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    Subject[PATCH 2/3] reliable stack trace support (x86-64)
    These are the x86_64-specific pieces to enable reliable stack traces. The
    only restriction with this is that it currently cannot unwind across the
    interrupt->normal stack boundary, as that transition is lacking proper
    annotation.

    Signed-off-by: Jan Beulich <jbeulich@novell.com>

    --- linux-2.6.17-rc4/arch/x86_64/kernel/entry.S 2006-05-16 15:15:32.000000000 +0200
    +++ 2.6.17-rc4-unwind-x86_64/arch/x86_64/kernel/entry.S 2006-05-16 15:16:38.000000000 +0200
    @@ -1051,3 +1051,36 @@ ENTRY(call_softirq)
    decl %gs:pda_irqcount
    ret
    CFI_ENDPROC
    +
    +#ifdef CONFIG_STACK_UNWIND
    +ENTRY(arch_unwind_init_running)
    + CFI_STARTPROC
    + movq %r15, R15(%rdi)
    + movq %r14, R14(%rdi)
    + xchgq %rsi, %rdx
    + movq %r13, R13(%rdi)
    + movq %r12, R12(%rdi)
    + xorl %eax, %eax
    + movq %rbp, RBP(%rdi)
    + movq %rbx, RBX(%rdi)
    + movq (%rsp), %rcx
    + movq %rax, R11(%rdi)
    + movq %rax, R10(%rdi)
    + movq %rax, R9(%rdi)
    + movq %rax, R8(%rdi)
    + movq %rax, RAX(%rdi)
    + movq %rax, RCX(%rdi)
    + movq %rax, RDX(%rdi)
    + movq %rax, RSI(%rdi)
    + movq %rax, RDI(%rdi)
    + movq %rax, ORIG_RAX(%rdi)
    + movq %rcx, RIP(%rdi)
    + leaq 8(%rsp), %rcx
    + movq $__KERNEL_CS, CS(%rdi)
    + movq %rax, EFLAGS(%rdi)
    + movq %rcx, RSP(%rdi)
    + movq $__KERNEL_DS, SS(%rdi)
    + jmpq *%rdx
    + CFI_ENDPROC
    +ENDPROC(arch_unwind_init_running)
    +#endif
    --- linux-2.6.17-rc4/arch/x86_64/kernel/process.c 2006-05-16 15:15:32.000000000 +0200
    +++ 2.6.17-rc4-unwind-x86_64/arch/x86_64/kernel/process.c 2006-05-16 15:16:38.000000000 +0200
    @@ -335,7 +335,7 @@ void show_regs(struct pt_regs *regs)
    {
    printk("CPU %d:", smp_processor_id());
    __show_regs(regs);
    - show_trace(&regs->rsp);
    + show_trace(NULL, regs, (void *)(regs + 1));
    }

    /*
    --- linux-2.6.17-rc4/arch/x86_64/kernel/traps.c 2006-05-16 15:15:32.000000000 +0200
    +++ 2.6.17-rc4-unwind-x86_64/arch/x86_64/kernel/traps.c 2006-05-16 15:16:38.000000000 +0200
    @@ -41,7 +41,7 @@
    #include <asm/i387.h>
    #include <asm/kdebug.h>
    #include <asm/processor.h>
    -
    +#include <asm/unwind.h>
    #include <asm/smp.h>
    #include <asm/pgalloc.h>
    #include <asm/pda.h>
    @@ -189,6 +189,23 @@ static unsigned long *in_exception_stack
    return NULL;
    }

    +static void show_trace_unwind(struct unwind_frame_info *info, void *context)
    +{
    + int i = 11;
    +
    + while (unwind(info) == 0 && UNW_PC(info)) {
    + if (i > 50) {
    + printk("\n ");
    + i = 7;
    + } else
    + i += printk(" ");
    + i += printk_address(UNW_PC(info));
    + if (arch_unw_user_mode(info))
    + break;
    + }
    + printk("\n");
    +}
    +
    /*
    * x86-64 can have upto three kernel stacks:
    * process stack
    @@ -196,15 +213,34 @@ static unsigned long *in_exception_stack
    * severe exception (double fault, nmi, stack fault, debug, mce) hardware stack
    */

    -void show_trace(unsigned long *stack)
    +void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * stack)
    {
    const unsigned cpu = safe_smp_processor_id();
    unsigned long *irqstack_end = (unsigned long *)cpu_pda(cpu)->irqstackptr;
    int i;
    unsigned used = 0;
    + struct unwind_frame_info info;

    printk("\nCall Trace:");

    + if (!tsk)
    + tsk = current;
    +
    + if (regs) {
    + if (unwind_init_frame_info(&info, tsk, regs) == 0) {
    + show_trace_unwind(&info, NULL);
    + return;
    + }
    + } else if (tsk == current) {
    + if (unwind_init_running(&info, show_trace_unwind, NULL) == 0)
    + return;
    + } else {
    + if (unwind_init_blocked(&info, tsk) == 0) {
    + show_trace_unwind(&info, NULL);
    + return;
    + }
    + }
    +
    #define HANDLE_STACK(cond) \
    do while (cond) { \
    unsigned long addr = *stack++; \
    @@ -262,7 +298,7 @@ void show_trace(unsigned long *stack)
    printk("\n");
    }

    -void show_stack(struct task_struct *tsk, unsigned long * rsp)
    +static void _show_stack(struct task_struct *tsk, struct pt_regs *regs, unsigned long * rsp)
    {
    unsigned long *stack;
    int i;
    @@ -296,7 +332,12 @@ void show_stack(struct task_struct *tsk,
    printk("%016lx ", *stack++);
    touch_nmi_watchdog();
    }
    - show_trace((unsigned long *)rsp);
    + show_trace(tsk, regs, rsp);
    +}
    +
    +void show_stack(struct task_struct *tsk, unsigned long * rsp)
    +{
    + _show_stack(tsk, NULL, rsp);
    }

    /*
    @@ -305,7 +346,7 @@ void show_stack(struct task_struct *tsk,
    void dump_stack(void)
    {
    unsigned long dummy;
    - show_trace(&dummy);
    + show_trace(NULL, NULL, &dummy);
    }

    EXPORT_SYMBOL(dump_stack);
    @@ -332,7 +373,7 @@ void show_registers(struct pt_regs *regs
    if (in_kernel) {

    printk("Stack: ");
    - show_stack(NULL, (unsigned long*)rsp);
    + _show_stack(NULL, regs, (unsigned long*)rsp);

    printk("\nCode: ");
    if (regs->rip < PAGE_OFFSET)
    --- linux-2.6.17-rc4/arch/x86_64/kernel/vmlinux.lds.S 2006-05-16 15:15:32.000000000 +0200
    +++ 2.6.17-rc4-unwind-x86_64/arch/x86_64/kernel/vmlinux.lds.S 2006-05-16 15:16:38.000000000 +0200
    @@ -45,6 +45,15 @@ SECTIONS

    RODATA

    +#ifdef CONFIG_STACK_UNWIND
    + . = ALIGN(8);
    + .eh_frame : AT(ADDR(.eh_frame) - LOAD_OFFSET) {
    + __start_unwind = .;
    + *(.eh_frame)
    + __end_unwind = .;
    + }
    +#endif
    +
    /* Data */
    .data : AT(ADDR(.data) - LOAD_OFFSET) {
    *(.data)
    --- linux-2.6.17-rc4/include/asm-x86_64/proto.h 2006-05-16 15:15:48.000000000 +0200
    +++ 2.6.17-rc4-unwind-x86_64/include/asm-x86_64/proto.h 2006-05-16 15:16:38.000000000 +0200
    @@ -75,7 +75,7 @@ extern void main_timer_handler(struct pt

    extern unsigned long end_pfn_map;

    -extern void show_trace(unsigned long * rsp);
    +extern void show_trace(struct task_struct *, struct pt_regs *, unsigned long * rsp);
    extern void show_registers(struct pt_regs *regs);

    extern void exception_table_check(void);
    --- linux-2.6.17-rc4/include/asm-x86_64/unwind.h 1970-01-01 01:00:00.000000000 +0100
    +++ 2.6.17-rc4-unwind-x86_64/include/asm-x86_64/unwind.h 2006-05-16 15:46:46.000000000 +0200
    @@ -0,0 +1,99 @@
    +#ifndef _ASM_X86_64_UNWIND_H
    +#define _ASM_X86_64_UNWIND_H
    +
    +/*
    + * Copyright (C) 2002-2006 Novell, Inc.
    + * Jan Beulich <jbeulich@novell.com>
    + */
    +
    +#include <linux/config.h>
    +
    +#ifdef CONFIG_STACK_UNWIND
    +
    +#include <asm/ptrace.h>
    +#include <asm/uaccess.h>
    +
    +struct unwind_frame_info {
    + struct pt_regs regs;
    + struct task_struct *task;
    +};
    +
    +#define UNW_PC(frame) (frame)->regs.rip
    +#define UNW_SP(frame) (frame)->regs.rsp
    +#ifdef CONFIG_FRAME_POINTER
    +#define UNW_FP(frame) (frame)->regs.rbp
    +#define FRAME_RETADDR_OFFSET 8
    +#define FRAME_LINK_OFFSET 0
    +#define STACK_BOTTOM(tsk) (((tsk)->thread.rsp0 - 1) & ~(THREAD_SIZE - 1))
    +#define STACK_TOP(tsk) ((tsk)->thread.rsp0)
    +#endif
    +
    +#define UNW_REGISTER_INFO \
    + PTREGS_INFO(rax), \
    + PTREGS_INFO(rdx), \
    + PTREGS_INFO(rcx), \
    + PTREGS_INFO(rbx), \
    + PTREGS_INFO(rsi), \
    + PTREGS_INFO(rdi), \
    + PTREGS_INFO(rbp), \
    + PTREGS_INFO(rsp), \
    + PTREGS_INFO(r8), \
    + PTREGS_INFO(r9), \
    + PTREGS_INFO(r10), \
    + PTREGS_INFO(r11), \
    + PTREGS_INFO(r12), \
    + PTREGS_INFO(r13), \
    + PTREGS_INFO(r14), \
    + PTREGS_INFO(r15), \
    + PTREGS_INFO(rip)
    +
    +static inline void
    +arch_unw_init_frame_info(struct unwind_frame_info *info, /*const*/ struct pt_regs *regs)
    +{
    + info->regs = *regs;
    +}
    +
    +static inline void
    +arch_unw_init_blocked(struct unwind_frame_info *info)
    +{
    + extern const char thread_return[];
    +
    + memset(&info->regs, 0, sizeof(info->regs));
    + info->regs.rip = (unsigned long)thread_return;
    + info->regs.cs = __KERNEL_CS;
    + __get_user(info->regs.rbp, (unsigned long *)info->task->thread.rsp);
    + info->regs.rsp = info->task->thread.rsp;
    + info->regs.ss = __KERNEL_DS;
    +}
    +
    +extern void
    +arch_unwind_init_running(struct unwind_frame_info *,
    + void (*callback)(struct unwind_frame_info *, void *arg),
    + void *arg);
    +
    +static inline int
    +arch_unw_user_mode(const struct unwind_frame_info *info)
    +{
    +#if 0 /* This can only work when selector register saves/restores
    + are properly annotated (and tracked in UNW_REGISTER_INFO). */
    + return user_mode(&info->regs);
    +#else
    + return (long)info->regs.rip >= 0;
    +#endif
    +}
    +
    +#else
    +
    +#define UNW_PC(frame) ((void)(frame), 0)
    +
    +static inline int
    +arch_unw_user_mode(const void *info)
    +{
    + return 0;
    +}
    +
    +#endif
    +
    +#include <asm-generic/unwind.h>
    +
    +#endif /* _ASM_X86_64_UNWIND_H */
    --- linux-2.6.17-rc4/lib/Kconfig.debug 2006-05-16 15:15:49.000000000 +0200
    +++ 2.6.17-rc4-unwind-x86_64/lib/Kconfig.debug 2006-05-16 15:16:46.000000000 +0200
    @@ -199,7 +199,7 @@ config UNWIND_INFO
    config STACK_UNWIND
    bool "Stack unwind support"
    depends on UNWIND_INFO
    - depends on n
    + depends on X86_64
    help
    This enables more precise stack traces, omitting all unrelated
    occurrences of pointers into kernel code from the dump.

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