From 42f25bddd0a226d2431e057b9e01c5cc61067e12 Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Sat, 12 Dec 2015 02:49:21 +0100 Subject: ARM: 8477/1: runtime patch udiv/sdiv instructions into __aeabi_{u}idiv() The ARM compiler inserts calls to __aeabi_idiv() and __aeabi_uidiv() when it needs to perform division on signed and unsigned integers. If a processor has support for the sdiv and udiv instructions, the kernel may overwrite the beginning of those functions with those instructions and a "bx lr" to get better performance. To ensure that those functions are aligned to a 32-bit word for easier patching (which might not always be the case in Thumb mode) and that the two patched instructions end up in the same cache line, a 8-byte alignment is enforced when ARM_PATCH_IDIV is selected. This was heavily inspired by a previous patch from Stephen Boyd. Signed-off-by: Nicolas Pitre Acked-by: Arnd Bergmann Signed-off-by: Russell King --- arch/arm/lib/lib1funcs.S | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/arm/lib') diff --git a/arch/arm/lib/lib1funcs.S b/arch/arm/lib/lib1funcs.S index af2267f6a529..9397b2e532af 100644 --- a/arch/arm/lib/lib1funcs.S +++ b/arch/arm/lib/lib1funcs.S @@ -205,6 +205,10 @@ Boston, MA 02111-1307, USA. */ .endm +#ifdef CONFIG_ARM_PATCH_IDIV + .align 3 +#endif + ENTRY(__udivsi3) ENTRY(__aeabi_uidiv) UNWIND(.fnstart) @@ -253,6 +257,10 @@ UNWIND(.fnstart) UNWIND(.fnend) ENDPROC(__umodsi3) +#ifdef CONFIG_ARM_PATCH_IDIV + .align 3 +#endif + ENTRY(__divsi3) ENTRY(__aeabi_idiv) UNWIND(.fnstart) -- cgit v1.2.1