Currently kernel never set KGDB_REASON_NMI. We do now, when we enter KGDB/KDB from an NMI.

This is not to be confused with kgdb_nmicallback(), NMI callback is an entry for the slave CPUs during CPUs roundup, but REASON_NMI is the entry for the master CPU.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- kernel/debug/kdb/kdb_debugger.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/kernel/debug/kdb/kdb_debugger.c b/kernel/debug/kdb/kdb_debugger.c index 8b68ce7..be7b33b 100644 --- a/kernel/debug/kdb/kdb_debugger.c +++ b/kernel/debug/kdb/kdb_debugger.c @@ -12,6 +12,7 @@ #include <linux/kdb.h> #include <linux/kdebug.h> #include <linux/export.h> +#include <linux/hardirq.h> #include "kdb_private.h" #include "../debug_core.h"

@@ -52,6 +53,9 @@ int kdb_stub(struct kgdb_state *ks) if (atomic_read(&kgdb_setting_breakpoint)) reason = KDB_REASON_KEYBOARD;

+ if (in_nmi()) + reason = KDB_REASON_NMI; + for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) { if ((bp->bp_enabled) && (bp->bp_addr == addr)) { reason = KDB_REASON_BREAK;

Just move the macros into header file as we would want to use them for KGDB FIQ entry code.

The following macros were moved:

- svc_entry - usr_entry - kuser_cmpxchg_check - vector_stub

To make kuser_cmpxchg_check actually work across different files, we also have to make kuser_cmpxchg64_fixup global.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- arch/arm/kernel/entry-armv.S | 167 +-------------------------------------- arch/arm/kernel/entry-header.S | 170 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 171 insertions(+), 166 deletions(-)

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 0d1851c..6aeb9b8 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -136,57 +136,6 @@ common_invalid: b bad_mode ENDPROC(__und_invalid)

-/* - * SVC mode handlers - */ - -#if defined(CONFIG_AEABI) && (__LINUX_ARM_ARCH__ >= 5) -#define SPFIX(code...) code -#else -#define SPFIX(code...) -#endif - - .macro svc_entry, stack_hole=0 - UNWIND(.fnstart ) - UNWIND(.save {r0 - pc} ) - sub sp, sp, #(S_FRAME_SIZE + \stack_hole - 4) -#ifdef CONFIG_THUMB2_KERNEL - SPFIX( str r0, [sp] ) @ temporarily saved - SPFIX( mov r0, sp ) - SPFIX( tst r0, #4 ) @ test original stack alignment - SPFIX( ldr r0, [sp] ) @ restored -#else - SPFIX( tst sp, #4 ) -#endif - SPFIX( subeq sp, sp, #4 ) - stmia sp, {r1 - r12} - - ldmia r0, {r3 - r5} - add r7, sp, #S_SP - 4 @ here for interlock avoidance - mov r6, #-1 @ "" "" "" "" - add r2, sp, #(S_FRAME_SIZE + \stack_hole - 4) - SPFIX( addeq r2, r2, #4 ) - str r3, [sp, #-4]! @ save the "real" r0 copied - @ from the exception stack - - mov r3, lr - - @ - @ We are now ready to fill in the remaining blanks on the stack: - @ - @ r2 - sp_svc - @ r3 - lr_svc - @ r4 - lr_<exception>, already fixed up for correct return/restart - @ r5 - spsr_<exception> - @ r6 - orig_r0 (see pt_regs definition in ptrace.h) - @ - stmia r7, {r2 - r6} - -#ifdef CONFIG_TRACE_IRQFLAGS - bl trace_hardirqs_off -#endif - .endm - .align 5 __dabt_svc: svc_entry @@ -328,71 +277,8 @@ ENDPROC(__pabt_svc)

/* * User mode handlers - * - * EABI note: sp_svc is always 64-bit aligned here, so should S_FRAME_SIZE */

