Re: [PATCH 2/2] Detect 64-bit-ness in PowerPC Book III-E

[Yao Qi <yao at codesourcery dot com>]

Ulrich Weigand <uweigand@de.ibm.com> writes:

> All this can be done using "getauxval (AT_HWCAP)", which is faster and works
> even if /proc is not mounted.  However, getauxval was only introduced with
> glibc 2.16, so we'll probably still need the fallback ...

In the updated patch below, I add configure check to function
getauxval.  If it exists, we use getauxval, otherwise fallback to
parsing /proc/self/auxv.  Manually test gdbserver and it works well.  My
target glibc is >= 2.16, so getauxval path is tested.

Is the patch OK?

-- 
Yao (éå)
Subject: [PATCH] Detect 64-bit-ness in PowerPC Book III-E

This patch is to teach both GDB and GDBServer to detect 64-bit inferior
correctly.  We find a problem that GDBServer is unable to detect on a
e5500 core processor.  Current GDBServer assumes that MSR is a 64-bit
register, but MSR is a 32-bit register in Book III-E.  This patch is
to fix this problem by checking the right bit in MSR, in order to handle
both Book III-S and Book III-E.  In order to detect Book III-S and
Book III-E, we check the PPC_FEATURE_BOOKE from the host's HWCAP (by
getauxval on glibc >= 2.16.  If getauxval doesn't exist, we implement
the fallback by parsing /proc/self/auxv), because it should an invariant
on the same machine cross different processes.

In order to share code, I add nat/ppc-linux.c for both GDB and
GDBserver side.

gdb:

2015-01-14  Yao Qi  <yao@codesourcery.com>

	* Makefile.in (ppc-linux.o): New rule.
	* config/powerpc/ppc64-linux.mh (NATDEPFILES): Add ppc-linux.o.
	* configure.ac: AC_CHECK_FUNCS(getauxval).
	* config.in: Re-generated.
	* configure: Re-generated.
	* nat/ppc-linux.h [__powerpc64__] (ppc64_64bit_inferior_p):
	Declare.
	* nat/ppc-linux.c: New file.
	* ppc-linux-nat.c (ppc_linux_target_wordsize) [__powerpc64__]:
	Call ppc64_64bit_inferior_p.

gdb/gdbserver:

2015-01-14  Yao Qi  <yao@codesourcery.com>

	* Makefile.in (SFILES): Add nat/ppc-linux.c.
	(ppc-linux.o): New rule.
	* configure.srv (powerpc*-*-linux*): Add ppc-linux.o.
	* configure.ac: AC_CHECK_FUNCS(getauxval).
	* config.in: Re-generated.
	* configure: Re-generated.
	* linux-ppc-low.c (ppc_arch_setup) [__powerpc64__]: Call
	ppc64_64bit_inferior_p

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index f519f0a..fc1c7fa 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -2271,6 +2271,10 @@ mips-linux-watch.o: ${srcdir}/nat/mips-linux-watch.c
 	$(COMPILE) $(srcdir)/nat/mips-linux-watch.c
 	$(POSTCOMPILE)
 
+ppc-linux.o: ${srcdir}/nat/ppc-linux.c
+	$(COMPILE) $(srcdir)/nat/ppc-linux.c
+	$(POSTCOMPILE)
+
 #
 # gdb/tui/ dependencies
 #
diff --git a/gdb/config.in b/gdb/config.in
index 9d3f32d..806cbac 100644
--- a/gdb/config.in
+++ b/gdb/config.in
@@ -138,6 +138,9 @@
 /* Define if <sys/procfs.h> has fpregset_t. */
 #undef HAVE_FPREGSET_T
 
+/* Define to 1 if you have the `getauxval' function. */
+#undef HAVE_GETAUXVAL
+
 /* Define to 1 if you have the `getgid' function. */
 #undef HAVE_GETGID
 
diff --git a/gdb/config/powerpc/ppc64-linux.mh b/gdb/config/powerpc/ppc64-linux.mh
index 4b91408..1b3fbc7 100644
--- a/gdb/config/powerpc/ppc64-linux.mh
+++ b/gdb/config/powerpc/ppc64-linux.mh
@@ -6,7 +6,7 @@ NAT_FILE= config/nm-linux.h
 NATDEPFILES= inf-ptrace.o fork-child.o \
 	ppc-linux-nat.o proc-service.o linux-thread-db.o \
 	linux-nat.o linux-osdata.o linux-fork.o linux-procfs.o linux-ptrace.o \
-	linux-waitpid.o
+	linux-waitpid.o ppc-linux.o
 NAT_CDEPS = $(srcdir)/proc-service.list
 
 # The PowerPC has severe limitations on TOC size, and uses them even
diff --git a/gdb/configure b/gdb/configure
index 7ff74ba..661d8a7 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -10509,6 +10509,19 @@ _ACEOF
 fi
 done
 
