/* GNU/Linux native-dependent code common to multiple platforms.
- Copyright (C) 2001-2020 Free Software Foundation, Inc.
+ Copyright (C) 2001-2021 Free Software Foundation, Inc.
This file is part of GDB.
#include "gdbsupport/fileio.h"
#include "gdbsupport/scope-exit.h"
#include "gdbsupport/gdb-sigmask.h"
-#include "debug.h"
+#include "gdbsupport/common-debug.h"
/* This comment documents high-level logic of this file.
value);
}
-/* Print a debug statement. Should be used through linux_nat_debug_printf. */
-
-static void ATTRIBUTE_PRINTF (2, 3)
-linux_nat_debug_printf_1 (const char *func_name, const char *fmt, ...)
-{
- va_list ap;
- va_start (ap, fmt);
- debug_prefixed_vprintf ("linux-nat", func_name, fmt, ap);
- va_end (ap);
-}
+/* Print a linux-nat debug statement. */
#define linux_nat_debug_printf(fmt, ...) \
- do { \
- if (debug_linux_nat) \
- linux_nat_debug_printf_1 (__func__, fmt, ##__VA_ARGS__); \
- } while (0)
+ debug_prefixed_printf_cond (debug_linux_nat, "linux-nat", fmt, ##__VA_ARGS__)
struct simple_pid_list
{
static void save_stop_reason (struct lwp_info *lp);
+static void maybe_close_proc_mem_file (pid_t pid);
+
\f
/* LWP accessors. */
ptid of the followed inferior. At return, inferior_ptid will be
unchanged. */
-bool
+void
linux_nat_target::follow_fork (bool follow_child, bool detach_fork)
{
if (!follow_child)
/* Let the thread_db layer learn about this new process. */
check_for_thread_db ();
}
-
- return false;
}
\f
static sigset_t blocked_mask;
/* SIGCHLD action. */
-struct sigaction sigchld_action;
+static struct sigaction sigchld_action;
/* Block child signals (SIGCHLD and linux threads signals), and store
the previous mask in PREV_MASK. */
{
int target_signo = gdb_signal_from_host (signo);
if (target_signo < pass_signals.size () && pass_signals[target_signo])
- sigaddset (&pass_mask, signo);
+ sigaddset (&pass_mask, signo);
}
}
ptrace stop. Make sure it is in a ptrace stop; from there we
can kill it, signal it, et cetera.
- First make sure there is a pending SIGSTOP. Since we are
+ First make sure there is a pending SIGSTOP. Since we are
already attached, the process can not transition from stopped
to running without a PTRACE_CONT; so we know this signal will
go into the queue. The SIGSTOP generated by PTRACE_ATTACH is
{
/* The pid we tried to attach has apparently just exited. */
linux_nat_debug_printf ("Failed to stop %d: %s", pid,
- status_to_str (status));
+ status_to_str (status).c_str ());
return status;
}
{
*signalled = 1;
linux_nat_debug_printf ("Received %s after attaching",
- status_to_str (status));
+ status_to_str (status).c_str ());
}
return status;
/* Save the wait status to report later. */
lp->resumed = 1;
linux_nat_debug_printf ("waitpid %ld, saving status %s",
- (long) lp->ptid.pid (), status_to_str (status));
+ (long) lp->ptid.pid (),
+ status_to_str (status).c_str ());
lp->status = status;
they're no longer running. */
iterate_over_lwps (ptid_t (pid), stop_wait_callback);
+ /* We can now safely remove breakpoints. We don't this in earlier
+ in common code because this target doesn't currently support
+ writing memory while the inferior is running. */
+ remove_breakpoints_inf (current_inferior ());
+
iterate_over_lwps (ptid_t (pid), detach_callback);
/* Only the initial process should be left right now. */
detach_success (inf);
}
+
+ maybe_close_proc_mem_file (pid);
}
/* Resume execution of the inferior process. If STEP is nonzero,
/* Save the wait status to report later. */
linux_nat_debug_printf
("waitpid of new LWP %ld, saving status %s",
- (long) new_lp->ptid.lwp (), status_to_str (status));
+ (long) new_lp->ptid.lwp (), status_to_str (status).c_str ());
new_lp->status = status;
}
else if (report_thread_events)
{
linux_nat_debug_printf ("Got exec event from LWP %ld", lp->ptid.lwp ());
+ /* Close the /proc/<pid>/mem file if it was open for this
+ inferior. */
+ maybe_close_proc_mem_file (lp->ptid.pid ());
+
ourstatus->kind = TARGET_WAITKIND_EXECD;
ourstatus->value.execd_pathname
= xstrdup (linux_proc_pid_to_exec_file (pid));
linux_nat_debug_printf ("waitpid %s received %s",
target_pid_to_str (lp->ptid).c_str (),
- status_to_str (status));
+ status_to_str (status).c_str ());
/* Check if the thread has exited. */
if (WIFEXITED (status) || WIFSIGNALED (status))
/* The thread was stopped with a signal other than SIGSTOP. */
linux_nat_debug_printf ("Pending event %s in %s",
- status_to_str ((int) status),
+ status_to_str ((int) status).c_str (),
target_pid_to_str (lp->ptid).c_str ());
/* Save the sigtrap event. */
}
/* Check if we should go on and pass this event to common code.
