[PATCH v3] gdb: clean up x86 cpuid implementations

Mike Frysinger
2013-05-07T15:11:26Z

We've currently got 3 files doing open coded implementations of cpuid.
Each has its own set of workarounds and varying levels of how well
they're written and are generally hardcoded to specific cpuid functions.
If you try to build the latest gdb as a PIE on an i386 system, the build
will fail because one of them lacks PIC workarounds (wrt ebx).

Specifically, we have:
common/linux-btrace.c:
two copies of cpuid asm w/specific args, one has no workarounds
while the other implicitly does to avoid memcpy
go32-nat.c:
two copies of cpuid asm w/specific args, one has workarounds to
avoid memcpy
gdb/testsuite/gdb.arch/i386-cpuid.h:
one general cpuid asm w/many workarounds copied from older gcc

Fortunately, that last header there is pretty damn good -- it handles
lots of edge cases, the code is nice & tight (uses gcc asm operands
rather than manual movs), and is already almost a general library type
header. It's also the basis of what is now the public cpuid.h that is
shipped with gcc-4.3+.

So what I've done is pull that test header out and into gdb/common/
(not sure if there's a better place), put a wrapper API around it,
and then cut over all the existing call points to this new header.

Since the func already has support for "is cpuid supported on this proc",
it makes it trivial to push the i386/x86_64 ifdefs down into this wrapper
API too. Now it can be safely used for all targets and gcc will elide
the unused code for us.

I've verified the gdb.arch testsuite still passes, and this code compiles
for an armv7a host as well as x86_64. The go32-nat code has been left
ifdef-ed out until someone can test & verify the new stuff works (and if
it doesn't, figure out how to make the new code work).

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
v3
- split wrapper api and gcc cpuid.h into sep files

gdb/Makefile.in | 2 +-
gdb/common/i386-cpuid.h | 68 ++++++++++
.../i386-cpuid.h => common/i386-gcc-cpuid.h} | 140 ++++++++++++++++-----
gdb/common/linux-btrace.c | 41 ++----
gdb/go32-nat.c | 22 ++++
gdb/testsuite/gdb.arch/i386-avx.c | 2 +-
gdb/testsuite/gdb.arch/i386-avx.exp | 2 +-
gdb/testsuite/gdb.arch/i386-sse.c | 5 +-
gdb/testsuite/gdb.arch/i386-sse.exp | 2 +-
9 files changed, 214 insertions(+), 70 deletions(-)
create mode 100644 gdb/common/i386-cpuid.h
rename gdb/{testsuite/gdb.arch/i386-cpuid.h => common/i386-gcc-cpuid.h} (59%)

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 625ca4a..e3f96e1 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -846,7 +846,7 @@ common/common-utils.h common/xml-utils.h common/buffer.h common/ptid.h \
common/format.h common/host-defs.h utils.h common/queue.h common/gdb_string.h \
common/linux-osdata.h gdb-dlfcn.h auto-load.h probe.h stap-probe.h \
gdb_bfd.h sparc-ravenscar-thread.h ppc-ravenscar-thread.h common/linux-btrace.h \
-ctf.h
+ctf.h common/i386-cpuid.h common/i386-gcc-cpuid.h