-#if defined(CONFIG_AEABI) && (__LINUX_ARM_ARCH__ >= 5) && (S_FRAME_SIZE & 7) -#error "sizeof(struct pt_regs) must be a multiple of 8" -#endif - - .macro usr_entry - UNWIND(.fnstart ) - UNWIND(.cantunwind ) @ don't unwind the user space - sub sp, sp, #S_FRAME_SIZE - ARM( stmib sp, {r1 - r12} ) - THUMB( stmia sp, {r0 - r12} ) - - ldmia r0, {r3 - r5} - add r0, sp, #S_PC @ here for interlock avoidance - mov r6, #-1 @ "" "" "" "" - - str r3, [sp] @ save the "real" r0 copied - @ from the exception stack - - @ - @ We are now ready to fill in the remaining blanks on the stack: - @ - @ r4 - lr_<exception>, already fixed up for correct return/restart - @ r5 - spsr_<exception> - @ r6 - orig_r0 (see pt_regs definition in ptrace.h) - @ - @ Also, separately save sp_usr and lr_usr - @ - stmia r0, {r4 - r6} - ARM( stmdb r0, {sp, lr}^ ) - THUMB( store_user_sp_lr r0, r1, S_SP - S_PC ) - - @ - @ Enable the alignment trap while in kernel mode - @ - alignment_trap r0 - - @ - @ Clear FP to mark the first stack frame - @ - zero_fp - -#ifdef CONFIG_IRQSOFF_TRACER - bl trace_hardirqs_off -#endif - .endm - - .macro kuser_cmpxchg_check -#if !defined(CONFIG_CPU_32v6K) && !defined(CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG) -#ifndef CONFIG_MMU -#warning "NPTL on non MMU needs fixing" -#else - @ Make sure our user space atomic helper is restarted - @ if it was interrupted in a critical region. Here we - @ perform a quick test inline since it should be false - @ 99.9999% of the time. The rest is done out of line. - cmp r4, #TASK_SIZE - blhs kuser_cmpxchg64_fixup -#endif -#endif - .endm - .align 5 __dabt_usr: usr_entry @@ -813,6 +699,7 @@ __kuser_cmpxchg64: @ 0xffff0f60 ldmfd sp!, {r4, r5, r6, pc}

.text + .global kuser_cmpxchg64_fixup kuser_cmpxchg64_fixup: @ Called from kuser_cmpxchg_fixup. @ r4 = address of interrupted insn (must be preserved). @@ -943,58 +830,6 @@ __kuser_helper_end:

THUMB( .thumb )

-/* - * Vector stubs. - * - * This code is copied to 0xffff0200 so we can use branches in the - * vectors, rather than ldr's. Note that this code must not - * exceed 0x300 bytes. - * - * Common stub entry macro: - * Enter in IRQ mode, spsr = SVC/USR CPSR, lr = SVC/USR PC - * - * SP points to a minimal amount of processor-private memory, the address - * of which is copied into r0 for the mode specific abort handler. - */ - .macro vector_stub, name, mode, correction=0 - .align 5 - -vector_\name: - .if \correction - sub lr, lr, #\correction - .endif - - @ - @ Save r0, lr_<exception> (parent PC) and spsr_<exception> - @ (parent CPSR) - @ - stmia sp, {r0, lr} @ save r0, lr - mrs lr, spsr - str lr, [sp, #8] @ save spsr - - @ - @ Prepare for SVC32 mode. IRQs remain disabled. - @ - mrs r0, cpsr - eor r0, r0, #(\mode ^ SVC_MODE | PSR_ISETSTATE) - msr spsr_cxsf, r0 - - @ - @ the branch table must immediately follow this code - @ - and lr, lr, #0x0f - THUMB( adr r0, 1f ) - THUMB( ldr lr, [r0, lr, lsl #2] ) - mov r0, sp - ARM( ldr lr, [pc, lr, lsl #2] ) - movs pc, lr @ branch to handler in SVC mode -ENDPROC(vector_\name) - - .align 2 - @ handler addresses follow this label -1: - .endm - .globl __stubs_start __stubs_start: /* diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S index 9a8531e..c3c09ac 100644 --- a/arch/arm/kernel/entry-header.S +++ b/arch/arm/kernel/entry-header.S @@ -73,6 +73,109 @@ msr cpsr_c, \rtemp @ switch back to the SVC mode .endm

