The FIQ debugger may be used to debug situations when the kernel stuck in uninterruptable sections, e.g. the kernel infinitely loops or deadlocked in an interrupt or with interrupts disabled.
By default KGDB FIQ is disabled in runtime, but can be enabled with kgdb_fiq.enable=1 kernel command line option.
Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- arch/arm/Kconfig | 18 ++++++ arch/arm/include/asm/kgdb.h | 7 +++ arch/arm/kernel/Makefile | 1 + arch/arm/kernel/kgdb_fiq.c | 118 +++++++++++++++++++++++++++++++++++++++ arch/arm/kernel/kgdb_fiq_entry.S | 87 +++++++++++++++++++++++++++++ 5 files changed, 231 insertions(+) create mode 100644 arch/arm/kernel/kgdb_fiq.c create mode 100644 arch/arm/kernel/kgdb_fiq_entry.S
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index f95ba14..bde27c1 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -178,6 +178,24 @@ config GENERIC_ISA_DMA config FIQ bool
+config ARCH_MIGHT_HAVE_KGDB_FIQ + bool + +config KGDB_FIQ + bool "KGDB/KDB FIQ debugger" + depends on KGDB_KDB && ARCH_MIGHT_HAVE_KGDB_FIQ && !THUMB2_KERNEL + select FIQ + help + The FIQ debugger may be used to debug situations when the + kernel stuck in uninterruptable sections, e.g. the kernel + infinitely loops or deadlocked in an interrupt or with + interrupts disabled. + + By default KGDB FIQ is disabled in runtime, but can be + enabled with kgdb_fiq.enable=1 kernel command line option. + + If unsure, say N. + config NEED_RET_TO_USER bool
diff --git a/arch/arm/include/asm/kgdb.h b/arch/arm/include/asm/kgdb.h index 48066ce..75019984 100644 --- a/arch/arm/include/asm/kgdb.h +++ b/arch/arm/include/asm/kgdb.h @@ -11,6 +11,8 @@ #define __ARM_KGDB_H__
#include <linux/ptrace.h> +#include <linux/linkage.h> +#include <asm/exception.h>
/* * GDB assumes that we're a user process being debugged, so @@ -47,6 +49,11 @@ static inline void arch_kgdb_breakpoint(void) extern void kgdb_handle_bus_error(void); extern int kgdb_fault_expected;
+extern char kgdb_fiq_handler; +extern char kgdb_fiq_handler_end; +asmlinkage void __exception_irq_entry kgdb_fiq_do_handle(struct pt_regs *regs); +extern int __init kgdb_register_fiq(void (*mach_kgdb_enable_fiq)(bool on), + bool (*mach_is_kgdb_fiq)(void)); #endif /* !__ASSEMBLY__ */
/* diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile index 5bbec7b..84ff575 100644 --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -56,6 +56,7 @@ endif obj-$(CONFIG_OABI_COMPAT) += sys_oabi-compat.o obj-$(CONFIG_ARM_THUMBEE) += thumbee.o obj-$(CONFIG_KGDB) += kgdb.o +obj-$(CONFIG_KGDB_FIQ) += kgdb_fiq_entry.o kgdb_fiq.o obj-$(CONFIG_ARM_UNWIND) += unwind.o obj-$(CONFIG_HAVE_TCM) += tcm.o obj-$(CONFIG_OF) += devtree.o diff --git a/arch/arm/kernel/kgdb_fiq.c b/arch/arm/kernel/kgdb_fiq.c new file mode 100644 index 0000000..bede9be --- /dev/null +++ b/arch/arm/kernel/kgdb_fiq.c @@ -0,0 +1,118 @@ +/* + * KGDB FIQ + * + * Copyright 2010 Google, Inc. + * Arve Hjønnevåg arve@android.com + * Colin Cross ccross@android.com + * Copyright 2012 Linaro Ltd. + * Anton Vorontsov anton.vorontsov@linaro.org + * + * 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. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/slab.h> +#include <linux/errno.h> +#include <linux/hardirq.h> +#include <linux/atomic.h> +#include <linux/kdb.h> +#include <linux/kgdb.h> +#include <asm/fiq.h> +#include <asm/exception.h> + +static int kgdb_fiq_enabled; +module_param_named(enable, kgdb_fiq_enabled, int, 0600); +MODULE_PARM_DESC(enable, "set to 1 to enable FIQ KGDB"); + +static bool (*is_kgdb_fiq)(void); +static void (*kgdb_enable_fiq)(bool on); + +asmlinkage void __exception_irq_entry kgdb_fiq_do_handle(struct pt_regs *regs) +{ + if (!is_kgdb_fiq()) + return; + if (!kgdb_nmi_poll_knock()) + return; + + nmi_enter(); + kgdb_handle_exception(1, 0, 0, regs); + nmi_exit(); +} + +static struct fiq_handler kgdb_fiq_desc = { + .name = "kgdb", +}; + +static long kgdb_fiq_setup_stack(void *info) +{ + struct pt_regs regs; + + regs.ARM_sp = __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER) + + THREAD_START_SP; + WARN_ON(!regs.ARM_sp); + + set_fiq_regs(®s); + return 0; +} + +/** + * kgdb_fiq_enable_nmi - Manage NMI-triggered entry to KGDB + * @on: Flag to either enable or disable an NMI + * + * This function manages NMIs that usually cause KGDB to enter. That is, not + * all NMIs should be enabled or disabled, but only those that issue + * kgdb_handle_exception(). + * + * The call counts disable requests, and thus allows to nest disables. But + * trying to enable already enabled NMI is an error. + */ +static void kgdb_fiq_enable_nmi(bool on) +{ + static atomic_t cnt; + int ret; + + ret = atomic_add_return(on ? 1 : -1, &cnt); + if (ret > 1 && on) { + /* + * There should be only one instance that calls this function + * in "enable, disable" order. All other users must call + * disable first, then enable. If not, something is wrong. + */ + WARN_ON(1); + return; + } + + kgdb_enable_fiq(ret > 0); +} + +int __init kgdb_register_fiq(void (*mach_kgdb_enable_fiq)(bool on), + bool (*mach_is_kgdb_fiq)(void)) +{ + int err; + int cpu; + + if (!kgdb_fiq_enabled) + return -ENODEV; + + kgdb_enable_fiq = mach_kgdb_enable_fiq; + is_kgdb_fiq = mach_is_kgdb_fiq; + + err = claim_fiq(&kgdb_fiq_desc); + if (err) { + pr_warn("%s: unable to claim fiq", __func__); + return err; + } + + for_each_possible_cpu(cpu) + work_on_cpu(cpu, kgdb_fiq_setup_stack, NULL); + + set_fiq_handler(&kgdb_fiq_handler, + &kgdb_fiq_handler_end - &kgdb_fiq_handler); + + arch_kgdb_ops.enable_nmi = kgdb_fiq_enable_nmi; + return 0; +} diff --git a/arch/arm/kernel/kgdb_fiq_entry.S b/arch/arm/kernel/kgdb_fiq_entry.S new file mode 100644 index 0000000..d6becca --- /dev/null +++ b/arch/arm/kernel/kgdb_fiq_entry.S @@ -0,0 +1,87 @@ +/* + * KGDB FIQ entry + * + * Copyright 1996,1997,1998 Russell King. + * Copyright 2012 Linaro Ltd. + * Anton Vorontsov anton.vorontsov@linaro.org + * + * 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. + */ + +#include <linux/linkage.h> +#include <asm/assembler.h> +#include <asm/memory.h> +#include <asm/unwind.h> +#include "entry-header.S" + + .text + +@ This is needed for usr_entry/alignment_trap +.LCcralign: + .long cr_alignment +.LCdohandle: + .long kgdb_fiq_do_handle + + .macro fiq_handler + ldr r1, =.LCdohandle + mov r0, sp + adr lr, BSYM(9997f) + ldr pc, [r1] +9997: + .endm + + .align 5 +__fiq_svc: + svc_entry + fiq_handler + mov r0, sp + ldmib r0, {r1 - r14} + msr cpsr_c, #FIQ_MODE | PSR_I_BIT | PSR_F_BIT + add r8, r0, #S_PC + ldr r9, [r0, #S_PSR] + msr spsr_cxsf, r9 + ldr r0, [r0, #S_R0] + ldmia r8, {pc}^ + + UNWIND(.fnend ) +ENDPROC(__fiq_svc) + .ltorg + + .align 5 +__fiq_usr: + usr_entry + kuser_cmpxchg_check + fiq_handler + get_thread_info tsk + mov why, #0 + b ret_to_user_from_irq + UNWIND(.fnend ) +ENDPROC(__fiq_usr) + .ltorg + + .global kgdb_fiq_handler +kgdb_fiq_handler: + + vector_stub fiq, FIQ_MODE, 4 + + .long __fiq_usr @ 0 (USR_26 / USR_32) + .long __fiq_svc @ 1 (FIQ_26 / FIQ_32) + .long __fiq_svc @ 2 (IRQ_26 / IRQ_32) + .long __fiq_svc @ 3 (SVC_26 / SVC_32) + .long __fiq_svc @ 4 + .long __fiq_svc @ 5 + .long __fiq_svc @ 6 + .long __fiq_svc @ 7 + .long __fiq_svc @ 8 + .long __fiq_svc @ 9 + .long __fiq_svc @ a + .long __fiq_svc @ b + .long __fiq_svc @ c + .long __fiq_svc @ d + .long __fiq_svc @ e + .long __fiq_svc @ f + + .global kgdb_fiq_handler_end +kgdb_fiq_handler_end: