[XEN] Fix compatibility with future guests which may try to

use hypercalls >= NR_hypercalls. These must fail with ENOSYS,
but the current strategy of masking off the high-order bits of
the hypercall number means we instead map those hypercalls onto
lower-numbered hypercalls with unpredictable results. This patch
replaces masking with an explicit compare-and-jump.
Signed-off-by: Keir Fraser <keir@xensource.com>

diff --git a/xen/arch/x86/x86_32/entry.S b/xen/arch/x86/x86_32/entry.S
index c0bc7e4e013e1d4b78a832afa6746fcf1873b161..71cbe20f68503049d0fd4899a182602dfc1d3f52 100644 (file)
--- a/xen/arch/x86/x86_32/entry.S
+++ b/xen/arch/x86/x86_32/entry.S
@@ -171,7 +171,8 @@ ENTRY(hypercall)
        SAVE_ALL(b)
         sti
         GET_CURRENT(%ebx)
-        andl $(NR_hypercalls-1),%eax
+        cmpl  $NR_hypercalls,%eax
+        jae   bad_hypercall
         PERFC_INCR(PERFC_hypercalls, %eax)
 #ifndef NDEBUG
         /* Deliberately corrupt parameter regs not used by this hypercall. */
@@ -261,6 +262,10 @@ process_nmi:
 1:      bts  $_VCPUF_nmi_pending,VCPU_flags(%ebx)
         jmp  test_guest_events
 
+bad_hypercall:
+        movl $-ENOSYS,UREGS_eax(%esp)
+        jmp  test_all_events
+
 /* CREATE A BASIC EXCEPTION FRAME ON GUEST OS (RING-1) STACK:            */
 /*   {EIP, CS, EFLAGS, [ESP, SS]}                                        */
 /* %edx == trap_bounce, %ebx == struct vcpu                       */

diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 62bb86510b0a7f89d5bc622631bc07a0d256af6f..853dfa5715a877ba11736485adc5b2dc943f5813 100644 (file)
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -130,7 +130,8 @@ ENTRY(syscall_enter)
 
 /*hypercall:*/
         movq  %r10,%rcx
-        andq  $(NR_hypercalls-1),%rax
+        cmpq  $NR_hypercalls,%rax
+        jae   bad_hypercall
 #ifndef NDEBUG
         /* Deliberately corrupt parameter regs not used by this hypercall. */
         pushq %rdi; pushq %rsi; pushq %rdx; pushq %rcx; pushq %r8 ; pushq %r9 
@@ -142,7 +143,6 @@ ENTRY(syscall_enter)
         rep   stosq
         popq  %r9 ; popq  %r8 ; popq  %rcx; popq  %rdx; popq  %rsi; popq  %rdi
         movq  UREGS_rax(%rsp),%rax
-        andq  $(NR_hypercalls-1),%rax
         pushq %rax
         pushq UREGS_rip+8(%rsp)
 #endif
@@ -217,7 +217,11 @@ process_nmi:
         jmp  test_all_events
 1:      bts  $_VCPUF_nmi_pending,VCPU_flags(%rbx)
         jmp  test_guest_events
-       
+
+bad_hypercall:
+        movq $-ENOSYS,UREGS_rax(%rsp)
+        jmp  test_all_events
+
 /* CREATE A BASIC EXCEPTION FRAME ON GUEST OS STACK:                     */
 /*   { RCX, R11, [DS-GS,] [CR2,] [ERRCODE,] RIP, CS, RFLAGS, RSP, SS }   */
 /* %rdx: trap_bounce, %rbx: struct vcpu                           */

diff --git a/xen/include/asm-ia64/config.h b/xen/include/asm-ia64/config.h
index c53a7e4f6deb88f85eb83caad22dfd1b0449a900..5e197f884918f08a67fd7a6fdbba1b0573ad3520 100644 (file)
--- a/xen/include/asm-ia64/config.h
+++ b/xen/include/asm-ia64/config.h
@@ -97,13 +97,8 @@ extern char _end[]; /* standard ELF symbol */
 //#define HZ 1000
 // FIXME SMP: leave SMP for a later time
 
-/* A power-of-two value greater than or equal to number of hypercalls. */
 #define NR_hypercalls 64
 
-#if NR_hypercalls & (NR_hypercalls - 1)
-#error "NR_hypercalls must be a power-of-two value"
-#endif
-
 ///////////////////////////////////////////////////////////////
 // xen/include/asm/config.h
 // Natural boundary upon TR size to define xenheap space

diff --git a/xen/include/asm-x86/config.h b/xen/include/asm-x86/config.h
index 2b80b5643d1b7351bcca2b9cc4b3d7747c7c3357..bf7e882afc80ce4a747c15067150bcf83e09ff8c 100644 (file)
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -63,13 +63,8 @@
   name:
 #endif
 
-/* A power-of-two value greater than or equal to number of hypercalls. */
 #define NR_hypercalls 64
 
-#if NR_hypercalls & (NR_hypercalls - 1)
-#error "NR_hypercalls must be a power-of-two value"
-#endif
-
 #ifndef NDEBUG
 #define MEMORY_GUARD
 #ifdef __x86_64__

diff --git a/xen/include/asm-x86/multicall.h b/xen/include/asm-x86/multicall.h
index 23d7c8e5ba4526fd40c96a9bd49838f87d81c6ae..5fe37176fab2bbe046d1988e0b600c3f6b1f1bb9 100644 (file)
--- a/xen/include/asm-x86/multicall.h
+++ b/xen/include/asm-x86/multicall.h
@@ -5,48 +5,59 @@
 #ifndef __ASM_X86_MULTICALL_H__
 #define __ASM_X86_MULTICALL_H__
 
