linux-kernel - Re: [PATCH v5 5/5] powerpc/perf: split callchain.c by bitness

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Message-Id: <4d996b0a225ca5b7d287ae46825d7da4a1d6e509.1567146554.git.christophe.leroy@c-s.fr>
Date:   Fri, 30 Aug 2019 06:35:11 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     linuxppc-dev@...ts.ozlabs.org, Michal Suchanek <msuchanek@...e.de>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@....fr>,
        Nicholas Piggin <npiggin@...il.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Joel Stanley <joel@....id.au>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Firoz Khan <firoz.khan@...aro.org>,
        Breno Leitao <leitao@...ian.org>,
        Russell Currey <ruscur@...sell.cc>,
        Nicolai Stange <nstange@...e.de>,
        Michael Neuling <mikey@...ling.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Christian Brauner <christian@...uner.io>,
        David Howells <dhowells@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Allison Randal <allison@...utok.net>,
        David Hildenbrand <david@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 5/5] powerpc/perf: split callchain.c by bitness

On 08/29/2019 10:28 PM, Michal Suchanek wrote:
> Building callchain.c with !COMPAT proved quite ugly with all the
> defines. Splitting out the 32bit and 64bit parts looks better.
> 
> Also rewrite current_is_64bit as common function. No other code change
> intended.

Nice result.

Could look even better by merging both read_user_stack_32(), see below.

Also a possible cosmetic change to Makefile.

---
 arch/powerpc/perf/Makefile       |  7 ++---
 arch/powerpc/perf/callchain_32.c | 65 ++++++++++++++++------------------------
 2 files changed, 29 insertions(+), 43 deletions(-)

diff --git a/arch/powerpc/perf/Makefile b/arch/powerpc/perf/Makefile
index e9f3202251d0..53d614e98537 100644
--- a/arch/powerpc/perf/Makefile
+++ b/arch/powerpc/perf/Makefile
@@ -1,9 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 
-obj-$(CONFIG_PERF_EVENTS)	+= callchain.o perf_regs.o
-ifdef CONFIG_PERF_EVENTS
-obj-y				+= callchain_$(BITS).o
-obj-$(CONFIG_COMPAT)		+= callchain_32.o
+obj-$(CONFIG_PERF_EVENTS)	+= callchain.o callchain_$(BITS).o perf_regs.o
+ifdef CONFIG_COMPAT
+obj-$(CONFIG_PERF_EVENTS)	+= callchain_32.o
 endif
 
 obj-$(CONFIG_PPC_PERF_CTRS)	+= core-book3s.o bhrb.o
diff --git a/arch/powerpc/perf/callchain_32.c b/arch/powerpc/perf/callchain_32.c
index 0bd4484eddaa..17c43ae03084 100644
--- a/arch/powerpc/perf/callchain_32.c
+++ b/arch/powerpc/perf/callchain_32.c
@@ -15,50 +15,13 @@
 #include <asm/sigcontext.h>
 #include <asm/ucontext.h>
 #include <asm/vdso.h>
-#ifdef CONFIG_PPC64
-#include "../kernel/ppc32.h"
-#endif
 #include <asm/pte-walk.h>
 
 #include "callchain.h"
 
 #ifdef CONFIG_PPC64
-static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
-{
-	if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
-	    ((unsigned long)ptr & 3))
-		return -EFAULT;
-
-	pagefault_disable();
-	if (!__get_user_inatomic(*ret, ptr)) {
-		pagefault_enable();
-		return 0;
-	}
-	pagefault_enable();
-
-	return read_user_stack_slow(ptr, ret, 4);
-}
-#else /* CONFIG_PPC64 */
-/*
- * On 32-bit we just access the address and let hash_page create a
- * HPTE if necessary, so there is no need to fall back to reading
- * the page tables.  Since this is called at interrupt level,
- * do_page_fault() won't treat a DSI as a page fault.
- */
-static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
-{
-	int rc;
-
-	if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
-	    ((unsigned long)ptr & 3))
-		return -EFAULT;
-
-	pagefault_disable();
-	rc = __get_user_inatomic(*ret, ptr);
-	pagefault_enable();
-
-	return rc;
-}
+#include "../kernel/ppc32.h"
+#else
 
 #define __SIGNAL_FRAMESIZE32	__SIGNAL_FRAMESIZE
 #define sigcontext32		sigcontext
@@ -95,6 +58,30 @@ struct rt_signal_frame_32 {
 	int			abigap[56];
 };
 
+/*
+ * On 32-bit we just access the address and let hash_page create a
+ * HPTE if necessary, so there is no need to fall back to reading
+ * the page tables.  Since this is called at interrupt level,
+ * do_page_fault() won't treat a DSI as a page fault.
+ */
+static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
+{
+	int rc;
+
+	if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
+	    ((unsigned long)ptr & 3))
+		return -EFAULT;
+
+	pagefault_disable();
+	rc = __get_user_inatomic(*ret, ptr);
+	pagefault_enable();
+
+	if (IS_ENABLED(CONFIG_PPC32) || !rc)
+		return rc;
+
+	return read_user_stack_slow(ptr, ret, 4);
+}
+
 static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
 {
 	if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
-- 
2.13.3