# Header files that already have srcdir in them, or which are in objdir.

diff --git a/gdb/common/i386-cpuid.h b/gdb/common/i386-cpuid.h
new file mode 100644
index 0000000..fca3233
--- /dev/null
+++ b/gdb/common/i386-cpuid.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2007-2013 Free Software Foundation, Inc.
+ *
+ * This file 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, or (at your option) any
+ * later version.
+ *
+ * This file 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.
+ *
+ * Under Section 7 of GPL version 3, you are granted additional
+ * permissions described in the GCC Runtime Library Exception, version
+ * 3.1, as published by the Free Software Foundation.
+ *
+ * You should have received a copy of the GNU General Public License and
+ * a copy of the GCC Runtime Library Exception along with this program;
+ * see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef I386_CPUID_COMMON_H
+#define I386_CPUID_COMMON_H
+
+/* Always include the header for the cpu bit defines. */
+#include "i386-gcc-cpuid.h"
+
+#if defined(__i386__) || defined(__x86_64__)
+
+/* Return cpuid data for requested cpuid level, as found in returned
+ eax, ebx, ecx and edx registers. The function checks if cpuid is
+ supported and returns 1 for valid cpuid information or 0 for
+ unsupported cpuid level. Pointers may be non-null. */
+
+static __inline int
+i386_cpuid (unsigned int __level,
+ unsigned int *__eax, unsigned int *__ebx,
+ unsigned int *__ecx, unsigned int *__edx)
+{
+ unsigned int __scratch;
+
+ if (!__eax)
+ __eax = &__scratch;
+ if (!__ebx)
+ __ebx = &__scratch;
+ if (!__ecx)
+ __ecx = &__scratch;
+ if (!__edx)
+ __edx = &__scratch;
+
+ return __get_cpuid (__level, __eax, __ebx, __ecx, __edx);
+}
+
+#else
+
+static __inline int
+i386_cpuid (unsigned int __level,
+ unsigned int *__eax, unsigned int *__ebx,
+ unsigned int *__ecx, unsigned int *__edx)
+{
+ return 0;
+}
+
+#endif /* i386 && x86_64 */
+
+#endif /* I386_CPUID_COMMON_H */
diff --git a/gdb/testsuite/gdb.arch/i386-cpuid.h b/gdb/common/i386-gcc-cpuid.h
similarity index 59%
rename from gdb/testsuite/gdb.arch/i386-cpuid.h
rename to gdb/common/i386-gcc-cpuid.h
index 084a083..e045ba8 100644
--- a/gdb/testsuite/gdb.arch/i386-cpuid.h
+++ b/gdb/common/i386-gcc-cpuid.h
@@ -1,6 +1,8 @@
-/* Helper file for i386 platform. Runtime check for MMX/SSE/SSE2/AVX
- * support. Copied from gcc 4.4.
- *
+/*
+ * Helper cpuid.h file copied from gcc-4.8.0. Code in gdb should not
+ * include this directly, but pull in i386-cpuid.h and use that func.
+ */
+/*
* Copyright (C) 2007-2013 Free Software Foundation, Inc.
*
* This file is free software; you can redistribute it and/or modify it
@@ -26,6 +28,7 @@
/* %ecx */
#define bit_SSE3 (1 << 0)
#define bit_PCLMUL (1 << 1)
+#define bit_LZCNT (1 << 5)
#define bit_SSSE3 (1 << 9)
#define bit_FMA (1 << 12)
#define bit_CMPXCHG16B (1 << 13)
@@ -37,6 +40,8 @@
#define bit_XSAVE (1 << 26)
#define bit_OSXSAVE (1 << 27)
#define bit_AVX (1 << 28)
+#define bit_F16C (1 << 29)
+#define bit_RDRND (1 << 30)

/* %edx */
#define bit_CMPXCHG8B (1 << 8)
@@ -51,49 +56,133 @@
#define bit_LAHF_LM (1 << 0)
#define bit_ABM (1 << 5)
#define bit_SSE4a (1 << 6)
+#define bit_PRFCHW (1 << 8)
#define bit_XOP (1 << 11)
#define bit_LWP (1 << 15)
#define bit_FMA4 (1 << 16)
+#define bit_TBM (1 << 21)

/* %edx */
+#define bit_MMXEXT (1 << 22)
#define bit_LM (1 << 29)
#define bit_3DNOWP (1 << 30)
#define bit_3DNOW (1 << 31)

+/* Extended Features (%eax == 7) */
+#define bit_FSGSBASE (1 << 0)
+#define bit_BMI (1 << 3)
+#define bit_HLE (1 << 4)
+#define bit_AVX2 (1 << 5)
+#define bit_BMI2 (1 << 8)
+#define bit_RTM (1 << 11)
+#define bit_RDSEED (1 << 18)
+#define bit_ADX (1 << 19)
+
+/* Extended State Enumeration Sub-leaf (%eax == 13, %ecx == 1) */
+#define bit_XSAVEOPT (1 << 0)
+
+/* Signatures for different CPU implementations as returned in uses
+ of cpuid with level 0. */
+#define signature_AMD_ebx 0x68747541
+#define signature_AMD_ecx 0x444d4163
+#define signature_AMD_edx 0x69746e65
+
+#define signature_CENTAUR_ebx 0x746e6543
+#define signature_CENTAUR_ecx 0x736c7561
+#define signature_CENTAUR_edx 0x48727561
+
+#define signature_CYRIX_ebx 0x69727943
+#define signature_CYRIX_ecx 0x64616574
+#define signature_CYRIX_edx 0x736e4978
+
+#define signature_INTEL_ebx 0x756e6547
+#define signature_INTEL_ecx 0x6c65746e
+#define signature_INTEL_edx 0x49656e69
+
+#define signature_TM1_ebx 0x6e617254
+#define signature_TM1_ecx 0x55504361
+#define signature_TM1_edx 0x74656d73
+
+#define signature_TM2_ebx 0x756e6547
+#define signature_TM2_ecx 0x3638784d
+#define signature_TM2_edx 0x54656e69
+
+#define signature_NSC_ebx 0x646f6547
+#define signature_NSC_ecx 0x43534e20
+#define signature_NSC_edx 0x79622065
+
+#define signature_NEXGEN_ebx 0x4778654e
+#define signature_NEXGEN_ecx 0x6e657669
+#define signature_NEXGEN_edx 0x72446e65
+
+#define signature_RISE_ebx 0x65736952
+#define signature_RISE_ecx 0x65736952
+#define signature_RISE_edx 0x65736952
+
+#define signature_SIS_ebx 0x20536953
+#define signature_SIS_ecx 0x20536953
+#define signature_SIS_edx 0x20536953
+
+#define signature_UMC_ebx 0x20434d55
+#define signature_UMC_ecx 0x20434d55
+#define signature_UMC_edx 0x20434d55
+
+#define signature_VIA_ebx 0x20414956
+#define signature_VIA_ecx 0x20414956
+#define signature_VIA_edx 0x20414956
+
+#define signature_VORTEX_ebx 0x74726f56
+#define signature_VORTEX_ecx 0x436f5320
+#define signature_VORTEX_edx 0x36387865

