Messages in this thread | | | Subject | Re: [PATCH v11 1/9] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature | From | David Long <> | Date | Fri, 18 Mar 2016 09:06:06 -0400 |
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On 03/11/2016 01:07 PM, James Morse wrote: > Hi David, > > On 09/03/16 05:32, David Long wrote: >> From: "David A. Long" <dave.long@linaro.org> >> >> Add HAVE_REGS_AND_STACK_ACCESS_API feature for arm64. >> >> Signed-off-by: David A. Long <dave.long@linaro.org> > >> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c >> index ff7f132..efebf0f 100644 >> --- a/arch/arm64/kernel/ptrace.c >> +++ b/arch/arm64/kernel/ptrace.c > > [ ... SNIP ... ] > >> +/** >> + * regs_within_kernel_stack() - check the address in the stack >> + * @regs: pt_regs which contains kernel stack pointer. >> + * @addr: address which is checked. >> + * >> + * regs_within_kernel_stack() checks @addr is within the kernel stack page(s). >> + * If @addr is within the kernel stack, it returns true. If not, returns false. >> + */ >> +bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr) >> +{ >> + return ((addr & ~(THREAD_SIZE - 1)) == >> + (kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1))); > > I'm not sure where this is called from, but if kernel_stack_pointer(regs) could > ever point into an irq_stack you will get the wrong result. > > arch/arm64/include/asm/irq.h has 'on_irq_stack(sp, cpu)' which should help, > although you will need to check the bounds of the irq_stack separately. > > > The horrible details... > > From arch/arm64/kernel/irq.c:20 >> /* irq stack only needs to be 16 byte aligned - not IRQ_STACK_SIZE aligned. */ >> DEFINE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack) >> __aligned(16); > > This was because per-cpu variables can be at-most page aligned. > 6cdf9c7ca687 ("arm64: Store struct thread_info in sp_el0") changed > current_thread_info() to work on these weirdly aligned irq_stacks. > > > Thanks, > > James > >
It looks like this is ultimately used (currently) only by the arch-independent kprobes tracing code. But it does seem like this will be recording the wrong data when stack contents are being traced from interrupt routine probes. I will put a fix in for the next spin.
Thanks, -dl
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