Reorganize syscall entry and leave handling.

Extend struct sysvec with three new elements:
sv_fetch_syscall_args - the method to fetch syscall arguments from
  usermode into struct syscall_args. The structure is machine-depended
  (this might be reconsidered after all architectures are converted).
sv_set_syscall_retval - the method to set a return value for usermode
  from the syscall. It is a generalization of
  cpu_set_syscall_retval(9) to allow ABIs to override the way to set a
  return value.
sv_syscallnames - the table of syscall names.

Use sv_set_syscall_retval in kern_sigsuspend() instead of hardcoding
the call to cpu_set_syscall_retval().

The new functions syscallenter(9) and syscallret(9) are provided that
use sv_*syscall* pointers and contain the common repeated code from
the syscall() implementations for the architecture-specific syscall
trap handlers.

Syscallenter() fetches arguments, calls syscall implementation from
ABI sysent table, and set up return frame. The end of syscall
bookkeeping is done by syscallret().

Take advantage of single place for MI syscall handling code and
implement ptrace_lwpinfo pl_flags PL_FLAG_SCE, PL_FLAG_SCX and
PL_FLAG_EXEC. The SCE and SCX flags notify the debugger that the
thread is stopped at syscall entry or return point respectively.  The
EXEC flag augments SCX and notifies debugger that the process address
space was changed by one of exec(2)-family syscalls.

The i386, amd64, sparc64, sun4v, powerpc and ia64 syscall()s are
changed to use syscallenter()/syscallret(). MIPS and arm are not
converted and use the mostly unchanged syscall() implementation.

Reviewed by:	jhb, marcel, marius, nwhitehorn, stas
Tested by:	marcel (ia64), marius (sparc64), nwhitehorn (powerpc),
	stas (mips)
MFC after:	1 month

1 files changed, 8 insertions, 0 deletions

diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index e32e494..1195019 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -364,6 +364,9 @@ do {									\
 #define	TDB_SUSPEND	0x00000001 /* Thread is suspended by debugger */
 #define	TDB_XSIG	0x00000002 /* Thread is exchanging signal under trace */
 #define	TDB_USERWR	0x00000004 /* Debugger modified memory or registers */
+#define	TDB_SCE		0x00000008 /* Thread performs syscall enter */
+#define	TDB_SCX		0x00000010 /* Thread performs syscall exit */
+#define	TDB_EXEC	0x00000020 /* TDB_SCX from exec(2) family */
 
 /*
  * "Private" flags kept in td_pflags:
@@ -837,9 +840,14 @@ void	cpu_switch(struct thread *, struct thread *, struct mtx *);
 void	cpu_throw(struct thread *, struct thread *) __dead2;
 void	unsleep(struct thread *);
 void	userret(struct thread *, struct trapframe *);
+struct syscall_args;
+int	syscallenter(struct thread *, struct syscall_args *);
+void	syscallret(struct thread *, int, struct syscall_args *);
 
 void	cpu_exit(struct thread *);
 void	exit1(struct thread *, int) __dead2;
+struct syscall_args;
+int	cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa);
 void	cpu_fork(struct thread *, struct proc *, struct thread *, int);
 void	cpu_set_fork_handler(struct thread *, void (*)(void *), void *);
 void	cpu_set_syscall_retval(struct thread *, int);