#if defined(__i386__) && defined(__PIC__)
/* %ebx may be the PIC register. */
#if __GNUC__ >= 3
#define __cpuid(level, a, b, c, d) \
- __asm__ ("xchg{l}\t{%%}ebx, %1\n\t" \
+ __asm__ ("xchg{l}\t{%%}ebx, %k1\n\t" \
"cpuid\n\t" \
- "xchg{l}\t{%%}ebx, %1\n\t" \
- : "=a" (a), "=r" (b), "=c" (c), "=d" (d) \
+ "xchg{l}\t{%%}ebx, %k1\n\t" \
+ : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
: "0" (level))

#define __cpuid_count(level, count, a, b, c, d) \
- __asm__ ("xchg{l}\t{%%}ebx, %1\n\t" \
+ __asm__ ("xchg{l}\t{%%}ebx, %k1\n\t" \
"cpuid\n\t" \
- "xchg{l}\t{%%}ebx, %1\n\t" \
- : "=a" (a), "=r" (b), "=c" (c), "=d" (d) \
+ "xchg{l}\t{%%}ebx, %k1\n\t" \
+ : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
: "0" (level), "2" (count))
#else
/* Host GCCs older than 3.0 weren't supporting Intel asm syntax
nor alternatives in i386 code. */
#define __cpuid(level, a, b, c, d) \
- __asm__ ("xchgl\t%%ebx, %1\n\t" \
+ __asm__ ("xchgl\t%%ebx, %k1\n\t" \
"cpuid\n\t" \
- "xchgl\t%%ebx, %1\n\t" \
- : "=a" (a), "=r" (b), "=c" (c), "=d" (d) \
+ "xchgl\t%%ebx, %k1\n\t" \
+ : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
: "0" (level))

#define __cpuid_count(level, count, a, b, c, d) \
- __asm__ ("xchgl\t%%ebx, %1\n\t" \
+ __asm__ ("xchgl\t%%ebx, %k1\n\t" \
"cpuid\n\t" \
- "xchgl\t%%ebx, %1\n\t" \
- : "=a" (a), "=r" (b), "=c" (c), "=d" (d) \
+ "xchgl\t%%ebx, %k1\n\t" \
+ : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
: "0" (level), "2" (count))
#endif
+#elif defined(__x86_64__) && (defined(__code_model_medium__) || defined(__code_model_large__)) && defined(__PIC__)
+/* %rbx may be the PIC register. */
+#define __cpuid(level, a, b, c, d) \
+ __asm__ ("xchg{q}\t{%%}rbx, %q1\n\t" \
+ "cpuid\n\t" \
+ "xchg{q}\t{%%}rbx, %q1\n\t" \
+ : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
+ : "0" (level))
+
+#define __cpuid_count(level, count, a, b, c, d) \
+ __asm__ ("xchg{q}\t{%%}rbx, %q1\n\t" \
+ "cpuid\n\t" \
+ "xchg{q}\t{%%}rbx, %q1\n\t" \
+ : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
+ : "0" (level), "2" (count))
#else
#define __cpuid(level, a, b, c, d) \
__asm__ ("cpuid\n\t" \
@@ -118,9 +207,9 @@ __get_cpuid_max (unsigned int __ext, unsigned int *__sig)
{
unsigned int __eax, __ebx, __ecx, __edx;

