[Xen-devel] [PATCH v4 04/19] x86/boot/reloc: reduce assembly usage as much as possible

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

Next patch will leave just required jmp instruction
in xen/x86/boot/reloc.c.

Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
---
 xen/arch/x86/boot/build32.lds |    1 +
 xen/arch/x86/boot/build32.mk  |    2 +-
 xen/arch/x86/boot/reloc.c     |   52 ++++++++++++++++++++---------------------
 3 files changed, 27 insertions(+), 28 deletions(-)

diff --git a/xen/arch/x86/boot/build32.lds b/xen/arch/x86/boot/build32.lds
index b14c7d5..a658ca8 100644
--- a/xen/arch/x86/boot/build32.lds
+++ b/xen/arch/x86/boot/build32.lds
@@ -24,6 +24,7 @@ SECTIONS
         *(.text)
         *(.text.*)
         *(.rodata)
+        *(.bss)
   }
 
   /DISCARD/ : {
diff --git a/xen/arch/x86/boot/build32.mk b/xen/arch/x86/boot/build32.mk
index eb02b4b..d54d259 100644
--- a/xen/arch/x86/boot/build32.mk
+++ b/xen/arch/x86/boot/build32.mk
@@ -23,7 +23,7 @@ CFLAGS := $(filter-out -flto,$(CFLAGS))
        $(OBJDUMP) -h $< | sed -n '/[0-9]/{s,00*,0,g;p;}' |\
                while read idx name sz rest; do \
                        case "$$name" in \
-                       .data|.data.*|.rodata.*|.bss|.bss.*) \
+                       .data|.data.*|.rodata.*|.bss.*) \
                                test $$sz != 0 || continue; \
                                echo "Error: non-empty $$name: 0x$$sz" >&2; \
                                exit $$(expr $$idx + 1);; \
diff --git a/xen/arch/x86/boot/reloc.c b/xen/arch/x86/boot/reloc.c
index 63045c0..9ae42e2 100644
--- a/xen/arch/x86/boot/reloc.c
+++ b/xen/arch/x86/boot/reloc.c
@@ -15,39 +15,33 @@ asm (
     "    .text                         \n"
     "    .globl _start                 \n"
     "_start:                           \n"
-    "    call 1f                       \n"
-    "1:  pop  %ebx                     \n"
-    "    mov  %eax,alloc-1b(%ebx)      \n"
-    "    jmp  reloc                    \n"
-    );
-
-/*
- * This is our data. Because the code must be relocatable, no BSS is
- * allowed. All data is accessed PC-relative with inline assembly.
- */
-asm (
-    "alloc:                            \n"
-    "    .long 0                       \n"
+    "    push %eax                     \n"
+    "    push 0x8(%esp)                \n"
+    "    call reloc                    \n"
+    "    ret  $0x4                     \n"
     );
 
 typedef unsigned int u32;
 #include "../../../include/xen/multiboot.h"
 
+#define __stdcall      __attribute__((__stdcall__))
+
+#define ALIGN_UP(arg, align) \
+                (((arg) + (align) - 1) & ~((typeof(arg))(align) - 1))
+
+static u32 alloc;
+
 static void *reloc_mbi_struct(void *old, unsigned int bytes)
 {
     void *new;
-    asm(
-    "    call 1f                      \n"
-    "1:  pop  %%edx                   \n"
-    "    mov  alloc-1b(%%edx),%0      \n"
-    "    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;
+
+    alloc -= ALIGN_UP(bytes, 16);
+    new = (void *)alloc;
+
+    while ( bytes-- )
+        *(char *)new++ = *(char *)old++;
+
+    return (void *)alloc;
 }
 
 static char *reloc_mbi_string(char *old)
@@ -58,11 +52,15 @@ static char *reloc_mbi_string(char *old)
     return reloc_mbi_struct(old, p - old + 1);
 }
 
-multiboot_info_t *reloc(multiboot_info_t *mbi_old)
+multiboot_info_t __stdcall *reloc(multiboot_info_t *mbi_old, u32 trampoline)
 {
-    multiboot_info_t *mbi = reloc_mbi_struct(mbi_old, sizeof(*mbi));
+    multiboot_info_t *mbi;
     int i;
 
+    alloc = trampoline;
+
+    mbi = reloc_mbi_struct(mbi_old, sizeof(*mbi));
+
     if ( mbi->flags & MBI_CMDLINE )
         mbi->cmdline = (u32)reloc_mbi_string((char *)mbi->cmdline);
 
-- 
1.7.10.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel