[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/2] xen/hypercall: fix hypercall fallback code for very old hypervisors
On Wed, Oct 31, 2012 at 08:55:54AM +0000, Jan Beulich wrote: > >>> On 30.10.12 at 16:44, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> > >>> wrote: > > On Mon, Oct 29, 2012 at 10:08:17AM -0400, Konrad Rzeszutek Wilk wrote: > >> From: Jan Beulich <jbeulich@xxxxxxxx> > >> > >> While copying the argument structures in HYPERVISOR_event_channel_op() > >> and HYPERVISOR_physdev_op() into the local variable is sufficiently > >> safe even if the actual structure is smaller than the container one, > >> copying back eventual output values the same way isn't: This may > >> collide with on-stack variables (particularly "rc") which may change > >> between the first and second memcpy() (i.e. the second memcpy() could > >> discard that change). > >> > >> Move the fallback code into out-of-line functions, and handle all of > >> the operations known by this old a hypervisor individually: Some don't > >> require copying back anything at all, and for the rest use the > >> individual argument structures' sizes rather than the container's. > >> > >> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> > >> [v2: Reduce #define/#undef usage in HYPERVISOR_physdev_op_compat().] > >> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> > > > > And it looks like I get > > > > ERROR: "HYPERVISOR_event_channel_op_compat" [drivers/xen/xen-evtchn.ko] > > undefined! > > > > when I build xen-evtchn as module. Jan did you encounter this issue on > > 2.6.18? > > No - the event channel driver there can't be built as a module, and > for the forward ported kernels I apparently never tried to build with > a compat setting of 3.0.2 or less (and I didn't care that much either > because the oldest we're actually concerned about is 3.0.4 to cover > some of those very old EC2 systems; I'll add the export at the right > point nevertheless). Ok, ended up with this version which I was thinking to for v3.7-rc5: >From 4ae4c7658a7c0501521c422d618038587c3edeca Mon Sep 17 00:00:00 2001 From: Jan Beulich <jbeulich@xxxxxxxx> Date: Fri, 19 Oct 2012 15:25:37 -0400 Subject: [PATCH] xen/hypercall: fix hypercall fallback code for very old hypervisors While copying the argument structures in HYPERVISOR_event_channel_op() and HYPERVISOR_physdev_op() into the local variable is sufficiently safe even if the actual structure is smaller than the container one, copying back eventual output values the same way isn't: This may collide with on-stack variables (particularly "rc") which may change between the first and second memcpy() (i.e. the second memcpy() could discard that change). Move the fallback code into out-of-line functions, and handle all of the operations known by this old a hypervisor individually: Some don't require copying back anything at all, and for the rest use the individual argument structures' sizes rather than the container's. Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> [v2: Reduce #define/#undef usage in HYPERVISOR_physdev_op_compat().] [v3: Fix compile errors when modules use said hypercalls] [v4: Add xen_ prefix to the HYPERCALL_..] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> --- arch/x86/include/asm/xen/hypercall.h | 21 ++++------ drivers/xen/Makefile | 2 +- drivers/xen/fallback.c | 81 ++++++++++++++++++++++++++++++++++++ 3 files changed, 89 insertions(+), 15 deletions(-) create mode 100644 drivers/xen/fallback.c diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h index 59c226d..4055421 100644 --- a/arch/x86/include/asm/xen/hypercall.h +++ b/arch/x86/include/asm/xen/hypercall.h @@ -359,18 +359,14 @@ HYPERVISOR_update_va_mapping(unsigned long va, pte_t new_val, return _hypercall4(int, update_va_mapping, va, new_val.pte, new_val.pte >> 32, flags); } +extern int __must_check xen_HYPERVISOR_event_channel_op_compat(int, void *); static inline int HYPERVISOR_event_channel_op(int cmd, void *arg) { int rc = _hypercall2(int, event_channel_op, cmd, arg); - if (unlikely(rc == -ENOSYS)) { - struct evtchn_op op; - op.cmd = cmd; - memcpy(&op.u, arg, sizeof(op.u)); - rc = _hypercall1(int, event_channel_op_compat, &op); - memcpy(arg, &op.u, sizeof(op.u)); - } + if (unlikely(rc == -ENOSYS)) + rc = xen_HYPERVISOR_event_channel_op_compat(cmd, arg); return rc; } @@ -386,17 +382,14 @@ HYPERVISOR_console_io(int cmd, int count, char *str) return _hypercall3(int, console_io, cmd, count, str); } +extern int __must_check xen_HYPERVISOR_physdev_op_compat(int, void *); + static inline int HYPERVISOR_physdev_op(int cmd, void *arg) { int rc = _hypercall2(int, physdev_op, cmd, arg); - if (unlikely(rc == -ENOSYS)) { - struct physdev_op op; - op.cmd = cmd; - memcpy(&op.u, arg, sizeof(op.u)); - rc = _hypercall1(int, physdev_op_compat, &op); - memcpy(arg, &op.u, sizeof(op.u)); - } + if (unlikely(rc == -ENOSYS)) + rc = xen_HYPERVISOR_physdev_op_compat(cmd, arg); return rc; } diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile index 0e863703..46de6cd 100644 --- a/drivers/xen/Makefile +++ b/drivers/xen/Makefile @@ -2,7 +2,7 @@ ifneq ($(CONFIG_ARM),y) obj-y += manage.o balloon.o obj-$(CONFIG_HOTPLUG_CPU) += cpu_hotplug.o endif -obj-y += grant-table.o features.o events.o +obj-y += grant-table.o features.o events.o fallback.o obj-y += xenbus/ nostackp := $(call cc-option, -fno-stack-protector) diff --git a/drivers/xen/fallback.c b/drivers/xen/fallback.c new file mode 100644 index 0000000..b29ce32 --- /dev/null +++ b/drivers/xen/fallback.c @@ -0,0 +1,81 @@ +#include <linux/kernel.h> +#include <linux/string.h> +#include <linux/bug.h> +#include <linux/export.h> +#include <asm/hypervisor.h> +#include <asm/xen/hypercall.h> + +int xen_HYPERVISOR_event_channel_op_compat(int cmd, void *arg) +{ + struct evtchn_op op; + int rc; + + op.cmd = cmd; + memcpy(&op.u, arg, sizeof(op.u)); + rc = _hypercall1(int, event_channel_op_compat, &op); + + switch (cmd) { + case EVTCHNOP_close: + case EVTCHNOP_send: + case EVTCHNOP_bind_vcpu: + case EVTCHNOP_unmask: + /* no output */ + break; + +#define COPY_BACK(eop) \ + case EVTCHNOP_##eop: \ + memcpy(arg, &op.u.eop, sizeof(op.u.eop)); \ + break + + COPY_BACK(bind_interdomain); + COPY_BACK(bind_virq); + COPY_BACK(bind_pirq); + COPY_BACK(status); + COPY_BACK(alloc_unbound); + COPY_BACK(bind_ipi); +#undef COPY_BACK + + default: + WARN_ON(rc != -ENOSYS); + break; + } + + return rc; +} +EXPORT_SYMBOL_GPL(xen_HYPERVISOR_event_channel_op_compat); + +int xen_HYPERVISOR_physdev_op_compat(int cmd, void *arg) +{ + struct physdev_op op; + int rc; + + op.cmd = cmd; + memcpy(&op.u, arg, sizeof(op.u)); + rc = _hypercall1(int, physdev_op_compat, &op); + + switch (cmd) { + case PHYSDEVOP_IRQ_UNMASK_NOTIFY: + case PHYSDEVOP_set_iopl: + case PHYSDEVOP_set_iobitmap: + case PHYSDEVOP_apic_write: + /* no output */ + break; + +#define COPY_BACK(pop, fld) \ + case PHYSDEVOP_##pop: \ + memcpy(arg, &op.u.fld, sizeof(op.u.fld)); \ + break + + COPY_BACK(irq_status_query, irq_status_query); + COPY_BACK(apic_read, apic_op); + COPY_BACK(ASSIGN_VECTOR, irq_op); +#undef COPY_BACK + + default: + WARN_ON(rc != -ENOSYS); + break; + } + + return rc; +} +EXPORT_SYMBOL_GPL(xen_HYPERVISOR_physdev_op_compat); -- 1.7.11.7 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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