-#ifndef __x86_64__
-#if __GNUC__ >= 3
+#ifdef __i386__
/* See if we can use cpuid. On AMD64 we always can. */
+#if __GNUC__ >= 3
__asm__ ("pushf{l|d}\n\t"
"pushf{l|d}\n\t"
"pop{l}\t%0\n\t"
@@ -181,20 +270,3 @@ __get_cpuid (unsigned int __level,
__cpuid (__level, *__eax, *__ebx, *__ecx, *__edx);
return 1;
}
-
-#ifndef NOINLINE
-#define NOINLINE __attribute__ ((noinline))
-#endif
-
-unsigned int i386_cpuid (void) NOINLINE;
-
-unsigned int NOINLINE
-i386_cpuid (void)
-{
- unsigned int eax, ebx, ecx, edx;
-
- if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
- return 0;
-
- return edx;
-}
diff --git a/gdb/common/linux-btrace.c b/gdb/common/linux-btrace.c
index d3c8705..6804e55 100644
--- a/gdb/common/linux-btrace.c
+++ b/gdb/common/linux-btrace.c
@@ -30,6 +30,7 @@
#include "gdb_assert.h"
#include "regcache.h"
#include "gdbthread.h"
+#include "i386-cpuid.h"

#if HAVE_LINUX_PERF_EVENT_H

@@ -339,13 +340,10 @@ kernel_supports_btrace (void)
static int
intel_supports_btrace (void)
{
-#if defined __i386__ || defined __x86_64__
unsigned int cpuid, model, family;

- __asm__ __volatile__ ("movl $1, %%eax;"
- "cpuid;"
- : "=a" (cpuid)
- :: "%ebx", "%ecx", "%edx");
+ if (!i386_cpuid (1, &cpuid, NULL, NULL, NULL))
+ return 0;

family = (cpuid >> 8) & 0xf;
model = (cpuid >> 4) & 0xf;
@@ -376,12 +374,6 @@ intel_supports_btrace (void)
}

return 1;
-
-#else /* !defined __i386__ && !defined __x86_64__ */
-
- return 0;
-
-#endif /* !defined __i386__ && !defined __x86_64__ */
}

/* Check whether the cpu supports branch tracing. */
@@ -389,22 +381,15 @@ intel_supports_btrace (void)
static int
cpu_supports_btrace (void)
{
-#if defined __i386__ || defined __x86_64__
+ unsigned int ebx, ecx, edx;
char vendor[13];

- __asm__ __volatile__ ("xorl %%ebx, %%ebx;"
- "xorl %%ecx, %%ecx;"
- "xorl %%edx, %%edx;"
- "movl $0, %%eax;"
- "cpuid;"
- "movl %%ebx, %0;"
- "movl %%edx, %1;"
- "movl %%ecx, %2;"
- : "=m" (vendor[0]),
- "=m" (vendor[4]),
- "=m" (vendor[8])
- :
- : "%eax", "%ebx", "%ecx", "%edx");
+ if (!i386_cpuid (0, NULL, &ebx, &ecx, &edx))
+ return 0;
+
+ memcpy (&vendor[0], &ebx, 4);
+ memcpy (&vendor[4], &ecx, 4);
+ memcpy (&vendor[8], &edx, 4);
vendor[12] = '\0';

if (strcmp (vendor, "GenuineIntel") == 0)
@@ -412,12 +397,6 @@ cpu_supports_btrace (void)

/* Don't know about others. Let's assume they do. */
return 1;
-
-#else /* !defined __i386__ && !defined __x86_64__ */
-
- return 0;
-
-#endif /* !defined __i386__ && !defined __x86_64__ */
}

