Is pic

doc/man/lttng-ust.3.txt

@@ -777,18 +777,20 @@ This event has no fields.
 This event has no fields.
 
 `lttng_ust_statedump:soinfo`::
-    Emitted when information about a currently loaded shared object is
-    found.
+    Emitted when information about a currently loaded executable or
+    shared object is found.
 +
 Fields:
 +
 [options="header"]
-|==============================================================
+|==================================================================
 | Field name                 | Description
-| `baddr`                    | Base address of loaded library
-| `memsz`                    | Size of loaded library in memory
-| `sopath`                   | Path to loaded library file
-|==============================================================
+| `baddr`                    | Base address of loaded executable
+| `memsz`                    | Size of loaded executable in memory
+| `sopath`                   | Path to loaded executable file
+| `is_pic`                   | Whether the executable is
+                               position-independent code
+|==================================================================
 
 `lttng_ust_statedump:build_id`::
     Emitted when a build ID is found in a currently loaded shared

include/lttng/ust-elf.h

@@ -219,6 +219,7 @@ int is_elf_native_endian(struct lttng_ust_elf *elf)
 
 struct lttng_ust_elf *lttng_ust_elf_create(const char *path);
 void lttng_ust_elf_destroy(struct lttng_ust_elf *elf);
+uint8_t lttng_ust_elf_is_pic(struct lttng_ust_elf *elf);
 int lttng_ust_elf_get_memsz(struct lttng_ust_elf *elf, uint64_t *memsz);
 int lttng_ust_elf_get_build_id(struct lttng_ust_elf *elf, uint8_t **build_id,
 			size_t *length, int *found);

liblttng-ust/lttng-ust-elf.c

@@ -316,6 +316,16 @@ struct lttng_ust_elf *lttng_ust_elf_create(const char *path)
 	return NULL;
 }
 
+/*
+ * Test whether the ELF file is position independent code (PIC)
+ */
+uint8_t lttng_ust_elf_is_pic(struct lttng_ust_elf *elf)
+{
+	/* PIC has and e_type value of ET_DYN, see ELF specification
+	 * version 1.1 p. 1-3. */
+	return elf->ehdr->e_type == ET_DYN;
+}
+
 /*
  * Destroy the given lttng_ust_elf instance.
  */

liblttng-ust/lttng-ust-statedump-provider.h

@@ -48,12 +48,14 @@ TRACEPOINT_EVENT(lttng_ust_statedump, soinfo,
 		struct lttng_session *, session,
 		void *, baddr,
 		const char*, sopath,
-		uint64_t, memsz
+		uint64_t, memsz,
+		uint8_t, is_pic
 	),
 	TP_FIELDS(
 		ctf_integer_hex(void *, baddr, baddr)
 		ctf_integer(uint64_t, memsz, memsz)
 		ctf_string(sopath, sopath)
+		ctf_integer(uint8_t, is_pic, is_pic)
 	)
 )
 

liblttng-ust/lttng-ust-statedump.c

@@ -52,6 +52,7 @@ struct soinfo_data {
 	size_t build_id_len;
 	int vdso;
 	uint32_t crc;
+	uint8_t is_pic;
 };
 
 typedef void (*tracepoint_cb)(struct lttng_session *session, void *priv);
@@ -84,7 +85,7 @@ void trace_soinfo_cb(struct lttng_session *session, void *priv)
 
 	tracepoint(lttng_ust_statedump, soinfo,
 		session, so_data->base_addr_ptr,
-		so_data->resolved_path, so_data->memsz);
+		so_data->resolved_path, so_data->memsz, so_data->is_pic);
 }
 
 static
@@ -147,6 +148,8 @@ int get_elf_info(struct soinfo_data *so_data, int *has_build_id,
 		goto end;
 	}
 
+	so_data->is_pic = lttng_ust_elf_is_pic(elf);
+
 end:
 	lttng_ust_elf_destroy(elf);
 	return ret;

tests/ust-elf/Makefile.am

@@ -7,7 +7,21 @@ prog_LDADD = $(top_builddir)/liblttng-ust/liblttng-ust.la \
 
 noinst_SCRIPTS = test_ust_elf
 CLEANFILES = $(noinst_SCRIPTS)
-EXTRA_DIST = test_ust_elf.in $(srcdir)/data/**
+EXTRA_DIST = test_ust_elf.in \
+	$(srcdir)/data/main.c \
+	$(srcdir)/data/aarch64_be/main.elf \
+	$(srcdir)/data/aarch64_be/main.elf.debug \
+	$(srcdir)/data/armeb/main.elf \
+	$(srcdir)/data/armeb/main.elf.debug \
+	$(srcdir)/data/x86/main.elf \
+	$(srcdir)/data/x86/main.elf.debug \
+	$(srcdir)/data/x86_64/main.elf \
+	$(srcdir)/data/x86_64/main.elf.debug \
+	$(srcdir)/data/pic/hello.exec \
+	$(srcdir)/data/pic/hello.pie \
+	$(srcdir)/data/pic/hello.pic \
+	$(srcdir)/data/pic/hello.c \
+	$(srcdir)/data/pic/libhello.c
 
