]> git.karo-electronics.de Git - karo-tx-linux.git/commit
ARM: 6640/1: Thumb-2: Symbol manipulation macros for function body copying
authorDave Martin <dave.martin@linaro.org>
Wed, 26 Jan 2011 17:34:26 +0000 (18:34 +0100)
committerRussell King <rmk+kernel@arm.linux.org.uk>
Thu, 27 Jan 2011 11:48:58 +0000 (11:48 +0000)
commit5756e9dd0de6d5c307773f8f734c0684b3098fdd
tree4a92eded1b93fd91d2c40bc5bb5cb0405daeed79
parent6fb1b304255efc5c4c93874ac8c066272e257e28
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: Dave Martin <dave.martin@linaro.org>
Tested-by: Jean Pihet <j-pihet@ti.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
arch/arm/include/asm/fncpy.h [new file with mode: 0644]