- Return the affected lwp if we should, or NULL otherwise. */
-static struct lwp_info *
+ If so, save the status to the lwp_info structure associated to LWPID. */
+
+static void
linux_nat_filter_event (int lwpid, int status)
{
struct lwp_info *lp;
if (WIFSTOPPED (status) && !lp)
{
linux_nat_debug_printf ("saving LWP %ld status %s in stopped_pids list",
- (long) lwpid, status_to_str (status));
+ (long) lwpid, status_to_str (status).c_str ());
add_to_pid_list (&stopped_pids, lwpid, status);
- return NULL;
+ return;
}
/* Make sure we don't report an event for the exit of an LWP not in
if we detach from a program we originally forked and then it
exits. */
if (!WIFSTOPPED (status) && !lp)
- return NULL;
+ return;
/* This LWP is stopped now. (And if dead, this prevents it from
ever being continued.) */
on. */
status = W_STOPCODE (SIGTRAP);
if (linux_handle_syscall_trap (lp, 0))
- return NULL;
+ return;
}
else
{
linux_nat_debug_printf ("Handling extended status 0x%06x", status);
if (linux_handle_extended_wait (lp, status))
- return NULL;
+ return;
}
/* Check if the thread has exited. */
was not the end of the debugged application and should be
ignored. */
exit_lwp (lp);
- return NULL;
+ return;
}
/* Note that even if the leader was ptrace-stopped, it can still
/* Store the pending event in the waitstatus, because
W_EXITCODE(0,0) == 0. */
store_waitstatus (&lp->waitstatus, status);
- return lp;
+ return;
}
/* Make sure we don't report a SIGSTOP that we sent ourselves in
linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
gdb_assert (lp->resumed);
- return NULL;
+ return;
}
}
gdb_assert (lp->resumed);
/* Discard the event. */
- return NULL;
+ return;
}
/* Don't report signals that GDB isn't interested in, such as
target_pid_to_str (lp->ptid).c_str (),
(signo != GDB_SIGNAL_0
? strsignal (gdb_signal_to_host (signo)) : "0"));
- return NULL;
+ return;
}
}
gdb_assert (lp);
lp->status = status;
save_stop_reason (lp);
- return lp;
}
/* Detect zombie thread group leaders, and "exit" them. We can't reap
if (lp != NULL)
{
linux_nat_debug_printf ("Using pending wait status %s for %s.",
- status_to_str (lp->status),
+ status_to_str (lp->status).c_str (),
target_pid_to_str (lp->ptid).c_str ());
}
if (lwpid > 0)
{
linux_nat_debug_printf ("waitpid %ld received %s",
- (long) lwpid, status_to_str (status));
+ (long) lwpid,
+ status_to_str (status).c_str ());
linux_nat_filter_event (lwpid, status);
/* Retry until nothing comes out of waitpid. A single
purge_lwp_list (pid);
+ /* Close the /proc/<pid>/mem file if it was open for this
+ inferior. */
+ maybe_close_proc_mem_file (pid);
+
if (! forks_exist_p ())
/* Normal case, no other forks available. */
inf_ptrace_target::mourn_inferior ();
static enum target_xfer_status
linux_xfer_siginfo (enum target_object object,
- const char *annex, gdb_byte *readbuf,
+ const char *annex, gdb_byte *readbuf,
const gdb_byte *writebuf, ULONGEST offset, ULONGEST len,
ULONGEST *xfered_len)
{
ULONGEST *xfered_len);
static enum target_xfer_status
-linux_proc_xfer_partial (enum target_object object,
- const char *annex, gdb_byte *readbuf,
- const gdb_byte *writebuf,
- ULONGEST offset, LONGEST len, ULONGEST *xfered_len);
+linux_proc_xfer_memory_partial (gdb_byte *readbuf, const gdb_byte *writebuf,
+ ULONGEST offset, LONGEST len, ULONGEST *xfered_len);
enum target_xfer_status
linux_nat_target::xfer_partial (enum target_object object,
const gdb_byte *writebuf,
ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
{
- enum target_xfer_status xfer;
-
if (object == TARGET_OBJECT_SIGNAL_INFO)
return linux_xfer_siginfo (object, annex, readbuf, writebuf,
offset, len, xfered_len);
return linux_nat_xfer_osdata (object, annex, readbuf, writebuf,
offset, len, xfered_len);
- /* GDB calculates all addresses in the largest possible address
- width.
