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Date: Fri, 16 Jun 2017 17:07:42 -0700 From: Florian Fainelli <f.fainelli@...il.com> To: linux-arm-kernel@...ts.infradead.org Cc: bcm-kernel-feedback-list@...adcom.com, Florian Fainelli <f.fainelli@...il.com>, Russell King <linux@...linux.org.uk>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, linux-kernel@...r.kernel.org (open list), linux-arch@...r.kernel.org (open list:GENERIC INCLUDE/ASM HEADER FILES), Dave Gerlach <d-gerlach@...com>, Tony Lindgren <tony@...mide.com>, Keerthy J <j-keerthy@...com>, Alexandre Belloni <alexandre.belloni@...e-electrons.com>, linux-omap@...r.kernel.org, Shawn Guo <shawnguo@...nel.org> Subject: [PATCH v3 2/4] asm-generic: Provide a fncpy() implementation Define a generic fncpy() implementation largely based on the ARM version that requires an 8 bytes alignment for the destination address where to copy this function as well as the function's own address. Signed-off-by: Florian Fainelli <f.fainelli@...il.com> --- include/asm-generic/fncpy.h | 93 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 include/asm-generic/fncpy.h diff --git a/include/asm-generic/fncpy.h b/include/asm-generic/fncpy.h new file mode 100644 index 000000000000..ec03b83b8535 --- /dev/null +++ b/include/asm-generic/fncpy.h @@ -0,0 +1,93 @@ +/* + * 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. \ + */ \ + BUG_ON((uintptr_t)(dest_buf) & (FNCPY_ALIGN - 1) || \ + (__funcp_address & (FNCPY_ALIGN - 1))); \ + \ + memcpy(dest_buf, (void const *)__funcp_address, size); \ + flush_icache_range((unsigned long)(dest_buf), \ + (unsigned long)(dest_buf) + (size)); \ + \ + asm("" : "=r" (__result) \ + : "0" ((uintptr_t)(dest_buf))); \ + \ + __result; \ +}) + +#endif /* !__ASM_FNCPY_H */ -- 2.9.3
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