+# glibc >= 2.16 provides getauxval().
+for ac_func in getauxval
+do :
+  ac_fn_c_check_func "$LINENO" "getauxval" "ac_cv_func_getauxval"
+if test "x$ac_cv_func_getauxval" = x""yes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_GETAUXVAL 1
+_ACEOF
+
+fi
+done
+
+
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for nl_langinfo and CODESET" >&5
 $as_echo_n "checking for nl_langinfo and CODESET... " >&6; }
diff --git a/gdb/configure.ac b/gdb/configure.ac
index ec776d7..dadaf76 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -1318,6 +1318,9 @@ AC_CHECK_FUNCS([getrusage getuid getgid \
 		ttrace wborder wresize setlocale iconvlist libiconvlist btowc \
 		setrlimit getrlimit posix_madvise waitpid \
 		ptrace64 sigaltstack mkdtemp])
+# glibc >= 2.16 provides getauxval().
+AC_CHECK_FUNCS(getauxval)
+
 AM_LANGINFO_CODESET
 GDB_AC_COMMON
 
diff --git a/gdb/gdbserver/Makefile.in b/gdb/gdbserver/Makefile.in
index 1ed2ec8..0e442fc 100644
--- a/gdb/gdbserver/Makefile.in
+++ b/gdb/gdbserver/Makefile.in
@@ -155,7 +155,7 @@ SFILES=	$(srcdir)/gdbreplay.c $(srcdir)/inferiors.c $(srcdir)/dll.c \
 	$(srcdir)/linux-m32r-low.c \
 	$(srcdir)/linux-m68k-low.c $(srcdir)/linux-mips-low.c \
 	$(srcdir)/linux-nios2-low.c \
-	$(srcdir)/linux-ppc-low.c \
+	$(srcdir)/linux-ppc-low.c $(srcdir)/nat/ppc-linux.c \
 	$(srcdir)/linux-s390-low.c \
 	$(srcdir)/linux-sh-low.c $(srcdir)/linux-sparc-low.c \
 	$(srcdir)/linux-x86-low.c \
@@ -581,6 +581,9 @@ linux-waitpid.o: ../nat/linux-waitpid.c
 mips-linux-watch.o: ../nat/mips-linux-watch.c
 	$(COMPILE) $<
 	$(POSTCOMPILE)
+ppc-linux.o: ../nat/ppc-linux.c
+	$(COMPILE) $<
+	$(POSTCOMPILE)
 
 aarch64.c : $(srcdir)/../regformats/aarch64.dat $(regdat_sh)
 	$(SHELL) $(regdat_sh) $(srcdir)/../regformats/aarch64.dat aarch64.c
diff --git a/gdb/gdbserver/config.in b/gdb/gdbserver/config.in
index fd80adc..8f68ed2 100644
--- a/gdb/gdbserver/config.in
+++ b/gdb/gdbserver/config.in
@@ -60,6 +60,9 @@
 /* Define to 1 if you have the `fdwalk' function. */
 #undef HAVE_FDWALK
 
+/* Define to 1 if you have the `getauxval' function. */
+#undef HAVE_GETAUXVAL
+
 /* Define to 1 if you have the `getrlimit' function. */
 #undef HAVE_GETRLIMIT
 
diff --git a/gdb/gdbserver/configure b/gdb/gdbserver/configure
index 45efc51..14594ec 100755
--- a/gdb/gdbserver/configure
+++ b/gdb/gdbserver/configure
@@ -4758,6 +4758,18 @@ _ACEOF
 fi
 done
 
+# glibc >= 2.16 provides getauxval().
+for ac_func in getauxval
+do :
+  ac_fn_c_check_func "$LINENO" "getauxval" "ac_cv_func_getauxval"
+if test "x$ac_cv_func_getauxval" = x""yes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_GETAUXVAL 1
+_ACEOF
+
+fi
+done
+
 
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ANSI C header files" >&5
diff --git a/gdb/gdbserver/configure.ac b/gdb/gdbserver/configure.ac
index 02082cc..93a5ed1 100644
--- a/gdb/gdbserver/configure.ac
+++ b/gdb/gdbserver/configure.ac
@@ -91,6 +91,8 @@ AC_CHECK_HEADERS(sgtty.h termio.h termios.h sys/reg.h string.h dnl
 		 sys/ioctl.h netinet/in.h sys/socket.h netdb.h dnl
 		 netinet/tcp.h arpa/inet.h)
 AC_CHECK_FUNCS(pread pwrite pread64)
+# glibc >= 2.16 provides getauxval().
+AC_CHECK_FUNCS(getauxval)
 
