) CFLAGS="$(GENDWARFKSYMS_CFLAGS)" \
+		LDFLAGS="$(GENDWARFKSYMS_LDFLAGS)"
+
+
+$(GENDWARFKSYMS): $(GENDWARFKSYMS_IN)
+	$(QUIET_LINK)$(HOSTCC) $(GENDWARFKSYMS_IN) $(GENDWARFKSYMS_LDFLAGS) -o $@
+
+clean:
+	$(call QUIET_CLEAN, gendwarfksyms) $(RM) $(GENDWARFKSYMS)
+
+FORCE:
+
+.PHONY: clean FORCE
diff --git a/tools/gendwarfksyms/gendwarfksyms.c b/tools/gendwarfksyms/gendwarfksyms.c
new file mode 100644
index 000000000000..4a2dea307849
--- /dev/null
+++ b/tools/gendwarfksyms/gendwarfksyms.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <fcntl.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <string.h>
+#include "gendwarfksyms.h"
+
+/*
+ * Options
+ */
+
+/* Print type descriptions and debugging output to stderr */
+bool debug;
+
+static const struct {
+	const char *arg;
+	bool *flag;
+} options[] = {
+	{ "--debug", &debug },
+};
+
+static int usage(void)
+{
+	error("usage: gendwarfksyms [options] elf-object-file < symbol-list");
+	return -1;
+}
+
+static int parse_options(int argc, const char **argv, const char **filename)
+{
+	*filename = NULL;
+
+	for (int i = 1; i < argc; i++) {
+		bool found = false;
+
+		for (int j = 0; j < ARRAY_SIZE(options); j++) {
+			if (!strcmp(argv[i], options[j].arg)) {
+				*options[j].flag = true;
+				found = true;
+				break;
+			}
+		}
+
+		if (!found) {
+			if (!*filename)
+				*filename = argv[i];
+			else
+				return -1;
+		}
+	}
+
+	return *filename ? 0 : -1;
+}
+
+static int process_modules(Dwfl_Module *mod, void **userdata, const char *name,
+			   Dwarf_Addr base, void *arg)
+{
+	Dwarf_Addr dwbias;
+	Dwarf_Die cudie;
+	Dwarf_CU *cu = NULL;
+	Dwarf *dbg;
+	int res;
+
+	debug("%s", name);
+	dbg = dwfl_module_getdwarf(mod, &dwbias);
+
+	do {
+		res = dwarf_get_units(dbg, cu, &cu, NULL, NULL, &cudie, NULL);
+		if (res < 0) {
+			error("dwarf_get_units failed: no debugging information?");
+			return -1;
+		} else if (res == 1) {
+			return DWARF_CB_OK; /* No more units */
+		}
+
+		check(process_module(mod, dbg, &cudie));
+	} while (cu);
+
+	return DWARF_CB_OK;
+}
+
+static const Dwfl_Callbacks callbacks = {
+	.section_address = dwfl_offline_section_address,
+	.find_debuginfo = dwfl_standard_find_debuginfo,
+};
+
+int main(int argc, const char **argv)
+{
+	const char *filename = NULL;
+	Dwfl *dwfl;
+	int fd;
+
+	if (parse_options(argc, argv, &filename) < 0)
+		return usage();
+
+	fd = open(filename, O_RDONLY);
+	if (fd == -1) {
+		error("open failed for '%s': %s", filename, strerror(errno));
+		return -1;
+	}
+
+	dwfl = dwfl_begin(&callbacks);
+	if (!dwfl) {
+		error("dwfl_begin failed for '%s': %s", filename,
+		      dwarf_errmsg(-1));
+		return -1;
+	}
+
+	if (!dwfl_report_offline(dwfl, filename, filename, fd)) {
+		error("dwfl_report_offline failed for '%s': %s", filename,
+		      dwarf_errmsg(-1));
+		return -1;
+	}
+
+	dwfl_report_end(dwfl, NULL, NULL);
+
+	if (dwfl_getmodules(dwfl, &process_modules, NULL, 0)) {
+		error("dwfl_getmodules failed for '%s'", filename);
+		return -1;
+	}
+
+	dwfl_end(dwfl);
+
+	return 0;
+}
diff --git a/tools/gendwarfksyms/gendwarfksyms.h b/tools/gendwarfksyms/gendwarfksyms.h
new file mode 100644
index 000000000000..44e94f1d9671
--- /dev/null
+++ b/tools/gendwarfksyms/gendwarfksyms.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <dwarf.h>
+#include <elfutils/libdw.h>
+#include <elfutils/libdwfl.h>
+#include <linux/hashtable.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#ifndef __GENDWARFKSYMS_H
+#define __GENDWARFKSYMS_H
+
+/*
+ * Options -- in gendwarfksyms.c
+ */
+extern bool debug;
+
+/*
+ * Output helpers
