[PATCH] ARM: pass syscall return value to sys_exit tracepoint

[Russell King - ARM Linux]

On Tue, Dec 04, 2012 at 09:48:28AM +0000, Gabbasov, Andrew wrote:
> The other registers in "regs" structure are not saved around ptrace_syscall_trace,
> and both audit_syscall_exit and trace_sys_exit get the register values, potentially
> changed by a debugger. Does it make sense to save the isolated return value
> for trace_sys_exit call only and not to save other registers, passed, for example,
> to audit_syscall_exit function that takes the return value from regs structure?
> Isn't it a reasonable assumption that a debugger will preserve important
> register values (or intentionally change them for some purpose) in case
> of syscall_exit, as we rely on this for syscall_enter case?

Actually, why are we doing things in a different order to x86?  If we
assume that x86 has this stuff correctly ordered, then shouldn't we
be following the sequence presented there?

x86 on entry does:
- secure_computing
- tracehook_report_syscall_entry
- trace_sys_enter
- audit_syscall_entry
and on exit:
- audit_syscall_exit
- trace_sys_exit
- tracehook_report_syscall_exit

We appear to be doing the _exact_ reverse ordering in our syscall exit
path - why is that?