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Subject[PATCH 3/3] Add ARM kernel debug macros for locating the boot problems quickly
Date
When we are porting Linux to a new board, we ofter encounter the problems
that the board can't boot up and there is no any messages output in
console. These debug macros can help the developers print registers' value
or messages easily and locate the root cause quickly.

All these debug macros are under CONFIG_DEBUG_LL. When CONFIG_DEBUG_LL is
enabled, the following messages will be printed in the boot procedure.

Uncompressing Linux... done, booting the kernel.
r13:005454ec
stext enter.
__lookup_processor_type enter.
__lookup_machine_type enter.
__vet_atags enter.
__create_page_tables enter.
__enable_mmu enter.
__mmap_switched enter.
__lookup_processor_type enter.
__lookup_machine_type enter.
secondary_startup enter.
__lookup_processor_type enter.
__enable_mmu enter.
__secondary_switched enter.
Linux version 2.6.38.rc1 ...

Signed-off-by: Stanley.Miao <stanley.miao@windriver.com>
---
arch/arm/kernel/debug_macro.S | 88 +++++++++++++++++++++++++++++++++++++++++
arch/arm/kernel/head-common.S | 8 ++++
arch/arm/kernel/head.S | 19 +++++++--
arch/arm/kernel/vmlinux.lds.S | 7 +++
4 files changed, 118 insertions(+), 4 deletions(-)
create mode 100644 arch/arm/kernel/debug_macro.S
diff --git a/arch/arm/kernel/debug_macro.S b/arch/arm/kernel/debug_macro.S
new file mode 100644
index 0000000..033acf3
--- /dev/null
+++ b/arch/arm/kernel/debug_macro.S
@@ -0,0 +1,88 @@
+/*
+ * linux/arch/arm/kernel/debug_macro.S
+ *
+ * Copyright (c) 2011 Wind River Systems, Inc.
+ * Stanley.Miao <stanley.miao@windriver.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 32-bit debugging code
+ */
+
+#ifdef CONFIG_DEBUG_LL
+
+ .macro kputc,val
+ mov r0, \val
+ bl printch
+ .endm
+
+ .macro dbgmsg, str
+ stmfd sp!, {r0-r3, lr}
+ adr r0, \str
+ bl printascii
+ ldmfd sp!, {r0-r3, lr}
+ .endm
+
+ .macro read_reg reg, num
+ stmfd sp!, {r0-r4, lr}
+ kputc #'r'
+ mov r4, #\num
+ cmp r4, #10
+ blt 901f
+ sub r4, r4, #10
+ kputc #'1'
+901: add r0, r4, #'0'
+ bl printch
+ kputc #':'
+ ldmfd sp, {r0-r4, lr}
+ mov r0, \reg
+ bl printhex8
+ kputc #'\n'
+ ldmfd sp!, {r0-r4, lr}
+ .endm
+
+ .macro PRINT_SCTLR
+ stmfd sp!, {r0-r4, lr}
+ kputc #'S'
+ kputc #'C'
+ kputc #'T'
+ kputc #'L'
+ kputc #'R'
+ kputc #':'
+ mrc p15, 0, r0, c1, c0, 0
+ bl printhex8
+ kputc #'\n'
+ ldmfd sp!, {r0-r4, lr}
+ .endm
+
+ .macro PRINT_CPSR
+ stmfd sp!, {r0-r4, lr}
+ kputc #'C'
+ kputc #'P'
+ kputc #'S'
+ kputc #'R'
+ kputc #':'
+ mrs r0, cpsr
+ bl printhex8
+ kputc #'\n'
+ ldmfd sp!, {r0-r4, lr}
+ .endm
+
+#define DBG_MSG(x) dbgmsg dbg_##x
+#define PRINT_REG(x) read_reg r##x, x
+
+#undef ENDPROC
+#define ENDPROC(name) \
+ .type name, %function; \
+ END(name); \
+ dbg_##name:; \
+ .ascii #name; \
+ .asciz " enter.\n"; \
+ .align 2
+
+#else
+#define DBG_MSG(x)
+#define PRINT_REG(x)
+#endif
diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 37cfa88..f916bb8 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -74,6 +74,7 @@ str_a3: .asciz "\nPlease check your kernel config and/or bootloader.\n"
* r5 = mach_info pointer in physical address space
*/
__lookup_machine_type:
+ DBG_MSG(__lookup_machine_type)
adr r3, __lookup_machine_type_data
ldmia r3, {r4, r5, r6}
sub r3, r3, r4 @ get offset between virt&phys
@@ -114,6 +115,7 @@ __lookup_machine_type_data:
* r5, r6 corrupted
*/
__vet_atags:
+ DBG_MSG(__vet_atags)
tst r2, #0x3 @ aligned?
bne 1f

@@ -149,6 +151,7 @@ ENDPROC(__vet_atags)
*/
__INIT
__mmap_switched:
+ DBG_MSG(__mmap_switched)
adr r3, __mmap_switched_data

ldmia r3!, {r4, r5, r6, r7}
@@ -225,6 +228,7 @@ ENDPROC(lookup_processor_type)
*/
__CPUINIT
__lookup_processor_type:
+ DBG_MSG(__lookup_processor_type)
adr r3, __lookup_processor_type_data
ldmia r3, {r4 - r6}
sub r3, r3, r4 @ get offset between virt&phys
@@ -284,3 +288,7 @@ __error:
1: mov r0, r0
b 1b
ENDPROC(__error)
+
+ .align
+ .section ".boot.stack", "aw"
+boot_stack: .space 512
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index dd6b369..bde50cd 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -33,6 +33,7 @@
#define KERNEL_RAM_VADDR (PAGE_OFFSET + TEXT_OFFSET)
#define KERNEL_RAM_PADDR (PHYS_OFFSET + TEXT_OFFSET)

+#include "debug_macro.S"

/*
* swapper_pg_dir is the virtual address of the initial page table.
@@ -82,6 +83,9 @@
ENTRY(stext)
setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode
@ and irqs disabled
+ ldr r13, =(__stack_end - PAGE_OFFSET + PHYS_OFFSET)
+ PRINT_REG(13)
+ DBG_MSG(stext)
mrc p15, 0, r9, c0, c0 @ get processor id
bl __lookup_processor_type @ r5=procinfo r9=cpuid
movs r10, r5 @ invalid processor (r5=0)?
@@ -102,8 +106,8 @@ ENTRY(stext)
* above. On return, the CPU will be ready for the MMU to be
* turned on, and r0 will hold the CPU control register value.
*/
- ldr r13, =__mmap_switched @ address to jump to after
- @ mmu has been enabled
+ ldr r0, =__mmap_switched @ address to jump to after
+ str r0, [r13, #-4]! @ mmu has been enabled
adr lr, BSYM(1f) @ return (PIC) address
ARM( add pc, r10, #PROCINFO_INITFUNC )
THUMB( add r12, r10, #PROCINFO_INITFUNC )
@@ -126,6 +130,7 @@ ENDPROC(stext)
* r4 = physical page table address
*/
__create_page_tables:
+ DBG_MSG(__create_page_tables)
pgtbl r4 @ page table address

/*
@@ -278,6 +283,8 @@ ENTRY(secondary_startup)
* as it has already been validated by the primary processor.
*/
setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9
+ ldr r13, =(__stack_end - PAGE_OFFSET + PHYS_OFFSET)
+ DBG_MSG(secondary_startup)
mrc p15, 0, r9, c0, c0 @ get processor id
bl __lookup_processor_type
movs r10, r5 @ invalid processor?
@@ -292,7 +299,7 @@ ENTRY(secondary_startup)
sub r4, r4, r5 @ mmu has been enabled
ldr r4, [r7, r4] @ get secondary_data.pgdir
adr lr, BSYM(__enable_mmu) @ return address
- mov r13, r12 @ __secondary_switched address
+ str r12, [r13, #-4]! @ __secondary_switched address
ARM( add pc, r10, #PROCINFO_INITFUNC ) @ initialise processor
@ (return control reg)
THUMB( add r12, r10, #PROCINFO_INITFUNC )
@@ -303,6 +310,7 @@ ENDPROC(secondary_startup)
* r6 = &secondary_data
*/
ENTRY(__secondary_switched)
+ DBG_MSG(__secondary_switched)
ldr sp, [r7, #4] @ get secondary_data.stack
mov fp, #0
b secondary_start_kernel
@@ -330,6 +338,7 @@ __secondary_data:
* r13 = *virtual* address to jump to upon completion
*/
__enable_mmu:
+ DBG_MSG(__enable_mmu)
#ifdef CONFIG_ALIGNMENT_TRAP
orr r0, r0, #CR_A
#else
@@ -373,7 +382,9 @@ __turn_mmu_on:
mcr p15, 0, r0, c1, c0, 0 @ write control reg
mrc p15, 0, r3, c0, c0, 0 @ read id reg
mov r3, r3
- mov r3, r13
+ sub r13, r13, #PHYS_OFFSET
+ add r13, r13, #PAGE_OFFSET
+ ldr r3, [r13], #4
mov pc, r3
__enable_mmu_end:
ENDPROC(__turn_mmu_on)
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index cead889..5030bc0 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -246,6 +246,13 @@ SECTIONS
#endif

BSS_SECTION(0, 0, 0)
+ .stack : {
+ . = ALIGN(4);
+ __stack_start = .;
+ *(.boot.stack)
+ . = ALIGN(4);
+ __stack_end = .;
+ }
_end = .;

STABS_DEBUG
--
1.5.4.3


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