/* See linux-btrace.h. */
diff --git a/gdb/go32-nat.c b/gdb/go32-nat.c
index ea6d1ca..0471d8f 100644
--- a/gdb/go32-nat.c
+++ b/gdb/go32-nat.c
@@ -96,6 +96,7 @@
#include "buildsym.h"
#include "i387-tdep.h"
#include "i386-tdep.h"
+#include "i386-cpuid.h"
#include "value.h"
#include "regcache.h"
#include "gdb_string.h"
@@ -1141,6 +1142,21 @@ go32_sysinfo (char *arg, int from_tty)
else if (u.machine[0] == 'i' && u.machine[1] > 4)
{
/* CPUID with EAX = 0 returns the Vendor ID. */
+#if 0
+ /* Ideally we would use i386_cpuid(), but it needs someone to run
+ native tests first to make sure things actually work. They should.
+ http://sourceware.org/ml/gdb-patches/2013-05/msg00164.html */
+ unsigned int eax, ebx, ecx, edx;
+
+ if (i386_cpuid (0, &eax, &ebx, &ecx, &edx))
+ {
+ cpuid_max = eax;
+ memcpy (&vendor[0], &ebx, 4);
+ memcpy (&vendor[4], &ecx, 4);
+ memcpy (&vendor[8], &edx, 4);
+ cpuid_vendor[12] = '\0';
+ }
+#else
__asm__ __volatile__ ("xorl %%ebx, %%ebx;"
"xorl %%ecx, %%ecx;"
"xorl %%edx, %%edx;"
@@ -1157,6 +1173,7 @@ go32_sysinfo (char *arg, int from_tty)
:
: "%eax", "%ebx", "%ecx", "%edx");
cpuid_vendor[12] = '\0';
+#endif
}

printf_filtered ("CPU Type.......................%s", u.machine);
@@ -1182,6 +1199,10 @@ go32_sysinfo (char *arg, int from_tty)
int amd_p = strcmp (cpuid_vendor, "AuthenticAMD") == 0;
unsigned cpu_family, cpu_model;

+#if 0
+ /* See comment above about cpuid usage. */
+ i386_cpuid (1, &cpuid_eax, &cpuid_ebx, NULL, &cpuid_edx);
+#else
__asm__ __volatile__ ("movl $1, %%eax;"
"cpuid;"
: "=a" (cpuid_eax),
@@ -1189,6 +1210,7 @@ go32_sysinfo (char *arg, int from_tty)
"=d" (cpuid_edx)
:
: "%ecx");
+#endif
brand_idx = cpuid_ebx & 0xff;
cpu_family = (cpuid_eax >> 8) & 0xf;
cpu_model = (cpuid_eax >> 4) & 0xf;
diff --git a/gdb/testsuite/gdb.arch/i386-avx.c b/gdb/testsuite/gdb.arch/i386-avx.c
index bcfa18f..7fd1217 100644
--- a/gdb/testsuite/gdb.arch/i386-avx.c
+++ b/gdb/testsuite/gdb.arch/i386-avx.c
@@ -53,7 +53,7 @@ have_avx (void)
{
unsigned int eax, ebx, ecx, edx;

- if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
+ if (!i386_cpuid (1, &eax, &ebx, &ecx, &edx))
return 0;

if ((ecx & (bit_AVX | bit_OSXSAVE)) == (bit_AVX | bit_OSXSAVE))
diff --git a/gdb/testsuite/gdb.arch/i386-avx.exp b/gdb/testsuite/gdb.arch/i386-avx.exp
index 964806c..bbbc6f4 100644
--- a/gdb/testsuite/gdb.arch/i386-avx.exp
+++ b/gdb/testsuite/gdb.arch/i386-avx.exp
@@ -34,7 +34,7 @@ if [get_compiler_info] {

set additional_flags ""
if [test_compiler_info gcc*] {
- set additional_flags "additional_flags=-mavx"
+ set additional_flags "additional_flags=-mavx -I${srcdir}/../common"
}

if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable [list debug $additional_flags]] != "" } {
diff --git a/gdb/testsuite/gdb.arch/i386-sse.c b/gdb/testsuite/gdb.arch/i386-sse.c
index d431527..8617c8a 100644
--- a/gdb/testsuite/gdb.arch/i386-sse.c
+++ b/gdb/testsuite/gdb.arch/i386-sse.c
@@ -51,7 +51,10 @@ v4sf_t data[] =
int
have_sse (void)
{
- int edx = i386_cpuid ();
+ int edx;
+
+ if (!i386_cpuid (1, NULL, NULL, NULL, &edx))
+ return 0;

if (edx & bit_SSE)
return 1;
diff --git a/gdb/testsuite/gdb.arch/i386-sse.exp b/gdb/testsuite/gdb.arch/i386-sse.exp
index 5923eca..c62a3a0 100644
--- a/gdb/testsuite/gdb.arch/i386-sse.exp
+++ b/gdb/testsuite/gdb.arch/i386-sse.exp
@@ -34,7 +34,7 @@ if [get_compiler_info] {

set additional_flags ""
if [test_compiler_info gcc*] {
- set additional_flags "additional_flags=-msse"
+ set additional_flags "additional_flags=-msse -I${srcdir}/../common"
}

if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable [list debug $additional_flags]] != "" } {
--
1.8.2.1