Merge branch 'master' into '6.0/stage'

libdrgn/Makefile.am

@@ -84,7 +84,7 @@ drgn.h: configure.ac build-aux/gen_drgn_h.awk build-aux/parse_arch.awk $(ARCH_IN
 		-v version=@PACKAGE_VERSION@ \
 		$(wordlist 4, $(words $^), $^) > $@
 
-elfutils_LIBS = elfutils/libdw/libdw.a elfutils/libelf/libelf.a -lz -llzma -lbz2
+elfutils_LIBS = elfutils/libdw/libdw.a elfutils/libelf/libelf.a -lz -llzma -lbz2 -ldl
 
 lib_LTLIBRARIES = libdrgn.la
 
@@ -142,3 +142,8 @@ python/docstrings.h: ../_drgn.pyi $(drgndoc_docstrings_deps)
 
 EXTRA_DIST = $(ARCH_INS) build-aux/gen_arch.awk build-aux/gen_constants.py \
 	     build-aux/gen_drgn_h.awk build-aux/parse_arch.awk
+
+EXTRA_PROGRAMS = examples/load_debug_info
+
+examples_load_debug_info_SOURCES = examples/load_debug_info.c
+examples_load_debug_info_LDADD = libdrgnimpl.la $(elfutils_LIBS)

libdrgn/drgn.h.in

@@ -1807,7 +1807,7 @@ drgn_object_set_float(struct drgn_object *res,
 struct drgn_error *
 drgn_object_set_buffer(struct drgn_object *res,
 		       struct drgn_qualified_type qualified_type,
-		       const char *buf, uint8_t bit_offset,
+		       const void *buf, uint8_t bit_offset,
 		       uint64_t bit_field_size,
 		       enum drgn_byte_order byte_order);
 

libdrgn/dwarf_info_cache.c

@@ -10,6 +10,7 @@
 #include "dwarf_index.h"
 #include "dwarf_info_cache.h"
 #include "hash_table.h"
+#include "object.h"
 #include "object_index.h"
 #include "type_index.h"
 #include "vector.h"
@@ -58,6 +59,63 @@ static void drgn_dwarf_type_free(struct drgn_dwarf_type *dwarf_type)
 	}
 }
 
+/**
+ * Return whether a DWARF DIE is little-endian.
+ *
+ * @param[in] check_attr Whether to check the DW_AT_endianity attribute. If @c
+ * false, only the ELF header is checked and this function cannot fail.
+ * @return @c NULL on success, non-@c NULL on error.
+ */
+static struct drgn_error *dwarf_die_is_little_endian(Dwarf_Die *die,
+						     bool check_attr, bool *ret)
+{
+	Dwarf_Attribute endianity_attr_mem, *endianity_attr;
+	Dwarf_Word endianity;
+	if (check_attr &&
+	    (endianity_attr = dwarf_attr_integrate(die, DW_AT_endianity,
+						   &endianity_attr_mem))) {
+		if (dwarf_formudata(endianity_attr, &endianity)) {
+			return drgn_error_create(DRGN_ERROR_OTHER,
+						 "invalid DW_AT_endianity");
+		}
+	} else {
+		endianity = DW_END_default;
+	}
+	switch (endianity) {
+	case DW_END_default: {
+		Elf *elf = dwarf_getelf(dwarf_cu_getdwarf(die->cu));
+		*ret = elf_getident(elf, NULL)[EI_DATA] == ELFDATA2LSB;
+		return NULL;
+	}
+	case DW_END_little:
+		*ret = true;
+		return NULL;
+	case DW_END_big:
+		*ret = false;
+		return NULL;
+	default:
+		return drgn_error_create(DRGN_ERROR_OTHER,
+					 "unknown DW_AT_endianity");
+	}
+}
+
+/** Like dwarf_die_is_little_endian(), but returns a @ref drgn_byte_order. */
+static struct drgn_error *dwarf_die_byte_order(Dwarf_Die *die,
+					       bool check_attr,
+					       enum drgn_byte_order *ret)
+{
+	bool little_endian;
+	struct drgn_error *err = dwarf_die_is_little_endian(die, check_attr,
+							    &little_endian);
+	/*
+	 * dwarf_die_is_little_endian() can't fail if check_attr is false, so
+	 * the !check_attr test suppresses maybe-uninitialized warnings.
+	 */
+	if (!err || !check_attr)
+		*ret = little_endian ? DRGN_LITTLE_ENDIAN : DRGN_BIG_ENDIAN;
+	return err;
+}
+
 static int dwarf_type(Dwarf_Die *die, Dwarf_Die *ret)
 {
 	Dwarf_Attribute attr_mem;
@@ -618,7 +676,8 @@ drgn_compound_type_from_dwarf(struct drgn_dwarf_info_cache *dicache,
 		goto err;
 	}
 
