[1/3] ARM: Generalize fncpy implementation
diff mbox

Message ID 20170615232117.29727-2-f.fainelli@gmail.com
State New
Headers show

Commit Message

Florian Fainelli June 15, 2017, 11:21 p.m. UTC
ARM's fncpy implementation is actually suitable for a large number of
platforms since the only assumption it makes is just the function's
alignment (8 bytes) which also happens to fulfil other architectures,
including but not limited to ARM64.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 arch/arm/include/asm/fncpy.h | 77 ++----------------------------------
 include/asm-generic/fncpy.h  | 94 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 97 insertions(+), 74 deletions(-)
 create mode 100644 include/asm-generic/fncpy.h

Comments

Florian Fainelli June 15, 2017, 11:23 p.m. UTC | #1
On 06/15/2017 04:21 PM, Florian Fainelli wrote:
> ARM's fncpy implementation is actually suitable for a large number of
> platforms since the only assumption it makes is just the function's
> alignment (8 bytes) which also happens to fulfil other architectures,
> including but not limited to ARM64.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
>  arch/arm/include/asm/fncpy.h | 77 ++----------------------------------
>  include/asm-generic/fncpy.h  | 94 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 97 insertions(+), 74 deletions(-)
>  create mode 100644 include/asm-generic/fncpy.h
> 
> diff --git a/arch/arm/include/asm/fncpy.h b/arch/arm/include/asm/fncpy.h
> index de5354746924..32465aef7932 100644
> --- a/arch/arm/include/asm/fncpy.h
> +++ b/arch/arm/include/asm/fncpy.h
> @@ -16,79 +16,8 @@
>   * along with this program; if not, write to the Free Software
>   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
>   */
> +#ifndef _ASMARM_FNCPY_H

and of course I missed a

#define _ASMARM_FNCPY_H

I will wait for feedback on whether this is acceptable before
resubmitting...
Tony Lindgren June 16, 2017, 8:35 a.m. UTC | #2
* Florian Fainelli <f.fainelli@gmail.com> [170615 16:27]:
> On 06/15/2017 04:21 PM, Florian Fainelli wrote:
> > ARM's fncpy implementation is actually suitable for a large number of
> > platforms since the only assumption it makes is just the function's
> > alignment (8 bytes) which also happens to fulfil other architectures,
> > including but not limited to ARM64.

Yeah I'm all for it. Maybe mention in the next version that this helps
with making SoC specific PM code into just regular Linux device drivers.

Regards,

Tony
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Russell King - ARM Linux admin June 16, 2017, 11:58 a.m. UTC | #3
On Thu, Jun 15, 2017 at 04:21:15PM -0700, Florian Fainelli wrote:
> ARM's fncpy implementation is actually suitable for a large number of
> platforms since the only assumption it makes is just the function's
> alignment (8 bytes) which also happens to fulfil other architectures,
> including but not limited to ARM64.

NAK.  This is really not "generic" because the whole point of this is
that it encapsulates architecture specific knowledge - in the case of
ARM, the fact that bit 1 is used to indicate whether the code is to be
run in Thumb mode or ARM mode.

That clearly does not belong in an asm-generic version of this.

I'm not saying "don't provide an asm-generic" version, I'm saying don't
use the ARM version as an asm-generic implementation, because it is
nothing of the sort.

Patch
diff mbox

diff --git a/arch/arm/include/asm/fncpy.h b/arch/arm/include/asm/fncpy.h
index de5354746924..32465aef7932 100644
--- a/arch/arm/include/asm/fncpy.h
+++ b/arch/arm/include/asm/fncpy.h
@@ -16,79 +16,8 @@ 
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  */
+#ifndef _ASMARM_FNCPY_H
 