+ */
+#define __PREFIX "gendwarfksyms: "
+#define __println(prefix, format, ...)                                \
+	fprintf(stderr, prefix __PREFIX "%s: " format "\n", __func__, \
+		##__VA_ARGS__)
+
+#define debug(format, ...)                                    \
+	do {                                                  \
+		if (debug)                                    \
+			__println("", format, ##__VA_ARGS__); \
+	} while (0)
+
+#define warn(format, ...) __println("warning: ", format, ##__VA_ARGS__)
+#define error(format, ...) __println("error: ", format, ##__VA_ARGS__)
+
+/*
+ * Error handling helpers
+ */
+#define check(expr)                                             \
+	({                                                      \
+		int __res = expr;                               \
+		if (__res < 0) {                                \
+			error("`%s` failed: %d", #expr, __res); \
+			return __res;                           \
+		}                                               \
+		__res;                                          \
+	})
+
+/*
+ * types.c
+ */
+
+struct state {
+	Dwfl_Module *mod;
+	Dwarf *dbg;
+};
+
+typedef int (*die_callback_t)(struct state *state, Dwarf_Die *die);
+typedef bool (*die_match_callback_t)(Dwarf_Die *die);
+extern bool match_all(Dwarf_Die *die);
+
+extern int process_die_container(struct state *state, Dwarf_Die *die,
+				 die_callback_t func,
+				 die_match_callback_t match);
+
+extern int process_module(Dwfl_Module *mod, Dwarf *dbg, Dwarf_Die *cudie);
+
+#endif /* __GENDWARFKSYMS_H */
diff --git a/tools/gendwarfksyms/types.c b/tools/gendwarfksyms/types.c
new file mode 100644
index 000000000000..2a8e45ae911c
--- /dev/null
+++ b/tools/gendwarfksyms/types.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include "gendwarfksyms.h"
+
+/*
+ * Type string processing
+ */
+static int process(struct state *state, const char *s)
+{
+	s = s ?: "<null>";
+
+	if (debug)
+		fputs(s, stderr);
+
+	return 0;
+}
+
+bool match_all(Dwarf_Die *die)
+{
+	return true;
+}
+
+int process_die_container(struct state *state, Dwarf_Die *die,
+			  die_callback_t func, die_match_callback_t match)
+{
+	Dwarf_Die current;
+	int res;
+
+	res = check(dwarf_child(die, &current));
+	while (!res) {
+		if (match(&current))
+			check(func(state, &current));
+		res = check(dwarf_siblingof(&current, &current));
+	}
+
+	return 0;
+}
+
+/*
+ * Symbol processing
+ */
+static int process_subprogram(struct state *state, Dwarf_Die *die)
+{
+	return check(process(state, "subprogram;\n"));
+}
+
+static int process_variable(struct state *state, Dwarf_Die *die)
+{
+	return check(process(state, "variable;\n"));
+}
+
+static int process_exported_symbols(struct state *state, Dwarf_Die *die)
+{
+	int tag = dwarf_tag(die);
+
+	switch (tag) {
+	/* Possible containers of exported symbols */
+	case DW_TAG_namespace:
+	case DW_TAG_class_type:
+	case DW_TAG_structure_type:
+		return check(process_die_container(
+			state, die, process_exported_symbols, match_all));
+
+	/* Possible exported symbols */
+	case DW_TAG_subprogram:
+	case DW_TAG_variable:
+		if (tag == DW_TAG_subprogram)
+			check(process_subprogram(state, die));
+		else
+			check(process_variable(state, die));
+
+		return 0;
+	default:
+		return 0;
+	}
+}
+
+int process_module(Dwfl_Module *mod, Dwarf *dbg, Dwarf_Die *cudie)
+{
+	struct state state = { .mod = mod, .dbg = dbg };
+
+	return check(process_die_container(
+		&state, cudie, process_exported_symbols, match_all));
+}
-- 
2.45.2.627.g7a2c4fd464-goog

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