On Thu, Jan 21, 2021 at 12:29:46PM +0100, Steffen Trumtrar wrote: > From: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx> > > 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@xxxxxxxxxxxxxx> > --- > arch/arm/include/asm/fncpy.h | 82 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 82 insertions(+) > create mode 100644 arch/arm/include/asm/fncpy.h Applied this patch for now, but with an update to v5.10 with the only change that the licence header is changed to SPDX now. Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