 GDB_AC_COMMON
 
diff --git a/gdb/gdbserver/configure.srv b/gdb/gdbserver/configure.srv
index 679fc9f..f52aee2 100644
--- a/gdb/gdbserver/configure.srv
+++ b/gdb/gdbserver/configure.srv
@@ -217,7 +217,7 @@ case "${target}" in
 			srv_regobj="${srv_regobj} powerpc-isa205-64l.o"
 			srv_regobj="${srv_regobj} powerpc-isa205-altivec64l.o"
 			srv_regobj="${srv_regobj} powerpc-isa205-vsx64l.o"
-			srv_tgtobj="$srv_linux_obj linux-ppc-low.o"
+			srv_tgtobj="$srv_linux_obj linux-ppc-low.o ppc-linux.o"
 			srv_xmlfiles="rs6000/powerpc-32l.xml"
 			srv_xmlfiles="${srv_xmlfiles} rs6000/powerpc-altivec32l.xml"
 			srv_xmlfiles="${srv_xmlfiles} rs6000/powerpc-cell32l.xml"
diff --git a/gdb/gdbserver/linux-ppc-low.c b/gdb/gdbserver/linux-ppc-low.c
index 6e880c1..188fac0 100644
--- a/gdb/gdbserver/linux-ppc-low.c
+++ b/gdb/gdbserver/linux-ppc-low.c
@@ -398,13 +398,11 @@ ppc_arch_setup (void)
   current_process ()->tdesc = tdesc;
   ppc_hwcap = 0;
 
-  /* Only if the high bit of the MSR is set, we actually have
-     a 64-bit inferior.  */
   regcache = new_register_cache (tdesc);
   fetch_inferior_registers (regcache, find_regno (tdesc, "msr"));
   collect_register_by_name (regcache, "msr", &msr);
   free_register_cache (regcache);
-  if (msr < 0)
+  if (ppc64_64bit_inferior_p (msr))
     {
       ppc_get_hwcap (&ppc_hwcap);
       if (ppc_hwcap & PPC_FEATURE_CELL)
diff --git a/gdb/nat/ppc-linux.c b/gdb/nat/ppc-linux.c
new file mode 100644
index 0000000..a29c9bd
--- /dev/null
+++ b/gdb/nat/ppc-linux.c
@@ -0,0 +1,77 @@
+/*Copyright (C) 2015 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "common-defs.h"
+#include "ppc-linux.h"
+#include <elf.h>
+
+#ifdef HAVE_GETAUXVAL
+#include <sys/auxv.h>
+#endif
+
+#ifdef __powerpc64__
+
+/* Get the HWCAP from the process of GDB or GDBserver.  If success,
+   save it in *VALP.   */
+
+static void
+ppc64_host_hwcap (unsigned long *valp)
+{
+#ifdef HAVE_GETAUXVAL
+  *valp = getauxval (AT_HWCAP);
+#else
+  unsigned char data[2 * 8];
+  FILE *f = fopen ("/proc/self/auxv", "r");
+
+  if (f == NULL)
+    return;
+
+  while (fread (data, sizeof (data), 1, f) > 0)
+    {
+      unsigned long *data_p = (unsigned long *) data;
+
+      if (data_p[0] == AT_HWCAP)
+	{
+	  *valp = data_p[1];
+	  break;
+	}
+    }
+
+  fclose (f);
+#endif /* HAVE_GETAUXVAL */
+}
+
+int
+ppc64_64bit_inferior_p (long msr)
+{
+  unsigned long ppc_host_hwcap = 0;
+
+  /* Get host's HWCAP to check whether the machine is Book E.  */
+  ppc64_host_hwcap (&ppc_host_hwcap);
+
+  /* We actually have a 64-bit inferior only if the certain bit of the
+     MSR is set.  The PowerISA Book III-S MSR is different from the
+     PowerISA Book III-E MSR.  The Book III-S MSR is 64 bits wide, and
+     its MSR[SF] is the bit 0 of a 64-bit value.  Book III-E MSR is 32
+     bits wide, and its MSR[CM] is the bit 0 of a 32-bit value.   */
+  if (ppc_host_hwcap & PPC_FEATURE_BOOKE)
+    return msr & 0x80000000;
+  else
+    return msr < 0;
+}
+
+#endif
diff --git a/gdb/nat/ppc-linux.h b/gdb/nat/ppc-linux.h
index 30d936f..0ff2223 100644
--- a/gdb/nat/ppc-linux.h
+++ b/gdb/nat/ppc-linux.h
@@ -82,4 +82,10 @@
 #define PTRACE_SETEVRREGS 21
 #endif
 
+#ifdef __powerpc64__
+/* Return whether the inferior is 64bit or not by checking certain bit
+   in MSR.  */
+int ppc64_64bit_inferior_p (long msr);
+#endif
+
 #endif
diff --git a/gdb/ppc-linux-nat.c b/gdb/ppc-linux-nat.c
index c5a286b..88ca49e 100644
--- a/gdb/ppc-linux-nat.c
+++ b/gdb/ppc-linux-nat.c
@@ -2367,7 +2367,7 @@ ppc_linux_target_wordsize (void)
 
   errno = 0;
   msr = (long) ptrace (PTRACE_PEEKUSER, tid, PT_MSR * 8, 0);
-  if (errno == 0 && msr < 0)
+  if (errno == 0 && ppc64_64bit_inferior_p (msr))
     wordsize = 8;
 #endif