[PATCH 02/15 v2] Remove some GDBSERVER checks from linux-ptrace

Gary Benson
2014-07-16T16:33:47Z

This patch removes some GDBSERVER checks from nat/linux-ptrace.c.
Currently the code uses a compile-time check to decide whether some
flags should be used. This changes the code to instead let users of
the module specify an additional set of flags; and then changes gdb's
linux-nat.c to call this function. At some later date, when the back
ends are fully merged, we will be able to remove this function again.

gdb/
2014-07-16 Tom Tromey <tromey@redhat.com>
Gary Benson <gbenson@redhat.com>

* nat/linux-ptrace.c (additional_flags): New global.
(linux_test_for_tracesysgood, linux_test_for_tracefork): Use
additional_flags; don't check GDBSERVER.
(linux_ptrace_set_additional_flags): New function.
* nat/linux-ptrace.h (linux_ptrace_set_additional_flags):
Declare.
* linux-nat.c (_initialize_linux_nat): Call
linux_ptrace_set_additional_flags.
---
gdb/ChangeLog | 12 +++++++++
gdb/linux-nat.c | 8 ++++++
gdb/nat/linux-ptrace.c | 64 ++++++++++++++++++++++++-----------------------
gdb/nat/linux-ptrace.h | 1 +
4 files changed, 54 insertions(+), 31 deletions(-)

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index c738abf..de31229 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -5033,6 +5033,14 @@ Enables printf debugging output."),
sigdelset (&suspend_mask, SIGCHLD);

sigemptyset (&blocked_mask);
+
+ /* Do not enable PTRACE_O_TRACEEXIT until GDB is more prepared to
+ support read-only process state. */
+ linux_ptrace_set_additional_flags (PTRACE_O_TRACESYSGOOD
+ | PTRACE_O_TRACEVFORKDONE
+ | PTRACE_O_TRACEVFORK
+ | PTRACE_O_TRACEFORK
+ | PTRACE_O_TRACEEXEC);
}
\f

diff --git a/gdb/nat/linux-ptrace.c b/gdb/nat/linux-ptrace.c
index 3ad2113..59c9bfa 100644
--- a/gdb/nat/linux-ptrace.c
+++ b/gdb/nat/linux-ptrace.c
@@ -37,6 +37,10 @@
there are no supported features. */
static int current_ptrace_options = -1;

+/* Additional flags to test. */
+
+static int additional_flags;
+
/* Find all possible reasons we could fail to attach PID and append
these as strings to the already initialized BUFFER. '\0'
termination of BUFFER must be done by the caller. */
@@ -359,16 +363,15 @@ linux_check_ptrace_features (void)
static void
linux_test_for_tracesysgood (int child_pid)
{
-#ifdef GDBSERVER
- /* gdbserver does not support PTRACE_O_TRACESYSGOOD. */
-#else
- int ret;
+ if ((additional_flags & PTRACE_O_TRACESYSGOOD) != 0)
+ {
+ int ret;

- ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
- (PTRACE_TYPE_ARG4) PTRACE_O_TRACESYSGOOD);
- if (ret == 0)
- current_ptrace_options |= PTRACE_O_TRACESYSGOOD;
-#endif
+ ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
+ (PTRACE_TYPE_ARG4) PTRACE_O_TRACESYSGOOD);
+ if (ret != 0)
+ additional_flags &= ~PTRACE_O_TRACESYSGOOD;
+ }
}

/* Determine if PTRACE_O_TRACEFORK can be used to follow fork
@@ -388,16 +391,15 @@ linux_test_for_tracefork (int child_pid)
if (ret != 0)
return;

-#ifdef GDBSERVER
- /* gdbserver does not support PTRACE_O_TRACEVFORKDONE yet. */
-#else
- /* Check if the target supports PTRACE_O_TRACEVFORKDONE. */
- ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
- (PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK
- | PTRACE_O_TRACEVFORKDONE));
- if (ret == 0)
- current_ptrace_options |= PTRACE_O_TRACEVFORKDONE;
-#endif
+ if ((additional_flags & PTRACE_O_TRACEVFORKDONE) != 0)
+ {
+ /* Check if the target supports PTRACE_O_TRACEVFORKDONE. */
+ ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
+ (PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK
+ | PTRACE_O_TRACEVFORKDONE));
+ if (ret != 0)
+ additional_flags &= ~PTRACE_O_TRACEVFORKDONE;
+ }

/* Setting PTRACE_O_TRACEFORK did not cause an error, however we
don't know for sure that the feature is available; old
@@ -433,18 +435,7 @@ linux_test_for_tracefork (int child_pid)

/* We got the PID from the grandchild, which means fork
tracing is supported. */
-#ifdef GDBSERVER
- /* Do not enable all the options for now since gdbserver does not
- properly support them. This restriction will be lifted when
- gdbserver is augmented to support them. */
- current_ptrace_options |= PTRACE_O_TRACECLONE;
-#else
- current_ptrace_options |= PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK
- | PTRACE_O_TRACECLONE | PTRACE_O_TRACEEXEC;
-
- /* Do not enable PTRACE_O_TRACEEXIT until GDB is more prepared to
- support read-only process state. */
-#endif
+ current_ptrace_options |= PTRACE_O_TRACECLONE | additional_flags;

/* Do some cleanup and kill the grandchild. */
my_waitpid (second_pid, &second_status, 0);
@@ -551,3 +542,14 @@ linux_ptrace_init_warnings (void)

linux_ptrace_test_ret_to_nx ();
}
+
+/* Set additional ptrace flags to use. Some such flags may be checked
+ by the implementation above. This function must be called before
+ any other function in this file; otherwise the flags may not take
+ effect appropriately. */
+
+void
+linux_ptrace_set_additional_flags (int flags)
+{
+ additional_flags = flags;
+}
diff --git a/gdb/nat/linux-ptrace.h b/gdb/nat/linux-ptrace.h
index cffb5ce..41b3198 100644
--- a/gdb/nat/linux-ptrace.h
+++ b/gdb/nat/linux-ptrace.h
@@ -91,5 +91,6 @@ extern int linux_supports_tracefork (void);
extern int linux_supports_traceclone (void);
extern int linux_supports_tracevforkdone (void);
extern int linux_supports_tracesysgood (void);
+extern void linux_ptrace_set_additional_flags (int);

#endif /* COMMON_LINUX_PTRACE_H */
--
1.7.1