-	bool little_endian = dwarf_die_is_little_endian(die);
+	bool little_endian;
+	dwarf_die_is_little_endian(die, false, &little_endian);
 	Dwarf_Die child;
 	int r = dwarf_child(die, &child);
 	while (r == 0) {
@@ -1453,52 +1512,111 @@ drgn_object_from_dwarf_subprogram(struct drgn_dwarf_info_cache *dicache,
 				  Dwarf_Die *die, uint64_t bias,
 				  const char *name, struct drgn_object *ret)
 {
-	struct drgn_error *err;
 	struct drgn_qualified_type qualified_type;
-	Dwarf_Addr low_pc;
-
-	err = drgn_type_from_dwarf(dicache, die, &qualified_type);
+	struct drgn_error *err = drgn_type_from_dwarf(dicache, die,
+						      &qualified_type);
 	if (err)
 		return err;
+	Dwarf_Addr low_pc;
 	if (dwarf_lowpc(die, &low_pc) == -1) {
 		return drgn_error_format(DRGN_ERROR_LOOKUP,
 					 "could not find address of '%s'",
 					 name);
 	}
+	enum drgn_byte_order byte_order;
+	dwarf_die_byte_order(die, false, &byte_order);
 	return drgn_object_set_reference(ret, qualified_type, low_pc + bias, 0,
-					 0, dwarf_die_byte_order(die));
+					 0, byte_order);
+}
+
+static struct drgn_error *
+drgn_object_from_dwarf_constant(struct drgn_dwarf_info_cache *dicache,
+				Dwarf_Die *die,
+				struct drgn_qualified_type qualified_type,
+				Dwarf_Attribute *attr, struct drgn_object *ret)
+{
+	struct drgn_object_type type;
+	enum drgn_object_kind kind;
+	uint64_t bit_size;
+	struct drgn_error *err = drgn_object_set_common(qualified_type, 0,
+							&type, &kind,
+							&bit_size);
+	if (err)
+		return err;
+	Dwarf_Block block;
+	if (dwarf_formblock(attr, &block) == 0) {
+		bool little_endian;
+		err = dwarf_die_is_little_endian(die, true, &little_endian);
+		if (err)
+			return err;
+		if (block.length < drgn_value_size(bit_size, 0)) {
+			return drgn_error_create(DRGN_ERROR_OTHER,
+						 "DW_AT_const_value block is too small");
+		}
+		return drgn_object_set_buffer_internal(ret, &type, kind,
+						       bit_size, block.data, 0,
+						       little_endian);
+	} else if (kind == DRGN_OBJECT_SIGNED) {
+		Dwarf_Sword svalue;
+		if (dwarf_formsdata(attr, &svalue)) {
+			return drgn_error_create(DRGN_ERROR_OTHER,
+						 "invalid DW_AT_const_value");
+		}
+		return drgn_object_set_signed_internal(ret, &type, bit_size,
+						       svalue);
+	} else if (kind == DRGN_OBJECT_UNSIGNED) {
+		Dwarf_Word uvalue;
+		if (dwarf_formudata(attr, &uvalue)) {
+			return drgn_error_create(DRGN_ERROR_OTHER,
+						 "invalid DW_AT_const_value");
+		}
+		return drgn_object_set_unsigned_internal(ret, &type, bit_size,
+							 uvalue);
+	} else {
+		return drgn_error_create(DRGN_ERROR_OTHER,
+					 "unknown DW_AT_const_value form");
+	}
 }
 
