[Valgrind-developers] [PATCH for review] Add aux vector support for PPC64 AT_DCACHEBSIZE and HWCAP2

[Carl E. L. <ce...@us...>]

Julian:

We had a bug reported against valgrind because the AT_DCACHEBSIZE was
not being passed to the user application.  The following patch adds the
AT_DCACHEBSIZE and HWCAP2 to the recognized aux vector entries for PPC64
LE and BE.  I am not very familiar with the aux vector stuff so I would
like to get an additional review of the patch.

If an aux vector value is not know, the default is to suppress it.  I
was wondering why?  I am also wondering if there is something somewhere
else that I am missing when enabling these entries.  I didn't find
anything.  Also, as noted in the comment, it would be good to verify the
valgrind hwcaps has the 2_07 flag set.  I don't see an easy way to do
that, any thoughts on that?   Thanks.

                   Carl Love
---------------------------------------------------------------------

Index: coregrind/m_initimg/initimg-linux.c
===================================================================
--- coregrind/m_initimg/initimg-linux.c	(revision 15017)
+++ coregrind/m_initimg/initimg-linux.c	(working copy)
@@ -246,6 +246,10 @@
 /*=== Setting up the client's stack                                ===*/
 /*====================================================================*/
 
+#ifndef AT_DCACHEBSIZE
+#define AT_DCACHEBSIZE		19
+#endif /* AT_DCACHEBSIZE */
+
 #ifndef AT_ICACHEBSIZE
 #define AT_ICACHEBSIZE		20
 #endif /* AT_ICACHEBSIZE */
@@ -262,6 +266,10 @@
 #define AT_RANDOM		25
 #endif /* AT_RANDOM */
 
+#ifndef AT_HWCAP2
+#define AT_HWCAP2		26
+#endif /* AT_HWCAP2 */
+
 #ifndef AT_EXECFN
 #define AT_EXECFN		31
 #endif /* AT_EXECFN */
@@ -690,8 +698,25 @@
             }
 #           endif
             break;
+#           if defined(VGP_ppc64be_linux) || defined(VGP_ppc64le_linux)
+         case AT_HWCAP2:
+           /* Do not squash this value for PPC64.  The HWCAP2 value has
+            * the entry arch_2_07 which indicates the processor is a
+            * Power 8 or beyond.  The Valgrind vai.hwcaps variable
+            * (coregrind/m_machine.c) has the VEX_HWCAPS_PPC64_ISA2_07
+            * flag set so Valgrind knows about Power8.  Need to pass the
+            * HWCAP2 value along so the user level programs can detect that
+            * the processor supports ISA 2.07 and beyond.
+            */
+           /* Would be nice to verify that vai.hwcaps has
+            * VEX_HWCAPS_PPC64_ISA2_07 set.  Not sure how to access vai.hwcaps
+            * from here.
+            */
+            break;
+#           endif
 
          case AT_ICACHEBSIZE:
+         case AT_DCACHEBSIZE:
          case AT_UCACHEBSIZE:
 #           if defined(VGP_ppc32_linux)
             /* acquire cache info */