[Xen-devel] [PATCH v2 9/9] x86/hypercall: Reduce the size of the hypercall tables

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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 <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c   |  8 ++++++--
 xen/arch/x86/hypercall.c | 14 ++++++++++----
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 23b0d17..ddb12cc 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4133,7 +4133,7 @@ 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),
@@ -4194,7 +4194,11 @@ 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 41be870..d2b5331 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),
@@ -148,7 +148,11 @@ void pv_hypercall(struct cpu_user_regs *regs)
 
     eax = is_pv_32bit_vcpu(curr) ? regs->_eax : regs->eax;
 
-    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 )
     {
         regs->eax = -ENOSYS;
         return;
@@ -257,7 +261,8 @@ 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]);
@@ -269,7 +274,8 @@ 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]);
-- 
2.1.4


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