From 6c23660d035e71de0e20b40460ad3050bd057665 Mon Sep 17 00:00:00 2001
From: Khem Raj <raj.khem@gmail.com>
Date: Thu, 31 Dec 2015 15:15:09 -0800
Subject: [PATCH] eglibc: Clear cache lines on ppc8xx

2007-06-13  Nathan Sidwell  <nathan@codesourcery.com>
            Mark Shinwell  <shinwell@codesourcery.com>

        * sysdeps/unix/sysv/linux/powerpc/libc-start.c
        (__libc_start_main): Detect 8xx parts and clear
        __cache_line_size if detected.
        * sysdeps/unix/sysv/linux/powerpc/dl-sysdep.c
        (DL_PLATFORM_AUXV): Likewise.

Upstream-Status: Pending

Signed-off-by: Khem Raj <raj.khem@gmail.com>
---
 sysdeps/unix/sysv/linux/powerpc/dl-sysdep.c  | 14 +++++++++++++-
 sysdeps/unix/sysv/linux/powerpc/libc-start.c | 16 +++++++++++++++-
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/powerpc/dl-sysdep.c b/sysdeps/unix/sysv/linux/powerpc/dl-sysdep.c
index 78051bc7bc..e24f442320 100644
--- a/sysdeps/unix/sysv/linux/powerpc/dl-sysdep.c
+++ b/sysdeps/unix/sysv/linux/powerpc/dl-sysdep.c
@@ -24,9 +24,21 @@ int __cache_line_size attribute_hidden;
 /* Scan the Aux Vector for the "Data Cache Block Size" entry.  If found
    verify that the static extern __cache_line_size is defined by checking
    for not NULL.  If it is defined then assign the cache block size
-   value to __cache_line_size.  */
+   value to __cache_line_size.  This is used by memset to
+   optimize setting to zero.  We have to detect 8xx processors, which
+   have buggy dcbz implementations that cannot report page faults
+   correctly.  That requires reading SPR, which is a privileged
+   operation.  Fortunately 2.2.18 and later emulates PowerPC mfspr
+   reads from the PVR register.   */
 #define DL_PLATFORM_AUXV						      \
       case AT_DCACHEBSIZE:						      \
+	if (__LINUX_KERNEL_VERSION >= 0x020218)				      \
+	  {								      \
+	    unsigned pvr = 0;						      \
+	    asm ("mfspr %0, 287" : "=r" (pvr));				      \
+	    if ((pvr & 0xffff0000) == 0x00500000)			      \
+	      break;							      \
+	  }								      \
 	__cache_line_size = av->a_un.a_val;				      \
 	break;
 
diff --git a/sysdeps/unix/sysv/linux/powerpc/libc-start.c b/sysdeps/unix/sysv/linux/powerpc/libc-start.c
index f2ad0c355d..3e6773795e 100644
--- a/sysdeps/unix/sysv/linux/powerpc/libc-start.c
+++ b/sysdeps/unix/sysv/linux/powerpc/libc-start.c
@@ -73,11 +73,25 @@ __libc_start_main (int argc, char **argv,
 
   /* Initialize the __cache_line_size variable from the aux vector.  For the
      static case, we also need _dl_hwcap, _dl_hwcap2 and _dl_platform, so we
-     can call __tcb_parse_hwcap_and_convert_at_platform ().  */
+     can call __tcb_parse_hwcap_and_convert_at_platform ().
+
+     This is used by memset to optimize setting to zero.  We have to
+     detect 8xx processors, which have buggy dcbz implementations that
+     cannot report page faults correctly.  That requires reading SPR,
+     which is a privileged operation.  Fortunately 2.2.18 and later
+     emulates PowerPC mfspr reads from the PVR register.  */
   for (ElfW (auxv_t) * av = auxvec; av->a_type != AT_NULL; ++av)
     switch (av->a_type)
       {
       case AT_DCACHEBSIZE:
+	if (__LINUX_KERNEL_VERSION >= 0x020218)
+	  {
+	    unsigned pvr = 0;
+
+	    asm ("mfspr %0, 287" : "=r" (pvr) :);
+	    if ((pvr & 0xffff0000) == 0x00500000)
+	      break;
+	  }
 	__cache_line_size = av->a_un.a_val;
 	break;
 #ifndef SHARED
