@@ -34,6 +34,7 @@
#include "nat/fork-inferior.h"
#include "utils.h"
#include "gdbarch.h"
+#include "nat/fork-inferior.h"
@@ -97,10 +98,23 @@ inf_ptrace_target::remove_fork_catchpoint (int pid)
/* Prepare to be traced. */
static void
-inf_ptrace_me (void)
+inf_ptrace_me (int trace_errno_wpipe)
{
/* "Trace me, Dr. Memory!" */
- if (ptrace (PT_TRACE_ME, 0, (PTRACE_TYPE_ARG3) 0, 0) < 0)
+ int ret = ptrace (PT_TRACE_ME, 0, (PTRACE_TYPE_ARG3) 0, 0);
+ int ptrace_errno = ret < 0 ? errno : 0;
+
+ try
+ {
+ write_trace_errno_to_pipe (trace_errno_wpipe, ptrace_errno);
+ }
+ catch (const gdb_exception &e)
+ {
+ warning ("%s", e.what ());
+ _exit (0177);
+ }
+
+ if (ret < 0)
trace_start_error_with_name ("ptrace");
}
@@ -31,6 +31,7 @@
#include "nat/linux-ptrace.h"
#include "nat/linux-procfs.h"
#include "nat/linux-personality.h"
+#include "nat/fork-inferior.h"
#include "linux-fork.h"
#include "gdbthread.h"
#include "gdbcmd.h"
@@ -1136,7 +1137,7 @@ attach_proc_task_lwp_callback (ptid_t ptid)
else
{
std::string reason
- = linux_ptrace_attach_fail_reason_string (ptid, err);
+ = linux_ptrace_attach_fail_reason_lwp (ptid, err);
warning (_("Cannot attach to lwp %d: %s"),
lwpid, reason.c_str ());
@@ -1191,8 +1192,9 @@ linux_nat_target::attach (const char *args, int from_tty)
}
catch (const gdb_exception_error &ex)
{
+ int saved_errno = errno;
pid_t pid = parse_pid_to_attach (args);
- std::string reason = linux_ptrace_attach_fail_reason (pid);
+ std::string reason = linux_ptrace_attach_fail_reason (pid, saved_errno);
if (!reason.empty ())
throw_error (ex.error, "warning: %s\n%s", reason.c_str (),
@@ -4582,6 +4584,10 @@ Enables printf debugging output."),
sigemptyset (&blocked_mask);
lwp_lwpid_htab_create ();
+
+ /* Set the proper function to generate a message when ptrace
+ fails. */
+ trace_me_fail_reason = linux_ptrace_me_fail_reason;
}
@@ -394,9 +394,9 @@ struct traceme_info
This function will usually perform the call to whatever trace
function needed to start tracing the inferior, but will also
- write its errno value to TRACE_ERRNO_PIPE, so that
+ write its errno value to TRACE_ERRNO_WPIPE, so that
fork_inferior_1 can check whether it suceeded. */
- void (*traceme_fun_check) (int trace_errno_pipe);
+ void (*traceme_fun_check) (int trace_errno_wpipe);
} u;
};
@@ -626,7 +626,7 @@ fork_inferior (const char *exec_file_arg, const std::string &allargs,
pid_t
fork_inferior (const char *exec_file_arg, const std::string &allargs,
- char **env, void (*traceme_fun) (int trace_errno_pipe),
+ char **env, void (*traceme_fun) (int trace_errno_wpipe),
gdb::function_view<void (int)> init_trace_fun,
void (*pre_trace_fun) (),
const char *shell_file_arg,
@@ -66,7 +66,7 @@ extern pid_t fork_inferior (const char *exec_file_arg,
extern pid_t fork_inferior (const char *exec_file_arg,
const std::string &allargs,
char **env,
- void (*traceme_fun) (int trace_errno_pipe),
+ void (*traceme_fun) (int trace_errno_wpipe),
gdb::function_view<void (int)> init_trace_fun,
void (*pre_trace_fun) (),
const char *shell_file_arg,
@@ -21,6 +21,9 @@
#include "linux-procfs.h"
#include "linux-waitpid.h"
#include "gdbsupport/buffer.h"
+#include "gdbsupport/gdb-dlfcn.h"
+#include "nat/fork-inferior.h"
+#include "gdbsupport/filestuff.h"
#ifdef HAVE_SYS_PROCFS_H
#include <sys/procfs.h>