- The address width must be masked before its final use - either by
- linux_proc_xfer_partial or inf_ptrace_target::xfer_partial.
-
- Compare ADDR_BIT first to avoid a compiler warning on shift overflow. */
-
if (object == TARGET_OBJECT_MEMORY)
{
+ /* GDB calculates all addresses in the largest possible address
+ width. The address width must be masked before its final use
+ by linux_proc_xfer_partial.
+
+ Compare ADDR_BIT first to avoid a compiler warning on shift overflow. */
int addr_bit = gdbarch_addr_bit (target_gdbarch ());
if (addr_bit < (sizeof (ULONGEST) * HOST_CHAR_BIT))
offset &= ((ULONGEST) 1 << addr_bit) - 1;
- }
- xfer = linux_proc_xfer_partial (object, annex, readbuf, writebuf,
- offset, len, xfered_len);
- if (xfer != TARGET_XFER_EOF)
- return xfer;
+ return linux_proc_xfer_memory_partial (readbuf, writebuf,
+ offset, len, xfered_len);
+ }
return inf_ptrace_target::xfer_partial (object, annex, readbuf, writebuf,
offset, len, xfered_len);
return linux_proc_pid_to_exec_file (pid);
}
-/* Implement the to_xfer_partial target method using /proc/<pid>/mem.
- Because we can use a single read/write call, this can be much more
- efficient than banging away at PTRACE_PEEKTEXT. */
+/* Keep the /proc/<pid>/mem file open between memory accesses, as a
+ cache to avoid constantly closing/opening the file in the common
+ case of multiple memory reads/writes from/to the same inferior.
+ Note we don't keep a file open per inferior to avoid keeping too
+ many file descriptors open, which can run into resource limits. */
+static struct
+{
+ /* The LWP this open file is for. Note that after opening the file,
+ even if the thread subsequently exits, the open file is still
+ usable for accessing memory. It's only when the whole process
+ exits or execs that the file becomes invalid (at which point
+ reads/writes return EOF). */
+ ptid_t ptid;
-static enum target_xfer_status
-linux_proc_xfer_partial (enum target_object object,
- const char *annex, gdb_byte *readbuf,
- const gdb_byte *writebuf,
- ULONGEST offset, LONGEST len, ULONGEST *xfered_len)
+ /* The file descriptor. -1 if file is not open. */
+ int fd = -1;
+
+ /* Close FD and clear it to -1. */
+ void close ()
+ {
+ linux_nat_debug_printf ("closing fd %d for /proc/%d/task/%ld/mem\n",
+ fd, ptid.pid (), ptid.lwp ());
+ ::close (fd);
+ fd = -1;
+ }
+} last_proc_mem_file;
+
+/* Close the /proc/<pid>/mem file if its LWP matches PTID. */
+
+static void
+maybe_close_proc_mem_file (pid_t pid)
{
- LONGEST ret;
- int fd;
- char filename[64];
+ if (last_proc_mem_file.ptid.pid () == pid)
+ last_proc_mem_file.close ();
+}
- if (object != TARGET_OBJECT_MEMORY)
- return TARGET_XFER_EOF;
+/* Helper for linux_proc_xfer_memory_partial. Accesses /proc via
+ PTID. Returns -1 on error, with errno set. Returns number of
+ read/written bytes otherwise. Returns 0 on EOF, which indicates
+ the address space is gone (because the process exited or
+ execed). */
- /* Don't bother for one word. */
- if (len < 3 * sizeof (long))
- return TARGET_XFER_EOF;
+static ssize_t
+linux_proc_xfer_memory_partial_pid (ptid_t ptid,
+ gdb_byte *readbuf, const gdb_byte *writebuf,
+ ULONGEST offset, LONGEST len)
+{
+ ssize_t ret;
- /* We could keep this file open and cache it - possibly one per
- thread. That requires some juggling, but is even faster. */
- xsnprintf (filename, sizeof filename, "/proc/%ld/mem",
- inferior_ptid.lwp ());
- fd = gdb_open_cloexec (filename, ((readbuf ? O_RDONLY : O_WRONLY)
- | O_LARGEFILE), 0);
- if (fd == -1)
- return TARGET_XFER_EOF;
+ /* As long as we're hitting the same inferior, the previously open
+ file is good, even if the thread it was open for exits. */
+ if (last_proc_mem_file.fd != -1
+ && last_proc_mem_file.ptid.pid () != ptid.pid ())
+ last_proc_mem_file.close ();
+
+ if (last_proc_mem_file.fd == -1)
+ {
+ /* Actually use /proc/<pid>/task/<lwp>/mem instead of
+ /proc/<lwp>/mem to avoid PID-reuse races, as we may be trying
+ to read memory via a thread which we've already reaped.
