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

Yao Qi
2015-01-14T14:22:00Z

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

>> +# glibc >= 2.16 provides getauxval().
>> +AC_CHECK_FUNCS(getauxval)
>> +
>
> Any reason why this has to be a second AC_CHECK_FUNCS ? I thought
> we usually just add functions to the one AC_CHECK_FUNCS call ...
>

I feel it is clearer on why do we check for getauxval, if we call
AC_CHECK_FUNCS separately for getauxval. I've removed the second
AC_CHECK_FUNCS in the updated patch.

>> + 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;
>
> Hmm, this looks a violation of C aliasing rules. It would
> be better to declare the array as unsigned long in the first
> place, and cast to char for the fread call. Sorry for not
> noticing that in the first review.

OK, it is fixed the updated patch.

>
> Otherwise this looks good.

Patch below is what I pushed in. Thanks for the review.

--
Yao (齐尧)

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..fdcf215 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -10490,7 +10490,7 @@ $as_echo "#define HAVE_WORKING_FORK 1" >>confdefs.h

fi

-for ac_func in getrusage getuid getgid \
+for ac_func in getauxval getrusage getuid getgid \
pipe poll pread pread64 pwrite resize_term \
sbrk setpgid setpgrp setsid \
sigaction sigprocmask sigsetmask socketpair \
diff --git a/gdb/configure.ac b/gdb/configure.ac
index ec776d7..cc18174 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -1311,7 +1311,7 @@ AC_C_BIGENDIAN

AC_FUNC_MMAP
AC_FUNC_VFORK
-AC_CHECK_FUNCS([getrusage getuid getgid \
+AC_CHECK_FUNCS([getauxval getrusage getuid getgid \
pipe poll pread pread64 pwrite resize_term \
sbrk setpgid setpgrp setsid \
sigaction sigprocmask sigsetmask socketpair \
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..55bd2c5 100755
--- a/gdb/gdbserver/configure
+++ b/gdb/gdbserver/configure
@@ -4745,7 +4745,7 @@ fi

done

-for ac_func in pread pwrite pread64
+for ac_func in getauxval pread pwrite pread64
do :
as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
diff --git a/gdb/gdbserver/configure.ac b/gdb/gdbserver/configure.ac
index 02082cc..39e3a06 100644
--- a/gdb/gdbserver/configure.ac
+++ b/gdb/gdbserver/configure.ac
@@ -90,7 +90,7 @@ AC_CHECK_HEADERS(sgtty.h termio.h termios.h sys/reg.h string.h dnl
fcntl.h signal.h sys/file.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)
+AC_CHECK_FUNCS(getauxval pread pwrite pread64)

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..76b3574
--- /dev/null
+++ b/gdb/nat/ppc-linux.c
@@ -0,0 +1,75 @@
+/*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 long data[2];
+ FILE *f = fopen ("/proc/self/auxv", "r");
+
+ if (f == NULL)
+ return;
+
+ while (fread (data, sizeof (data), 1, f) > 0)
+ {
+ if (data[0] == AT_HWCAP)
+ {
+ *valp = data[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