 $(noinst_SCRIPTS): %: %.in
 	sed "s#@ABSTOPSRCDIR@#$(abs_top_srcdir)#g" < $< > $@

tests/ust-elf/README.md

@@ -40,3 +40,13 @@ is added to the executable. The commands used are as follow:
     $ objcopy --only-keep-debug main.elf main.elf.debug
     $ strip -g main.elf
     $ objcopy --add-gnu-debuglink=main.elf.debug main.elf
+
+There is also a series of tests used to check detection of
+position-independent code (PIC). These tests use three pre-compiled
+ELF files found under `data/pic/`, namely `hello.exec`, `hello.pie`,
+and `hello.pic`. These can be re-generated using the files `hello.c`
+and `libhello.c`, with the following commands:
+
+    $ gcc hello.c -o hello.exec
+    $ gcc hello.c -fPIC -pie -o hello.pie
+    $ gcc -shared -o hello.pic -fPIC libhello.c

tests/ust-elf/data/pic/hello.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+int main()
+{
+	puts("hello, world");
+
+	return 0;
+}

tests/ust-elf/data/pic/libhello.c

@@ -0,0 +1,6 @@
+#include <stdio.h>
+
+void hello()
+{
+	puts("hello, world");
+}

tests/ust-elf/prog.c

@@ -26,7 +26,8 @@
 
 #define NUM_ARCH 4
 #define NUM_TESTS_PER_ARCH 11
-#define NUM_TESTS (NUM_ARCH * NUM_TESTS_PER_ARCH) + 1
+#define NUM_TESTS_PIC 3
+#define NUM_TESTS (NUM_ARCH * NUM_TESTS_PER_ARCH) + NUM_TESTS_PIC + 1
 
 /*
  * Expected memsz were computed using libelf, build ID and debug link
@@ -115,6 +116,35 @@ void test_elf(const char *test_dir, const char *arch, uint64_t exp_memsz,
 	lttng_ust_elf_destroy(elf);
 }
 
+static
+void test_pic(const char *test_dir)
+{
+	char exec_path[PATH_MAX];
+	char pie_path[PATH_MAX];
+	char pic_path[PATH_MAX];
+	struct lttng_ust_elf *elf = NULL;
+	uint8_t is_pic;
+
+	snprintf(exec_path, PATH_MAX, "%s/data/pic/hello.exec", test_dir);
+	snprintf(pie_path, PATH_MAX, "%s/data/pic/hello.pie", test_dir);
+	snprintf(pic_path, PATH_MAX, "%s/data/pic/hello.pic", test_dir);
+
+	elf = lttng_ust_elf_create(exec_path);
+	is_pic = lttng_ust_elf_is_pic(elf);
+	ok(is_pic == 0, "hello.exec is not PIC");
+	lttng_ust_elf_destroy(elf);
+
+	elf = lttng_ust_elf_create(pie_path);
+	is_pic = lttng_ust_elf_is_pic(elf);
+	ok(is_pic == 1, "hello.pie is PIC");
+	lttng_ust_elf_destroy(elf);
+
+	elf = lttng_ust_elf_create(pic_path);
+	is_pic = lttng_ust_elf_is_pic(elf);
+	ok(is_pic == 1, "hello.pic is PIC");
+	lttng_ust_elf_destroy(elf);
+}
+
 int main(int argc, char **argv)
 {
 	const char *test_dir;
@@ -133,6 +163,7 @@ int main(int argc, char **argv)
 	test_elf(test_dir, "armeb", ARMEB_MEMSZ, armeb_build_id, ARMEB_CRC);
 	test_elf(test_dir, "aarch64_be", AARCH64_BE_MEMSZ, aarch64_be_build_id,
 		AARCH64_BE_CRC);
+	test_pic(test_dir);
 
 	return EXIT_SUCCESS;
 }