diff options
| -rw-r--r-- | arch/x86_64/kernel/traps.c | 61 |
1 files changed, 60 insertions, 1 deletions
diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c index 02dc155da56f..79d05c482072 100644 --- a/arch/x86_64/kernel/traps.c +++ b/arch/x86_64/kernel/traps.c @@ -152,10 +152,22 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack, }; unsigned k; + /* + * Iterate over all exception stacks, and figure out whether + * 'stack' is in one of them: + */ for (k = 0; k < N_EXCEPTION_STACKS; k++) { unsigned long end; + /* + * set 'end' to the end of the exception stack. + */ switch (k + 1) { + /* + * TODO: this block is not needed i think, because + * setup64.c:cpu_init() sets up t->ist[DEBUG_STACK] + * properly too. + */ #if DEBUG_STKSZ > EXCEPTION_STKSZ case DEBUG_STACK: end = cpu_pda(cpu)->debugstack + DEBUG_STKSZ; @@ -165,19 +177,43 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack, end = per_cpu(init_tss, cpu).ist[k]; break; } + /* + * Is 'stack' above this exception frame's end? + * If yes then skip to the next frame. + */ if (stack >= end) continue; + /* + * Is 'stack' above this exception frame's start address? + * If yes then we found the right frame. + */ if (stack >= end - EXCEPTION_STKSZ) { + /* + * Make sure we only iterate through an exception + * stack once. If it comes up for the second time + * then there's something wrong going on - just + * break out and return NULL: + */ if (*usedp & (1U << k)) break; *usedp |= 1U << k; *idp = ids[k]; return (unsigned long *)end; } + /* + * If this is a debug stack, and if it has a larger size than + * the usual exception stacks, then 'stack' might still + * be within the lower portion of the debug stack: + */ #if DEBUG_STKSZ > EXCEPTION_STKSZ if (k == DEBUG_STACK - 1 && stack >= end - DEBUG_STKSZ) { unsigned j = N_EXCEPTION_STACKS - 1; + /* + * Black magic. A large debug stack is composed of + * multiple exception stack entries, which we + * iterate through now. Dont look: + */ do { ++j; end -= EXCEPTION_STKSZ; @@ -247,6 +283,11 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s } } + /* + * Print function call entries within a stack. 'cond' is the + * "end of stackframe" condition, that the 'stack++' + * iteration will eventually trigger. + */ #define HANDLE_STACK(cond) \ do while (cond) { \ unsigned long addr = *stack++; \ @@ -263,7 +304,12 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s } \ } while (0) - for( ; ; ) { + /* + * Print function call entries in all stacks, starting at the + * current stack address. If the stacks consist of nested + * exceptions + */ + for ( ; ; ) { const char *id; unsigned long *estack_end; estack_end = in_exception_stack(cpu, (unsigned long)stack, @@ -273,6 +319,11 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s printk(" <%s>", id); HANDLE_STACK (stack < estack_end); printk(" <EOE>"); + /* + * We link to the next stack via the + * second-to-last pointer (index -2 to end) in the + * exception stack: + */ stack = (unsigned long *) estack_end[-2]; continue; } @@ -284,6 +335,11 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s if (stack >= irqstack && stack < irqstack_end) { printk(" <IRQ>"); HANDLE_STACK (stack < irqstack_end); + /* + * We link to the next stack (which would be + * the process stack normally) the last + * pointer (index -1 to end) in the IRQ stack: + */ stack = (unsigned long *) (irqstack_end[-1]); irqstack_end = NULL; printk(" <EOI>"); @@ -293,6 +349,9 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s break; } + /* + * This prints the process stack: + */ HANDLE_STACK (((long) stack & (THREAD_SIZE-1)) != 0); #undef HANDLE_STACK |