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xen: remove pre-xen3 fallback handlers

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The legacy hypercall handlers were originally added with
a comment explaining that "copying the argument structures in
HYPERVISOR_event_channel_op() and HYPERVISOR_physdev_op() into the local
variable is sufficiently safe" and only made sure to not write
past the end of the argument structure, the checks in linux/string.h
disagree with that, when link-time optimizations are used:

In function 'memcpy',
    inlined from 'pirq_query_unmask' at drivers/xen/fallback.c:53:2,
    inlined from '__startup_pirq' at drivers/xen/events/events_base.c:529:2,
    inlined from 'restore_pirqs' at drivers/xen/events/events_base.c:1439:3,
    inlined from 'xen_irq_resume' at drivers/xen/events/events_base.c:1581:2:
include/linux/string.h:350:3: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
   __read_overflow2();
   ^

Further research turned out that only Xen 3.0.2 or earlier required the
fallback at all, while all versions in use today don't need it.
As far as I can tell, it is not even possible to run a mainline kernel
on those old Xen releases, at the time when they were in use, only
a patched kernel was supported anyway.

Fixes: cf47a83fb0 ("xen/hypercall: fix hypercall fallback code for very old hypervisors")
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Arnd Bergmann 2019-03-04 21:52:39 +01:00 committed by Juergen Gross
parent 85eb278c18
commit b1ddd406cd
3 changed files with 2 additions and 93 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
arch/x86/include/asm/xen/hypercall.h
View File

@ -332,15 +332,11 @@ 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_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))
rc = xen_event_channel_op_compat(cmd, arg);
return rc;
return _hypercall2(int, event_channel_op, cmd, arg);
}
static inline int
@ -355,15 +351,10 @@ HYPERVISOR_console_io(int cmd, int count, char *str)
return _hypercall3(int, console_io, cmd, count, str);
}
extern int __must_check xen_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))
rc = xen_physdev_op_compat(cmd, arg);
return rc;
return _hypercall2(int, physdev_op, cmd, arg);
}
static inline int

1
drivers/xen/Makefile
View File

@ -1,6 +1,5 @@
# SPDX-License-Identifier: GPL-2.0
obj-$(CONFIG_HOTPLUG_CPU) += cpu_hotplug.o
obj-$(CONFIG_X86) += fallback.o
obj-y += grant-table.o features.o balloon.o manage.o preempt.o time.o
obj-y += mem-reservation.o
obj-y += events/

81
drivers/xen/fallback.c
View File

@ -1,81 +0,0 @@
#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_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_event_channel_op_compat);
int xen_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_physdev_op_compat);