x86 ptrace: unify syscall tracing

This unifies and cleans up the syscall tracing code on i386 and x86_64.

Using a single function for entry and exit tracing on 32-bit made the
do_syscall_trace() into some terrible spaghetti.  The logic is clear and
simple using separate syscall_trace_enter() and syscall_trace_leave()
functions as on 64-bit.

The unification adds PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support
on x86_64, for 32-bit ptrace() callers and for 64-bit ptrace() callers
tracing either 32-bit or 64-bit tasks.  It behaves just like 32-bit.

Changing syscall_trace_enter() to return the syscall number shortens
all the assembly paths, while adding the SYSEMU feature in a simple way.

Signed-off-by: Roland McGrath <roland@redhat.com>

1 files changed, 7 insertions, 12 deletions

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 0ad987d02b72..cadf73f70d33 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -332,7 +332,7 @@ sysenter_past_esp:
         GET_THREAD_INFO(%ebp)
 
         /* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */
-        testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
+        testw $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
         jnz syscall_trace_entry
         cmpl $(nr_syscalls), %eax
         jae syscall_badsys
@@ -370,7 +370,7 @@ ENTRY(system_call)
         GET_THREAD_INFO(%ebp)
                                         # system call tracing in operation / emulation
         /* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */
-        testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
+        testw $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
         jnz syscall_trace_entry
         cmpl $(nr_syscalls), %eax
         jae syscall_badsys
@@ -510,12 +510,8 @@ END(work_pending)
 syscall_trace_entry:
         movl $-ENOSYS,PT_EAX(%esp)
         movl %esp, %eax
-        xorl %edx,%edx
-        call do_syscall_trace
-        cmpl $0, %eax
-        jne resume_userspace            # ret != 0 -> running under PTRACE_SYSEMU,
-                                        # so must skip actual syscall
-        movl PT_ORIG_EAX(%esp), %eax
+        call syscall_trace_enter
+        /* What it returned is what we'll actually use.  */
         cmpl $(nr_syscalls), %eax
         jnae syscall_call
         jmp syscall_exit
@@ -524,14 +520,13 @@ END(syscall_trace_entry)
         # perform syscall exit tracing
         ALIGN
 syscall_exit_work:
-        testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP), %cl
+        testb $_TIF_WORK_SYSCALL_EXIT, %cl
         jz work_pending
         TRACE_IRQS_ON
-        ENABLE_INTERRUPTS(CLBR_ANY)     # could let do_syscall_trace() call
+        ENABLE_INTERRUPTS(CLBR_ANY)     # could let syscall_trace_leave() call
                                         # schedule() instead
         movl %esp, %eax
-        movl $1, %edx
-        call do_syscall_trace
+        call syscall_trace_leave
         jmp resume_userspace
 END(syscall_exit_work)
         CFI_ENDPROC