+ /proc/<lwp>/mem could open a file for the wrong process. If
+ the LWPID is reused for the same process it's OK, we can read
+ memory through it just fine. If the LWPID is reused for a
+ different process, then the open will fail because the path
+ won't exist. */
+ char filename[64];
+ xsnprintf (filename, sizeof filename,
+ "/proc/%d/task/%ld/mem", ptid.pid (), ptid.lwp ());
+
+ last_proc_mem_file.fd
+ = gdb_open_cloexec (filename, O_RDWR | O_LARGEFILE, 0);
+
+ if (last_proc_mem_file.fd == -1)
+ {
+ linux_nat_debug_printf ("opening %s failed: %s (%d)\n",
+ filename, safe_strerror (errno), errno);
+ return -1;
+ }
+ last_proc_mem_file.ptid = ptid;
+
+ linux_nat_debug_printf ("opened fd %d for %s\n",
+ last_proc_mem_file.fd, filename);
+ }
+
+ int fd = last_proc_mem_file.fd;
/* Use pread64/pwrite64 if available, since they save a syscall and can
handle 64-bit offsets even on 32-bit platforms (for instance, SPARC
: write (fd, writebuf, len));
#endif
- close (fd);
+ if (ret == -1)
+ {
+ linux_nat_debug_printf ("accessing fd %d for pid %ld failed: %s (%d)\n",
+ fd, ptid.lwp (),
+ safe_strerror (errno), errno);
+ }
+ else if (ret == 0)
+ {
+ linux_nat_debug_printf ("accessing fd %d for pid %ld got EOF\n",
+ fd, ptid.lwp ());
+ }
- if (ret == -1 || ret == 0)
- return TARGET_XFER_EOF;
+ return ret;
+}
+
+/* Implement the to_xfer_partial target method using /proc/<pid>/mem.
+ Because we can use a single read/write call, this can be much more
+ efficient than banging away at PTRACE_PEEKTEXT. Also, unlike
+ PTRACE_PEEKTEXT/PTRACE_POKETEXT, this works with running
+ threads. */
+
+static enum target_xfer_status
+linux_proc_xfer_memory_partial (gdb_byte *readbuf, const gdb_byte *writebuf,
+ ULONGEST offset, LONGEST len,
+ ULONGEST *xfered_len)
+{
+ /* Unlike PTRACE_PEEKTEXT/PTRACE_POKETEXT, reading/writing from/to
+ /proc/<pid>/mem works with running threads, and even exited
+ threads if the file was already open. If we need to open or
+ reopen the /proc file though, we may get an EACCES error
+ ("Permission denied"), meaning the thread is gone but its exit
+ status isn't reaped yet, or ENOENT if the thread is gone and
+ already reaped. In that case, just try opening the file for
+ another thread in the process. If all threads fail, then it must
+ mean the whole process exited, in which case there's nothing else
+ to do and we just fail the memory access.
+
+ Note we don't simply always access via the leader thread because
+ the leader may exit without exiting the whole process. See
+ gdb.threads/leader-exit.exp, for example. */
+
+ /* It's frequently the case that the selected thread is stopped, and
+ is thus not likely to exit (unless something kills the process
+ outside our control, with e.g., SIGKILL). Give that one a try
+ first.