#endif
@@ -30,11 +33,93 @@
of 0 means there are no supported features. */
static int supported_ptrace_options = -1;
-/* Find all possible reasons we could fail to attach PID and return these
- as a string. An empty string is returned if we didn't find any reason. */
+typedef int (*selinux_ftype) (const char *);
-std::string
-linux_ptrace_attach_fail_reason (pid_t pid)
+/* Helper function which checks if ptrace is probably restricted
+ (i.e., if ERR is either EACCES or EPERM), and returns a string with
+ possible workarounds. */
+
+static std::string
+linux_ptrace_restricted_fail_reason (int err)
+{
+ if (err != EACCES && err != EPERM)
+ {
+ /* It just makes sense to perform the checks below if errno was
+ either EACCES or EPERM. */
+ return {};
+ }
+
+ std::string ret;
+ gdb_dlhandle_up handle;
+
+ try
+ {
+ handle = gdb_dlopen ("libselinux.so.1");
+ }
+ catch (const gdb_exception_error &e)
+ {
+ }
+
+ if (handle != nullptr)
+ {
+ selinux_ftype selinux_get_bool
+ = (selinux_ftype) gdb_dlsym (handle, "security_get_boolean_active");
+
+ if (selinux_get_bool != NULL
+ && (*selinux_get_bool) ("deny_ptrace") == 1)
+ string_appendf (ret,
+ _("\n\
+The SELinux 'deny_ptrace' option is enabled and preventing GDB\n\
+from using 'ptrace'. You can disable it by executing (as root):\n\
+\n\
+ setsebool deny_ptrace off\n"));
+ }
+
+ gdb_file_up yama_ptrace_scope
+ = gdb_fopen_cloexec ("/proc/sys/kernel/yama/ptrace_scope", "r");
+
+ if (yama_ptrace_scope != nullptr)
+ {
+ char yama_scope = fgetc (yama_ptrace_scope.get ());
+
+ if (yama_scope != '0')
+ string_appendf (ret,
+ _("\n\
+The Linux kernel's Yama ptrace scope is in effect, which can prevent\n\
+GDB from using 'ptrace'. You can disable it by executing (as root):\n\
+\n\
+ echo 0 > /proc/sys/kernel/yama/ptrace_scope\n"));
+ }
+
+ if (ret.empty ())
+ {
+ /* It wasn't possible to determine the exact reason for the
+ ptrace error. Let's just emit a generic error message
+ pointing the user to our documentation, where she can find
+ instructions on how to try to diagnose the problem. */
+ ret = _("\n\
+There might be restrictions preventing ptrace from working. Please see\n\
+the appendix \"Linux kernel ptrace restrictions\" in the GDB documentation\n\
+for more details.");
+ }
+
+ /* The user may be debugging remotely, so we have to warn that
+ the instructions above should be performed in the target. */
+ string_appendf (ret,
+ _("\n\
+If you are debugging the inferior remotely, the ptrace restriction(s) must\n\
+be disabled in the target system (e.g., where GDBserver is running)."));
+
+ return ret;
+}
+
+/* Find all possible reasons we could fail to attach PID and return
+ these as a string. An empty string is returned if we didn't find
+ any reason. Helper for linux_ptrace_attach_fail_reason and
+ linux_ptrace_attach_fail_reason_lwp. */
+
+static std::string
+linux_ptrace_attach_fail_reason_1 (pid_t pid)
{
pid_t tracerpid = linux_proc_get_tracerpid_nowarn (pid);
std::string result;
@@ -56,10 +141,24 @@ linux_ptrace_attach_fail_reason (pid_t pid)
/* See linux-ptrace.h. */
std::string
-linux_ptrace_attach_fail_reason_string (ptid_t ptid, int err)
+linux_ptrace_attach_fail_reason (pid_t pid, int err)
+{
+ std::string result = linux_ptrace_attach_fail_reason_1 (pid);
