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* [PATCH 01/13] ARM: add fncpy.h from linux v4.6
@ 2021-01-21 11:29 Steffen Trumtrar
  2021-01-21 11:29 ` [PATCH 02/13] ARM: mmu: inherit pte flags from pmd Steffen Trumtrar
                   ` (12 more replies)
  0 siblings, 13 replies; 17+ messages in thread
From: Steffen Trumtrar @ 2021-01-21 11:29 UTC (permalink / raw)
  To: barebox; +Cc: Steffen Trumtrar

From: Steffen Trumtrar <s.trumtrar@pengutronix.de>

Description from the linux commit 5756e9dd0de6d5c307773f8f734c0684b3098fdd:

    ARM: 6640/1: Thumb-2: Symbol manipulation macros for function body copying

    In low-level board support code, there is sometimes a need to
    copy a function body to another location at run-time.

    A straightforward call to memcpy doesn't work in Thumb-2,
    because bit 0 of external Thumb function symbols is set to 1,
    indicating that the function is Thumb.  Without corrective
    measures, this will cause an off-by-one copy, and the copy
    may be called using the wrong instruction set.

    This patch adds an fncpy() macro to help with such copies.

    Particular care is needed, because C doesn't guarantee any
    defined behaviour when casting a function pointer to any other
    type.  This has been observed to lead to strange optimisation
    side-effects when doing the arithmetic which is required in
    order to copy/move function bodies correctly in Thumb-2.

    Thanks to Russell King and Nicolas Pitre for their input
    on this patch.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
---
 arch/arm/include/asm/fncpy.h | 82 ++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 arch/arm/include/asm/fncpy.h

diff --git a/arch/arm/include/asm/fncpy.h b/arch/arm/include/asm/fncpy.h
new file mode 100644
index 0000000000..d13876bffa
--- /dev/null
+++ b/arch/arm/include/asm/fncpy.h
@@ -0,0 +1,82 @@
+/*
+ * arch/arm/include/asm/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>
+
+/*
+ * 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));			\
+									\
+	memcpy(dest_buf, (void const *)(__funcp_address & ~1), size);	\
+									\
+	asm("" : "=r" (__result)					\
+		: "0" ((uintptr_t)(dest_buf) | (__funcp_address & 1)));	\
+									\
+	__result;							\
+})
+
+#endif /* !__ASM_FNCPY_H */
-- 
2.20.1


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^ permalink raw reply related	[flat|nested] 17+ messages in thread
end of thread, other threads:[~2021-01-26 11:02 UTC | newest]

Thread overview: 17+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2021-01-21 11:29 [PATCH 01/13] ARM: add fncpy.h from linux v4.6 Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 02/13] ARM: mmu: inherit pte flags from pmd Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 03/13] firmware: socfpga: set APPLYCFG after loading bitstream Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 04/13] reset: add of_reset_control_get to header Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 05/13] drivers: add fpga bridge framework Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 06/13] drivers: fpga: add socfpga bridges Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 07/13] firmware: socfpga: change function prefixes Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 08/13] firmware: import fpga-mgr.h from linux Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 09/13] of: kconfig: of_overlay uses firmwaremgr_load_file Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 10/13] of: of_firmware: add support for fpga bridges Steffen Trumtrar
2021-01-25  9:52   ` Sascha Hauer
2021-01-26  8:47     ` Steffen Trumtrar
2021-01-26 11:02       ` Sascha Hauer
2021-01-21 11:29 ` [PATCH 11/13] commands: firmwareload: allow loading firmware from dt Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 12/13] drivers: firmware: socfpga: remove bridges shutdown Steffen Trumtrar
2021-01-21 11:29 ` [PATCH 13/13] firmware: add support for compressed images Steffen Trumtrar
2021-01-25  9:56 ` [PATCH 01/13] ARM: add fncpy.h from linux v4.6 Sascha Hauer

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