On Thu, May 24, 2018 at 7:37 AM Alexey Budankov < [email protected]> wrote:
> Hi, > On 23.05.2018 16:09, Peter Zijlstra wrote: > > On Wed, May 23, 2018 at 01:06:58PM +0300, Alexey Budankov wrote: > > > >> Is the patch ready to be up streamed now? > > > > Please post a new one where you modify the comment about the syscalls > > not saving registers and ideally find the commit that made it so. > Sent v3 with adjusted comment. > As far comments become outdated quickly tried to be terse. > > > > Also; I think Andy would appreciate a comment near the syscall code that > > refers back to this code and states what registers we rely upon being > > there (+BP for this patch). > Not sure if I can find all proper places to put comments there. > However there is PUSH_AND_CLEAR_REGS macro that is employed at system > call implementation so it is possible to put something like this there: > .macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0 > /* > ... > * perf/core subsystem relies on bp register value stored > * at pt_regs->bp; see arch/x86/kernel/perf_regs.c: perf_get_regs_user() > * for more details; > ... > */ Near the top of entry_SYSCALL_64 would be reasonable, as would no comment at all, I think. > Thanks, > Alexey > > > >