+/* + * Vector stubs. + * + * This code is copied to 0xffff0200 so we can use branches in the + * vectors, rather than ldr's. Note that this code must not + * exceed 0x300 bytes. + * + * Common stub entry macro: + * Enter in IRQ mode, spsr = SVC/USR CPSR, lr = SVC/USR PC + * + * SP points to a minimal amount of processor-private memory, the address + * of which is copied into r0 for the mode specific abort handler. + */ + .macro vector_stub, name, mode, correction=0 + .align 5 + +vector_\name: + .if \correction + sub lr, lr, #\correction + .endif + + @ + @ Save r0, lr_<exception> (parent PC) and spsr_<exception> + @ (parent CPSR) + @ + stmia sp, {r0, lr} @ save r0, lr + mrs lr, spsr + str lr, [sp, #8] @ save spsr + + @ + @ Prepare for SVC32 mode. IRQs remain disabled. + @ + mrs r0, cpsr + eor r0, r0, #(\mode ^ SVC_MODE | PSR_ISETSTATE) + msr spsr_cxsf, r0 + + @ + @ the branch table must immediately follow this code + @ + and lr, lr, #0x0f + THUMB( adr r0, 1f ) + THUMB( ldr lr, [r0, lr, lsl #2] ) + mov r0, sp + ARM( ldr lr, [pc, lr, lsl #2] ) + movs pc, lr @ branch to handler in SVC mode +ENDPROC(vector_\name) + + .align 2 + @ handler addresses follow this label +1: + .endm + +/* + * SVC mode handlers + */ + +#if defined(CONFIG_AEABI) && (__LINUX_ARM_ARCH__ >= 5) +#define SPFIX(code...) code +#else +#define SPFIX(code...) +#endif + + .macro svc_entry, stack_hole=0 + UNWIND(.fnstart ) + UNWIND(.save {r0 - pc} ) + sub sp, sp, #(S_FRAME_SIZE + \stack_hole - 4) +#ifdef CONFIG_THUMB2_KERNEL + SPFIX( str r0, [sp] ) @ temporarily saved + SPFIX( mov r0, sp ) + SPFIX( tst r0, #4 ) @ test original stack alignment + SPFIX( ldr r0, [sp] ) @ restored +#else + SPFIX( tst sp, #4 ) +#endif + SPFIX( subeq sp, sp, #4 ) + stmia sp, {r1 - r12} + + ldmia r0, {r3 - r5} + add r7, sp, #S_SP - 4 @ here for interlock avoidance + mov r6, #-1 @ "" "" "" "" + add r2, sp, #(S_FRAME_SIZE + \stack_hole - 4) + SPFIX( addeq r2, r2, #4 ) + str r3, [sp, #-4]! @ save the "real" r0 copied + @ from the exception stack + + mov r3, lr + + @ + @ We are now ready to fill in the remaining blanks on the stack: + @ + @ r2 - sp_svc + @ r3 - lr_svc + @ r4 - lr_<exception>, already fixed up for correct return/restart + @ r5 - spsr_<exception> + @ r6 - orig_r0 (see pt_regs definition in ptrace.h) + @ + stmia r7, {r2 - r6} + +#ifdef CONFIG_TRACE_IRQFLAGS + bl trace_hardirqs_off +#endif + .endm + #ifndef CONFIG_THUMB2_KERNEL .macro svc_exit, rpsr msr spsr_cxsf, \rpsr @@ -164,6 +267,73 @@ #endif /* !CONFIG_THUMB2_KERNEL */