+ std::string ptrace_restrict = linux_ptrace_restricted_fail_reason (err);
+
+ if (!ptrace_restrict.empty ())
+ result += "\n" + ptrace_restrict;
+
+ return result;
+}
+
+/* See linux-ptrace.h. */
+
+std::string
+linux_ptrace_attach_fail_reason_lwp (ptid_t ptid, int err)
{
long lwpid = ptid.lwp ();
- std::string reason = linux_ptrace_attach_fail_reason (lwpid);
+ std::string reason = linux_ptrace_attach_fail_reason_1 (lwpid);
if (!reason.empty ())
return string_printf ("%s (%d), %s", safe_strerror (err), err,
@@ -68,6 +167,14 @@ linux_ptrace_attach_fail_reason_string (ptid_t ptid, int err)
return string_printf ("%s (%d)", safe_strerror (err), err);
}
+/* See linux-ptrace.h. */
+
+std::string
+linux_ptrace_me_fail_reason (int err)
+{
+ return linux_ptrace_restricted_fail_reason (err);
+}
+
#if defined __i386__ || defined __x86_64__
/* Address of the 'ret' instruction in asm code block below. */
@@ -257,6 +364,12 @@ linux_ptrace_test_ret_to_nx (void)
#endif /* defined __i386__ || defined __x86_64__ */
}
+/* If the PTRACE_TRACEME call on linux_child_function errors, we need
+ to be able to send ERRNO back to the parent so that it can check
+ whether there are restrictions in place preventing ptrace from
+ working. We do that with a pipe. */
+static int errno_pipe[2];
+
/* Helper function to fork a process and make the child process call
the function FUNCTION, passing CHILD_STACK as parameter.
@@ -321,7 +434,30 @@ linux_grandchild_function (void *child_stack)
static int
linux_child_function (void *child_stack)
{
- ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0);
+ /* Close read end. */
+ close (errno_pipe[0]);
+
+ int ret = ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0,
+ (PTRACE_TYPE_ARG4) 0);
+ int ptrace_errno = ret < 0 ? errno : 0;
+
+ /* Write ERRNO to the pipe, even if it's zero, and close the writing
+ end of the pipe. */
+ try
+ {
+ write_trace_errno_to_pipe (errno_pipe[1], ptrace_errno);
+ }
+ catch (const gdb_exception &e)
+ {
+ warning ("%s", e.what ());
+ _exit (0177);
+ }
+
+ close (errno_pipe[1]);
+
+ if (ret != 0)
+ trace_start_error_with_name ("ptrace");
+
kill (getpid (), SIGSTOP);
/* Fork a grandchild. */
@@ -346,12 +482,40 @@ linux_check_ptrace_features (void)
/* Initialize the options. */
supported_ptrace_options = 0;
+ /* Initialize our pipe. */
+ if (gdb_pipe_cloexec (errno_pipe) < 0)
+ perror_with_name ("gdb_pipe_cloexec");
+
/* Fork a child so we can do some testing. The child will call
linux_child_function and will get traced. The child will
eventually fork a grandchild so we can test fork event
reporting. */
child_pid = linux_fork_to_function (NULL, linux_child_function);
+ /* We don't need the write end of the pipe anymore. */
+ close (errno_pipe[1]);
+
+ try
+ {
+ /* Check whether 'ptrace (PTRACE_ME, ...)' failed when being
+ invoked by the child. If it did, we might get the
+ possible reason for it as the exception message. */
+ check_child_trace_me_errno (errno_pipe[0]);
+ }
+ catch (const gdb_exception &e)
+ {
+ /* Close the pipe so we don't leak fd's. */
+ close (errno_pipe[0]);
+
+ /* A failure here means that PTRACE_ME failed, which means that
+ GDB/gdbserver will most probably not work correctly. If we
+ want to be pedantic, we could just call 'exit' here.
+ However, let's just re-throw the exception. */
+ throw;
+ }
+
+ close (errno_pipe[0]);
+
ret = my_waitpid (child_pid, &status, 0);
if (ret == -1)
perror_with_name (("waitpid"));
@@ -176,12 +176,27 @@ struct buffer;
# define TRAP_HWBKPT 4
#endif
-extern std::string linux_ptrace_attach_fail_reason (pid_t pid);
-
-/* Find all possible reasons we could have failed to attach to PTID
- and return them as a string. ERR is the error PTRACE_ATTACH failed
- with (an errno). */
-extern std::string linux_ptrace_attach_fail_reason_string (ptid_t ptid, int err);
+/* Find all possible reasons we could fail to attach PID and return
+ these as a string. An empty string is returned if we didn't find
+ any reason. If ERR is EACCES or EPERM, we also add a warning about
+ possible restrictions to use ptrace. */
+extern std::string linux_ptrace_attach_fail_reason (pid_t pid, int err);
+
+/* Find all possible reasons we could have failed to attach to PID's
+ LWPID and return them as a string. ERR is the error PTRACE_ATTACH
+ failed with (an errno). Unlike linux_ptrace_attach_fail_reason,
+ this function should be used when attaching to an LWP other than
+ the leader; it does not warn about ptrace restrictions. */
+extern std::string linux_ptrace_attach_fail_reason_lwp (ptid_t pid, int err);
+
+/* When the call to 'ptrace (PTRACE_TRACEME...' fails, and we have
+ already forked, this function can be called in order to try to
+ obtain the reason why ptrace failed. ERR should be the ERRNO value
+ returned by ptrace.
+
+ This function will return a 'std::string' containing the fail
+ reason, or an empty string otherwise. */
+extern std::string linux_ptrace_me_fail_reason (int err);
extern void linux_ptrace_init_warnings (void);
extern void linux_check_ptrace_features (void);
@@ -5882,9 +5882,26 @@ extended_remote_target::attach (const char *args, int from_tty)
break;
case PACKET_UNKNOWN:
error (_("This target does not support attaching to a process"));
+ case PACKET_ERROR:
+ {
+ std::string errmsg = rs->buf.data ();
+
+ /* Check if we have a specific error (i.e., not a generic
+ "E01") coming from the target. If there is, we print it
+ here. */
+ if (startswith (errmsg.c_str (), "E."))
+ {
+ /* Get rid of the "E." prefix. */
+ errmsg.erase (0, 2);
+ }
+
+ error (_("Attaching to %s failed%s%s"),
+ target_pid_to_str (ptid_t (pid)).c_str (),
+ !errmsg.empty () ? "\n" : "",
+ errmsg.c_str ());
+ }
default:
- error (_("Attaching to %s failed"),
- target_pid_to_str (ptid_t (pid)).c_str ());
+ gdb_assert_not_reached (_("bad switch"));
}
set_current_inferior (remote_add_inferior (false, pid, 1, 0));
@@ -10003,8 +10020,23 @@ remote_target::extended_remote_run (const std::string &args)
error (_("Running the default executable on the remote target failed; "
"try \"set remote exec-file\"?"));
else
- error (_("Running \"%s\" on the remote target failed"),
- remote_exec_file);
+ {
+ std::string errmsg = rs->buf.data ();
+
+ /* Check if we have a specific error (i.e., not a generic
+ "E01") coming from the target. If there is, we print it
+ here. */
+ if (startswith (errmsg.c_str (), "E."))
+ {
+ /* Get rid of the "E." prefix. */
+ errmsg.erase (0, 2);
+ }
+
+ error (_("Running \"%s\" on the remote target failed%s%s"),
+ remote_exec_file,
+ !errmsg.empty () ? "\n" : "",
+ errmsg.c_str ());
+ }
default:
gdb_assert_not_reached (_("bad switch"));
}
@@ -968,10 +968,24 @@ add_lwp (ptid_t ptid)
actually initiating the tracing of the inferior. */
static void
-linux_ptrace_fun ()
+linux_ptrace_fun (int ptrace_errno_wpipe)
{
- if (ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0,
- (PTRACE_TYPE_ARG4) 0) < 0)
+ int ret = ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0,
+ (PTRACE_TYPE_ARG4) 0);
+ int ptrace_errno = ret < 0 ? errno : 0;
+
+ try
+ {
+ write_trace_errno_to_pipe (ptrace_errno_wpipe, ptrace_errno);
+ }
+ catch (const gdb_exception &e)
+ {
+ warning ("%s", e.what ());
+ _exit (0177);
+ }
+
+ errno = ptrace_errno;
+ if (ret < 0)
trace_start_error_with_name ("ptrace");
if (setpgid (0, 0) < 0)
@@ -1170,7 +1184,7 @@ attach_proc_task_lwp_callback (ptid_t ptid)
else if (err != 0)
{
std::string reason
- = linux_ptrace_attach_fail_reason_string (ptid, err);
+ = linux_ptrace_attach_fail_reason_lwp (ptid, err);
warning (_("Cannot attach to lwp %d: %s"), lwpid, reason.c_str ());
}
@@ -1202,8 +1216,8 @@ linux_process_target::attach (unsigned long pid)
{
remove_process (proc);
- std::string reason = linux_ptrace_attach_fail_reason_string (ptid, err);
- error ("Cannot attach to process %ld: %s", pid, reason.c_str ());
+ std::string reason = linux_ptrace_attach_fail_reason (pid, err);
+ error (_("Cannot attach to process %ld: %s"), pid, reason.c_str ());
}
/* Don't ignore the initial SIGSTOP if we just attached to this
@@ -7552,5 +7566,10 @@ initialize_low (void)
initialize_low_arch ();
+ /* Initialize the 'trace_me_fail_reason' function pointer. We will
+ use this to determine the reason for possible failures when
+ invoking 'ptrace (PTRACE_ME, ...)'. */
+ trace_me_fail_reason = linux_ptrace_me_fail_reason;
+
linux_check_ptrace_features ();
}
@@ -2891,9 +2891,31 @@ handle_v_attach (char *own_buf)
{
client_state &cs = get_client_state ();
int pid;
+ int ret;
pid = strtol (own_buf + 8, NULL, 16);
- if (pid != 0 && attach_inferior (pid) == 0)
+
+ if (pid <= 0)
+ {
+ write_enn (own_buf);
+ return 0;
+ }
+
+ try
+ {
+ /* Attach to the specified PID. This function can throw, so we
+ make sure to catch the exception and send it (as an error
+ packet) back to GDB. */
+ ret = attach_inferior (pid);
+ }
+ catch (const gdb_exception_error &e)
+ {
+ fprintf (stderr, "%s\n", e.what ());
+ snprintf (own_buf, PBUFSIZ, "E.%s", e.what ());
+ return 0;
+ }
+
+ if (ret == 0)
{
/* Don't report shared library events after attaching, even if
some libraries are preloaded. GDB will always poll the
@@ -3029,7 +3051,19 @@ handle_v_run (char *own_buf)
free_vector_argv (program_args);
program_args = new_argv;
- target_create_inferior (program_path.get (), program_args);
+ try
+ {
+ /* Create the inferior. This function can throw, so we make
+ sure to catch the exception and send it (as an error packet)
+ back to GDB. */
+ target_create_inferior (program_path.get (), program_args);
+ }
+ catch (const gdb_exception_error &e)
+ {
+ fprintf (stderr, "%s\n", e.what ());
+ snprintf (own_buf, PBUFSIZ, "E.%s", e.what ());
+ return 0;
+ }
if (cs.last_status.kind == TARGET_WAITKIND_STOPPED)
{
@@ -224,7 +224,7 @@ attach_thread (const td_thrhandle_t *th_p, td_thrinfo_t *ti_p)
err = linux_attach_lwp (ptid);
if (err != 0)
{
- std::string reason = linux_ptrace_attach_fail_reason_string (ptid, err);
+ std::string reason = linux_ptrace_attach_fail_reason_lwp (ptid, err);
warning ("Could not attach to thread %ld (LWP %d): %s",
(unsigned long) ti_p->ti_tid, ti_p->ti_lid, reason.c_str ());