[RFA] Darwin: handle shared libraries in attached processes

Tristan Gingold
2011-09-27T13:41:47Z

Hi,

this patch adds support for shared libraries in attached processes. This was not supported until now.

The basic issue is to know the address at which the dynamic loader is loaded. This is done using a method similar to linux: an address is read from the target object space TARGET_OBJECT_DARWIN_DYLD_INFO (not unlike TARGET_OBJECT_AUXV).

Most of the code is within my area maintenance, except the new macro in target.h

Manually tested on x86_64-apple-darwin11

Ok for trunk ?

Tristan.

2011-09-27 Tristan Gingold <gingold@adacore.com>

* target.h (enum target_object): Add TARGET_OBJECT_DARWIN_DYLD_INFO.
* solib-darwin.c (DYLD_VERSION_MAX): Update number.
(darwin_solib_get_all_image_info_addr_at_init): New function.
(darwin_solib_read_all_image_info_addr): Likewise.
(darwin_solib_create_inferior_hook): Use the above two functions.
* darwin-nat.c (darwin_execvp): Renames retval to res.
(darwin_read_write_inferior): Update comment.
(darwin_read_dyld_info): New function.
(darwin_xfer_partial): Handle DYLD_INFO.

diff --git a/gdb/darwin-nat.c b/gdb/darwin-nat.c
index 7c0ff5b..94f49d6 100644
--- a/gdb/darwin-nat.c
+++ b/gdb/darwin-nat.c
@@ -1512,10 +1512,10 @@ darwin_execvp (const char *file, char * const argv[], char * const env[])
{
posix_spawnattr_t attr;
short ps_flags = 0;
- int retval;
+ int res;

- retval = posix_spawnattr_init (&attr);
- if (retval != 0)
+ res = posix_spawnattr_init (&attr);
+ if (res != 0)
{
fprintf_unfiltered
(gdb_stderr, "Cannot initialize attribute for posix_spawn\n");
@@ -1531,11 +1531,10 @@ darwin_execvp (const char *file, char * const argv[], char * const env[])
#define _POSIX_SPAWN_DISABLE_ASLR 0x0100
#endif
ps_flags |= _POSIX_SPAWN_DISABLE_ASLR;
- retval = posix_spawnattr_setflags (&attr, ps_flags);
- if (retval != 0)
+ res = posix_spawnattr_setflags (&attr, ps_flags);
+ if (res != 0)
{
- fprintf_unfiltered
- (gdb_stderr, "Cannot set posix_spawn flags\n");
+ fprintf_unfiltered (gdb_stderr, "Cannot set posix_spawn flags\n");
return;
}

@@ -1695,7 +1694,7 @@ darwin_thread_alive (struct target_ops *ops, ptid_t ptid)
copy it to RDADDR in gdb's address space.
If WRADDR is not NULL, write gdb's LEN bytes from WRADDR and copy it
to ADDR in inferior task's address space.
- Return 0 on failure; number of bytes read / writen otherwise. */
+ Return 0 on failure; number of bytes read / writen otherwise. */
static int
darwin_read_write_inferior (task_t task, CORE_ADDR addr,
char *rdaddr, const char *wraddr, int length)
@@ -1824,6 +1823,32 @@ out:
return length;
}

+/* Read LENGTH bytes at offset ADDR of task_dyld_info for TASK, and copy them
+ to RDADDR.
+ Return 0 on failure; number of bytes read / writen otherwise. */
+
+static int
+darwin_read_dyld_info (task_t task, CORE_ADDR addr, char *rdaddr, int length)
+{
+ struct task_dyld_info task_dyld_info;
+ mach_msg_type_number_t count = TASK_DYLD_INFO_COUNT;
+ int sz = TASK_DYLD_INFO_COUNT * sizeof (natural_t);
+ kern_return_t kret;
+
+ if (addr >= sz)
+ return 0;
+
+ kret = task_info (task, TASK_DYLD_INFO, (task_info_t) &task_dyld_info, &count);
+ MACH_CHECK_ERROR (kret);
+ if (kret != KERN_SUCCESS)
+ return -1;
+ /* Truncate. */
+ if (addr + length > sz)
+ length = sz - addr;
+ memcpy (rdaddr, (char *)&task_dyld_info + addr, length);
+ return length;
+}
+

/* Return 0 on failure, number of bytes handled otherwise. TARGET
is ignored. */
@@ -1860,11 +1885,22 @@ darwin_xfer_partial (struct target_ops *ops,
host_address_to_string (readbuf), host_address_to_string (writebuf),
inf->pid);

- if (object != TARGET_OBJECT_MEMORY)
- return -1;
+ switch (object)
+ {
+ case TARGET_OBJECT_MEMORY:
+ return darwin_read_write_inferior (inf->private->task, offset,
+ readbuf, writebuf, len);
+ case TARGET_OBJECT_DARWIN_DYLD_INFO:
+ if (writebuf != NULL || readbuf == NULL)
+ {
+ /* Support only read. */
+ return -1;
+ }
+ return darwin_read_dyld_info (inf->private->task, offset, readbuf, len);
+ default:
+ return -1;
+ }

