feat: 基于汇编实现内核对用户态内存清零的功能

背景：LOS_UserMemClear接口原有实现是通过在内核中
申请一块堆内存并对其清零，调用copy_to_user来达到
对用户态内存清零的目的，需要使用堆内存。
修改方案：基于汇编实现内核对用户态内存清零的功能。

close #I3XXT0

Change-Id: I27cb1e45559cb75a9b330799fe427abd54f51c15
Signed-off-by: NHaryslee <lihao189@huawei.com>

arch/arm/arm/include/arm_user_clear.h

+/*
+ * Copyright (c) 2021-2021 Huawei Device Co., Ltd. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list
+ *    of conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be used
+ *    to endorse or promote products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _ARM_USER_CLEAR_H
+#define _ARM_USER_CLEAR_H
+
+#include "los_typedef.h"
+
+#ifdef __cplusplus
+#if __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+#endif /* __cplusplus */
+
+size_t _arm_clear_user(void *addr, size_t bytes);
+
+#ifdef __cplusplus
+#if __cplusplus
+}
+#endif /* __cplusplus */
+#endif /* __cplusplus */
+
+#endif /* _ARM_USER_CLEAR_H */

arch/arm/arm/src/clear_user.S

+/*
+ * Copyright (c) 2021-2021 Huawei Device Co., Ltd. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list
+ *    of conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be used
+ *    to endorse or promote products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "asm.h"
+
+.syntax unified
+.arm
+
+// size_t _arm_clear_user(void *addr, size_t bytes)
+FUNCTION(_arm_clear_user)
+    push    {r0-r6, lr}
+    cmp     r1, #0
+    beq     .Lclear_user_return
+    tst     r0, #7
+    beq     .Lclear_user_aligned
+
+.Lclear_user_byte:
+    mov     r2, #0
+0:  strb    r2, [r0], #1
+    subs    r1, r1, #1
+    beq     .Lclear_user_return
+    tst     r0, #7
+    bne     0b
+
+.Lclear_user_aligned:
+    eor     r3, r3
+    eor     r4, r4
+    bics    r2, r1, #15
+    bne     .Lclear_user_16bytes
+    bics    r2, r1, #7
+    bne     .Lclear_user_8bytes
+    b       .Lclear_user_remaining
+
+.Lclear_user_16bytes:
+    eor     r5, r5
+    eor     r6, r6
+1:  stmia   r0!, {r3, r4, r5, r6}
+    subs    r2, r2, #16
+    bne     1b
+    ands    r1, r1, #15
+    beq     .Lclear_user_return
+    bics    r2, r1, #7
+    beq     .Lclear_user_remaining
+
+.Lclear_user_8bytes:
+2:  stmia   r0!, {r3, r4}
+    ands    r1, r1, #7
+    beq     .Lclear_user_return
+
+.Lclear_user_remaining:
+    mov     r2, #0
+3:  strb    r2, [r0], #1
+    subs    r1, r1, #1
+    bne     3b
+
+.Lclear_user_return:
+    pop     {r0-r6, lr}
+    mov     r0, #0
+    bx      lr
+
+.Lclear_user_err:
+    pop     {r0, r1}
+    sub     r0, r2, r0
+    sub     r0, r1, r0
+    pop     {r2-r6, lr}
+    bx      lr
+
+.pushsection __exc_table, "a"
+    .long   0b,  .Lclear_user_err
+    .long   1b,  .Lclear_user_err
+    .long   2b,  .Lclear_user_err
+    .long   3b,  .Lclear_user_err
+.popsection

arch/arm/arm/src/user_copy.c

@@ -31,6 +31,7 @@
 
 #include "user_copy.h"
 #include "arm_user_copy.h"
+#include "arm_user_clear.h"
 #include "securec.h"
 #include "los_memory.h"
 #include "los_vm_map.h"
@@ -96,15 +97,9 @@ INT32 LOS_UserMemClear(unsigned char *buf, UINT32 len)
     if (!LOS_IsUserAddressRange((vaddr_t)(UINTPTR)buf, len)) {
         (VOID)memset_s(buf, len, 0, len);
     } else {
-        unsigned char *tmp = (unsigned char *)LOS_MemAlloc(OS_SYS_MEM_ADDR, len);
-        if (tmp == NULL) {
-            return -ENOMEM;
+        if (_arm_clear_user(buf, len)) {
+            return -EFAULT;
         }
-        (VOID)memset_s(tmp, len, 0, len);
-        if (_arm_user_copy(buf, tmp, len) != 0) {
-            ret = -EFAULT;
-        }
-        LOS_MemFree(OS_SYS_MEM_ADDR, tmp);
     }
     return ret;
 }

kernel/extended/dynload/src/los_load_elf.c

@@ -416,42 +416,20 @@ INT32 OsGetKernelVaddr(const LosVmSpace *space, VADDR_T vaddr, VADDR_T *kvaddr)
 
 STATIC INT32 OsSetBss(const LD_ELF_PHDR *elfPhdr, INT32 fd, UINTPTR bssStart, UINT32 bssEnd, UINT32 elfProt)
 {
-    UINTPTR bssPageStart, bssStartPageAlign, bssEndPageAlign;
+    UINTPTR bssStartPageAlign, bssEndPageAlign;
     UINTPTR mapBase;
-    UINT32 offset, size;
     UINT32 bssMapSize;
     INT32 stackFlags;
     INT32 ret;
-    vaddr_t kvaddr = 0;
 
-    bssPageStart = ROUNDDOWN(bssStart, PAGE_SIZE);
     bssStartPageAlign = ROUNDUP(bssStart, PAGE_SIZE);
     bssEndPageAlign = ROUNDUP(bssEnd, PAGE_SIZE);
-    ret = LOS_UnMMap(bssPageStart, (bssEndPageAlign - bssPageStart));
-    if ((ret != LOS_OK) && (bssPageStart != 0)) {
-        PRINT_ERR("%s[%d], Failed to unmap a region, vaddr: %#x!\n", __FUNCTION__, __LINE__, bssPageStart);
-    }
 
-    ret = LOS_UserSpaceVmAlloc(OsCurrProcessGet()->vmSpace, PAGE_SIZE, (VOID **)&bssPageStart,
-                               0, OsCvtProtFlagsToRegionFlags(elfProt, MAP_FIXED));
-    if (ret != LOS_OK) {
-        PRINT_ERR("%s[%d], Failed to do vmm alloc!\n", __FUNCTION__, __LINE__);
-        return -ENOMEM;
-    }
-    ret = OsGetKernelVaddr(OsCurrProcessGet()->vmSpace, bssPageStart, &kvaddr);
-    if (ret != LOS_OK) {
-        PRINT_ERR("%s[%d]\n", __FUNCTION__, __LINE__);
+    ret = LOS_UserMemClear((VOID *)bssStart, PAGE_SIZE - ROUNDOFFSET(bssStart, PAGE_SIZE));
+    if (ret != 0) {
+        PRINT_ERR("%s[%d], Failed to clear bss\n", __FUNCTION__, __LINE__);
         return -EFAULT;
     }
-    (VOID)memset_s((VOID *)(UINTPTR)kvaddr, PAGE_SIZE, 0, PAGE_SIZE);
-
-    offset = ROUNDDOWN(elfPhdr->offset + elfPhdr->fileSize, PAGE_SIZE);
-    size = ROUNDOFFSET(elfPhdr->offset + elfPhdr->fileSize, PAGE_SIZE);
-    ret = OsReadELFInfo(fd, (UINT8 *)(UINTPTR)kvaddr, size, offset);
-    if (ret != LOS_OK) {
-        PRINT_ERR("%s[%d]\n", __FUNCTION__, __LINE__);
-        return -EIO;
-    }
 
     bssMapSize = bssEndPageAlign - bssStartPageAlign;
     if (bssMapSize > 0) {