[RFC 3/3] [gdb] Use ptrace events to get current syscall

[Tom de Vries <tdevries@suse.de>]

Add a powerpc implementation of gdbarch_extended_event_to_syscall, for the
moment only mapping PTRACE_EVENT_EXEC to execve.

Use gdbarch_extended_event_to_syscall in linux_handle_extended_wait to
update the cached syscall number.
---
 gdb/linux-nat.c      |  5 +++++
 gdb/ppc-linux-tdep.c | 17 +++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index efc5053cf85..6122050a982 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1959,6 +1959,11 @@ linux_handle_extended_wait (struct lwp_info *lp, int status)
      you have to be using PTRACE_SEIZE to get that.  */
   lp->syscall_state = TARGET_WAITKIND_SYSCALL_ENTRY;
 
+  struct gdbarch *gdbarch = target_thread_architecture (lp->ptid);
+  int syscall_number = gdbarch_extended_event_to_syscall (gdbarch, event);
+  if (syscall_number != -1)
+    lp->syscall_number = syscall_number;
+
   if (event == PTRACE_EVENT_FORK || event == PTRACE_EVENT_VFORK
       || event == PTRACE_EVENT_CLONE)
     {
diff --git a/gdb/ppc-linux-tdep.c b/gdb/ppc-linux-tdep.c
index 1cc26ed69a5..b4ca660a9fb 100644
--- a/gdb/ppc-linux-tdep.c
+++ b/gdb/ppc-linux-tdep.c
@@ -64,6 +64,7 @@
 #include "elf-bfd.h"
 #include "producer.h"
 #include "target-float.h"
+#include "nat/linux-ptrace.h"
 
 #include "features/rs6000/powerpc-32l.c"
 #include "features/rs6000/powerpc-altivec32l.c"
@@ -1373,6 +1374,19 @@ ppc_linux_get_syscall_number (struct gdbarch *gdbarch,
 static struct linux_record_tdep ppc_linux_record_tdep;
 static struct linux_record_tdep ppc64_linux_record_tdep;
 
+static int
+ppc_linux_extended_event_to_syscall (struct gdbarch *gdbarch, int event)
+{
+  switch (event)
+    {
+    case PTRACE_EVENT_EXEC:
+      /* Execve syscall.  */
+      return 11;
+    }
+
+  return -1;
+}
+
 /* ppc_canonicalize_syscall maps from the native PowerPC Linux set of
    syscall ids into a canonical set of syscall ids used by process
    record.  (See arch/powerpc/include/uapi/asm/unistd.h in kernel tree.)
@@ -2173,6 +2187,9 @@ ppc_linux_init_abi (struct gdbarch_info info,
   /* Get the syscall number from the arch's register.  */
   set_gdbarch_get_syscall_number (gdbarch, ppc_linux_get_syscall_number);
 
+  set_gdbarch_extended_event_to_syscall (gdbarch,
+					 ppc_linux_extended_event_to_syscall);
+
   /* SystemTap functions.  */
   set_gdbarch_stap_integer_prefixes (gdbarch, stap_integer_prefixes);
   set_gdbarch_stap_register_indirection_prefixes (gdbarch,
-- 
2.35.3