[PATCH v2 1/5] ARM: head-common.S: speed up startup code
From: geert@linux-m68k.org (Geert Uytterhoeven)
Date: 2017-10-03 12:41:29
Also in:
linux-renesas-soc
Hi Nicolas, On Wed, Aug 30, 2017 at 4:55 AM, 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. 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 <redacted> Reviewed-by: Ard Biesheuvel <redacted>
This is now commit 9520b1a1b5f7a348 ("ARM: head-common.S: speed up startup
code") in arm/for-next.
If CONFIG_DEBUG_LOCK_ALLOC=y, the kernel log is spammed with a few hundred
identical messages on various Renesas systems:
unwind: Unknown symbol address c0800300
unwind: Index not found c0800300
I've bisected this to the aforementioned commit.
c0800300 points to the instruction just after the __memzero call, cfr. below.
Do you have a clue? Thanks!
quoted hunk ↗ jump to hunk
--- 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 +
c0800300 is the address of the next instruction:
+ 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 __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 @ 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
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds