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Date: Fri, 18 Jul 2008 11:44:29 -0700
From: Deepak Saxena <dsaxena@...xity.net>
To: Jason Wessel <jason.wessel@...driver.com>
Cc: linux-kernel@...r.kernel.org, rmk@....linux.org.uk,
linux-arm-kernel@...ts.arm.linux.org.uk
Subject: Re: [PATCH 1/4] kgdb: support for ARCH=arm
On Jul 15 2008, at 07:27, Jason Wessel was caught saying:
> This patch adds the ARCH=arm specific a kgdb backend, originally
> written by Deepak Saxena <dsaxena@...xity.net> and George Davis
> <gdavis@...sta.com>. Geoff Levand <geoffrey.levand@...sony.com>,
> Nicolas Pitre, Manish Lachwani, and Jason Wessel have contributed
> various fixups here as well.
Acked-By: Deepak Saxena <dsaxena@...xity.net>
> The KGDB patch makes one change to the core ARM architecture such that
> the traps are initialized early for use with the debugger or other
> subsystems.
>
> [ mingo@...e.hu: small cleanups. ]
> [ ben-linux@...ff.org: fixed early_trap_init ]
>
> Signed-off-by: Jason Wessel <jason.wessel@...driver.com>
> ---
> arch/arm/Kconfig | 1 +
> arch/arm/kernel/Makefile | 1 +
> arch/arm/kernel/kgdb.c | 201 ++++++++++++++++++++++++++++++++++++++++++++++
> arch/arm/kernel/setup.c | 2 +
> arch/arm/kernel/traps.c | 5 +
> include/asm-arm/kgdb.h | 104 ++++++++++++++++++++++++
> include/asm-arm/traps.h | 2 +
> 7 files changed, 316 insertions(+), 0 deletions(-)
> create mode 100644 arch/arm/kernel/kgdb.c
> create mode 100644 include/asm-arm/kgdb.h
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 258f136..fd4d803 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -12,6 +12,7 @@ config ARM
> select RTC_LIB
> select SYS_SUPPORTS_APM_EMULATION
> select HAVE_OPROFILE
> + select HAVE_ARCH_KGDB
> select HAVE_KPROBES if (!XIP_KERNEL)
> select HAVE_KRETPROBES if (HAVE_KPROBES)
> select HAVE_FTRACE if (!XIP_KERNEL)
> diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
> index eb9092c..1d296fc 100644
> --- a/arch/arm/kernel/Makefile
> +++ b/arch/arm/kernel/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_KPROBES) += kprobes.o kprobes-decode.o
> obj-$(CONFIG_ATAGS_PROC) += atags.o
> obj-$(CONFIG_OABI_COMPAT) += sys_oabi-compat.o
> obj-$(CONFIG_ARM_THUMBEE) += thumbee.o
> +obj-$(CONFIG_KGDB) += kgdb.o
>
> obj-$(CONFIG_CRUNCH) += crunch.o crunch-bits.o
> AFLAGS_crunch-bits.o := -Wa,-mcpu=ep9312
> diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c
> new file mode 100644
> index 0000000..aaffaec
> --- /dev/null
> +++ b/arch/arm/kernel/kgdb.c
> @@ -0,0 +1,201 @@
> +/*
> + * arch/arm/kernel/kgdb.c
> + *
> + * ARM KGDB support
> + *
> + * Copyright (c) 2002-2004 MontaVista Software, Inc
> + * Copyright (c) 2008 Wind River Systems, Inc.
> + *
> + * Authors: George Davis <davis_g@...sta.com>
> + * Deepak Saxena <dsaxena@...xity.net>
> + */
> +#include <linux/kgdb.h>
> +#include <asm/traps.h>
> +
> +/* Make a local copy of the registers passed into the handler (bletch) */
> +void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
> +{
> + int regno;
> +
> + /* Initialize all to zero. */
> + for (regno = 0; regno < GDB_MAX_REGS; regno++)
> + gdb_regs[regno] = 0;
> +
> + gdb_regs[_R0] = kernel_regs->ARM_r0;
> + gdb_regs[_R1] = kernel_regs->ARM_r1;
> + gdb_regs[_R2] = kernel_regs->ARM_r2;
> + gdb_regs[_R3] = kernel_regs->ARM_r3;
> + gdb_regs[_R4] = kernel_regs->ARM_r4;
> + gdb_regs[_R5] = kernel_regs->ARM_r5;
> + gdb_regs[_R6] = kernel_regs->ARM_r6;
> + gdb_regs[_R7] = kernel_regs->ARM_r7;
> + gdb_regs[_R8] = kernel_regs->ARM_r8;
> + gdb_regs[_R9] = kernel_regs->ARM_r9;
> + gdb_regs[_R10] = kernel_regs->ARM_r10;
> + gdb_regs[_FP] = kernel_regs->ARM_fp;
> + gdb_regs[_IP] = kernel_regs->ARM_ip;
> + gdb_regs[_SPT] = kernel_regs->ARM_sp;
> + gdb_regs[_LR] = kernel_regs->ARM_lr;
> + gdb_regs[_PC] = kernel_regs->ARM_pc;
> + gdb_regs[_CPSR] = kernel_regs->ARM_cpsr;
> +}
> +
> +/* Copy local gdb registers back to kgdb regs, for later copy to kernel */
> +void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
> +{
> + kernel_regs->ARM_r0 = gdb_regs[_R0];
> + kernel_regs->ARM_r1 = gdb_regs[_R1];
> + kernel_regs->ARM_r2 = gdb_regs[_R2];
> + kernel_regs->ARM_r3 = gdb_regs[_R3];
> + kernel_regs->ARM_r4 = gdb_regs[_R4];
> + kernel_regs->ARM_r5 = gdb_regs[_R5];
> + kernel_regs->ARM_r6 = gdb_regs[_R6];
> + kernel_regs->ARM_r7 = gdb_regs[_R7];
> + kernel_regs->ARM_r8 = gdb_regs[_R8];
> + kernel_regs->ARM_r9 = gdb_regs[_R9];
> + kernel_regs->ARM_r10 = gdb_regs[_R10];
> + kernel_regs->ARM_fp = gdb_regs[_FP];
> + kernel_regs->ARM_ip = gdb_regs[_IP];
> + kernel_regs->ARM_sp = gdb_regs[_SPT];
> + kernel_regs->ARM_lr = gdb_regs[_LR];
> + kernel_regs->ARM_pc = gdb_regs[_PC];
> + kernel_regs->ARM_cpsr = gdb_regs[_CPSR];
> +}
> +
> +void
> +sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
> +{
> + struct pt_regs *thread_regs;
> + int regno;
> +
> + /* Just making sure... */
> + if (task == NULL)
> + return;
> +
> + /* Initialize to zero */
> + for (regno = 0; regno < GDB_MAX_REGS; regno++)
> + gdb_regs[regno] = 0;
> +
> + /* Otherwise, we have only some registers from switch_to() */
> + thread_regs = task_pt_regs(task);
> + gdb_regs[_R0] = thread_regs->ARM_r0;
> + gdb_regs[_R1] = thread_regs->ARM_r1;
> + gdb_regs[_R2] = thread_regs->ARM_r2;
> + gdb_regs[_R3] = thread_regs->ARM_r3;
> + gdb_regs[_R4] = thread_regs->ARM_r4;
> + gdb_regs[_R5] = thread_regs->ARM_r5;
> + gdb_regs[_R6] = thread_regs->ARM_r6;
> + gdb_regs[_R7] = thread_regs->ARM_r7;
> + gdb_regs[_R8] = thread_regs->ARM_r8;
> + gdb_regs[_R9] = thread_regs->ARM_r9;
> + gdb_regs[_R10] = thread_regs->ARM_r10;
> + gdb_regs[_FP] = thread_regs->ARM_fp;
> + gdb_regs[_IP] = thread_regs->ARM_ip;
> + gdb_regs[_SPT] = thread_regs->ARM_sp;
> + gdb_regs[_LR] = thread_regs->ARM_lr;
> + gdb_regs[_PC] = thread_regs->ARM_pc;
> + gdb_regs[_CPSR] = thread_regs->ARM_cpsr;
> +}
> +
> +static int compiled_break;
> +
> +int kgdb_arch_handle_exception(int exception_vector, int signo,
> + int err_code, char *remcom_in_buffer,
> + char *remcom_out_buffer,
> + struct pt_regs *linux_regs)
> +{
> + unsigned long addr;
> + char *ptr;
> +
> + switch (remcom_in_buffer[0]) {
> + case 'D':
> + case 'k':
> + case 'c':
> + kgdb_contthread = NULL;
> +
> + /*
> + * Try to read optional parameter, pc unchanged if no parm.
