![Russell King](/assets/img/avatar_default.png)
Avoid adding kprobes to any of the kernel entry/exit or startup assembly code, or code in the identity-mapped region. This code does not conform to the standard C conventions, which means that the expectations of the kprobes code is not forfilled. Placing kprobes at some of these locations results in the kernel trying to return to userspace addresses while retaining the CPU in kernel mode. Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
172 lines
4.3 KiB
C
172 lines
4.3 KiB
C
#include <linux/export.h>
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#include <linux/sched.h>
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#include <linux/sched/debug.h>
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#include <linux/stacktrace.h>
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#include <asm/sections.h>
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#include <asm/stacktrace.h>
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#include <asm/traps.h>
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#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
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/*
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* Unwind the current stack frame and store the new register values in the
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* structure passed as argument. Unwinding is equivalent to a function return,
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* hence the new PC value rather than LR should be used for backtrace.
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*
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* With framepointer enabled, a simple function prologue looks like this:
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* mov ip, sp
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* stmdb sp!, {fp, ip, lr, pc}
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* sub fp, ip, #4
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*
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* A simple function epilogue looks like this:
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* ldm sp, {fp, sp, pc}
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*
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* Note that with framepointer enabled, even the leaf functions have the same
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* prologue and epilogue, therefore we can ignore the LR value in this case.
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*/
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int notrace unwind_frame(struct stackframe *frame)
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{
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unsigned long high, low;
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unsigned long fp = frame->fp;
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/* only go to a higher address on the stack */
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low = frame->sp;
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high = ALIGN(low, THREAD_SIZE);
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/* check current frame pointer is within bounds */
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if (fp < low + 12 || fp > high - 4)
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return -EINVAL;
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/* restore the registers from the stack frame */
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frame->fp = *(unsigned long *)(fp - 12);
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frame->sp = *(unsigned long *)(fp - 8);
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frame->pc = *(unsigned long *)(fp - 4);
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return 0;
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}
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#endif
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void notrace walk_stackframe(struct stackframe *frame,
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int (*fn)(struct stackframe *, void *), void *data)
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{
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while (1) {
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int ret;
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if (fn(frame, data))
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break;
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ret = unwind_frame(frame);
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if (ret < 0)
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break;
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}
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}
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EXPORT_SYMBOL(walk_stackframe);
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#ifdef CONFIG_STACKTRACE
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struct stack_trace_data {
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struct stack_trace *trace;
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unsigned int no_sched_functions;
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unsigned int skip;
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};
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static int save_trace(struct stackframe *frame, void *d)
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{
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struct stack_trace_data *data = d;
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struct stack_trace *trace = data->trace;
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struct pt_regs *regs;
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unsigned long addr = frame->pc;
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if (data->no_sched_functions && in_sched_functions(addr))
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return 0;
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if (data->skip) {
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data->skip--;
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return 0;
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}
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trace->entries[trace->nr_entries++] = addr;
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if (trace->nr_entries >= trace->max_entries)
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return 1;
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if (!in_entry_text(frame->pc))
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return 0;
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regs = (struct pt_regs *)frame->sp;
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trace->entries[trace->nr_entries++] = regs->ARM_pc;
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return trace->nr_entries >= trace->max_entries;
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}
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/* This must be noinline to so that our skip calculation works correctly */
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static noinline void __save_stack_trace(struct task_struct *tsk,
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struct stack_trace *trace, unsigned int nosched)
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{
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struct stack_trace_data data;
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struct stackframe frame;
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data.trace = trace;
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data.skip = trace->skip;
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data.no_sched_functions = nosched;
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if (tsk != current) {
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#ifdef CONFIG_SMP
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/*
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* What guarantees do we have here that 'tsk' is not
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* running on another CPU? For now, ignore it as we
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* can't guarantee we won't explode.
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*/
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if (trace->nr_entries < trace->max_entries)
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trace->entries[trace->nr_entries++] = ULONG_MAX;
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return;
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#else
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frame.fp = thread_saved_fp(tsk);
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frame.sp = thread_saved_sp(tsk);
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frame.lr = 0; /* recovered from the stack */
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frame.pc = thread_saved_pc(tsk);
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#endif
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} else {
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/* We don't want this function nor the caller */
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data.skip += 2;
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frame.fp = (unsigned long)__builtin_frame_address(0);
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frame.sp = current_stack_pointer;
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frame.lr = (unsigned long)__builtin_return_address(0);
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frame.pc = (unsigned long)__save_stack_trace;
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}
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walk_stackframe(&frame, save_trace, &data);
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if (trace->nr_entries < trace->max_entries)
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trace->entries[trace->nr_entries++] = ULONG_MAX;
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}
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void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
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{
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struct stack_trace_data data;
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struct stackframe frame;
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data.trace = trace;
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data.skip = trace->skip;
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data.no_sched_functions = 0;
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frame.fp = regs->ARM_fp;
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frame.sp = regs->ARM_sp;
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frame.lr = regs->ARM_lr;
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frame.pc = regs->ARM_pc;
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walk_stackframe(&frame, save_trace, &data);
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if (trace->nr_entries < trace->max_entries)
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trace->entries[trace->nr_entries++] = ULONG_MAX;
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}
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void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
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{
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__save_stack_trace(tsk, trace, 1);
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}
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EXPORT_SYMBOL(save_stack_trace_tsk);
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void save_stack_trace(struct stack_trace *trace)
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{
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__save_stack_trace(current, trace, 0);
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}
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EXPORT_SYMBOL_GPL(save_stack_trace);
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#endif
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