/* + * User mode handlers + * + * EABI note: sp_svc is always 64-bit aligned here, so should S_FRAME_SIZE + */ + +#if defined(CONFIG_AEABI) && (__LINUX_ARM_ARCH__ >= 5) && (S_FRAME_SIZE & 7) +#error "sizeof(struct pt_regs) must be a multiple of 8" +#endif + + .macro usr_entry + UNWIND(.fnstart ) + UNWIND(.cantunwind ) @ don't unwind the user space + sub sp, sp, #S_FRAME_SIZE + ARM( stmib sp, {r1 - r12} ) + THUMB( stmia sp, {r0 - r12} ) + + ldmia r0, {r3 - r5} + add r0, sp, #S_PC @ here for interlock avoidance + mov r6, #-1 @ "" "" "" "" + + str r3, [sp] @ save the "real" r0 copied + @ from the exception stack + + @ + @ We are now ready to fill in the remaining blanks on the stack: + @ + @ r4 - lr_<exception>, already fixed up for correct return/restart + @ r5 - spsr_<exception> + @ r6 - orig_r0 (see pt_regs definition in ptrace.h) + @ + @ Also, separately save sp_usr and lr_usr + @ + stmia r0, {r4 - r6} + ARM( stmdb r0, {sp, lr}^ ) + THUMB( store_user_sp_lr r0, r1, S_SP - S_PC ) + + @ + @ Enable the alignment trap while in kernel mode + @ + alignment_trap r0 + + @ + @ Clear FP to mark the first stack frame + @ + zero_fp + +#ifdef CONFIG_IRQSOFF_TRACER + bl trace_hardirqs_off +#endif + .endm + + .macro kuser_cmpxchg_check +#if !defined(CONFIG_CPU_32v6K) && !defined(CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG) +#ifndef CONFIG_MMU +#warning "NPTL on non MMU needs fixing" +#else + @ Make sure our user space atomic helper is restarted + @ if it was interrupted in a critical region. Here we + @ perform a quick test inline since it should be false + @ 99.9999% of the time. The rest is done out of line. + cmp r4, #TASK_SIZE + blhs kuser_cmpxchg64_fixup +#endif +#endif + .endm + +/* * These are the registers used in the syscall handler, and allow us to * have in theory up to 7 arguments to a function - r0 to r6. *

As Colin Cross noticed, serial ports could be noisy, so occasional characters once in a while are possible. So, considering the noise possibility, entering the debugger on any received byte is unacceptable for production devices.

This changes KGDB FIQ behaviour in a such way so that we have to type the GDB-protocol "$3#33" command to actually enter the debugger, the kernel will print the following prompt:

Type $3#33 to enter the debugger.

This is the exactly the same command we use to escape from KGDB to KDB, so it should be all pretty familiar.

For convenience, there is a kgdb_fiq.knock kernel command line option, when set to 0, this turns the special command to just a return key press, so the kernel will be printing this:

Hit <return> to enter the debugger.

Suggested-by: Colin Cross ccross@android.com Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- arch/arm/kernel/kgdb_fiq.c | 48 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+)

diff --git a/arch/arm/kernel/kgdb_fiq.c b/arch/arm/kernel/kgdb_fiq.c index 7ec9979..5308697 100644 --- a/arch/arm/kernel/kgdb_fiq.c +++ b/arch/arm/kernel/kgdb_fiq.c @@ -17,6 +17,7 @@ #include <linux/init.h> #include <linux/slab.h> #include <linux/hardirq.h> +#include <linux/kdb.h> #include <linux/kgdb.h> #include <asm/fiq.h> #include <asm/exception.h> @@ -25,6 +26,51 @@ 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 kgdb_fiq_knock = 1; +module_param_named(knock, kgdb_fiq_knock, bool, 0600); +MODULE_PARM_DESC(knock, "'$3#33' command must be used to enter the debugger"); + +/* + * "Serial ports are often noisy, especially when muxed over another port (we + * often use serial over the headset connector). Noise on the async command + * line just causes characters that are ignored, on a command line that blocked + * execution noise would be catastrophic." -- Colin Cross + * + * So, this small function implements KGDB/KDB knocking on the serial line: we + * won't enter the debugger until we receive a known magic phrase (which is + * actually "$3#33", known as "escape to KDB" command. If knocking is disabled, + * just pressing the return key is enough to enter the debugger. + */ +static bool kgdb_fiq_poll_knock(void) +{ + static int n; + int c = -1; + get_char_func *getc; + const char *magic = "$3#33"; + size_t m = strlen(magic); + + for (getc = &kdb_poll_funcs[0]; *getc; ++getc) { + c = (*getc)(); + if (c >= 0) + break; + } + + if (!kgdb_fiq_knock && (c == '\r' || c == '\n')) { + return 1; + } else if (c == magic[n]) { + kdb_printf("%c", c); + n = (n + 1) % m; + if (!n) + return 1; + } else { + n = 0; + kdb_printf("\n%s %s to enter the debugger.\n", + kgdb_fiq_knock ? "Type" : "Hit", + kgdb_fiq_knock ? magic : "<return>"); + } + return 0; +} + static unsigned int kgdb_fiq; static void (*kgdb_enable_fiq)(unsigned int irq, bool on); static bool (*is_kgdb_fiq)(unsigned int irq); @@ -33,6 +79,8 @@ asmlinkage void __exception_irq_entry kgdb_fiq_do_handle(struct pt_regs *regs) { if (!is_kgdb_fiq(kgdb_fiq)) return; + if (!kgdb_fiq_poll_knock()) + return;

nmi_enter(); kgdb_handle_exception(1, 0, 0, regs);