+
+ Also, inferior_ptid may actually point at an LWP not in lwp_list.
+ This happens when we're detaching from a fork child that we don't
+ want to debug ("set detach-on-fork on"), and the breakpoints
+ module uninstalls breakpoints from the fork child. Which process
+ to access is given by inferior_ptid. */
+ int res = linux_proc_xfer_memory_partial_pid (inferior_ptid,
+ readbuf, writebuf,
+ offset, len);
+ if (res == 0)
+ {
+ /* EOF means the address space is gone, the whole
+ process exited or execed. */
+ return TARGET_XFER_EOF;
+ }
+ else if (res != -1)
+ {
+ *xfered_len = res;
+ return TARGET_XFER_OK;
+ }
else
{
- *xfered_len = ret;
+ /* If we simply raced with the thread exiting (EACCES), or the
+ current thread is THREAD_EXITED (ENOENT), try some other
+ thread. It's easier to handle an ENOENT failure than check
+ for THREAD_EXIT upfront because this function is called
+ before a thread for inferior_ptid is added to the thread
+ list. */
+ if (errno != EACCES && errno != ENOENT)
+ return TARGET_XFER_EOF;
+ }
+
+ int cur_pid = current_inferior ()->pid;
+
+ if (inferior_ptid.pid () != cur_pid)
+ {
+ /* We're accessing a fork child, and the access above failed.
+ Don't bother iterating the LWP list, since there's no other
+ LWP for this process. */
+ return TARGET_XFER_EOF;
+ }
+
+ /* Iterate over LWPs of the current inferior, trying to access
+ memory through one of them. */
+ for (lwp_info *lp = lwp_list; lp != nullptr; lp = lp->next)
+ {
+ if (lp->ptid.pid () != cur_pid)
+ continue;
+
+ res = linux_proc_xfer_memory_partial_pid (lp->ptid,
+ readbuf, writebuf,
+ offset, len);
+
+ if (res == 0)
+ {
+ /* EOF means the address space is gone, the whole process
+ exited or execed. */
+ return TARGET_XFER_EOF;
+ }
+ else if (res == -1)
+ {
+ if (errno == EACCES)
+ {
+ /* This LWP is gone, try another one. */
+ continue;
+ }
+
+ return TARGET_XFER_EOF;
+ }
+
+ *xfered_len = res;
return TARGET_XFER_OK;
}
-}
+ /* No luck. */
+ return TARGET_XFER_EOF;
+}
/* Parse LINE as a signal set and add its set bits to SIGS. */
bool
linux_nat_target::supports_disable_randomization ()
{
-#ifdef HAVE_PERSONALITY
return true;
-#else
- return false;
-#endif
}
/* SIGCHLD handler that serves two purposes: In non-stop/async mode,
if (!linux_async_pipe (1))
{
add_file_handler (linux_nat_event_pipe[0],
- handle_target_event, NULL);
+ handle_target_event, NULL,
+ "linux-nat");
/* There may be pending events to handle. Tell the event loop
to poll them. */
async_file_mark ();
the GNU/Linux Threads library and therefore doesn't really belong
here. */
-/* Return the set of signals used by the threads library in *SET. */
+/* NPTL reserves the first two RT signals, but does not provide any
+ way for the debugger to query the signal numbers - fortunately
+ they don't change. */
+static int lin_thread_signals[] = { __SIGRTMIN, __SIGRTMIN + 1 };
-void
-lin_thread_get_thread_signals (sigset_t *set)
+/* See linux-nat.h. */
+
+unsigned int
+lin_thread_get_thread_signal_num (void)
{
- sigemptyset (set);
+ return sizeof (lin_thread_signals) / sizeof (lin_thread_signals[0]);
+}
+
+/* See linux-nat.h. */
- /* NPTL reserves the first two RT signals, but does not provide any
- way for the debugger to query the signal numbers - fortunately
- they don't change. */
- sigaddset (set, __SIGRTMIN);
- sigaddset (set, __SIGRTMIN + 1);
+int
+lin_thread_get_thread_signal (unsigned int i)
+{
+ gdb_assert (i < lin_thread_get_thread_signal_num ());
+ return lin_thread_signals[i];
}
projects / deliverable / binutils-gdb.git / blobdiff