Add is_pic field to statedump soinfo event

This field indicates whether the executable or library is position
independent code (PIC). The field is not added to the similar dlopen
event from liblttng-ust-dl because in that case all dlopened libraries
are necessarily PIC.

This allows a posteriori analyses to be performed without having to
read the executable file to know whether adresses are relative to the
base address or absolute.

Signed-off-by: Antoine Busque <abusque@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/doc/man/lttng-ust.3.txt b/doc/man/lttng-ust.3.txt
index 1f4d7e481e95fb1f0957a8dc86fa5a4817654b66..c7b82c1a61876762a0026b183b8c3d1aabdce890 100644 (file)
--- a/doc/man/lttng-ust.3.txt
+++ b/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

diff --git a/include/lttng/ust-elf.h b/include/lttng/ust-elf.h
index 6e9d99518dce20027b11e9a2ebf343a8dec42d25..e9b0ac7b4e3ea22b86a53781b908f26f27749623 100644 (file)
--- a/include/lttng/ust-elf.h
+++ b/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);

diff --git a/liblttng-ust/lttng-ust-elf.c b/liblttng-ust/lttng-ust-elf.c
index e90626906b6ea72c24d19bbcd4a3b7cee92e0821..346545583c3a23b399b9a71911c59e5ded6bc387 100644 (file)
--- a/liblttng-ust/lttng-ust-elf.c
+++ b/liblttng-ust/lttng-ust-elf.c
@@ -316,6 +316,18 @@ error:
        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.
  */

diff --git a/liblttng-ust/lttng-ust-statedump-provider.h b/liblttng-ust/lttng-ust-statedump-provider.h
index 5e212d9e3cce0e79cd6f8ffb9b4807c5b64fc825..427ba2710d7643674d082a8170485155bfd8e773 100644 (file)
--- a/liblttng-ust/lttng-ust-statedump-provider.h
+++ b/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)
        )
 )
 

diff --git a/liblttng-ust/lttng-ust-statedump.c b/liblttng-ust/lttng-ust-statedump.c
index 93a035b35a0ead7032e2ae121d8168f5c624c6da..b160e197376f70116ad6a34e304f399a92daeea0 100644 (file)
--- a/liblttng-ust/lttng-ust-statedump.c
+++ b/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;