If enabled, kernel will able to enter KGDB upon serial line activity on UART ports.

Note that even with this patch and CONFIG_KGDB_FIQ is enabled, you still need to pass kgdb_fiq.enable=1 kernel command line option, otherwise UART will behave in a normal way.

By default UART0 is used, but this can be changed via kgdb_fiq.uart_num kernel command line option.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- arch/arm/Kconfig | 1 + arch/arm/mach-versatile/Makefile | 1 + arch/arm/mach-versatile/include/mach/irqs.h | 1 + arch/arm/mach-versatile/kgdb_fiq.c | 31 +++++++++++++++++++++++++++ 4 files changed, 34 insertions(+) create mode 100644 arch/arm/mach-versatile/kgdb_fiq.c

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index ae6ddf1..c0df1ba 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -311,6 +311,7 @@ config ARCH_VERSATILE select ICST select GENERIC_CLOCKEVENTS select ARCH_WANT_OPTIONAL_GPIOLIB + select ARCH_MIGHT_HAVE_FIQ select NEED_MACH_IO_H if PCI select PLAT_VERSATILE select PLAT_VERSATILE_CLCD diff --git a/arch/arm/mach-versatile/Makefile b/arch/arm/mach-versatile/Makefile index 81fa3fe..bfd761f 100644 --- a/arch/arm/mach-versatile/Makefile +++ b/arch/arm/mach-versatile/Makefile @@ -7,3 +7,4 @@ obj-$(CONFIG_ARCH_VERSATILE_PB) += versatile_pb.o obj-$(CONFIG_MACH_VERSATILE_AB) += versatile_ab.o obj-$(CONFIG_MACH_VERSATILE_DT) += versatile_dt.o obj-$(CONFIG_PCI) += pci.o +obj-$(CONFIG_KGDB_FIQ) += kgdb_fiq.o diff --git a/arch/arm/mach-versatile/include/mach/irqs.h b/arch/arm/mach-versatile/include/mach/irqs.h index bf44c61..fcd2a95 100644 --- a/arch/arm/mach-versatile/include/mach/irqs.h +++ b/arch/arm/mach-versatile/include/mach/irqs.h @@ -26,6 +26,7 @@ * held within platform.h */ #define IRQ_VIC_START 0 +#define FIQ_START IRQ_VIC_START #define IRQ_WDOGINT (IRQ_VIC_START + INT_WDOGINT) #define IRQ_SOFTINT (IRQ_VIC_START + INT_SOFTINT) #define IRQ_COMMRx (IRQ_VIC_START + INT_COMMRx) diff --git a/arch/arm/mach-versatile/kgdb_fiq.c b/arch/arm/mach-versatile/kgdb_fiq.c new file mode 100644 index 0000000..3cdf71d --- /dev/null +++ b/arch/arm/mach-versatile/kgdb_fiq.c @@ -0,0 +1,31 @@ +/* + * KGDB FIQ board support + * + * 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/module.h> +#include <linux/init.h> +#include <linux/kgdb.h> +#include <mach/hardware.h> +#include <mach/platform.h> +#include <asm/hardware/vic.h> + +static int kgdb_fiq; +module_param_named(uart_num, kgdb_fiq, int, 0600); +MODULE_PARM_DESC(uart_num, "UART<number> port to use for KGDB FIQ"); + +static int __init kgdb_fiq_init(void) +{ + WARN_ON(kgdb_fiq > INT_UARTINT2 - INT_UARTINT0); + + return kgdb_register_fiq(INT_UARTINT0 + kgdb_fiq, + vic_fiq_select, + vic_is_fiq_rised); +} +console_initcall(kgdb_fiq_init);