 static struct drgn_error *
 drgn_object_from_dwarf_variable(struct drgn_dwarf_info_cache *dicache,
 				Dwarf_Die *die, uint64_t bias, const char *name,
 				struct drgn_object *ret)
 {
-	struct drgn_error *err;
 	struct drgn_qualified_type qualified_type;
-	Dwarf_Attribute attr_mem;
-	Dwarf_Attribute *attr;
-	Dwarf_Op *loc;
-	size_t nloc;
-
-	err = drgn_type_from_dwarf_child(dicache, die, NULL, "DW_TAG_variable",
-					 true, true, NULL, &qualified_type);
+	struct drgn_error *err = drgn_type_from_dwarf_child(dicache, die, NULL,
+							    "DW_TAG_variable",
+							    true, true, NULL,
+							    &qualified_type);
 	if (err)
 		return err;
-	if (!(attr = dwarf_attr_integrate(die, DW_AT_location, &attr_mem))) {
+	Dwarf_Attribute attr_mem, *attr;
+	if ((attr = dwarf_attr_integrate(die, DW_AT_location, &attr_mem))) {
+		Dwarf_Op *loc;
+		size_t nloc;
+		if (dwarf_getlocation(attr, &loc, &nloc))
+			return drgn_error_libdw();
+		if (nloc != 1 || loc[0].atom != DW_OP_addr) {
+			return drgn_error_create(DRGN_ERROR_OTHER,
+						 "DW_AT_location has unimplemented operation");
+		}
+		enum drgn_byte_order byte_order;
+		err = dwarf_die_byte_order(die, true, &byte_order);
+		if (err)
+			return err;
+		return drgn_object_set_reference(ret, qualified_type,
+						 loc[0].number + bias, 0, 0,
+						 byte_order);
+	} else if ((attr = dwarf_attr_integrate(die, DW_AT_const_value,
+						&attr_mem))) {
+		return drgn_object_from_dwarf_constant(dicache, die,
+						       qualified_type, attr,
+						       ret);
+	} else {
 		return drgn_error_format(DRGN_ERROR_LOOKUP,
-					 "could not find address of '%s'",
+					 "could not find address or value of '%s'",
 					 name);
 	}
-	if (dwarf_getlocation(attr, &loc, &nloc))
-		return drgn_error_libdw();
-	if (nloc != 1 || loc[0].atom != DW_OP_addr) {
-		return drgn_error_create(DRGN_ERROR_OTHER,
-					 "DW_AT_location has unimplemented operation");
-	}
-	return drgn_object_set_reference(ret, qualified_type,
-					 loc[0].number + bias, 0, 0,
-					 dwarf_die_byte_order(die));
 }
 
 struct drgn_error *

libdrgn/examples/load_debug_info.c

@@ -0,0 +1,90 @@
+#include <getopt.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "drgn.h"
+
+static void usage(bool error)
+{
+	fprintf(error ? stderr : stdout,
+		"usage: load_debug_info [-k|-c CORE|-p PID]\n"
+		"\n"
+		"Example libdrgn program that loads default debug information\n"
+		"\n"
+		"Options:\n"
+		"  -k, --kernel            debug the running kernel (default)\n"
+		"  -c PATH, --core PATH    debug the given core dump\n"
+		"  -p PID, --pid PID       debug the running process with the given PID\n"
+		"  -h, --help              display this help message and exit\n");
+	exit(error ? EXIT_FAILURE : EXIT_SUCCESS);
+}
+
+int main(int argc, char **argv)
+{
+	struct option long_options[] = {
+		{"kernel", no_argument, NULL, 'k'},
+		{"core", required_argument, NULL, 'c'},
+		{"pid", required_argument, NULL, 'p'},
+		{"help", no_argument, NULL, 'h'},
+		{},
+	};
+	bool kernel = false;
+	const char *core = NULL;
+	const char *pid = NULL;
+	for (;;) {
+		int c = getopt_long(argc, argv, "kc:p:h", long_options, NULL);
+		if (c == -1)
+			break;
+		switch (c) {
+		case 'k':
+			kernel = true;
+			break;
+		case 'c':
+			core = optarg;
+			break;
+		case 'p':
+			pid = optarg;
+			break;
+		case 'h':
+			usage(false);
+		default:
+			usage(true);
+		}
+	}
+	if (optind != argc || kernel + !!core + !!pid > 1)
+		usage(true);
+
+	struct drgn_program *prog;
+	struct drgn_error *err = drgn_program_create(NULL, &prog);
+	if (err) {
+		prog = NULL;
+		goto out;
+	}
+
+	if (core)
+		err = drgn_program_set_core_dump(prog, core);
+	else if (pid)
+		err = drgn_program_set_pid(prog, atoi(pid) ?: getpid());
+	else
+		err = drgn_program_set_kernel(prog);
+	if (err)
+		goto out;
+
+	err = drgn_program_load_debug_info(prog, NULL, 0, true, true);
+
+out:;
+	int status;
+	if (err) {
+		if (err->code == DRGN_ERROR_MISSING_DEBUG_INFO)
+			status = EXIT_SUCCESS;
+		else
+			status = EXIT_FAILURE;
+		drgn_error_fwrite(stderr, err);
+		drgn_error_destroy(err);
+	} else {
+		status = EXIT_SUCCESS;
+	}
+	drgn_program_destroy(prog);
+	return status;
+}