[PATCH 2/6, 2nd try] reliable stack trace support (x86-64)

From: Jan Beulich
Date: Mon May 22 2006 - 09:14:55 EST

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@xxxxxxxxxx>

Index: unwind-2.6.17-rc4/arch/x86_64/kernel/entry.S
===================================================================
--- unwind-2.6.17-rc4.orig/arch/x86_64/kernel/entry.S 2006-05-22 15:00:37.000000000 +0200
+++ unwind-2.6.17-rc4/arch/x86_64/kernel/entry.S 2006-05-22 15:01:04.000000000 +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
Index: unwind-2.6.17-rc4/arch/x86_64/kernel/process.c
===================================================================
--- unwind-2.6.17-rc4.orig/arch/x86_64/kernel/process.c 2006-05-22 15:00:37.000000000 +0200
+++ unwind-2.6.17-rc4/arch/x86_64/kernel/process.c 2006-05-22 15:01:04.000000000 +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));
}

/*
Index: unwind-2.6.17-rc4/arch/x86_64/kernel/traps.c
===================================================================
--- unwind-2.6.17-rc4.orig/arch/x86_64/kernel/traps.c 2006-05-22 15:00:37.000000000 +0200
+++ unwind-2.6.17-rc4/arch/x86_64/kernel/traps.c 2006-05-22 15:01:04.000000000 +0200
@@ -31,6 +31,7 @@
#include <linux/nmi.h>
#include <linux/kprobes.h>
#include <linux/kexec.h>
+#include <linux/unwind.h>

#include <asm/system.h>
#include <asm/uaccess.h>
@@ -189,6 +190,23 @@ 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 +214,34 @@ 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 +299,7 @@ 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 +333,12 @@ 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 +347,7 @@ 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 +374,7 @@ 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)
Index: unwind-2.6.17-rc4/arch/x86_64/kernel/vmlinux.lds.S
===================================================================
--- unwind-2.6.17-rc4.orig/arch/x86_64/kernel/vmlinux.lds.S 2006-05-22 15:00:37.000000000 +0200
+++ unwind-2.6.17-rc4/arch/x86_64/kernel/vmlinux.lds.S 2006-05-22 15:01:04.000000000 +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)
Index: unwind-2.6.17-rc4/include/asm-x86_64/proto.h
===================================================================
--- unwind-2.6.17-rc4.orig/include/asm-x86_64/proto.h 2006-05-22 15:00:37.000000000 +0200
+++ unwind-2.6.17-rc4/include/asm-x86_64/proto.h 2006-05-22 15:01:04.000000000 +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);
Index: unwind-2.6.17-rc4/include/asm-x86_64/unwind.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ unwind-2.6.17-rc4/include/asm-x86_64/unwind.h 2006-05-22 15:01:04.000000000 +0200
@@ -0,0 +1,106 @@
+#ifndef _ASM_X86_64_UNWIND_H
+#define _ASM_X86_64_UNWIND_H
+
+/*
+ * Copyright (C) 2002-2006 Novell, Inc.
+ * Jan Beulich <jbeulich@xxxxxxxxxx>
+ * This code is released under version 2 of the GNU GPL.
+ */
+
+#ifdef CONFIG_STACK_UNWIND
+
+#include <linux/sched.h>
+#include <asm/ptrace.h>
+#include <asm/uaccess.h>
+#include <asm/vsyscall.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
+/* Might need to account for the special exception and interrupt handling
+ stacks here, since normally
+ EXCEPTION_STACK_ORDER < THREAD_ORDER < IRQSTACK_ORDER,
+ but the construct is needed only for getting across the stack switch to
+ the interrupt stack - thus considering the IRQ stack itself is unnecessary,
+ and the overhead of comparing against all exception handling stacks seems
+ not desirable. */
+#define STACK_LIMIT(ptr) (((ptr) - 1) & ~(THREAD_SIZE - 1))
+
+#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
+ || (info->regs.rip >= VSYSCALL_START && info->regs.rip < VSYSCALL_END)
+ || (long)info->regs.rsp >= 0;
+#endif
+}
+
+#else
+
+#define UNW_PC(frame) ((void)(frame), 0)
+
+static inline int arch_unw_user_mode(const void *info)
+{
+ return 0;
+}
+
+#endif
+
+#endif /* _ASM_X86_64_UNWIND_H */
Index: unwind-2.6.17-rc4/lib/Kconfig.debug
===================================================================
--- unwind-2.6.17-rc4.orig/lib/Kconfig.debug 2006-05-22 14:58:52.000000000 +0200
+++ unwind-2.6.17-rc4/lib/Kconfig.debug 2006-05-22 15:01:04.000000000 +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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