static void __kprobes
post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
-static inline unsigned long min_stack_size(unsigned long addr)
-{
- unsigned long size;
-
- if (on_irq_stack(addr, raw_smp_processor_id()))
- size = IRQ_STACK_PTR(raw_smp_processor_id()) - addr;
- else
- size = (unsigned long)current_thread_info() + THREAD_START_SP - addr;
-
- return min(size, FIELD_SIZEOF(struct kprobe_ctlblk, jprobes_stack));
-}
-
static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
{
/* prepare insn slot */
}
/*
- * The D-flag (Debug mask) is set (masked) upon debug exception entry.
- * Kprobes needs to clear (unmask) D-flag -ONLY- in case of recursive
- * probe i.e. when probe hit from kprobe handler context upon
- * executing the pre/post handlers. In this case we return with
- * D-flag clear so that single-stepping can be carried-out.
- *
- * Leave D-flag set in all other cases.
+ * When PSTATE.D is set (masked), then software step exceptions can not be
+ * generated.
+ * SPSR's D bit shows the value of PSTATE.D immediately before the
+ * exception was taken. PSTATE.D is set while entering into any exception
+ * mode, however software clears it for any normal (none-debug-exception)
+ * mode in the exception entry. Therefore, when we are entering into kprobe
+ * breakpoint handler from any normal mode then SPSR.D bit is already
+ * cleared, however it is set when we are entering from any debug exception
+ * mode.
+ * Since we always need to generate single step exception after a kprobe
+ * breakpoint exception therefore we need to clear it unconditionally, when
+ * we become sure that the current breakpoint exception is for kprobe.
*/
static void __kprobes
spsr_set_debug_flag(struct pt_regs *regs, int mask)
set_ss_context(kcb, slot); /* mark pending ss */
- if (kcb->kprobe_status == KPROBE_REENTER)
- spsr_set_debug_flag(regs, 0);
- else
- WARN_ON(regs->pstate & PSR_D_BIT);
+ spsr_set_debug_flag(regs, 0);
/* IRQs and single stepping do not mix well. */
kprobes_save_local_irqflag(kcb, regs);
BUG();
kernel_disable_single_step();
- if (kcb->kprobe_status == KPROBE_REENTER)
- spsr_set_debug_flag(regs, 1);
if (kcb->kprobe_status == KPROBE_REENTER)
restore_previous_kprobe(kcb);
kprobes_restore_local_irqflag(kcb, regs);
kernel_disable_single_step();
- if (kcb->kprobe_status == KPROBE_REENTER)
- spsr_set_debug_flag(regs, 1);
-
post_kprobe_handler(kcb, regs);
}
{
struct jprobe *jp = container_of(p, struct jprobe, kp);
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
- long stack_ptr = kernel_stack_pointer(regs);
kcb->jprobe_saved_regs = *regs;
/*
- * As Linus pointed out, gcc assumes that the callee
- * owns the argument space and could overwrite it, e.g.
- * tailcall optimization. So, to be absolutely safe
- * we also save and restore enough stack bytes to cover
- * the argument area.
+ * Since we can't be sure where in the stack frame "stacked"
+ * pass-by-value arguments are stored we just don't try to
+ * duplicate any of the stack. Do not use jprobes on functions that
+ * use more than 64 bytes (after padding each to an 8 byte boundary)
+ * of arguments, or pass individual arguments larger than 16 bytes.
*/
- kasan_disable_current();
- memcpy(kcb->jprobes_stack, (void *)stack_ptr,
- min_stack_size(stack_ptr));
- kasan_enable_current();
instruction_pointer_set(regs, (unsigned long) jp->entry);
preempt_disable();
}
unpause_graph_tracing();
*regs = kcb->jprobe_saved_regs;
- kasan_disable_current();
- memcpy((void *)stack_addr, kcb->jprobes_stack,
- min_stack_size(stack_addr));
- kasan_enable_current();
preempt_enable_no_resched();
return 1;
}