> + * If this was a compiled breakpoint, we need to move
> + * to the next instruction or we will just breakpoint
> + * over and over again.
> + */
> + ptr = &remcom_in_buffer[1];
> + if (kgdb_hex2long(&ptr, &addr))
> + linux_regs->ARM_pc = addr;
> + else if (compiled_break == 1)
> + linux_regs->ARM_pc += 4;
> +
> + compiled_break = 0;
> +
> + return 0;
> + }
> +
> + return -1;
> +}
> +
> +static int kgdb_brk_fn(struct pt_regs *regs, unsigned int instr)
> +{
> + kgdb_handle_exception(1, SIGTRAP, 0, regs);
> +
> + return 0;
> +}
> +
> +static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr)
> +{
> + compiled_break = 1;
> + kgdb_handle_exception(1, SIGTRAP, 0, regs);
> +
> + return 0;
> +}
> +
> +static struct undef_hook kgdb_brkpt_hook = {
> + .instr_mask = 0xffffffff,
> + .instr_val = KGDB_BREAKINST,
> + .fn = kgdb_brk_fn
> +};
> +
> +static struct undef_hook kgdb_compiled_brkpt_hook = {
> + .instr_mask = 0xffffffff,
> + .instr_val = KGDB_COMPILED_BREAK,
> + .fn = kgdb_compiled_brk_fn
> +};
> +
> +/**
> + * kgdb_arch_init - Perform any architecture specific initalization.
> + *
> + * This function will handle the initalization of any architecture
> + * specific callbacks.
> + */
> +int kgdb_arch_init(void)
> +{
> + register_undef_hook(&kgdb_brkpt_hook);
> + register_undef_hook(&kgdb_compiled_brkpt_hook);
> +
> + return 0;
> +}
> +
> +/**
> + * kgdb_arch_exit - Perform any architecture specific uninitalization.
> + *
> + * This function will handle the uninitalization of any architecture
> + * specific callbacks, for dynamic registration and unregistration.
> + */
> +void kgdb_arch_exit(void)
> +{
> + unregister_undef_hook(&kgdb_brkpt_hook);
> + unregister_undef_hook(&kgdb_compiled_brkpt_hook);
> +}
> +
> +/*
> + * Register our undef instruction hooks with ARM undef core.
> + * We regsiter a hook specifically looking for the KGB break inst
> + * and we handle the normal undef case within the do_undefinstr
> + * handler.
> + */
> +struct kgdb_arch arch_kgdb_ops = {
> +#ifndef __ARMEB__
> + .gdb_bpt_instr = {0xfe, 0xde, 0xff, 0xe7}
> +#else /* ! __ARMEB__ */
> + .gdb_bpt_instr = {0xe7, 0xff, 0xde, 0xfe}
> +#endif
> +};
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index b7b0720..38f0e79 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -36,6 +36,7 @@
> #include <asm/mach/arch.h>
> #include <asm/mach/irq.h>
> #include <asm/mach/time.h>
> +#include <asm/traps.h>
>
> #include "compat.h"
> #include "atags.h"
> @@ -853,6 +854,7 @@ void __init setup_arch(char **cmdline_p)
> conswitchp = &dummy_con;
> #endif
> #endif
> + early_trap_init();
> }
>
>
> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
> index 5595fdd..7277aef 100644
> --- a/arch/arm/kernel/traps.c
> +++ b/arch/arm/kernel/traps.c
> @@ -708,6 +708,11 @@ EXPORT_SYMBOL(abort);
>
> void __init trap_init(void)
> {
> + return;
> +}
> +
> +void __init early_trap_init(void)
> +{
> unsigned long vectors = CONFIG_VECTORS_BASE;
> extern char __stubs_start[], __stubs_end[];
> extern char __vectors_start[], __vectors_end[];
> diff --git a/include/asm-arm/kgdb.h b/include/asm-arm/kgdb.h
> new file mode 100644
> index 0000000..67af4b8
> --- /dev/null
> +++ b/include/asm-arm/kgdb.h
> @@ -0,0 +1,104 @@
> +/*
> + * ARM KGDB support
> + *
> + * Author: Deepak Saxena <dsaxena@...sta.com>
> + *
> + * Copyright (C) 2002 MontaVista Software Inc.
