On Tue, Nov 12, 2013 at 09:01:16AM -0500, Nicolas Pitre wrote:
> What about this patch which I think is currently your best option. Note
> it would need to use the facilities from asm/opcodes.h to make it endian
> agnostic.
>
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 6a1b8a81b1..379cffe4ab 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -383,6 +383,34 @@ static void __init cpuid_init_hwcaps(void)
> elf_hwcap |= HWCAP_IDIVT;
> }
>
> + /*
> + * Patch our division routines with the corresponding opcode
> + * if the hardware supports it.
> + */
> + if (IS_ENABLED(CONFIG_THUMB2_KERNEL) && (elf_hwcap & HWCAP_IDIVT)) {
> + extern char __aeabi_uidiv, __aeabi_idiv;
> + u16 *uidiv = (u16 *)&__aeabi_uidiv;
> + u16 *idiv = (u16 *)&__aeabi_idiv;
> +
> + uidiv[0] = 0xfbb0; /* udiv r0, r0, r1 */
> + uidiv[1] = 0xf0f1;
> + uidiv[2] = 0x4770; /* bx lr */
> +
> + idiv[0] = 0xfb90; /* sdiv r0, r0, r1 */
> + idiv[1] = 0xf0f1;
> + idiv[2] = 0x4770; /* bx lr */
> + } else if (!IS_ENABLED(CONFIG_THUMB2_KERNEL) && (elf_hwcap &
> HWCAP_IDIVA)) {
> + extern char __aeabi_uidiv, __aeabi_idiv;
> + u32 *uidiv = (u32 *)&__aeabi_uidiv;
> + u32 *idiv = (u32 *)&__aeabi_idiv;
> +
> + uidiv[0] = 0xe730f110; /* udiv r0, r0, r1 */
> + uidiv[1] = 0xe12fff1e; /* bx lr */
> +
> + idiv[0] = 0xe710f110; /* sdiv r0, r0, r1 */
> + idiv[1] = 0xe12fff1e; /* bx lr */
> + }
What about endianness, and what if XIP is enabled?
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