translate-all: ensure host page mask is always extended with 1's

Anthony reported that >4GB guests on Xen with 32bit QEMU broke after
commit 4ed023c ("Round up RAMBlock sizes to host page sizes", 2015-11-05).

In that patch sizes are masked against qemu_host_page_size/mask which
are uintptr_t, and thus 32bit on a 32bit QEMU, even though the ram space
might be bigger than 4GB on Xen.

Since ram_addr_t is not available on user-mode emulation targets, ensure
that we get a sign extension when masking away the low bits of the address.
Remove the ~10 year old scary comment that the type of these variables
is probably wrong, with another equally scary comment.  The new comment
however does not have "???" in it, which is arguably an improvement.

For completeness use the alignment macros in linux-user and bsd-user
instead of manually doing an &.  linux-user and bsd-user are not affected
by the Xen issue, however.

Reviewed-by: Juan Quintela <quintela@redhat.com>
Reported-by: Anthony PERARD <anthony.perard@citrix.com>
Fixes: 4ed023ce2a39ab5812d33cf4d819def168965a7f
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/bsd-user/elfload.c b/bsd-user/elfload.c
index 351aab12e7939b2fd4cfcc0fade387648dfc504e..59a7bdf0cc9fa1bcaf2b7beb9c0cdbedc3b793a1 100644 (file)
--- a/bsd-user/elfload.c
+++ b/bsd-user/elfload.c
@@ -740,8 +740,7 @@ static void padzero(abi_ulong elf_bss, abi_ulong last_bss)
            size must be known */
         if (qemu_real_host_page_size < qemu_host_page_size) {
             abi_ulong end_addr, end_addr1;
-            end_addr1 = (elf_bss + qemu_real_host_page_size - 1) &
-                ~(qemu_real_host_page_size - 1);
+            end_addr1 = REAL_HOST_PAGE_ALIGN(elf_bss);
             end_addr = HOST_PAGE_ALIGN(elf_bss);
             if (end_addr1 < end_addr) {
                 mmap((void *)g2h(end_addr1), end_addr - end_addr1,

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index f9998b9732b95b8ef082067f3b57cf6cb7777a3a..83b1781afc132cc8ab3f8bd76f422c36ce4625a2 100644 (file)
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -174,11 +174,13 @@ extern unsigned long reserved_va;
 #define TARGET_PAGE_MASK ~(TARGET_PAGE_SIZE - 1)
 #define TARGET_PAGE_ALIGN(addr) (((addr) + TARGET_PAGE_SIZE - 1) & TARGET_PAGE_MASK)
 
-/* ??? These should be the larger of uintptr_t and target_ulong.  */
+/* Using intptr_t ensures that qemu_*_page_mask is sign-extended even
+ * when intptr_t is 32-bit and we are aligning a long long.
+ */
 extern uintptr_t qemu_real_host_page_size;
-extern uintptr_t qemu_real_host_page_mask;
+extern intptr_t qemu_real_host_page_mask;
 extern uintptr_t qemu_host_page_size;
-extern uintptr_t qemu_host_page_mask;
+extern intptr_t qemu_host_page_mask;
 
 #define HOST_PAGE_ALIGN(addr) (((addr) + qemu_host_page_size - 1) & qemu_host_page_mask)
 #define REAL_HOST_PAGE_ALIGN(addr) (((addr) + qemu_real_host_page_size - 1) & \

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index d68f5a16ca4f0211c39338be41250689460f8575..8b17c0e94b336f496ef26ff9c540b773d86ed38b 100644 (file)
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1478,8 +1478,7 @@ static void zero_bss(abi_ulong elf_bss, abi_ulong last_bss, int prot)
 
     host_start = (uintptr_t) g2h(elf_bss);
     host_end = (uintptr_t) g2h(last_bss);
-    host_map_start = (host_start + qemu_real_host_page_size - 1);
-    host_map_start &= -qemu_real_host_page_size;
+    host_map_start = REAL_HOST_PAGE_ALIGN(host_start);
 
     if (host_map_start < host_end) {
         void *p = mmap((void *)host_map_start, host_end - host_map_start,

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 5606bcd16457b3abab026210109016378dfa734b..7b459d5100c52a9e2d56c2d8bd5f239ba451977e 100644 (file)
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -444,9 +444,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
            /* If so, truncate the file map at eof aligned with 
               the hosts real pagesize. Additional anonymous maps
               will be created beyond EOF.  */
-           len = (sb.st_size - offset);
-           len += qemu_real_host_page_size - 1;
-           len &= ~(qemu_real_host_page_size - 1);
+           len = REAL_HOST_PAGE_ALIGN(sb.st_size - offset);
        }
     }
 

diff --git a/translate-all.c b/translate-all.c
index a940bd2e5e8200670b498092b0c984fbcb36ceb0..042a8576ac5336325c2940350037b02599e15327 100644 (file)
--- a/translate-all.c
+++ b/translate-all.c
@@ -118,7 +118,7 @@ typedef struct PageDesc {
 #define V_L1_SHIFT (L1_MAP_ADDR_SPACE_BITS - TARGET_PAGE_BITS - V_L1_BITS)
 
 uintptr_t qemu_host_page_size;
-uintptr_t qemu_host_page_mask;
+intptr_t qemu_host_page_mask;
 
 /* The bottom level has pointers to PageDesc */
 static void *l1_map[V_L1_SIZE];
@@ -326,14 +326,14 @@ void page_size_init(void)
     /* NOTE: we can always suppose that qemu_host_page_size >=
        TARGET_PAGE_SIZE */
     qemu_real_host_page_size = getpagesize();
-    qemu_real_host_page_mask = ~(qemu_real_host_page_size - 1);
+    qemu_real_host_page_mask = -(intptr_t)qemu_real_host_page_size;
     if (qemu_host_page_size == 0) {
         qemu_host_page_size = qemu_real_host_page_size;
     }
     if (qemu_host_page_size < TARGET_PAGE_SIZE) {
         qemu_host_page_size = TARGET_PAGE_SIZE;
     }
-    qemu_host_page_mask = ~(qemu_host_page_size - 1);
+    qemu_host_page_mask = -(intptr_t)qemu_host_page_size;
 }
 
 static void page_init(void)

diff --git a/translate-common.c b/translate-common.c
index 619feb466ec1f8056f9fbfaf9eb51c9ae4b15dc8..171222d03722d37f1558546a2b45889872add3b4 100644 (file)
--- a/translate-common.c
+++ b/translate-common.c
@@ -21,7 +21,7 @@
 #include "qom/cpu.h"
 
 uintptr_t qemu_real_host_page_size;
-uintptr_t qemu_real_host_page_mask;
+intptr_t qemu_real_host_page_mask;
 
 #ifndef CONFIG_USER_ONLY
 /* mask must never be zero, except for A20 change call */