mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-23 14:13:49 +07:00
a2bbe75089
rbp is used in SAVE_ARGS_IRQ to save the old stack pointer in order to restore it later in ret_from_intr. It is convenient because we save its value in the irq regs and it's easily restored using the leave instruction. However this is a kind of abuse of the frame pointer which role is to help unwinding the kernel by chaining frames together, each node following the return address to the previous frame. But although we are breaking the frame by changing the stack pointer, there is no preceding return address before the new frame. Hence using the frame pointer to link the two stacks breaks the stack unwinders that find a random value instead of a return address here. There is no workaround that can work in every case. We are using the fixup_bp_irq_link() function to dereference that abused frame pointer in the case of non nesting interrupt (which means stack changed). But that doesn't fix the case of interrupts that don't change the stack (but we still have the unconditional frame link), which is the case of hardirq interrupting softirq. We have no way to detect this transition so the frame irq link is considered as a real frame pointer and the return address is dereferenced but it is still a spurious one. There are two possible results of this: either the spurious return address, a random stack value, luckily belongs to the kernel text and then the unwinding can continue and we just have a weird entry in the stack trace. Or it doesn't belong to the kernel text and unwinding stops there. This is the reason why stacktraces (including perf callchains) on irqs that interrupted softirqs don't work very well. To solve this, we don't save the old stack pointer on rbp anymore but we save it to a scratch register that we push on the new stack and that we pop back later on irq return. This preserves the whole frame chain without spurious return addresses in the middle and drops the need for the horrid fixup_bp_irq_link() workaround. And finally irqs that interrupt softirq are sanely unwinded. Before: 99.81% perf [kernel.kallsyms] [k] perf_pending_event | --- perf_pending_event irq_work_run smp_irq_work_interrupt irq_work_interrupt | |--41.60%-- __read | | | |--99.90%-- create_worker | | bench_sched_messaging | | cmd_bench | | run_builtin | | main | | __libc_start_main | --0.10%-- [...] After: 1.64% swapper [kernel.kallsyms] [k] perf_pending_event | --- perf_pending_event irq_work_run smp_irq_work_interrupt irq_work_interrupt | |--95.00%-- arch_irq_work_raise | irq_work_queue | __perf_event_overflow | perf_swevent_overflow | perf_swevent_event | perf_tp_event | perf_trace_softirq | __do_softirq | call_softirq | do_softirq | irq_exit | | | |--73.68%-- smp_apic_timer_interrupt | | apic_timer_interrupt | | | | | |--96.43%-- amd_e400_idle | | | cpu_idle | | | start_secondary Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jan Beulich <JBeulich@novell.com>
308 lines
7.3 KiB
C
308 lines
7.3 KiB
C
/*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
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*/
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#include <linux/kallsyms.h>
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#include <linux/kprobes.h>
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#include <linux/uaccess.h>
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#include <linux/hardirq.h>
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#include <linux/kdebug.h>
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#include <linux/module.h>
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#include <linux/ptrace.h>
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#include <linux/kexec.h>
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#include <linux/sysfs.h>
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#include <linux/bug.h>
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#include <linux/nmi.h>
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#include <asm/stacktrace.h>
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#define N_EXCEPTION_STACKS_END \
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(N_EXCEPTION_STACKS + DEBUG_STKSZ/EXCEPTION_STKSZ - 2)
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static char x86_stack_ids[][8] = {
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[ DEBUG_STACK-1 ] = "#DB",
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[ NMI_STACK-1 ] = "NMI",
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[ DOUBLEFAULT_STACK-1 ] = "#DF",
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[ STACKFAULT_STACK-1 ] = "#SS",
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[ MCE_STACK-1 ] = "#MC",
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#if DEBUG_STKSZ > EXCEPTION_STKSZ
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[ N_EXCEPTION_STACKS ...
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N_EXCEPTION_STACKS_END ] = "#DB[?]"