> + *
> + */
> +
> +#ifndef __ARM_KGDB_H__
> +#define __ARM_KGDB_H__
> +
> +#include <linux/ptrace.h>
> +
> +/*
> + * GDB assumes that we're a user process being debugged, so
> + * it will send us an SWI command to write into memory as the
> + * debug trap. When an SWI occurs, the next instruction addr is
> + * placed into R14_svc before jumping to the vector trap.
> + * This doesn't work for kernel debugging as we are already in SVC
> + * we would loose the kernel's LR, which is a bad thing. This
> + * is bad thing.
> + *
> + * By doing this as an undefined instruction trap, we force a mode
> + * switch from SVC to UND mode, allowing us to save full kernel state.
> + *
> + * We also define a KGDB_COMPILED_BREAK which can be used to compile
> + * in breakpoints. This is important for things like sysrq-G and for
> + * the initial breakpoint from trap_init().
> + *
> + * Note to ARM HW designers: Add real trap support like SH && PPC to
> + * make our lives much much simpler. :)
> + */
> +#define BREAK_INSTR_SIZE 4
> +#define GDB_BREAKINST 0xef9f0001
> +#define KGDB_BREAKINST 0xe7ffdefe
> +#define KGDB_COMPILED_BREAK 0xe7ffdeff
> +#define CACHE_FLUSH_IS_SAFE 1
> +
> +#ifndef __ASSEMBLY__
> +
> +static inline void arch_kgdb_breakpoint(void)
> +{
> + asm(".word 0xe7ffdeff");
> +}
> +
> +extern void kgdb_handle_bus_error(void);
> +extern int kgdb_fault_expected;
> +
> +#endif /* !__ASSEMBLY__ */
> +
> +/*
> + * From Kevin Hilman:
> + *
> + * gdb is expecting the following registers layout.
> + *
> + * r0-r15: 1 long word each
> + * f0-f7: unused, 3 long words each !!
> + * fps: unused, 1 long word
> + * cpsr: 1 long word
> + *
> + * Even though f0-f7 and fps are not used, they need to be
> + * present in the registers sent for correct processing in
> + * the host-side gdb.
> + *
> + * In particular, it is crucial that CPSR is in the right place,
> + * otherwise gdb will not be able to correctly interpret stepping over
> + * conditional branches.
> + */
> +#define _GP_REGS 16
> +#define _FP_REGS 8
> +#define _EXTRA_REGS 2
> +#define GDB_MAX_REGS (_GP_REGS + (_FP_REGS * 3) + _EXTRA_REGS)
> +
> +#define KGDB_MAX_NO_CPUS 1
> +#define BUFMAX 400
> +#define NUMREGBYTES (GDB_MAX_REGS << 2)
> +#define NUMCRITREGBYTES (32 << 2)
> +
> +#define _R0 0
> +#define _R1 1
> +#define _R2 2
> +#define _R3 3
> +#define _R4 4
> +#define _R5 5
> +#define _R6 6
> +#define _R7 7
> +#define _R8 8
> +#define _R9 9
> +#define _R10 10
> +#define _FP 11
> +#define _IP 12
> +#define _SPT 13
> +#define _LR 14
> +#define _PC 15
> +#define _CPSR (GDB_MAX_REGS - 1)
> +
> +/*
> + * So that we can denote the end of a frame for tracing,
> + * in the simple case:
> + */
> +#define CFI_END_FRAME(func) __CFI_END_FRAME(_PC, _SPT, func)
> +
> +#endif /* __ASM_KGDB_H__ */
> diff --git a/include/asm-arm/traps.h b/include/asm-arm/traps.h
> index f1541af..aa399ae 100644
> --- a/include/asm-arm/traps.h
> +++ b/include/asm-arm/traps.h
> @@ -24,4 +24,6 @@ static inline int in_exception_text(unsigned long ptr)
> ptr < (unsigned long)&__exception_text_end;
> }
>
> +extern void __init early_trap_init(void);
> +
> #endif
> --
> 1.5.5.1
>
> --
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--
_____ __o Deepak Saxena - Living CarFree and CareFree (o>
------ -\<, "When I see an adult on a bicycle, I do not despair //\
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