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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v13 4/9] x86: add multiboot2 protocol support for EFI platforms
On Wed, Jan 25, 2017 at 04:20:30PM -0600, Doug Goldstein wrote:
> On 1/25/17 4:11 PM, Daniel Kiper wrote:
> > This way Xen can be loaded on EFI platforms using GRUB2 and
> > other boot loaders which support multiboot2 protocol.
> >
> > Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
> > ---
> > v13 - suggestions/fixes:
> > - move vga_text_buffer and efi_platform to .init.data section
> > (suggested by Jan Beulich),
> > - reduce number of error branches in EFI code in
> > xen/arch/x86/boot/head.S
> > (suggested by Jan Beulich),
> > - rename run_bs label to .Lrun_bs
> > (suggested by Jan Beulich),
> > - align the stack as UEFI spec requires
> > (suggested by Jan Beulich),
> > - change trampoline region memory layout
> > (suggested by Jan Beulich),
> > - revert changes in efi_arch_pre_exit_boot()
> > (suggested by Jan Beulich),
> > - relocate_trampoline() must set trampoline_phys for all bootloaders;
> > otherwise fallback allocator is always used if Xen was loaded with
> > Multiboot2 protocol,
> > - change err type in efi_multiboot2() to "static const CHAR16
> > __initconst"
> > (suggested by Jan Beulich),
> > - change asm "g" constraint to "rm" in efi_multiboot2()
> > (suggested by Jan Beulich),
> > - improve comments
> > (suggested by Jan Beulich and Doug Goldstein).
>
> This is a huge change and would really be helpful to have the diff of
> what's changed to work from.
Please look below...
Daniel
diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index b8f727a..2ecdcb3 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -109,13 +109,6 @@ gdt_boot_descr:
.long sym_phys(trampoline_gdt)
.long 0 /* Needed for 64-bit lgdt */
- .align 4
-vga_text_buffer:
- .long 0xb8000
-
-efi_platform:
- .byte 0
-
.Lbad_cpu_msg: .asciz "ERR: Not a 64-bit CPU!"
.Lbad_ldr_msg: .asciz "ERR: Not a Multiboot bootloader!"
.Lbad_ldr_nbs: .asciz "ERR: Bootloader shutdown EFI x64 boot services!"
@@ -123,6 +116,15 @@ efi_platform:
.Lbad_ldr_nih: .asciz "ERR: EFI ImageHandle is not provided by bootloader!"
.Lbad_efi_msg: .asciz "ERR: EFI IA-32 platforms are not supported!"
+ .section .init.data, "a", @progbits
+ .align 4
+
+vga_text_buffer:
+ .long 0xb8000
+
+efi_platform:
+ .byte 0
+
.section .init.text, "ax", @progbits
bad_cpu:
@@ -170,6 +172,12 @@ not_multiboot:
.code64
__efi64_mb2_start:
+ /*
+ * Multiboot2 spec says that here CPU is in 64-bit mode. However, there
+ * is also guarantee that all code and data is always put by the
bootloader
+ * below 4 GiB. Hence, we can safely use in most cases 32-bit
addressing.
+ */
+
cld
/* VGA is not available on EFI platforms. */
@@ -180,7 +188,7 @@ __efi64_mb2_start:
je .Lefi_multiboot2_proto
/* Jump to not_multiboot after switching CPU to x86_32 mode. */
- lea not_multiboot(%rip),%edi
+ lea not_multiboot(%rip),%r15d
jmp x86_32_switch
.Lefi_multiboot2_proto:
@@ -197,7 +205,7 @@ __efi64_mb2_start:
mov %ecx,%r8d
sub %ebx,%r8d
cmp %r8d,MB2_fixed_total_size(%rbx)
- jbe run_bs
+ jbe .Lrun_bs
/* Are EFI boot services available? */
cmpl $MULTIBOOT2_TAG_TYPE_EFI_BS,MB2_tag_type(%rcx)
@@ -226,7 +234,7 @@ __efi64_mb2_start:
/* Is it the end of Multiboot2 information? */
cmpl $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%rcx)
- je run_bs
+ je .Lrun_bs
.Lefi_mb2_next_tag:
/* Go to next Multiboot2 information tag. */
@@ -235,34 +243,32 @@ __efi64_mb2_start:
and $~(MULTIBOOT2_TAG_ALIGN-1),%ecx
jmp .Lefi_mb2_tsize
-run_bs:
+.Lrun_bs:
/* Are EFI boot services available? */
cmpb $0,efi_platform(%rip)
- jnz 0f
/* Jump to .Lmb2_no_bs after switching CPU to x86_32 mode. */
- lea .Lmb2_no_bs(%rip),%edi
- jmp x86_32_switch
+ lea .Lmb2_no_bs(%rip),%r15d
+ jz x86_32_switch
-0:
/* Is EFI SystemTable address provided by boot loader? */
test %rsi,%rsi
- jnz 1f
/* Jump to .Lmb2_no_st after switching CPU to x86_32 mode. */
- lea .Lmb2_no_st(%rip),%edi
- jmp x86_32_switch
+ lea .Lmb2_no_st(%rip),%r15d
+ jz x86_32_switch
-1:
/* Is EFI ImageHandle address provided by boot loader? */
test %rdi,%rdi
- jnz 2f
/* Jump to .Lmb2_no_ih after switching CPU to x86_32 mode. */
- lea .Lmb2_no_ih(%rip),%edi
- jmp x86_32_switch
+ lea .Lmb2_no_ih(%rip),%r15d
+ jz x86_32_switch
+
+ /* Align the stack as UEFI spec requires. */
+ add $15,%rsp
+ and $~15,%rsp
-2:
push %rax
push %rdi
@@ -280,13 +286,13 @@ run_bs:
pop %rdi
+ /* Align the stack as UEFI spec requires. */
+ push %rdi
+
/*
* efi_multiboot2() is called according to System V AMD64 ABI:
- * - IN: %rdi - EFI ImageHandle, %rsi - EFI SystemTable,
- * - OUT: %rax - highest allocated memory address below 1 MiB;
- * memory below this address is used for trampoline
- * stack, trampoline itself and as a storage for
- * mbi struct created in reloc().
+ * - IN: %rdi - EFI ImageHandle, %rsi - EFI SystemTable,
+ * - OUT: %rax - trampoline address.
*
* MULTIBOOT2_TAG_TYPE_BASIC_MEMINFO tag is not provided
* on EFI platforms. Hence, it could not be used like
@@ -298,12 +304,15 @@ run_bs:
shr $4,%eax
mov %eax,%ecx
+ pop %rdi
pop %rax
/* Jump to trampoline_setup after switching CPU to x86_32 mode. */
- lea trampoline_setup(%rip),%edi
+ lea trampoline_setup(%rip),%r15d
x86_32_switch:
+ mov %r15d,%edi
+
cli
/* Initialize GDTR. */
@@ -424,26 +433,44 @@ trampoline_bios_setup:
cmp %ecx,%edx /* compare with BDA value */
cmovb %edx,%ecx /* and use the smaller */
- /* Reserve memory for the trampoline. */
- sub $((MB_TRAMPOLINE_SIZE+MB_TRAMPOLINE_STACK_SIZE)>>4),%ecx
+ /* Reserve memory for the trampoline and the low-memory stack. */
+ sub $((TRAMPOLINE_SPACE+TRAMPOLINE_STACK_SPACE)>>4),%ecx
/* From arch/x86/smpboot.c: start_eip had better be page-aligned! */
xor %cl, %cl
trampoline_setup:
- /* Save trampoline address for later use. */
shl $4, %ecx
mov %ecx,sym_phys(trampoline_phys)
+ /* Get topmost low-memory stack address. */
+ add $TRAMPOLINE_SPACE,%ecx
+
/* Save the Multiboot info struct (after relocation) for later use. */
mov $sym_phys(cpu0_stack)+1024,%esp
- push %ecx /* Boot trampoline address. */
+ push %ecx /* Topmost low-memory stack address. */
push %ebx /* Multiboot information address. */
push %eax /* Multiboot magic. */
call reloc
mov %eax,sym_phys(multiboot_ptr)
/*
+ * Now trampoline_phys points to the following structure (lowest
+ * address is at the top):
+ *
+ * +------------------------+
+ * | TRAMPOLINE_SPACE |
+ * +- - - - - - - - - - - - +
+ * | mbi struct |
+ * +------------------------+
+ * | TRAMPOLINE_STACK_SPACE |
+ * +------------------------+
+ *
+ * mbi struct lives at the end of TRAMPOLINE_SPACE. The rest of
+ * TRAMPOLINE_SPACE is reserved for trampoline code and data.
+ */
+
+ /*
* Do not zero BSS on EFI platform here.
* It was initialized earlier.
*/
@@ -526,7 +553,7 @@ trampoline_setup:
1:
/* Switch to low-memory stack which lives at the end of trampoline
region. */
mov sym_phys(trampoline_phys),%edi
- lea MB_TRAMPOLINE_SIZE+MB_TRAMPOLINE_STACK_SIZE(%edi),%esp
+ lea TRAMPOLINE_SPACE+TRAMPOLINE_STACK_SPACE(%edi),%esp
lea trampoline_boot_cpu_entry-trampoline_start(%edi),%eax
pushl $BOOT_CS32
push %eax
diff --git a/xen/arch/x86/boot/reloc.c b/xen/arch/x86/boot/reloc.c
index 0f2e372..b992678 100644
--- a/xen/arch/x86/boot/reloc.c
+++ b/xen/arch/x86/boot/reloc.c
@@ -16,7 +16,7 @@
* This entry point is entered from xen/arch/x86/boot/head.S with:
* - 0x4(%esp) = MULTIBOOT_MAGIC,
* - 0x8(%esp) = MULTIBOOT_INFORMATION_ADDRESS,
- * - 0xc(%esp) = BOOT_TRAMPOLINE_ADDRESS.
+ * - 0xc(%esp) = TOPMOST_LOW_MEMORY_STACK_ADDRESS.