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#endif
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};
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static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
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unsigned *usedp, char **idp)
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{
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unsigned k;
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/*
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* Iterate over all exception stacks, and figure out whether
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* 'stack' is in one of them:
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*/
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for (k = 0; k < N_EXCEPTION_STACKS; k++) {
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unsigned long end = per_cpu(orig_ist, cpu).ist[k];
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/*
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* Is 'stack' above this exception frame's end?
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* If yes then skip to the next frame.
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*/
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if (stack >= end)
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continue;
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/*
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* Is 'stack' above this exception frame's start address?
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* If yes then we found the right frame.
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*/
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if (stack >= end - EXCEPTION_STKSZ) {
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/*
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* Make sure we only iterate through an exception
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* stack once. If it comes up for the second time
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* then there's something wrong going on - just
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* break out and return NULL:
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*/
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if (*usedp & (1U << k))
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break;
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*usedp |= 1U << k;
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*idp = x86_stack_ids[k];
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return (unsigned long *)end;
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}
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/*
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* If this is a debug stack, and if it has a larger size than
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* the usual exception stacks, then 'stack' might still
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* be within the lower portion of the debug stack:
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*/
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#if DEBUG_STKSZ > EXCEPTION_STKSZ
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if (k == DEBUG_STACK - 1 && stack >= end - DEBUG_STKSZ) {
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unsigned j = N_EXCEPTION_STACKS - 1;
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/*
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* Black magic. A large debug stack is composed of
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* multiple exception stack entries, which we
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* iterate through now. Dont look:
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*/
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do {
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++j;
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end -= EXCEPTION_STKSZ;
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x86_stack_ids[j][4] = '1' +
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(j - N_EXCEPTION_STACKS);
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} while (stack < end - EXCEPTION_STKSZ);
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if (*usedp & (1U << j))
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break;
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*usedp |= 1U << j;
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*idp = x86_stack_ids[j];
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return (unsigned long *)end;
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}
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#endif
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}
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return NULL;
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}
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static inline int
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in_irq_stack(unsigned long *stack, unsigned long *irq_stack,
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unsigned long *irq_stack_end)
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{
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return (stack >= irq_stack && stack < irq_stack_end);
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}
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/*
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* x86-64 can have up to three kernel stacks:
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* process stack
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* interrupt stack
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* severe exception (double fault, nmi, stack fault, debug, mce) hardware stack
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*/
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void dump_trace(struct task_struct *task, struct pt_regs *regs,
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unsigned long *stack, unsigned long bp,
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const struct stacktrace_ops *ops, void *data)
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{
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const unsigned cpu = get_cpu();
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unsigned long *irq_stack_end =
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(unsigned long *)per_cpu(irq_stack_ptr, cpu);
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unsigned used = 0;
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struct thread_info *tinfo;
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int graph = 0;
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unsigned long dummy;
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if (!task)
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task = current;
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if (!stack) {
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if (regs)
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stack = (unsigned long *)regs->sp;
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else if (task && task != current)
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stack = (unsigned long *)task->thread.sp;
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else
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stack = &dummy;
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}
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if (!bp)
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bp = stack_frame(task, regs);
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/*
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* Print function call entries in all stacks, starting at the
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* current stack address. If the stacks consist of nested
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* exceptions
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*/
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tinfo = task_thread_info(task);
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for (;;) {
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char *id;
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unsigned long *estack_end;
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estack_end = in_exception_stack(cpu, (unsigned long)stack,
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&used, &id);
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if (estack_end) {
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if (ops->stack(data, id) < 0)
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break;
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bp = ops->walk_stack(tinfo, stack, bp, ops,
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data, estack_end, &graph);
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ops->stack(data, "<EOE>");
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/*
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* We link to the next stack via the
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* second-to-last pointer (index -2 to end) in the
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* exception stack:
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*/
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stack = (unsigned long *) estack_end[-2];
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continue;
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}
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if (irq_stack_end) {
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unsigned long *irq_stack;
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irq_stack = irq_stack_end -
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(IRQ_STACK_SIZE - 64) / sizeof(*irq_stack);
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if (in_irq_stack(stack, irq_stack, irq_stack_end)) {
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if (ops->stack(data, "IRQ") < 0)
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break;
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bp = ops->walk_stack(tinfo, stack, bp,
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ops, data, irq_stack_end, &graph);
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/*
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* We link to the next stack (which would be
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* the process stack normally) the last
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* pointer (index -1 to end) in the IRQ stack:
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*/
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stack = (unsigned long *) (irq_stack_end[-1]);
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irq_stack_end = NULL;
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ops->stack(data, "EOI");
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continue;
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}
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}
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break;
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}
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/*
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* This handles the process stack:
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*/
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bp = ops->walk_stack(tinfo, stack, bp, ops, data, NULL, &graph);
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put_cpu();
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}
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EXPORT_SYMBOL(dump_trace);
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void
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show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
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unsigned long *sp, unsigned long bp, char *log_lvl)
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{
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unsigned long *irq_stack_end;
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unsigned long *irq_stack;
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unsigned long *stack;
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int cpu;
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int i;
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preempt_disable();
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cpu = smp_processor_id();
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irq_stack_end = (unsigned long *)(per_cpu(irq_stack_ptr, cpu));
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irq_stack = (unsigned long *)(per_cpu(irq_stack_ptr, cpu) - IRQ_STACK_SIZE);
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/*
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* Debugging aid: "show_stack(NULL, NULL);" prints the
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* back trace for this cpu:
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*/
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if (sp == NULL) {
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if (task)
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sp = (unsigned long *)task->thread.sp;
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else
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sp = (unsigned long *)&sp;
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}
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stack = sp;
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for (i = 0; i < kstack_depth_to_print; i++) {
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if (stack >= irq_stack && stack <= irq_stack_end) {
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if (stack == irq_stack_end) {
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stack = (unsigned long *) (irq_stack_end[-1]);
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printk(KERN_CONT " <EOI> ");
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}
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} else {
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if (((long) stack & (THREAD_SIZE-1)) == 0)
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break;
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}
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if (i && ((i % STACKSLOTS_PER_LINE) == 0))
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printk(KERN_CONT "\n");
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printk(KERN_CONT " %016lx", *stack++);
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touch_nmi_watchdog();
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}
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preempt_enable();
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printk(KERN_CONT "\n");
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show_trace_log_lvl(task, regs, sp, bp, log_lvl);
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}
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void show_registers(struct pt_regs *regs)
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{
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int i;
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unsigned long sp;
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const int cpu = smp_processor_id();
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struct task_struct *cur = current;
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sp = regs->sp;
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printk("CPU %d ", cpu);
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print_modules();
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__show_regs(regs, 1);
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printk("Process %s (pid: %d, threadinfo %p, task %p)\n",
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cur->comm, cur->pid, task_thread_info(cur), cur);
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/*
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* When in-kernel, we also print out the stack and code at the
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* time of the fault..
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*/
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if (!user_mode(regs)) {
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unsigned int code_prologue = code_bytes * 43 / 64;
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unsigned int code_len = code_bytes;
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unsigned char c;
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u8 *ip;
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printk(KERN_EMERG "Stack:\n");
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show_stack_log_lvl(NULL, regs, (unsigned long *)sp,
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0, KERN_EMERG);
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printk(KERN_EMERG "Code: ");
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ip = (u8 *)regs->ip - code_prologue;
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if (ip < (u8 *)PAGE_OFFSET || probe_kernel_address(ip, c)) {
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/* try starting at IP */
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ip = (u8 *)regs->ip;
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code_len = code_len - code_prologue + 1;
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}
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for (i = 0; i < code_len; i++, ip++) {
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if (ip < (u8 *)PAGE_OFFSET ||
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probe_kernel_address(ip, c)) {
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printk(" Bad RIP value.");
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break;
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}
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if (ip == (u8 *)regs->ip)
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printk("<%02x> ", c);
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else
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printk("%02x ", c);
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}
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}
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printk("\n");
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}
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int is_valid_bugaddr(unsigned long ip)
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{
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unsigned short ud2;
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if (__copy_from_user(&ud2, (const void __user *) ip, sizeof(ud2)))
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return 0;
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return ud2 == 0x0b0f;
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}
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