Re: PowerPC: Reserve TCB space for EBB framework

["Ryan S. Arnold" <ryan dot arnold at gmail dot com>]

On Tue, Jun 4, 2013 at 4:14 PM, Adhemerval Zanella
<azanella@linux.vnet.ibm.com> wrote:
> Hi all,
>
> This patch reserves four pointer to be used in future Event-Based
> Branch (EBB) framework for PowerPC. The EBB is a new facility
> described at Power ISA 2.07, Book II, Chapter 7 and POWER8 will
> implement it for Processor Monitoring Units (PMU). The idea is
> to trigger some function callback when certain PMU event (for
> instance a branch prediction counter) happen.
>
> Initial kernel support is already upstream (commit
> 9353374b8e1585d5fa47a1e5c1d3e9155dd0eb7c), however full support
> (EBB initialization using perf subsystem) is not already complete.
>
> The idea is to provide an API to a callback function (thread_handler
> ) along with per-thread context field (context_pointer) to be used
> along with EBB field. This initial patch is to push the TCB size
> adjustment on 2.18.
>
> ---
>
> 2013-05-30  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>
>
>         * nptl/sysdeps/powerpc/tcb-offsets.sym (STACK_GUARD): Add TCB
>         stack_guard offset.
>         * nptl/sysdeps/powerpc/tls.h (tcbhead_t): Add Event-Based Branch
>         fields.
>         * sysdeps/powerpc/powerpc32/stackguard-macros.h (STACK_CHK_GUARD):
>         Adjust the stack_guard offset.
>         * sysdeps/powerpc/powerpc64/stackguard-macros.h: Likewise.
>
> --
>
> diff --git a/nptl/sysdeps/powerpc/tcb-offsets.sym b/nptl/sysdeps/powerpc/tcb-offsets.sym
> index 8ac133d..39d05cd 100644
> --- a/nptl/sysdeps/powerpc/tcb-offsets.sym
> +++ b/nptl/sysdeps/powerpc/tcb-offsets.sym
> @@ -15,6 +15,7 @@ MULTIPLE_THREADS_OFFSET               thread_offsetof (header.multiple_threads)
>  PID                            thread_offsetof (pid)
>  TID                            thread_offsetof (tid)
>  POINTER_GUARD                  (offsetof (tcbhead_t, pointer_guard) - TLS_TCB_OFFSET - sizeof (tcbhead_t))
> +STACK_GUARD                    (offsetof (tcbhead_t, stack_guard) - TLS_TCB_OFFSET - sizeof (tcbhead_t))
>  #ifndef __ASSUME_PRIVATE_FUTEX
>  PRIVATE_FUTEX_OFFSET           thread_offsetof (header.private_futex)
>  #endif
> diff --git a/nptl/sysdeps/powerpc/tls.h b/nptl/sysdeps/powerpc/tls.h
> index 46dac9e..56198fa 100644
> --- a/nptl/sysdeps/powerpc/tls.h
> +++ b/nptl/sysdeps/powerpc/tls.h
> @@ -64,6 +64,10 @@ typedef struct
>    uintptr_t pointer_guard;
>    uintptr_t stack_guard;
>    dtv_t *dtv;
> +  uintptr_t thread_handler;

This is a bit non-descriptive.  I'd prefer something like ebb_handler,
which describes the intended usage.

> +  uintptr_t context_pointer;

Likewise ebb_context_pointer.

> +  uintptr_t reserved1;
> +  uintptr_t reserved2;

Should these be marked ebb_ as well?  ebb_reserved1 and ebb_reserved2?

>  } tcbhead_t;
>
>  /* This is the size of the initial TCB.  */
> diff --git a/sysdeps/powerpc/powerpc32/stackguard-macros.h b/sysdeps/powerpc/powerpc32/stackguard-macros.h
> index 839f6a4..2165bfc 100644
> --- a/sysdeps/powerpc/powerpc32/stackguard-macros.h
> +++ b/sysdeps/powerpc/powerpc32/stackguard-macros.h
> @@ -1,4 +1,7 @@
>  #include <stdint.h>
> +#include "tcb-offsets.h"
>
>  #define STACK_CHK_GUARD \
> -  ({ uintptr_t x; asm ("lwz %0,-28680(2)" : "=r" (x)); x; })
> +  ({ uintptr_t x;                                              \
> +     asm ("lwz %0,%1(2)" : "=r" (x)                            \
> +          : "i" (STACK_GUARD)); x; })
> diff --git a/sysdeps/powerpc/powerpc64/stackguard-macros.h b/sysdeps/powerpc/powerpc64/stackguard-macros.h
> index 9da879c..2f59a8a 100644
> --- a/sysdeps/powerpc/powerpc64/stackguard-macros.h
> +++ b/sysdeps/powerpc/powerpc64/stackguard-macros.h
> @@ -1,4 +1,7 @@
>  #include <stdint.h>
> +#include "tcb-offsets.h"
>
>  #define STACK_CHK_GUARD \
> -  ({ uintptr_t x; asm ("ld %0,-28688(13)" : "=r" (x)); x; })
> +  ({ uintptr_t x;                                              \
> +     asm ("ld %0,%1(13)" : "=r" (x)                            \
> +         : "i" (STACK_GUARD)); x; })
> --
> 1.7.1
>