Jan Beulich
2011-Aug-17 14:45 UTC
[Xen-devel] [PATCH 1/2] x86: make run-time part of trampoline relocatable
In order to eliminate an initial hack in the EFI boot code (where
memory for the trampoline was just "claimed" instead of properly
allocated), the trampoline code must no longer make assumption on the
address at which it would be located. For the time being, the fixed
address is being retained for the traditional multiboot path.
As an additional benefit (at least from my pov) it allows confining
the visibility of the BOOT_TRAMPOLINE definition to just the boot
code.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
--- a/xen/arch/x86/boot/Makefile
+++ b/xen/arch/x86/boot/Makefile
@@ -2,8 +2,8 @@ obj-bin-y += head.o
head.o: reloc.S
-BOOT_TRAMPOLINE := $(shell sed -n
''s,^\#define[[:space:]]\{1\,\}BOOT_TRAMPOLINE[[:space:]]\{1\,\},,p''
$(BASEDIR)/include/asm-x86/config.h)
+BOOT_TRAMPOLINE := $(shell sed -n
''s,^\#define[[:space:]]\{1\,\}BOOT_TRAMPOLINE[[:space:]]\{1\,\},,p''
head.S)
%.S: %.c
RELOC=$(BOOT_TRAMPOLINE) $(MAKE) -f build32.mk $@
-reloc.S: $(BASEDIR)/include/asm-x86/config.h
+reloc.S: head.S
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -9,7 +9,7 @@
.text
.code32
-#undef bootsym_phys
+#define BOOT_TRAMPOLINE 0x7c000
#define sym_phys(sym) ((sym) - __XEN_VIRT_START)
#define bootsym_phys(sym) ((sym) - trampoline_start + BOOT_TRAMPOLINE)
@@ -189,6 +189,17 @@ __start:
mov %edi,sym_phys(idle_pg_table_l2) + (__PAGE_OFFSET>>18)
#endif
+ /* Apply relocations to bootstrap trampoline. */
+ mov $BOOT_TRAMPOLINE,%edx
+ mov $sym_phys(__trampoline_rel_start),%edi
+ mov %edx,sym_phys(trampoline_phys)
+1:
+ mov (%edi),%eax
+ add %edx,(%edi,%eax)
+ add $4,%edi
+ cmp $sym_phys(__trampoline_rel_stop),%edi
+ jb 1b
+
/* Copy bootstrap trampoline to low memory, below 1MB. */
mov $sym_phys(trampoline_start),%esi
mov $bootsym_phys(trampoline_start),%edi
--- a/xen/arch/x86/boot/trampoline.S
+++ b/xen/arch/x86/boot/trampoline.S
@@ -4,6 +4,13 @@
#undef bootsym
#define bootsym(s) ((s)-trampoline_start)
+#define bootsym_rel(sym, off, opnd...) \
+ bootsym(sym),##opnd; \
+111:; \
+ .pushsection .trampoline_rel, "a"; \
+ .long 111b - (off) - .; \
+ .popsection
+
.globl trampoline_realmode_entry
trampoline_realmode_entry:
mov %cs,%ax
@@ -17,11 +24,11 @@ trampoline_realmode_entry:
xor %ax, %ax
inc %ax
lmsw %ax # CR0.PE = 1 (enter protected mode)
- ljmpl $BOOT_CS32,$bootsym_phys(trampoline_protmode_entry)
+ ljmpl $BOOT_CS32,$bootsym_rel(trampoline_protmode_entry,6)
idt_48: .word 0, 0, 0 # base = limit = 0
gdt_48: .word 6*8-1
- .long bootsym_phys(trampoline_gdt)
+ .long bootsym_rel(trampoline_gdt,4)
trampoline_gdt:
/* 0x0000: unused */
.quad 0x0000000000000000
@@ -32,11 +39,16 @@ trampoline_gdt:
/* 0x0018: ring 0 data */
.quad 0x00cf92000000ffff
/* 0x0020: real-mode code @ BOOT_TRAMPOLINE */
- .long 0x0000ffff | ((BOOT_TRAMPOLINE & 0x00ffff) << 16)
- .long 0x00009a00 | ((BOOT_TRAMPOLINE & 0xff0000) >> 16)
+ .long 0x0000ffff
+ .long 0x00009a00
/* 0x0028: real-mode data @ BOOT_TRAMPOLINE */
- .long 0x0000ffff | ((BOOT_TRAMPOLINE & 0x00ffff) << 16)
- .long 0x00009200 | ((BOOT_TRAMPOLINE & 0xff0000) >> 16)
+ .long 0x0000ffff
+ .long 0x00009200
+
+ .pushsection .trampoline_rel, "a"
+ .long trampoline_gdt + BOOT_PSEUDORM_CS + 2 - .
+ .long trampoline_gdt + BOOT_PSEUDORM_DS + 2 - .
+ .popsection
.globl cpuid_ext_features
cpuid_ext_features:
@@ -66,11 +78,11 @@ trampoline_protmode_entry:
/* Load pagetable base register. */
mov $sym_phys(idle_pg_table),%eax
- add bootsym_phys(trampoline_xen_phys_start),%eax
+ add bootsym_rel(trampoline_xen_phys_start,4,%eax)
mov %eax,%cr3
/* Set up EFER (Extended Feature Enable Register). */
- mov bootsym_phys(cpuid_ext_features),%edi
+ mov bootsym_rel(cpuid_ext_features,4,%edi)
test $0x20100800,%edi /* SYSCALL/SYSRET, No Execute, Long Mode? */
jz .Lskip_efer
movl $MSR_EFER,%ecx
@@ -93,7 +105,7 @@ trampoline_protmode_entry:
#if defined(__x86_64__)
/* Now in compatibility mode. Long-jump into 64-bit mode. */
- ljmp $BOOT_CS64,$bootsym_phys(start64)
+ ljmp $BOOT_CS64,$bootsym_rel(start64,6)
.code64
start64:
--- a/xen/arch/x86/boot/wakeup.S
+++ b/xen/arch/x86/boot/wakeup.S
@@ -42,15 +42,13 @@ ENTRY(wakeup_start)
# boot trampoline is under 1M, and shift its start into
# %fs to reference symbols in that area
- movl $BOOT_TRAMPOLINE, %eax
- shrl $4, %eax
- movl %eax, %fs
+ mov wakesym(trampoline_seg), %fs
lidt %fs:bootsym(idt_48)
lgdt %fs:bootsym(gdt_48)
movw $1, %ax
lmsw %ax # Turn on CR0.PE
- ljmpl $BOOT_CS32, $bootsym_phys(wakeup_32)
+ ljmpl $BOOT_CS32, $bootsym_rel(wakeup_32, 6)
/* This code uses an extended set of video mode numbers. These include:
* Aliases for standard modes
@@ -103,6 +101,10 @@ real_magic: .long 0x12345678
.globl video_mode, video_flags
video_mode: .long 0
video_flags: .long 0
+trampoline_seg: .word BOOT_TRAMPOLINE >> 4
+ .pushsection .trampoline_seg, "a"
+ .long trampoline_seg - .
+ .popsection
.code32
@@ -114,11 +116,11 @@ wakeup_32:
mov $BOOT_DS, %eax
mov %eax, %ds
mov %eax, %ss
- mov $bootsym_phys(early_stack), %esp
+ mov $bootsym_rel(early_stack, 4, %esp)
# check saved magic again
mov $sym_phys(saved_magic), %eax
- add bootsym_phys(trampoline_xen_phys_start), %eax
+ add bootsym_rel(trampoline_xen_phys_start, 4, %eax)
mov (%eax), %eax
cmp $0x9abcdef0, %eax
jne bogus_saved_magic
@@ -131,12 +133,12 @@ wakeup_32:
/* Load pagetable base register */
mov $sym_phys(idle_pg_table),%eax
- add bootsym_phys(trampoline_xen_phys_start),%eax
+ add bootsym_rel(trampoline_xen_phys_start,4,%eax)
mov %eax,%cr3
/* Will cpuid feature change after resume? */
/* Set up EFER (Extended Feature Enable Register). */
- mov bootsym_phys(cpuid_ext_features),%edi
+ mov bootsym_rel(cpuid_ext_features,4,%edi)
test $0x20100800,%edi /* SYSCALL/SYSRET, No Execute, Long Mode? */
jz .Lskip_eferw
movl $MSR_EFER,%ecx
@@ -162,7 +164,7 @@ wakeup_32:
#if defined(__x86_64__)
/* Now in compatibility mode. Long-jump to 64-bit mode */
- ljmp $BOOT_CS64, $bootsym_phys(wakeup_64)
+ ljmp $BOOT_CS64, $bootsym_rel(wakeup_64,6)
.code64
wakeup_64:
--- a/xen/arch/x86/efi/boot.c
+++ b/xen/arch/x86/efi/boot.c
@@ -599,6 +599,9 @@ static void __init relocate_image(unsign
}
}
+extern const s32 __trampoline_rel_start[], __trampoline_rel_stop[];
+extern const s32 __trampoline_seg_start[], __trampoline_seg_stop[];
+
void EFIAPI __init __attribute__((__noreturn__))
efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
{
@@ -614,9 +617,10 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SY
EFI_GRAPHICS_OUTPUT_MODE_INFORMATION *mode_info;
EFI_FILE_HANDLE dir_handle;
union string section = { NULL }, name;
+ const s32 *trampoline_ptr;
struct e820entry *e;
u64 efer;
- bool_t base_video = 0, trampoline_okay = 0;
+ bool_t base_video = 0;
efi_ih = ImageHandle;
efi_bs = SystemTable->BootServices;
@@ -914,15 +918,27 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SY
dmi_efi_get_table((void *)(long)efi.smbios);
/* Allocate space for trampoline (in first Mb). */
- cfg.addr = BOOT_TRAMPOLINE;
+ cfg.addr = 0x100000;
cfg.size = trampoline_end - trampoline_start;
- status = efi_bs->AllocatePages(AllocateAddress, EfiLoaderData,
+ status = efi_bs->AllocatePages(AllocateMaxAddress, EfiLoaderData,
PFN_UP(cfg.size), &cfg.addr);
if ( EFI_ERROR(status) )
{
cfg.addr = 0;
- PrintErr(L"Note: Trampoline area is in use\r\n");
+ blexit(L"No memory for trampoline\r\n");
}
+ trampoline_phys = cfg.addr;
+ /* Apply relocations to trampoline. */
+ for ( trampoline_ptr = __trampoline_rel_start;
+ trampoline_ptr < __trampoline_rel_stop;
+ ++trampoline_ptr )
+ *(u32 *)(*trampoline_ptr + (long)trampoline_ptr) ++
trampoline_phys;
+ for ( trampoline_ptr = __trampoline_seg_start;
+ trampoline_ptr < __trampoline_seg_stop;
+ ++trampoline_ptr )
+ *(u16 *)(*trampoline_ptr + (long)trampoline_ptr) +
trampoline_phys >> 4;
/* Initialise L2 identity-map and xen page table entries (16MB). */
for ( i = 0; i < 8; ++i )
@@ -1096,14 +1112,8 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SY
e->type = type;
++e820nr;
}
- if ( type == E820_RAM && e->addr <= BOOT_TRAMPOLINE
&&
- e->addr + e->size >= BOOT_TRAMPOLINE + cfg.size )
- trampoline_okay = 1;
}
- if ( !trampoline_okay )
- blexit(L"Trampoline area unavailable\r\n");
-
status = efi_bs->ExitBootServices(ImageHandle, map_key);
if ( EFI_ERROR(status) )
PrintErrMesg(L"Cannot exit boot services", status);
@@ -1117,7 +1127,7 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SY
efi_fw_vendor = (void *)efi_fw_vendor + DIRECTMAP_VIRT_START;
relocate_image(__XEN_VIRT_START - xen_phys_start);
- memcpy((void *)(long)BOOT_TRAMPOLINE, trampoline_start, cfg.size);
+ memcpy((void *)trampoline_phys, trampoline_start, cfg.size);
/* Set system registers and transfer control. */
asm volatile("pushq $0\n\tpopfq");
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -48,6 +48,8 @@
#define setup_trampoline() (bootsym_phys(trampoline_realmode_entry))
+unsigned long __read_mostly trampoline_phys;
+
/* representing HT siblings of each logical CPU */
DEFINE_PER_CPU_READ_MOSTLY(cpumask_t, cpu_sibling_map);
/* representing HT and core siblings of each logical CPU */
--- a/xen/arch/x86/x86_32/mm.c
+++ b/xen/arch/x86/x86_32/mm.c
@@ -166,8 +166,9 @@ void __init zap_low_mappings(l2_pgentry_
flush_all(FLUSH_TLB_GLOBAL);
/* Replace with mapping of the boot trampoline only. */
- map_pages_to_xen(BOOT_TRAMPOLINE, BOOT_TRAMPOLINE >> PAGE_SHIFT,
- 0x10, __PAGE_HYPERVISOR);
+ map_pages_to_xen(trampoline_phys, trampoline_phys >> PAGE_SHIFT,
+ PFN_UP(trampoline_end - trampoline_start),
+ __PAGE_HYPERVISOR);
}
void __init subarch_init_memory(void)
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -829,7 +829,7 @@ void __init zap_low_mappings(void)
flush_local(FLUSH_TLB_GLOBAL);
/* Replace with mapping of the boot trampoline only. */
- map_pages_to_xen(BOOT_TRAMPOLINE, BOOT_TRAMPOLINE >> PAGE_SHIFT,
+ map_pages_to_xen(trampoline_phys, trampoline_phys >> PAGE_SHIFT,
PFN_UP(trampoline_end - trampoline_start),
__PAGE_HYPERVISOR);
}
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -103,6 +103,13 @@ SECTIONS
*(.init.data)
*(.init.data.rel)
*(.init.data.rel.*)
+ . = ALIGN(4);
+ __trampoline_rel_start = .;
+ *(.trampoline_rel)
+ __trampoline_rel_stop = .;
+ __trampoline_seg_start = .;
+ *(.trampoline_seg)
+ __trampoline_seg_stop = .;
} :text
. = ALIGN(32);
.init.setup : {
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -95,13 +95,13 @@
/* Primary stack is restricted to 8kB by guard pages. */
#define PRIMARY_STACK_SIZE 8192
-#define BOOT_TRAMPOLINE 0x7c000
+#ifndef __ASSEMBLY__
+extern unsigned long trampoline_phys;
#define bootsym_phys(sym) \
- (((unsigned long)&(sym)-(unsigned
long)&trampoline_start)+BOOT_TRAMPOLINE)
+ (((unsigned long)&(sym)-(unsigned
long)&trampoline_start)+trampoline_phys)
#define bootsym(sym) \
(*RELOC_HIDE((typeof(&(sym)))__va(__pa(&(sym))), \
- BOOT_TRAMPOLINE-__pa(trampoline_start)))
-#ifndef __ASSEMBLY__
+ trampoline_phys-__pa(trampoline_start)))
extern char trampoline_start[], trampoline_end[];
extern char trampoline_realmode_entry[];
extern unsigned int trampoline_xen_phys_start;
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