[9/9] x86/hypercall: Reduce the size of the hypercall tables

Commit Message

Andrew Cooper July 18, 2016, 9:51 a.m. UTC

The highest populated entry in each hypercall table is currently at index 49.
There is no need to extend both to tables to 64 entries.

Range check eax against the hypercall table array size, and use a
BUILD_BUG_ON() to ensure that the hypercall tables don't grow larger than the
args table.

Signed-off-by: Andrew Cooper <[e-mail]>
---
CC: Jan Beulich <[e-mail]>
---
 xen/arch/x86/hvm/hvm.c   |  8 ++++++--
 xen/arch/x86/hypercall.c | 14 ++++++++++----
 2 files changed, 16 insertions(+), 6 deletions(-)

Comments

Jan Beulich Aug. 3, 2016, 3:17 p.m. UTC | #1

>>> On 18.07.16 at 11:51, <[e-mail]> wrote:
> The highest populated entry in each hypercall table is currently at index 49.
> There is no need to extend both to tables to 64 entries.
> 
> Range check eax against the hypercall table array size, and use a
> BUILD_BUG_ON() to ensure that the hypercall tables don't grow larger than the
> args table.
> 
> Signed-off-by: Andrew Cooper <[e-mail]>

Reviewed-by: Jan Beulich <[e-mail]>

Patch

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 198fe34..df177da 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4094,7 +4094,7 @@  static long hvm_physdev_op_compat32(
 #define compat_grant_table_op hvm_grant_table_op_compat32
 #define do_arch_1             paging_domctl_continuation
 
-static const hypercall_table_t hvm_hypercall_table[NR_hypercalls] = {
+static const hypercall_table_t hvm_hypercall_table[] = {
     COMPAT_CALL(memory_op),
     COMPAT_CALL(grant_table_op),
     COMPAT_CALL(vcpu_op),
@@ -4153,7 +4153,11 @@  int hvm_do_hypercall(struct cpu_user_regs *regs)
     if ( (eax & 0x80000000) && is_viridian_domain(currd) )
         return viridian_hypercall(regs);
 
-    if ( (eax >= NR_hypercalls) || !hvm_hypercall_table[eax].native )
+    BUILD_BUG_ON(ARRAY_SIZE(hvm_hypercall_table) >
+                 ARRAY_SIZE(hypercall_args_table));
+
+    if ( (eax >= ARRAY_SIZE(hvm_hypercall_table)) ||
+         !hvm_hypercall_table[eax].native )
     {
         regs->eax = -ENOSYS;
         return HVM_HCALL_completed;
diff --git a/xen/arch/x86/hypercall.c b/xen/arch/x86/hypercall.c
index 373bedf..1bf0a1c 100644
--- a/xen/arch/x86/hypercall.c
+++ b/xen/arch/x86/hypercall.c
@@ -82,7 +82,7 @@  const hypercall_args_t hypercall_args_table[NR_hypercalls] =
 
 #define do_arch_1             paging_domctl_continuation
 
-static const hypercall_table_t pv_hypercall_table[NR_hypercalls] = {
+static const hypercall_table_t pv_hypercall_table[] = {
     COMPAT_CALL(set_trap_table),
     HYPERCALL(mmu_update),
     COMPAT_CALL(set_gdt),
@@ -147,7 +147,11 @@  long pv_hypercall(struct cpu_user_regs *regs)
 
     ASSERT(curr->arch.flags & TF_kernel_mode);
 
-    if ( (eax >= NR_hypercalls) || !pv_hypercall_table[eax].native )
+    BUILD_BUG_ON(ARRAY_SIZE(pv_hypercall_table) >
+                 ARRAY_SIZE(hypercall_args_table));
+
+    if ( (eax >= ARRAY_SIZE(pv_hypercall_table)) ||
+         !pv_hypercall_table[eax].native )
          return -ENOSYS;
 
     if ( !is_pv_32bit_vcpu(curr) )
@@ -255,7 +259,8 @@  void arch_do_multicall_call(struct mc_state *state)
     {
         struct multicall_entry *call = &state->call;
 
-        if ( (call->op < NR_hypercalls) && pv_hypercall_table[call->op].native )
+        if ( (call->op < ARRAY_SIZE(pv_hypercall_table)) &&
+             pv_hypercall_table[call->op].native )
             call->result = pv_hypercall_table[call->op].native(
                 call->args[0], call->args[1], call->args[2],
                 call->args[3], call->args[4], call->args[5]);
@@ -267,7 +272,8 @@  void arch_do_multicall_call(struct mc_state *state)
     {
         struct compat_multicall_entry *call = &state->compat_call;
 
-        if ( (call->op < NR_hypercalls) && pv_hypercall_table[call->op].compat )
+        if ( (call->op < ARRAY_SIZE(pv_hypercall_table)) &&
+             pv_hypercall_table[call->op].compat )
             call->result = pv_hypercall_table[call->op].compat(
                 call->args[0], call->args[1], call->args[2],
                 call->args[3], call->args[4], call->args[5]);