[PATCH 1/3] ARM: head-common.S: speed up startup code
From: Ard Biesheuvel <hidden>
Date: 2017-08-26 10:49:35
On 25 August 2017 at 17:25, Nicolas Pitre [off-list ref] wrote:
Let's use optimized routines such as memcpy to copy .data and memzero to clear .bss in the startup code instead of doing it one word at a time. Those routines don't use any global data so they're safe to use even if .data and .bss segments are not initialized. In the .data copy case a temporary stack is installed in the .bss area as the actual kernel stack is located within the copied data area. Finally, make the .data copy and related pointers surrounded by CONFIG_XIP_KERNEL to make it obvious what it is all about. This will allow for some cleanup in the non-XIP linker script as well. Signed-off-by: Nicolas Pitre <redacted>
Reviewed by: Ard Biesheuvel [off-list ref]
quoted hunk ↗ jump to hunk
--- arch/arm/kernel/head-common.S | 76 +++++++++++++++++++++++++------------------ 1 file changed, 44 insertions(+), 32 deletions(-)diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S index 8733012d23..63a21fe03f 100644 --- a/arch/arm/kernel/head-common.S +++ b/arch/arm/kernel/head-common.S@@ -79,47 +79,59 @@ ENDPROC(__vet_atags) */ __INIT __mmap_switched: - adr r3, __mmap_switched_data - - ldmia r3!, {r4, r5, r6, r7} - cmp r4, r5 @ Copy data segment if needed -1: cmpne r5, r6 - ldrne fp, [r4], #4 - strne fp, [r5], #4 - bne 1b - - mov fp, #0 @ Clear BSS (and zero fp) -1: cmp r6, r7 - strcc fp, [r6],#4 - bcc 1b - - ARM( ldmia r3, {r4, r5, r6, r7, sp}) - THUMB( ldmia r3, {r4, r5, r6, r7} ) - THUMB( ldr sp, [r3, #16] ) - str r9, [r4] @ Save processor ID - str r1, [r5] @ Save machine type - str r2, [r6] @ Save atags pointer - cmp r7, #0 - strne r0, [r7] @ Save control register values + + mov r7, r1 + mov r8, r2 + mov r10, r0 + + adr r4, __mmap_switched_data + mov fp, #0 + +#ifdef CONFIG_XIP_KERNEL + ARM( ldmia r4!, {r0, r1, r2, sp} ) + THUMB( ldmia r4!, {r0, r1, r2, r3} ) + THUMB( mov sp, r3 ) + sub r2, r2, r1 + bl memcpy @ copy .data to RAM +#endif + + ARM( ldmia r4!, {r0, r1, sp} ) + THUMB( ldmia r4!, {r0, r1, r3} ) + THUMB( mov sp, r3 ) + sub r1, r1, r0 + bl __memzero @ clear .bss + + ldmia r4, {r0, r1, r2, r3} + str r9, [r0] @ Save processor ID + str r7, [r1] @ Save machine type + str r8, [r2] @ Save atags pointer + cmp r3, #0 + strne r10, [r3] @ Save control register values b start_kernel ENDPROC(__mmap_switched) .align 2 .type __mmap_switched_data, %object __mmap_switched_data: - .long __data_loc @ r4 - .long _sdata @ r5 - .long __bss_start @ r6 - .long _end @ r7 - .long processor_id @ r4 - .long __machine_arch_type @ r5 - .long __atags_pointer @ r6 +#ifdef CONFIG_XIP_KERNEL + .long _sdata @ r0 + .long __data_loc @ r1 + .long _edata_loc @ r2 + .long _end @ sp (temporary stack in .bss) +#endif + + .long __bss_start @ r0 + .long _end @ r1 + .long init_thread_union + THREAD_START_SP @ sp + + .long processor_id @ r0 + .long __machine_arch_type @ r1 + .long __atags_pointer @ r2 #ifdef CONFIG_CPU_CP15 - .long cr_alignment @ r7 + .long cr_alignment @ r3 #else - .long 0 @ r7 + .long 0 @ r3 #endif - .long init_thread_union + THREAD_START_SP @ sp .size __mmap_switched_data, . - __mmap_switched_data /* --2.9.5 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel at lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel