[PATCH 6/9 v2] Implement mount namespace support for native Linux targets

Gary Benson
2015-04-30T12:05:54Z

This commit allows GDB to access executables and shared libraries
on native Linux targets where GDB and the inferior have different
mount namespaces.

gdb/ChangeLog:

* linux-nat.c (nat/linux-namespaces.h): New include.
(fileio.h): Likewise.
(linux_nat_filesystem_is_local): New function.
(linux_nat_fileio_pid_of): Likewise.
(linux_nat_fileio_open): Likewise.
(linux_nat_fileio_readlink): Likewise.
(linux_nat_fileio_unlink): Likewise.
(linux_nat_add_target): Initialize to_filesystem_is_local,
to_fileio_open, to_fileio_readlink and to_fileio_unlink.
(_initialize_linux_nat): New "set/show debug lin-ns" commands.
* NEWS: Mention new "set/show debug lin-ns" commands.
---
gdb/ChangeLog | 14 +++++++
gdb/NEWS | 4 ++
gdb/linux-nat.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 132 insertions(+), 0 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index d463b52..1c0e5ea 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -89,6 +89,10 @@ set|show record btrace bts buffer-size
The obtained size may differ from the requested size. Use "info
record" to see the obtained buffer size.

+set debug lin-ns
+show debug lin-ns
+ Control display of debugging info regarding Linux namespaces.
+
* The command 'thread apply all' can now support new option '-ascending'
to call its specified command for all threads in ascending order.

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index b04aa68..85149a2 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -66,6 +66,8 @@
#include "target-descriptions.h"
#include "filestuff.h"
#include "objfiles.h"
+#include "nat/linux-namespaces.h"
+#include "fileio.h"

#ifndef SPUFS_MAGIC
#define SPUFS_MAGIC 0x23c9b64e
@@ -4842,6 +4844,104 @@ linux_nat_core_of_thread (struct target_ops *ops, ptid_t ptid)
return -1;
}

+/* Implementation of to_filesystem_is_local. */
+
+static int
+linux_nat_filesystem_is_local (struct target_ops *ops)
+{
+ struct inferior *inf = current_inferior ();
+
+ if (inf->fake_pid_p || inf->pid == 0)
+ return 1;
+
+ return linux_ns_same (inf->pid, LINUX_NS_MNT);
+}
+
+/* Convert the INF argument passed to a to_fileio_* method
+ to a process ID suitable for passing to its corresponding
+ linux_mntns_* function. If INF is non-NULL then the
+ caller is requesting the filesystem seen by INF. If INF
+ is NULL then the caller is requesting the filesystem seen
+ by the GDB. We fall back to GDB's filesystem in the case
+ that INF is non-NULL but its PID is unknown. */
+
+static pid_t
+linux_nat_fileio_pid_of (struct inferior *inf)
+{
+ if (inf == NULL || inf->fake_pid_p || inf->pid == 0)
+ return getpid ();
+ else
+ return inf->pid;
+}
+
+/* Implementation of to_fileio_open. */
+
+static int
+linux_nat_fileio_open (struct target_ops *self,
+ struct inferior *inf, const char *filename,
+ int flags, int mode, int *target_errno)
+{
+ int nat_flags;
+ int fd;
+
+ if (fileio_to_host_openflags (flags, &nat_flags) == -1)
+ {
+ *target_errno = FILEIO_EINVAL;
+ return -1;
+ }
+
+ /* We do not need to convert MODE, since the fileio protocol
+ uses the standard values. */
+ fd = linux_mntns_open_cloexec (linux_nat_fileio_pid_of (inf),
+ filename, nat_flags, mode);
+ if (fd == -1)
+ *target_errno = host_to_fileio_error (errno);
+
+ return fd;
+}
+
+/* Implementation of to_fileio_readlink. */
+
+static char *
+linux_nat_fileio_readlink (struct target_ops *self,
+ struct inferior *inf, const char *filename,
+ int *target_errno)
+{
+ char buf[PATH_MAX];
+ int len;
+ char *ret;
+
+ len = linux_mntns_readlink (linux_nat_fileio_pid_of (inf),
+ filename, buf, sizeof (buf));
+ if (len < 0)
+ {
+ *target_errno = host_to_fileio_error (errno);
+ return NULL;
+ }
+
+ ret = xmalloc (len + 1);
+ memcpy (ret, buf, len);
+ ret[len] = '\0';
+ return ret;
+}
+
+/* Implementation of to_fileio_unlink. */
+
+static int
+linux_nat_fileio_unlink (struct target_ops *self,
+ struct inferior *inf, const char *filename,
+ int *target_errno)
+{
+ int ret;
+
+ ret = linux_mntns_unlink (linux_nat_fileio_pid_of (inf),
+ filename);
+ if (ret == -1)
+ *target_errno = host_to_fileio_error (errno);
+
+ return ret;
+}
+
void
linux_nat_add_target (struct target_ops *t)
{
@@ -4895,6 +4995,11 @@ linux_nat_add_target (struct target_ops *t)

t->to_core_of_thread = linux_nat_core_of_thread;

+ t->to_filesystem_is_local = linux_nat_filesystem_is_local;
+ t->to_fileio_open = linux_nat_fileio_open;
+ t->to_fileio_readlink = linux_nat_fileio_readlink;
+ t->to_fileio_unlink = linux_nat_fileio_unlink;
+
/* We don't change the stratum; this target will sit at
process_stratum and thread_db will set at thread_stratum. This
is a little strange, since this is a multi-threaded-capable
@@ -5012,6 +5117,15 @@ Enables printf debugging output."),
show_debug_linux_nat,
&setdebuglist, &showdebuglist);

+ add_setshow_boolean_cmd ("lin-ns", class_maintenance,
+ &debug_linux_namespaces, _("\
+Set debugging of GNU/Linux namespaces module."), _("\
+Show debugging of GNU/Linux namespaces module."), _("\
+Enables printf debugging output."),
+ NULL,
+ NULL,
+ &setdebuglist, &showdebuglist);
+
/* Save this mask as the default. */
sigprocmask (SIG_SETMASK, NULL, &normal_mask);

--
1.7.1