[Xen-devel] [PATCH v2 05/23] x86/boot/reloc: create generic alloc and copy functions

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

Create generic alloc and copy functions. We need
separate tools for memory allocation and copy to
provide multiboot2 protocol support.

Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
v2 - suggestions/fixes:
   - generalize new functions names
     (suggested by Jan Beulich),
   - reduce number of casts
     (suggested by Jan Beulich).
---
 xen/arch/x86/boot/reloc.c |   59 ++++++++++++++++++++++++++++-----------------
 1 file changed, 37 insertions(+), 22 deletions(-)

diff --git a/xen/arch/x86/boot/reloc.c b/xen/arch/x86/boot/reloc.c
index 708898f..09fd540 100644
--- a/xen/arch/x86/boot/reloc.c
+++ b/xen/arch/x86/boot/reloc.c
@@ -45,9 +45,10 @@ asm (
 typedef unsigned int u32;
 #include "../../../include/xen/multiboot.h"
 
-static void *reloc_mbi_struct(void *old, unsigned int bytes)
+static u32 alloc_mem(u32 bytes)
 {
-    void *new;
+    u32 s;
+
     asm(
     "    call 1f                      \n"
     "1:  pop  %%edx                   \n"
@@ -55,50 +56,64 @@ static void *reloc_mbi_struct(void *old, unsigned int bytes)
     "    sub  %1,%0                   \n"
     "    and  $~15,%0                 \n"
     "    mov  %0,alloc-1b(%%edx)      \n"
-    "    mov  %0,%%edi                \n"
-    "    rep  movsb                   \n"
-       : "=&r" (new), "+c" (bytes), "+S" (old)
-       : : "edx", "edi", "memory");
-    return new;
+       : "=&r" (s) : "r" (bytes) : "edx", "memory");
+
+    return s;
 }
 
-static char *reloc_mbi_string(char *old)
+static u32 copy_mem(u32 src, u32 bytes)
 {
-    char *p;
-    for ( p = old; *p != '\0'; p++ )
+    u32 dst, dst_asm;
+
+    dst = alloc_mem(bytes);
+    dst_asm = dst;
+
+    asm volatile("rep movsb" : "+S" (src), "+D" (dst_asm), "+c" (bytes) : : 
"memory");
+
+    return dst;
+}
+
+static u32 copy_string(u32 src)
+{
+    u32 p;
+
+    if ( src == 0 )
+        return 0;
+
+    for ( p = src; *(char *)p != '\0'; p++ )
         continue;
-    return reloc_mbi_struct(old, p - old + 1);
+
+    return copy_mem(src, p - src + 1);
 }
 
-multiboot_info_t *reloc(multiboot_info_t *mbi_old)
+multiboot_info_t *reloc(u32 mbi_old)
 {
-    multiboot_info_t *mbi = reloc_mbi_struct(mbi_old, sizeof(*mbi));
+    multiboot_info_t *mbi = (multiboot_info_t *)copy_mem(mbi_old, 
sizeof(*mbi));
     int i;
 
     if ( mbi->flags & MBI_CMDLINE )
-        mbi->cmdline = (u32)reloc_mbi_string((char *)mbi->cmdline);
+        mbi->cmdline = copy_string(mbi->cmdline);
 
     if ( mbi->flags & MBI_MODULES )
     {
-        module_t *mods = reloc_mbi_struct(
-            (module_t *)mbi->mods_addr, mbi->mods_count * sizeof(module_t));
+        module_t *mods;
 
-        mbi->mods_addr = (u32)mods;
+        mbi->mods_addr = copy_mem(mbi->mods_addr, mbi->mods_count * 
sizeof(module_t));
+
+        mods = (module_t *)mbi->mods_addr;
 
         for ( i = 0; i < mbi->mods_count; i++ )
         {
             if ( mods[i].string )
-                mods[i].string = (u32)reloc_mbi_string((char *)mods[i].string);
+                mods[i].string = copy_string(mods[i].string);
         }
     }
 
     if ( mbi->flags & MBI_MEMMAP )
-        mbi->mmap_addr = (u32)reloc_mbi_struct(
-            (memory_map_t *)mbi->mmap_addr, mbi->mmap_length);
+        mbi->mmap_addr = copy_mem(mbi->mmap_addr, mbi->mmap_length);
 
     if ( mbi->flags & MBI_LOADERNAME )
-        mbi->boot_loader_name = (u32)reloc_mbi_string(
-            (char *)mbi->boot_loader_name);
+        mbi->boot_loader_name = copy_string(mbi->boot_loader_name);
 
     /* Mask features we don't understand or don't relocate. */
     mbi->flags &= (MBI_MEMLIMITS |
-- 
1.7.10.4


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