x86, boot: make kernel_alignment adjustable; new bzImage fields

Make the kernel_alignment field adjustable; this allows us to set it
to a large value (intended to be 16 MB to avoid ZONE_DMA contention,
memory holes and other weirdness) while a smart bootloader can still
force a loading at a lesser alignment if absolutely necessary.

Also export pref_address (preferred loading address, corresponding to
the link-time address) and init_size, the total amount of linear
memory the kernel will require during initialization.

[ Impact: allows better kernel placement, gives bootloader more info ]

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

2 files changed, 15 insertions, 6 deletions

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 2b8e0dfa4b27..75e4f001e706 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -69,8 +69,11 @@ ENTRY(startup_32)
 
 #ifdef CONFIG_RELOCATABLE
         movl    %ebp, %ebx
-        addl    $(CONFIG_PHYSICAL_ALIGN - 1), %ebx
-        andl    $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebx
+        movl    BP_kernel_alignment(%esi), %eax
+        decl    %eax
+        addl    %eax, %ebx
+        notl    %eax
+        andl    %eax, %ebx
 #else
         movl    $LOAD_PHYSICAL_ADDR, %ebx
 #endif
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 2bb500af1bd7..f62c284db9eb 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -84,8 +84,11 @@ ENTRY(startup_32)
 
 #ifdef CONFIG_RELOCATABLE
         movl    %ebp, %ebx
-        addl    $(PMD_PAGE_SIZE -1), %ebx
-        andl    $PMD_PAGE_MASK, %ebx
+        movl    BP_kernel_alignment(%esi), %eax
+        decl    %eax
+        addl    %eax, %ebx
+        notl    %eax
+        andl    %eax, %ebx
 #else
         movl    $LOAD_PHYSICAL_ADDR, %ebx
 #endif
@@ -224,8 +227,11 @@ ENTRY(startup_64)
         /* Start with the delta to where the kernel will run at. */
 #ifdef CONFIG_RELOCATABLE
         leaq    startup_32(%rip) /* - $startup_32 */, %rbp
-        addq    $(PMD_PAGE_SIZE - 1), %rbp
-        andq    $PMD_PAGE_MASK, %rbp
+        movl    BP_kernel_alignment(%rsi), %eax
+        decl    %eax
+        addq    %rax, %rbp
+        notq    %rax
+        andq    %rax, %rbp
 #else
         movq    $LOAD_PHYSICAL_ADDR, %rbp
 #endif