+#include <xen/errno.h>
 #include <asm/asm_defns.h>
 
 #ifdef __x86_64__
 
-#define do_multicall_call(_call)                         \
-    do {                                                 \
-        __asm__ __volatile__ (                           \
-            "movq  "STR(MULTICALL_op)"(%0),%%rax; "      \
-            "andq  $("STR(NR_hypercalls)"-1),%%rax; "    \
-            "leaq  "STR(hypercall_table)"(%%rip),%%rdi; "\
-            "leaq  (%%rdi,%%rax,8),%%rax; "              \
-            "movq  "STR(MULTICALL_arg0)"(%0),%%rdi; "    \
-            "movq  "STR(MULTICALL_arg1)"(%0),%%rsi; "    \
-            "movq  "STR(MULTICALL_arg2)"(%0),%%rdx; "    \
-            "movq  "STR(MULTICALL_arg3)"(%0),%%rcx; "    \
-            "movq  "STR(MULTICALL_arg4)"(%0),%%r8; "     \
-            "callq *(%%rax); "                           \
-            "movq  %%rax,"STR(MULTICALL_result)"(%0); "  \
-            : : "b" (_call)                              \
-              /* all the caller-saves registers */       \
-            : "rax", "rcx", "rdx", "rsi", "rdi",         \
-              "r8",  "r9",  "r10", "r11" );              \
+#define do_multicall_call(_call)                             \
+    do {                                                     \
+        __asm__ __volatile__ (                               \
+            "    movq  "STR(MULTICALL_op)"(%0),%%rax; "      \
+            "    cmpq  $("STR(NR_hypercalls)"),%%rax; "      \
+            "    jae   2f; "                                 \
+            "    leaq  "STR(hypercall_table)"(%%rip),%%rdi; "\
+            "    leaq  (%%rdi,%%rax,8),%%rax; "              \
+            "    movq  "STR(MULTICALL_arg0)"(%0),%%rdi; "    \
+            "    movq  "STR(MULTICALL_arg1)"(%0),%%rsi; "    \
+            "    movq  "STR(MULTICALL_arg2)"(%0),%%rdx; "    \
+            "    movq  "STR(MULTICALL_arg3)"(%0),%%rcx; "    \
+            "    movq  "STR(MULTICALL_arg4)"(%0),%%r8; "     \
+            "    callq *(%%rax); "                           \
+            "1:  movq  %%rax,"STR(MULTICALL_result)"(%0)\n"  \
+            ".section .fixup,\"ax\"\n"                       \
+            "2:  movq  $-"STR(ENOSYS)",%%rax\n"              \
+            "    jmp   1b\n"                                 \
+            ".previous\n"                                    \
+            : : "b" (_call)                                  \
+              /* all the caller-saves registers */           \
+            : "rax", "rcx", "rdx", "rsi", "rdi",             \
+              "r8",  "r9",  "r10", "r11" );                  \
     } while ( 0 )
 
 #else
 
-#define do_multicall_call(_call)                       \
-    do {                                               \
-        __asm__ __volatile__ (                         \
-            "pushl "STR(MULTICALL_arg4)"(%0); "        \
-            "pushl "STR(MULTICALL_arg3)"(%0); "        \
-            "pushl "STR(MULTICALL_arg2)"(%0); "        \
-            "pushl "STR(MULTICALL_arg1)"(%0); "        \
-            "pushl "STR(MULTICALL_arg0)"(%0); "        \
-            "movl  "STR(MULTICALL_op)"(%0),%%eax; "    \
-            "andl  $("STR(NR_hypercalls)"-1),%%eax; "  \
-            "call  *hypercall_table(,%%eax,4); "       \
-            "movl  %%eax,"STR(MULTICALL_result)"(%0); "\
-            "addl  $20,%%esp; "                        \
-            : : "b" (_call)                            \
-              /* all the caller-saves registers */     \
-            : "eax", "ecx", "edx" );                   \
+#define do_multicall_call(_call)                             \
+    do {                                                     \
+        __asm__ __volatile__ (                               \
+            "    pushl "STR(MULTICALL_arg4)"(%0); "          \
+            "    pushl "STR(MULTICALL_arg3)"(%0); "          \
+            "    pushl "STR(MULTICALL_arg2)"(%0); "          \
+            "    pushl "STR(MULTICALL_arg1)"(%0); "          \
+            "    pushl "STR(MULTICALL_arg0)"(%0); "          \
+            "    movl  "STR(MULTICALL_op)"(%0),%%eax; "      \
+            "    cmpl  $("STR(NR_hypercalls)"),%%eax; "      \
+            "    jae   2f; "                                 \
+            "    call  *hypercall_table(,%%eax,4); "         \
+            "1:  movl  %%eax,"STR(MULTICALL_result)"(%0); "  \
+            "    addl  $20,%%esp\n"                          \
+            ".section .fixup,\"ax\"\n"                       \
+            "2:  movl  $-"STR(ENOSYS)",%%eax\n"              \
+            "    jmp   1b\n"                                 \
+            ".previous\n"                                    \
+            : : "b" (_call)                                  \
+              /* all the caller-saves registers */           \
+            : "eax", "ecx", "edx" );                         \
     } while ( 0 )
 
 #endif