| Message ID | 20220607165105.639716-3-kaleshsingh@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM nVHE Hypervisor stack unwinder | expand |
On Tue, 07 Jun 2022 17:50:44 +0100, Kalesh Singh <kaleshsingh@google.com> wrote: > > Recompile stack unwinding code for use with the nVHE hypervisor. This is > a preparatory patch that will allow reusing most of the kernel unwinding > logic in the nVHE hypervisor. > > Suggested-by: Mark Rutland <mark.rutland@arm.com> > Signed-off-by: Kalesh Singh <kaleshsingh@google.com> > Reviewed-by: Mark Brown <broonie@kernel.org> > --- > > Changes in v3: > - Add Mark's Reviewed-by tag > > Changes in v2: > - Split out refactoring of common unwinding logic into a separate patch, > per Mark Brown > > arch/arm64/include/asm/stacktrace.h | 18 +++++++++----- > arch/arm64/kernel/stacktrace.c | 37 ++++++++++++++++------------- > arch/arm64/kvm/hyp/nvhe/Makefile | 3 ++- > 3 files changed, 35 insertions(+), 23 deletions(-) > > diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h > index aec9315bf156..f5af9a94c5a6 100644 > --- a/arch/arm64/include/asm/stacktrace.h > +++ b/arch/arm64/include/asm/stacktrace.h > @@ -16,12 +16,14 @@ > #include <asm/sdei.h> > > enum stack_type { > - STACK_TYPE_UNKNOWN, > +#ifndef __KVM_NVHE_HYPERVISOR__ > STACK_TYPE_TASK, > STACK_TYPE_IRQ, > STACK_TYPE_OVERFLOW, > STACK_TYPE_SDEI_NORMAL, > STACK_TYPE_SDEI_CRITICAL, > +#endif /* !__KVM_NVHE_HYPERVISOR__ */ > + STACK_TYPE_UNKNOWN, What is the reason for this reordering? I have the sinking feeling that this could play badly with the logic that assumes that it is legal to switch from a lesser stack type to a higher one, and could allow switching to a duff stack. I would at least like to see a justification of why this isn't less safe than the current code. [...] > index f9fe4dc21b1f..c0ff0d6fc403 100644 > --- a/arch/arm64/kvm/hyp/nvhe/Makefile > +++ b/arch/arm64/kvm/hyp/nvhe/Makefile > @@ -14,7 +14,8 @@ lib-objs := $(addprefix ../../../lib/, $(lib-objs)) > > obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \ > hyp-main.o hyp-smp.o psci-relay.o early_alloc.o page_alloc.o \ > - cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o > + cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o \ > + ../../../kernel/stacktrace.o This, I positively hate. It is only a marginally better than the cross-arch references we used to have with arch/arm/kvm. I'd be much more happy with an include file containing the shared code. It would also allow the removal of some of the #ifdeferry. Note that this is the approach that we ended up adopting for the VHE/nVHE split. Thanks, M.
On Wed, Jun 8, 2022 at 12:33 AM Marc Zyngier <maz@kernel.org> wrote: > > On Tue, 07 Jun 2022 17:50:44 +0100, > Kalesh Singh <kaleshsingh@google.com> wrote: > > > > Recompile stack unwinding code for use with the nVHE hypervisor. This is > > a preparatory patch that will allow reusing most of the kernel unwinding > > logic in the nVHE hypervisor. > > > > Suggested-by: Mark Rutland <mark.rutland@arm.com> > > Signed-off-by: Kalesh Singh <kaleshsingh@google.com> > > Reviewed-by: Mark Brown <broonie@kernel.org> > > --- > > > > Changes in v3: > > - Add Mark's Reviewed-by tag > > > > Changes in v2: > > - Split out refactoring of common unwinding logic into a separate patch, > > per Mark Brown > > > > arch/arm64/include/asm/stacktrace.h | 18 +++++++++----- > > arch/arm64/kernel/stacktrace.c | 37 ++++++++++++++++------------- > > arch/arm64/kvm/hyp/nvhe/Makefile | 3 ++- > > 3 files changed, 35 insertions(+), 23 deletions(-) > > > > diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h > > index aec9315bf156..f5af9a94c5a6 100644 > > --- a/arch/arm64/include/asm/stacktrace.h > > +++ b/arch/arm64/include/asm/stacktrace.h > > @@ -16,12 +16,14 @@ > > #include <asm/sdei.h> > > > > enum stack_type { > > - STACK_TYPE_UNKNOWN, > > +#ifndef __KVM_NVHE_HYPERVISOR__ > > STACK_TYPE_TASK, > > STACK_TYPE_IRQ, > > STACK_TYPE_OVERFLOW, > > STACK_TYPE_SDEI_NORMAL, > > STACK_TYPE_SDEI_CRITICAL, > > +#endif /* !__KVM_NVHE_HYPERVISOR__ */ > > + STACK_TYPE_UNKNOWN, > > What is the reason for this reordering? I have the sinking feeling > that this could play badly with the logic that assumes that it is > legal to switch from a lesser stack type to a higher one, and could > allow switching to a duff stack. HI Marc. Thanks for reviewing. I only reordered the enum to group the common types. But I don't have a strong opinion on it. The unwinding doesn't depend on the ordering in this enum. When we transition form stack 'A'-->'B', we set the stack_done bit for stack A so that we never transition back to 'A', as it's not valid to transition back to a previous stack. But the order of the sequence itself is not something enforced. > > I would at least like to see a justification of why this isn't less > safe than the current code. > > [...] > > > index f9fe4dc21b1f..c0ff0d6fc403 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/Makefile > > +++ b/arch/arm64/kvm/hyp/nvhe/Makefile > > @@ -14,7 +14,8 @@ lib-objs := $(addprefix ../../../lib/, $(lib-objs)) > > > > obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \ > > hyp-main.o hyp-smp.o psci-relay.o early_alloc.o page_alloc.o \ > > - cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o > > + cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o \ > > + ../../../kernel/stacktrace.o > > This, I positively hate. It is only a marginally better than the > cross-arch references we used to have with arch/arm/kvm. I'd be much > more happy with an include file containing the shared code. It would > also allow the removal of some of the #ifdeferry. Note that this is > the approach that we ended up adopting for the VHE/nVHE split. > Also thought about moving stuff to some header file, but I thought this might be less intrusive. Let me prototype to see how they compare. Thanks, Kalesh > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible. > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index aec9315bf156..f5af9a94c5a6 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -16,12 +16,14 @@ #include <asm/sdei.h> enum stack_type { - STACK_TYPE_UNKNOWN, +#ifndef __KVM_NVHE_HYPERVISOR__ STACK_TYPE_TASK, STACK_TYPE_IRQ, STACK_TYPE_OVERFLOW, STACK_TYPE_SDEI_NORMAL, STACK_TYPE_SDEI_CRITICAL, +#endif /* !__KVM_NVHE_HYPERVISOR__ */ + STACK_TYPE_UNKNOWN, __NR_STACK_TYPES }; @@ -31,11 +33,6 @@ struct stack_info { enum stack_type type; }; -extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, - const char *loglvl); - -DECLARE_PER_CPU(unsigned long *, irq_stack_ptr); - static inline bool on_stack(unsigned long sp, unsigned long size, unsigned long low, unsigned long high, enum stack_type type, struct stack_info *info) @@ -54,6 +51,12 @@ static inline bool on_stack(unsigned long sp, unsigned long size, return true; } +#ifndef __KVM_NVHE_HYPERVISOR__ +extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, + const char *loglvl); + +DECLARE_PER_CPU(unsigned long *, irq_stack_ptr); + static inline bool on_irq_stack(unsigned long sp, unsigned long size, struct stack_info *info) { @@ -88,6 +91,7 @@ static inline bool on_overflow_stack(unsigned long sp, unsigned long size, static inline bool on_overflow_stack(unsigned long sp, unsigned long size, struct stack_info *info) { return false; } #endif +#endif /* !__KVM_NVHE_HYPERVISOR__ */ /* @@ -101,6 +105,7 @@ static inline bool on_accessible_stack(const struct task_struct *tsk, if (info) info->type = STACK_TYPE_UNKNOWN; +#ifndef __KVM_NVHE_HYPERVISOR__ if (on_task_stack(tsk, sp, size, info)) return true; if (tsk != current || preemptible()) @@ -111,6 +116,7 @@ static inline bool on_accessible_stack(const struct task_struct *tsk, return true; if (on_sdei_stack(sp, size, info)) return true; +#endif /* !__KVM_NVHE_HYPERVISOR__ */ return false; } diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index ee60c279511c..a84e38d41d38 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -129,6 +129,26 @@ static int notrace __unwind_next(struct task_struct *tsk, } NOKPROBE_SYMBOL(__unwind_next); +static int notrace unwind_next(struct task_struct *tsk, + struct unwind_state *state); + +static void notrace unwind(struct task_struct *tsk, + struct unwind_state *state, + stack_trace_consume_fn consume_entry, void *cookie) +{ + while (1) { + int ret; + + if (!consume_entry(cookie, state->pc)) + break; + ret = unwind_next(tsk, state); + if (ret < 0) + break; + } +} +NOKPROBE_SYMBOL(unwind); + +#ifndef __KVM_NVHE_HYPERVISOR__ static int notrace unwind_next(struct task_struct *tsk, struct unwind_state *state) { @@ -171,22 +191,6 @@ static int notrace unwind_next(struct task_struct *tsk, } NOKPROBE_SYMBOL(unwind_next); -static void notrace unwind(struct task_struct *tsk, - struct unwind_state *state, - stack_trace_consume_fn consume_entry, void *cookie) -{ - while (1) { - int ret; - - if (!consume_entry(cookie, state->pc)) - break; - ret = unwind_next(tsk, state); - if (ret < 0) - break; - } -} -NOKPROBE_SYMBOL(unwind); - static bool dump_backtrace_entry(void *arg, unsigned long where) { char *loglvl = arg; @@ -238,3 +242,4 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry, unwind(task, &state, consume_entry, cookie); } +#endif /* !__KVM_NVHE_HYPERVISOR__ */ diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile index f9fe4dc21b1f..c0ff0d6fc403 100644 --- a/arch/arm64/kvm/hyp/nvhe/Makefile +++ b/arch/arm64/kvm/hyp/nvhe/Makefile @@ -14,7 +14,8 @@ lib-objs := $(addprefix ../../../lib/, $(lib-objs)) obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \ hyp-main.o hyp-smp.o psci-relay.o early_alloc.o page_alloc.o \ - cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o + cache.o setup.o mm.o mem_protect.o sys_regs.o pkvm.o \ + ../../../kernel/stacktrace.o obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \ ../fpsimd.o ../hyp-entry.o ../exception.o ../pgtable.o obj-$(CONFIG_DEBUG_LIST) += list_debug.o