ARM: head-common.S: speed up startup code
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. The
XIP kernel linker script ensures a 8 byte alignment for that purpose.
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 further cleanups in the non-XIP linker script.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Chris Brandt <Chris.Brandt@renesas.com>
diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 8733012..bf9c4e3 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -79,47 +79,59 @@
*/
__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 r7, r1
+ mov r8, r2
+ mov r10, r0
- mov fp, #0 @ Clear BSS (and zero fp)
-1: cmp r6, r7
- strcc fp, [r6],#4
- bcc 1b
+ adr r4, __mmap_switched_data
+ mov fp, #0
- 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
+#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_CPU_CP15
- .long cr_alignment @ r7
-#else
- .long 0 @ r7
+#ifdef CONFIG_XIP_KERNEL
+ .long _sdata @ r0
+ .long __data_loc @ r1
+ .long _edata_loc @ r2
+ .long __bss_stop @ sp (temporary stack in .bss)
#endif
+
+ .long __bss_start @ r0
+ .long __bss_stop @ 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 @ r3
+#else
+ .long 0 @ r3
+#endif
.size __mmap_switched_data, . - __mmap_switched_data
/*
diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S
index 8265b11..1598caa 100644
--- a/arch/arm/kernel/vmlinux-xip.lds.S
+++ b/arch/arm/kernel/vmlinux-xip.lds.S
@@ -301,7 +301,7 @@
}
#endif
- BSS_SECTION(0, 0, 0)
+ BSS_SECTION(0, 0, 8)
_end = .;
STABS_DEBUG