*/
asm (
" .text \n"
@@ -235,3 +235,13 @@ multiboot_info_t __stdcall *reloc(u32 mb_magic, u32
mbi_in, u32 trampoline)
else
return mbi_reloc(mbi_in);
}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index c1285ad..d193847 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -100,10 +100,11 @@ static void __init relocate_trampoline(unsigned long phys)
{
const s32 *trampoline_ptr;
- if ( !efi_enabled(EFI_LOADER) || trampoline_phys )
+ trampoline_phys = phys;
+
+ if ( !efi_enabled(EFI_LOADER) )
return;
- trampoline_phys = phys;
/* Apply relocations to trampoline. */
for ( trampoline_ptr = __trampoline_rel_start;
trampoline_ptr < __trampoline_rel_stop;
@@ -213,10 +214,12 @@ static void *__init efi_arch_allocate_mmap_buffer(UINTN
map_size)
static void __init efi_arch_pre_exit_boot(void)
{
- if ( !cfg.addr )
- blexit(L"No memory for trampoline");
-
- relocate_trampoline(cfg.addr);
+ if ( !trampoline_phys )
+ {
+ if ( !cfg.addr )
+ blexit(L"No memory for trampoline");
+ relocate_trampoline(cfg.addr);
+ }
}
static void __init noreturn efi_arch_post_exit_boot(void)
@@ -555,7 +558,7 @@ static void __init efi_arch_memory_setup(void)
if ( efi_enabled(EFI_LOADER) )
cfg.size = trampoline_end - trampoline_start;
else
- cfg.size = MB_TRAMPOLINE_SIZE + MB_TRAMPOLINE_STACK_SIZE + MBI_SIZE;
+ cfg.size = TRAMPOLINE_SPACE + TRAMPOLINE_STACK_SPACE;
status = efi_bs->AllocatePages(AllocateMaxAddress, EfiLoaderData,
PFN_UP(cfg.size), &cfg.addr);
@@ -696,8 +699,8 @@ paddr_t __init efi_multiboot2(EFI_HANDLE ImageHandle,
EFI_SYSTEM_TABLE *SystemTa
efi_exit_boot(ImageHandle, SystemTable);
- /* Return highest allocated memory address below 1 MiB. */
- return cfg.addr + cfg.size;
+ /* Return trampoline address. */
+ return trampoline_phys;
}
/*
diff --git a/xen/arch/x86/efi/stub.c b/xen/arch/x86/efi/stub.c
index b81adc0..8df9ba2 100644
--- a/xen/arch/x86/efi/stub.c
+++ b/xen/arch/x86/efi/stub.c
@@ -20,7 +20,8 @@
paddr_t __init noreturn efi_multiboot2(EFI_HANDLE ImageHandle,
EFI_SYSTEM_TABLE *SystemTable)
{
- CHAR16 *err = L"Xen does not have EFI code build in!!!\r\nSystem
halted!!!\r\n";
+ static const CHAR16 __initconst err[] =
+ L"(XEN) Xen does not have EFI code build in!\r\n(XEN) System
halted!\r\n";
SIMPLE_TEXT_OUTPUT_INTERFACE *StdErr;
StdErr = SystemTable->StdErr ? SystemTable->StdErr : SystemTable->ConOut;
@@ -36,7 +37,7 @@ paddr_t __init noreturn efi_multiboot2(EFI_HANDLE ImageHandle,
" call *%2 \n"
"0: hlt \n"
" jmp 0b \n"
- : "+c" (StdErr), "+d" (err) : "g" (StdErr->OutputString)
+ : "+c" (StdErr), "+d" (err) : "rm" (StdErr->OutputString)
: "rax", "r8", "r9", "r10", "r11", "memory");
unreachable();
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 3a02b2b..addf2ef 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -334,5 +334,5 @@ ASSERT(IS_ALIGNED(trampoline_end, 4), "trampoline_end
misaligned")
ASSERT(IS_ALIGNED(__bss_start, 8), "__bss_start misaligned")
ASSERT(IS_ALIGNED(__bss_end, 8), "__bss_end misaligned")
-ASSERT((trampoline_end - trampoline_start) < MB_TRAMPOLINE_SIZE,
+ASSERT((trampoline_end - trampoline_start) < TRAMPOLINE_SPACE,
"not enough room for trampoline")
diff --git a/xen/include/asm-x86/config.h b/xen/include/asm-x86/config.h
index a86ea12..9cd05a2 100644
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -73,10 +73,8 @@
#define STACK_ORDER 3
#define STACK_SIZE (PAGE_SIZE << STACK_ORDER)
-#define MB_TRAMPOLINE_STACK_SIZE PAGE_SIZE
-#define MB_TRAMPOLINE_SIZE (KB(64) - MB_TRAMPOLINE_STACK_SIZE)
-
-#define MBI_SIZE (2 * PAGE_SIZE)
+#define TRAMPOLINE_STACK_SPACE PAGE_SIZE
+#define TRAMPOLINE_SPACE (KB(64) - TRAMPOLINE_STACK_SPACE)
/* Primary stack is restricted to 8kB by guard pages. */
#define PRIMARY_STACK_SIZE 8192
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