- return darwin_read_write_inferior (inf->private->task, offset,
- readbuf, writebuf, len);
}

static void
diff --git a/gdb/solib-darwin.c b/gdb/solib-darwin.c
index 24301d9..d592809 100644
--- a/gdb/solib-darwin.c
+++ b/gdb/solib-darwin.c
@@ -68,7 +68,7 @@ struct gdb_dyld_all_image_infos

/* Current all_image_infos version. */
#define DYLD_VERSION_MIN 1
-#define DYLD_VERSION_MAX 7
+#define DYLD_VERSION_MAX 12

/* Address of structure dyld_all_image_infos in inferior. */
static CORE_ADDR dyld_all_image_addr;
@@ -293,22 +293,19 @@ darwin_special_symbol_handling (void)
{
}

-/* Shared library startup support. See documentation in solib-svr4.c. */
+/* Extract dyld_all_image_addr when the process was just created, assuming the
+ current PC is at the entry of the dynamic linker. */

static void
-darwin_solib_create_inferior_hook (int from_tty)
+darwin_solib_get_all_image_info_addr_at_init (void)
{
- struct minimal_symbol *msymbol;
- char **bkpt_namep;
- asection *interp_sect;
gdb_byte *interp_name;
- CORE_ADDR sym_addr;
CORE_ADDR load_addr = 0;
- int load_addr_found = 0;
- int loader_found_in_list = 0;
- struct so_list *so;
bfd *dyld_bfd = NULL;
- struct inferior *inf = current_inferior ();
+
+ /* This method doesn't work with an attached process. */
+ if (current_inferior ()->attach_flag)
+ return;

/* Find the program interpreter. */
interp_name = find_program_interpreter ();
@@ -316,7 +313,6 @@ darwin_solib_create_inferior_hook (int from_tty)
return;

/* Create a bfd for the interpreter. */
- sym_addr = 0;
dyld_bfd = bfd_openr (interp_name, gnutarget);
if (dyld_bfd)
{
@@ -335,21 +331,11 @@ darwin_solib_create_inferior_hook (int from_tty)
if (!dyld_bfd)
return;

- if (!inf->attach_flag)
- {
- /* We find the dynamic linker's base address by examining
- the current pc (which should point at the entry point for the
- dynamic linker) and subtracting the offset of the entry point. */
- load_addr = (regcache_read_pc (get_current_regcache ())
- - bfd_get_start_address (dyld_bfd));
- }
- else
- {
- /* FIXME: todo.
- Get address of __DATA.__dyld in exec_bfd, read address at offset 0.
- */
- return;
- }
+ /* We find the dynamic linker's base address by examining
+ the current pc (which should point at the entry point for the
+ dynamic linker) and subtracting the offset of the entry point. */
+ load_addr = (regcache_read_pc (get_current_regcache ())
+ - bfd_get_start_address (dyld_bfd));

/* Now try to set a breakpoint in the dynamic linker. */
dyld_all_image_addr =
@@ -361,6 +347,40 @@ darwin_solib_create_inferior_hook (int from_tty)
return;

dyld_all_image_addr += load_addr;
+}
+
+/* Extract dyld_all_image_addr reading it from
+ TARGET_OBJECT_DARWIN_DYLD_INFO. */
+
+static void
+darwin_solib_read_all_image_info_addr (void)
+{
+ gdb_byte buf[8 + 8 + 4];
+ LONGEST len;
+ enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
+
+ len = target_read (&current_target, TARGET_OBJECT_DARWIN_DYLD_INFO, NULL,
+ buf, 0, sizeof (buf));
+ if (len != sizeof (buf))
+ return;
+
+ dyld_all_image_addr = extract_unsigned_integer (buf, 8, byte_order);
+}
+
+/* Shared library startup support. See documentation in solib-svr4.c. */
+
+static void
+darwin_solib_create_inferior_hook (int from_tty)
+{
+ dyld_all_image_addr = 0;
+
+ darwin_solib_read_all_image_info_addr ();
+
+ if (dyld_all_image_addr == 0)
+ darwin_solib_get_all_image_info_addr_at_init ();
+
+ if (dyld_all_image_addr == 0)
+ return;

darwin_load_image_infos ();

diff --git a/gdb/target.h b/gdb/target.h
index e264657..173e60b 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -276,6 +276,8 @@ enum target_object
TARGET_OBJECT_TRACEFRAME_INFO,
/* Load maps for FDPIC systems. */
TARGET_OBJECT_FDPIC,
+ /* Darwin dynamic linker info data. */
+ TARGET_OBJECT_DARWIN_DYLD_INFO
/* Possible future objects: TARGET_OBJECT_FILE, ... */
};