[PATCH 8/9 v2] Implement vFile:setfs in gdbserver

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

This commit implements the "vFile:setfs" packet in gdbserver.

gdb/gdbserver/ChangeLog:

* target.h (struct target_ops) <multifs_open>: New field.
<multifs_unlink>: Likewise.
<multifs_readlink>: Likewise.
* linux-low.c (nat/linux-namespaces.h): New include.
(linux_target_ops): Initialize the_target->multifs_open,
the_target->multifs_unlink and the_target->multifs_readlink.
* hostio.c (hostio_fs_pid): New static variable.
(handle_setfs): New function.
(handle_open): Use the_target->multifs_open as appropriate.
(handle_unlink): Use the_target->multifs_unlink as appropriate.
(handle_readlink): Use the_target->multifs_readlink as
appropriate.
(handle_vFile): Handle vFile:setfs packets.
---
gdb/gdbserver/ChangeLog | 16 +++++++++++
gdb/gdbserver/hostio.c | 62 ++++++++++++++++++++++++++++++++++++++++++--
gdb/gdbserver/linux-low.c | 4 +++
gdb/gdbserver/target.h | 21 +++++++++++++++
4 files changed, 100 insertions(+), 3 deletions(-)

diff --git a/gdb/gdbserver/hostio.c b/gdb/gdbserver/hostio.c
index 9e858d9..10cff5a 100644
--- a/gdb/gdbserver/hostio.c
+++ b/gdb/gdbserver/hostio.c
@@ -243,6 +243,47 @@ hostio_reply_with_data (char *own_buf, char *buffer, int len,
return input_index;
}

+/* Process ID of inferior whose filesystem hostio functions
+ that take FILENAME arguments will use. Zero means to use
+ our own filesystem. */
+
+static int hostio_fs_pid = 0;
+
+/* Handle a "vFile:setfs:" packet. */
+
+static void
+handle_setfs (char *own_buf)
+{
+ char *p;
+ int pid;
+
+ /* If the target doesn't have any of the in-filesystem-of methods
+ then there's no point in GDB sending "vFile:setfs:" packets. We
+ reply with an empty packet (i.e. we pretend we don't understand
+ "vFile:setfs:") and that should stop GDB sending any more. */
+ if (the_target->multifs_open == NULL
+ && the_target->multifs_unlink == NULL
+ && the_target->multifs_readlink == NULL)
+ {
+ own_buf[0] = '\0';
+ return;
+ }
+
+ p = own_buf + strlen ("vFile:setfs:");
+
+ if (require_int (&p, &pid)
+ || pid < 0
+ || require_end (p))
+ {
+ hostio_packet_error (own_buf);
+ return;
+ }
+
+ hostio_fs_pid = pid;
+
+ hostio_reply (own_buf, 0);
+}
+
static void
handle_open (char *own_buf)
{
@@ -267,7 +308,11 @@ handle_open (char *own_buf)

/* We do not need to convert MODE, since the fileio protocol
uses the standard values. */
- fd = open (filename, flags, mode);
+ if (hostio_fs_pid != 0 && the_target->multifs_open != NULL)
+ fd = the_target->multifs_open (hostio_fs_pid, filename,
+ flags, mode);
+ else
+ fd = open (filename, flags, mode);

if (fd == -1)
{
@@ -471,7 +516,10 @@ handle_unlink (char *own_buf)
return;
}

- ret = unlink (filename);
+ if (hostio_fs_pid != 0 && the_target->multifs_unlink != NULL)
+ ret = the_target->multifs_unlink (hostio_fs_pid, filename);
+ else
+ ret = unlink (filename);

if (ret == -1)
{
@@ -498,7 +546,13 @@ handle_readlink (char *own_buf, int *new_packet_len)
return;
}

- ret = readlink (filename, linkname, sizeof (linkname) - 1);
+ if (hostio_fs_pid != 0 && the_target->multifs_readlink != NULL)
+ ret = the_target->multifs_readlink (hostio_fs_pid, filename,
+ linkname,
+ sizeof (linkname) - 1);
+ else
+ ret = readlink (filename, linkname, sizeof (linkname) - 1);
+
if (ret == -1)
{
hostio_error (own_buf);
@@ -532,6 +586,8 @@ handle_vFile (char *own_buf, int packet_len, int *new_packet_len)
handle_unlink (own_buf);
else if (startswith (own_buf, "vFile:readlink:"))
handle_readlink (own_buf, new_packet_len);
+ else if (startswith (own_buf, "vFile:setfs:"))
+ handle_setfs (own_buf);
else
return 0;

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 1c4c2d7..42e8a9e 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -51,6 +51,7 @@
definition of elf_fpregset_t. */
#include <elf.h>
#endif
+#include "nat/linux-namespaces.h"

#ifndef SPUFS_MAGIC
#define SPUFS_MAGIC 0x23c9b64e
@@ -6434,6 +6435,9 @@ static struct target_ops linux_target_ops = {
#endif
linux_supports_range_stepping,
linux_proc_pid_to_exec_file,
+ linux_mntns_open_cloexec,
+ linux_mntns_unlink,
+ linux_mntns_readlink,
};

static void
diff --git a/gdb/gdbserver/target.h b/gdb/gdbserver/target.h
index 6280c26..7f4a1de 100644
--- a/gdb/gdbserver/target.h
+++ b/gdb/gdbserver/target.h
@@ -402,6 +402,27 @@ struct target_ops
string should be copied into a buffer by the client if the string
will not be immediately used, or if it must persist. */
char *(*pid_to_exec_file) (int pid);
+
+ /* Multiple-filesystem-aware open. Like open(2), but operating in
+ the filesystem as it appears to process PID. Systems where all
+ processes share a common filesystem should set this to NULL.
+ If NULL, the caller should fall back to open(2). */
+ int (*multifs_open) (int pid, const char *filename,
+ int flags, mode_t mode);
+
+ /* Multiple-filesystem-aware unlink. Like unlink(2), but operates
+ in the filesystem as it appears to process PID. Systems where
+ all processes share a common filesystem should set this to NULL.
+ If NULL, the caller should fall back to unlink(2). */
+ int (*multifs_unlink) (int pid, const char *filename);
+
+ /* Multiple-filesystem-aware readlink. Like readlink(2), but
+ operating in the filesystem as it appears to process PID.
+ Systems where all processes share a common filesystem should
+ set this to NULL. If NULL, the caller should fall back to
+ readlink(2). */
+ ssize_t (*multifs_readlink) (int pid, const char *filename,
+ char *buf, size_t bufsiz);
};

extern struct target_ops *the_target;
--
1.7.1