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>

6 files changed, 45 insertions, 8 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
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 27285143adeb..a0b426978d55 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -116,7 +116,7 @@ _start:
         # Part 2 of the header, from the old setup.S
 
                 .ascii  "HdrS"          # header signature
-                .word   0x0209          # header version number (>= 0x0105)
+                .word   0x020a          # header version number (>= 0x0105)
                                         # or else old loadlin-1.5 will fail)
                 .globl realmode_swtch
 realmode_swtch: .word   0, 0            # default_switch, SETUPSEG
@@ -201,7 +201,7 @@ relocatable_kernel:    .byte 1
 #else
 relocatable_kernel:    .byte 0
 #endif
-pad2:                   .byte 0
+min_alignment:          .byte MIN_KERNEL_ALIGN_LG2      # minimum alignment
 pad3:                   .word 0
 
 cmdline_size:   .long   COMMAND_LINE_SIZE-1     #length of the command line,
@@ -220,6 +220,17 @@ setup_data:		.quad 0			# 64-bit physical pointer to
                                                 # single linked list of
                                                 # struct setup_data
 
+pref_address:           .quad LOAD_PHYSICAL_ADDR        # preferred load addr
+
+#define ZO_INIT_SIZE    (ZO__end - ZO_startup_32 + ZO_extract_offset)
+#define VO_INIT_SIZE    (VO__end - VO__text)
+#if ZO_INIT_SIZE > VO_INIT_SIZE
+#define INIT_SIZE ZO_INIT_SIZE
+#else
+#define INIT_SIZE VO_INIT_SIZE
+#endif
+init_size:              .long INIT_SIZE         # kernel initialization size
+
 # End of setup header #####################################################
 
         .section ".inittext", "ax"
diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h
index 6ba23dd9fc92..418e632d4a80 100644
--- a/arch/x86/include/asm/boot.h
+++ b/arch/x86/include/asm/boot.h
@@ -8,11 +8,26 @@
 
 #ifdef __KERNEL__
 
+#include <asm/page_types.h>
+
 /* Physical address where kernel should be loaded. */
 #define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \
                                 + (CONFIG_PHYSICAL_ALIGN - 1)) \
                                 & ~(CONFIG_PHYSICAL_ALIGN - 1))
 
+/* Minimum kernel alignment, as a power of two */
+#ifdef CONFIG_x86_64
+#define MIN_KERNEL_ALIGN_LG2    PMD_SHIFT
+#else
+#define MIN_KERNEL_ALIGN_LG2    (PAGE_SHIFT+1)
+#endif
+#define MIN_KERNEL_ALIGN        (_AC(1, UL) << MIN_KERNEL_ALIGN_LG2)
+
+#if (CONFIG_PHYSICAL_ALIGN & (CONFIG_PHYSICAL_ALIGN-1)) || \
+        (CONFIG_PHYSICAL_ALIGN < (_AC(1, UL) << MIN_KERNEL_ALIGN_LG2))
+#error "Invalid value for CONFIG_PHYSICAL_ALIGN"
+#endif
+
 #ifdef CONFIG_KERNEL_BZIP2
 #define BOOT_HEAP_SIZE             0x400000
 #else /* !CONFIG_KERNEL_BZIP2 */
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index 5a6aa1c1162f..1a830cbd7015 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -146,4 +146,5 @@ void foo(void)
         OFFSET(BP_loadflags, boot_params, hdr.loadflags);
         OFFSET(BP_hardware_subarch, boot_params, hdr.hardware_subarch);
         OFFSET(BP_version, boot_params, hdr.version);
+        OFFSET(BP_kernel_alignment, boot_params, hdr.kernel_alignment);
 }
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index e72f062fb4b5..898ecc47e129 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -125,6 +125,7 @@ int main(void)
         OFFSET(BP_loadflags, boot_params, hdr.loadflags);
         OFFSET(BP_hardware_subarch, boot_params, hdr.hardware_subarch);
         OFFSET(BP_version, boot_params, hdr.version);
+        OFFSET(BP_kernel_alignment, boot_params, hdr.kernel_alignment);
 
         BLANK();
         DEFINE(PAGE_SIZE_asm, PAGE_SIZE);