-/*
- * These macros are intended for use when there is a need to copy a low-level
- * function body into special memory.
- *
- * For example, when reconfiguring the SDRAM controller, the code doing the
- * reconfiguration may need to run from SRAM.
- *
- * NOTE: that the copied function body must be entirely self-contained and
- * position-independent in order for this to work properly.
- *
- * NOTE: in order for embedded literals and data to get referenced correctly,
- * the alignment of functions must be preserved when copying.  To ensure this,
- * the source and destination addresses for fncpy() must be aligned to a
- * multiple of 8 bytes: you will be get a BUG() if this condition is not met.
- * You will typically need a ".align 3" directive in the assembler where the
- * function to be copied is defined, and ensure that your allocator for the
- * destination buffer returns 8-byte-aligned pointers.
- *
- * Typical usage example:
- *
- * extern int f(args);
- * extern uint32_t size_of_f;
- * int (*copied_f)(args);
- * void *sram_buffer;
- *
- * copied_f = fncpy(sram_buffer, &f, size_of_f);
- *
- * ... later, call the function: ...
- *
- * copied_f(args);
- *
- * The size of the function to be copied can't be determined from C:
- * this must be determined by other means, such as adding assmbler directives
- * in the file where f is defined.
- */
-
-#ifndef __ASM_FNCPY_H
-#define __ASM_FNCPY_H
-
-#include <linux/types.h>
-#include <linux/string.h>
-
-#include <asm/bug.h>
-#include <asm/cacheflush.h>
-
-/*
- * Minimum alignment requirement for the source and destination addresses
- * for function copying.
- */
-#define FNCPY_ALIGN 8
-
-#define fncpy(dest_buf, funcp, size) ({					\
-	uintptr_t __funcp_address;					\
-	typeof(funcp) __result;						\
-									\
-	asm("" : "=r" (__funcp_address) : "0" (funcp));			\
-									\
-	/*								\
-	 * Ensure alignment of source and destination addresses,	\
-	 * disregarding the function's Thumb bit:			\
-	 */								\
-	BUG_ON((uintptr_t)(dest_buf) & (FNCPY_ALIGN - 1) ||		\
-		(__funcp_address & ~(uintptr_t)1 & (FNCPY_ALIGN - 1)));	\
-									\
-	memcpy(dest_buf, (void const *)(__funcp_address & ~1), size);	\
-	flush_icache_range((unsigned long)(dest_buf),			\
-		(unsigned long)(dest_buf) + (size));			\
-									\
-	asm("" : "=r" (__result)					\
-		: "0" ((uintptr_t)(dest_buf) | (__funcp_address & 1)));	\
-									\
-	__result;							\
-})
+#include <asm-generic/fncpy.h>
 
-#endif /* !__ASM_FNCPY_H */
+#endif /* !__ASMARM_FNCPY_H */
diff --git a/include/asm-generic/fncpy.h b/include/asm-generic/fncpy.h
new file mode 100644
index 000000000000..bf7577725652
--- /dev/null
+++ b/include/asm-generic/fncpy.h
@@ -0,0 +1,94 @@ 
+/*
+ * include/asm-generic/fncpy.h - helper macros for function body copying
+ *
+ * Copyright (C) 2011 Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+/*
+ * These macros are intended for use when there is a need to copy a low-level
+ * function body into special memory.
+ *
+ * For example, when reconfiguring the SDRAM controller, the code doing the
+ * reconfiguration may need to run from SRAM.
+ *
+ * NOTE: that the copied function body must be entirely self-contained and
+ * position-independent in order for this to work properly.
+ *
+ * NOTE: in order for embedded literals and data to get referenced correctly,
+ * the alignment of functions must be preserved when copying.  To ensure this,
+ * the source and destination addresses for fncpy() must be aligned to a
+ * multiple of 8 bytes: you will be get a BUG() if this condition is not met.
+ * You will typically need a ".align 3" directive in the assembler where the
+ * function to be copied is defined, and ensure that your allocator for the
+ * destination buffer returns 8-byte-aligned pointers.
+ *
+ * Typical usage example:
+ *
+ * extern int f(args);
+ * extern uint32_t size_of_f;
+ * int (*copied_f)(args);
+ * void *sram_buffer;
+ *
+ * copied_f = fncpy(sram_buffer, &f, size_of_f);
+ *
+ * ... later, call the function: ...
+ *
+ * copied_f(args);
+ *
+ * The size of the function to be copied can't be determined from C:
+ * this must be determined by other means, such as adding assmbler directives
+ * in the file where f is defined.
+ */
+
+#ifndef __ASM_FNCPY_H
+#define __ASM_FNCPY_H
+
+#include <linux/types.h>
+#include <linux/string.h>
+
+#include <asm/bug.h>
+#include <asm/cacheflush.h>
+
+/*
+ * Minimum alignment requirement for the source and destination addresses
+ * for function copying.
+ */
+#define FNCPY_ALIGN 8
+
+#define fncpy(dest_buf, funcp, size) ({					\
+	uintptr_t __funcp_address;					\
+	typeof(funcp) __result;						\
+									\
+	asm("" : "=r" (__funcp_address) : "0" (funcp));			\
+									\
+	/*								\
+	 * Ensure alignment of source and destination addresses,	\
+	 * disregarding the function's Thumb bit:			\
+	 */								\
+	BUG_ON((uintptr_t)(dest_buf) & (FNCPY_ALIGN - 1) ||		\
+		(__funcp_address & ~(uintptr_t)1 & (FNCPY_ALIGN - 1)));	\
+									\
+	memcpy(dest_buf, (void const *)(__funcp_address & ~1), size);	\
+	flush_icache_range((unsigned long)(dest_buf),			\
+		(unsigned long)(dest_buf) + (size));			\
+									\
+	asm("" : "=r" (__result)					\
+		: "0" ((uintptr_t)(dest_buf) | (__funcp_address & 1)));	\
+									\
+	__result;							\
+})
+
+#endif /* !__ASM_FNCPY_H */