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Venkataraman" Cc: Mark Brown , Josh Poimboeuf , Mark Rutland , Julien Thierry , Catalin Marinas , Will Deacon , James Morris , Pavel Tatashin , Linux ARM , live-patching@vger.kernel.org, Linux Kernel Mailing List X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210505_123052_256151_68DEFCE8 X-CRM114-Status: GOOD ( 34.59 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 3 May 2021 at 19:38, wrote: > > From: "Madhavan T. Venkataraman" > > Create a sym_code_ranges[] array to cover the following text sections that > contain functions defined as SYM_CODE_*(). These functions are low-level > functions (and do not have a proper frame pointer prolog and epilog). So, > they are inherently unreliable from a stack unwinding perspective. > > .entry.text > .idmap.text > .hyp.idmap.text > .hyp.text > .hibernate_exit.text > .entry.tramp.text > > If a return PC falls in any of these, mark the stack trace unreliable. > > The only exception to this is - if the unwinder has reached the last > frame already, it will not mark the stack trace unreliable since there > is no more unwinding to do. E.g., > > - ret_from_fork() occurs at the end of the stack trace of > kernel tasks. > > - el0_*() functions occur at the end of EL0 exception stack > traces. This covers all user task entries into the kernel. > > NOTE: > - EL1 exception handlers are in .entry.text. So, stack traces that > contain those functions will be marked not reliable. This covers > interrupts, exceptions and breakpoints encountered while executing > in the kernel. > > - At the end of an interrupt, the kernel can preempt the current > task if required. So, the stack traces of all preempted tasks will > show the interrupt frame and will be considered unreliable. > > Signed-off-by: Madhavan T. Venkataraman > --- > arch/arm64/kernel/stacktrace.c | 54 ++++++++++++++++++++++++++++++++++ > 1 file changed, 54 insertions(+) > > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index c21a1bca28f3..1ff14615a55a 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -15,9 +15,48 @@ > > #include > #include > +#include > #include > #include > > +struct code_range { > + unsigned long start; > + unsigned long end; > +}; > + > +struct code_range sym_code_ranges[] = This should be static and const > +{ > + /* non-unwindable ranges */ > + { (unsigned long)__entry_text_start, > + (unsigned long)__entry_text_end }, > + { (unsigned long)__idmap_text_start, > + (unsigned long)__idmap_text_end }, > + { (unsigned long)__hyp_idmap_text_start, > + (unsigned long)__hyp_idmap_text_end }, > + { (unsigned long)__hyp_text_start, > + (unsigned long)__hyp_text_end }, > +#ifdef CONFIG_HIBERNATION > + { (unsigned long)__hibernate_exit_text_start, > + (unsigned long)__hibernate_exit_text_end }, > +#endif > +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 > + { (unsigned long)__entry_tramp_text_start, > + (unsigned long)__entry_tramp_text_end }, > +#endif > + { /* sentinel */ } > +}; > + > +static struct code_range *lookup_range(unsigned long pc) const struct code_range * > +{ > + struct code_range *range; const struct code_range * > + > + for (range = sym_code_ranges; range->start; range++) { > + if (pc >= range->start && pc < range->end) > + return range; > + } > + return range; > +} > + > /* > * AArch64 PCS assigns the frame pointer to x29. > * > @@ -43,6 +82,7 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) > { > unsigned long fp = frame->fp; > struct stack_info info; > + struct code_range *range; const struct code_range * > > frame->reliable = true; > > @@ -103,6 +143,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) > return 0; > } > > + range = lookup_range(frame->pc); > + > #ifdef CONFIG_FUNCTION_GRAPH_TRACER > if (tsk->ret_stack && > frame->pc == (unsigned long)return_to_handler) { > @@ -118,9 +160,21 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) > return -EINVAL; > frame->pc = ret_stack->ret; > frame->pc = ptrauth_strip_insn_pac(frame->pc); > + return 0; > } > #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > > + if (!range->start) > + return 0; > + > + /* > + * The return PC falls in an unreliable function. If the final frame > + * has been reached, no more unwinding is needed. Otherwise, mark the > + * stack trace not reliable. > + */ > + if (frame->fp) > + frame->reliable = false; > + > return 0; > } > NOKPROBE_SYMBOL(unwind_frame); > -- > 2.25.1 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel