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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v14 4/9] x86: add multiboot2 protocol support for EFI platforms
On Thu, Feb 02, 2017 at 11:01:14PM +0100, 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>
> ---
> v14 - suggestions/fixes:
> - mark .init.data section as writable; by the way we must change
> similar definition in xen/arch/x86/boot/x86_64.S because otherwise
> compiler complains about section types conflicts
> (suggested by Jan Beulich),
> - use %r15 instead of %r15d
> (suggested by Jan Beulich),
> - remove redundant add from UEFI stack alignment
> (suggested by Jan Beulich),
> - use "mov (%rsp),%rdi" instead of "pop %rdi/push %rdi"
> (suggested by Jan Beulich),
> - return void instead of paddr_t from efi_multiboot2()
> and then simplify a bit trampoline setup assembly
> (suggested by Jan Beulich),
> - remove "(XEN)" from efi_multiboot2() stub error messages
> (suggested by Jan Beulich),
> - move err from inline assembly OutputOperands to InputOperands in
> stub.c:efi_multiboot2(); this way we avoid following compile time error:
> stub.c: In function ‘efi_multiboot2’:
> stub.c:36:5: error: read-only variable ‘err’ used as ‘asm’ output
> asm volatile(
> ^~~
> issue was introduced by changing err type to "static const CHAR16
> __initconst";
> potentially we can revert this change but move to InputOperands looks
> better IMO;
> even if we are not able to specify %rdx in Clobbers; simply we do not
> care
> because next instruction after call is hlt
> (discovered by Konrad Rzeszutek Wilk and Marcos Matsunaga),
> - take into account MBI_SPACE_MIN in ASSERT((trampoline_end -
> trampoline_start) < ...)
> (suggested by Jan Beulich),
> - improve comments
> (suggested by Jan Beulich).
Diff as Doug asked:
diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index 2ecdcb3..5147204 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -116,7 +116,7 @@ gdt_boot_descr:
.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
+ .section .init.data, "aw", @progbits
.align 4
vga_text_buffer:
@@ -173,9 +173,10 @@ not_multiboot:
__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.
+ * 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 truncate
+ * addresses to 32-bits in most cases below.
*/
cld
@@ -188,7 +189,7 @@ __efi64_mb2_start:
je .Lefi_multiboot2_proto
/* Jump to not_multiboot after switching CPU to x86_32 mode. */
- lea not_multiboot(%rip),%r15d
+ lea not_multiboot(%rip),%r15
jmp x86_32_switch
.Lefi_multiboot2_proto:
@@ -248,28 +249,34 @@ __efi64_mb2_start:
cmpb $0,efi_platform(%rip)
/* Jump to .Lmb2_no_bs after switching CPU to x86_32 mode. */
- lea .Lmb2_no_bs(%rip),%r15d
+ lea .Lmb2_no_bs(%rip),%r15
jz x86_32_switch
/* Is EFI SystemTable address provided by boot loader? */
test %rsi,%rsi
/* Jump to .Lmb2_no_st after switching CPU to x86_32 mode. */
- lea .Lmb2_no_st(%rip),%r15d
+ lea .Lmb2_no_st(%rip),%r15
jz x86_32_switch
/* Is EFI ImageHandle address provided by boot loader? */
test %rdi,%rdi
/* Jump to .Lmb2_no_ih after switching CPU to x86_32 mode. */
- lea .Lmb2_no_ih(%rip),%r15d
+ lea .Lmb2_no_ih(%rip),%r15
jz x86_32_switch
- /* Align the stack as UEFI spec requires. */
- add $15,%rsp
+ /*
+ * Align the stack as UEFI spec requires. Keep it aligned
+ * before efi_multiboot2() call by pushing/popping even
+ * numbers of items on it.
+ */
and $~15,%rsp
+ /* Save Multiboot2 magic on the stack. */
push %rax
+
+ /* Save EFI ImageHandle on the stack. */
push %rdi
/*
@@ -284,34 +291,26 @@ __efi64_mb2_start:
xor %eax,%eax
rep stosq
- pop %rdi
-
- /* Align the stack as UEFI spec requires. */
- push %rdi
+ /* Keep the stack aligned. Do not pop a single item off it. */
+ mov (%rsp),%rdi
/*
* efi_multiboot2() is called according to System V AMD64 ABI:
- * - 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
- * on legacy BIOS platforms.
+ * - IN: %rdi - EFI ImageHandle, %rsi - EFI SystemTable.
*/
call efi_multiboot2
- /* Convert memory address to bytes/16 and store it in safe place. */
- shr $4,%eax
- mov %eax,%ecx
+ /* Just pop an item from the stack. */
+ pop %rax
- pop %rdi
+ /* Restore Multiboot2 magic. */
pop %rax
/* Jump to trampoline_setup after switching CPU to x86_32 mode. */
- lea trampoline_setup(%rip),%r15d
+ lea trampoline_setup(%rip),%r15
x86_32_switch:
- mov %r15d,%edi
+ mov %r15,%rdi
cli
@@ -428,46 +427,49 @@ trampoline_bios_setup:
* multiboot structure (if available) and use the smallest.
*/
cmp $0x100,%edx /* is the multiboot value too small? */
- jb trampoline_setup /* if so, do not use it */
+ jb 2f /* if so, do not use it */
shl $10-4,%edx
cmp %ecx,%edx /* compare with BDA value */
cmovb %edx,%ecx /* and use the smaller */
+2:
/* 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:
shl $4, %ecx
mov %ecx,sym_phys(trampoline_phys)
- /* Get topmost low-memory stack address. */
+trampoline_setup:
+ mov sym_phys(trampoline_phys),%ecx
+
+ /* Get bottom-most 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 /* Topmost low-memory stack address. */
+ push %ecx /* Bottom-most 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):
+ * Now trampoline_phys points to the following structure (lowest
address
+ * is at the bottom):
*
* +------------------------+
- * | TRAMPOLINE_SPACE |
- * +- - - - - - - - - - - - +
- * | mbi struct |
- * +------------------------+
* | TRAMPOLINE_STACK_SPACE |
* +------------------------+
+ * | mbi data |
+ * +- - - - - - - - - - - - +
+ * | TRAMPOLINE_SPACE |
+ * +------------------------+
*
- * mbi struct lives at the end of TRAMPOLINE_SPACE. The rest of
- * TRAMPOLINE_SPACE is reserved for trampoline code and data.
+ * mbi data grows downwards from the highest address of
TRAMPOLINE_SPACE
+ * region to the end of the trampoline. The rest of TRAMPOLINE_SPACE is
+ * reserved for trampoline code and data.
*/
/*
diff --git a/xen/arch/x86/boot/x86_64.S b/xen/arch/x86/boot/x86_64.S
index 139b2ca..4d507fb 100644
--- a/xen/arch/x86/boot/x86_64.S
+++ b/xen/arch/x86/boot/x86_64.S
@@ -186,7 +186,7 @@ GLOBAL(idle_pg_table)
GLOBAL(__page_tables_end)
/* Init pagetables. Enough page directories to map into the bottom 1GB. */
- .section .init.data, "a", @progbits
+ .section .init.data, "aw", @progbits
.align PAGE_SIZE, 0
GLOBAL(l2_bootmap)
diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index d193847..94418bf 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -665,7 +665,7 @@ static bool_t __init
efi_arch_use_config_file(EFI_SYSTEM_TABLE *SystemTable)
static void efi_arch_flush_dcache_area(const void *vaddr, UINTN size) { }
-paddr_t __init efi_multiboot2(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE
*SystemTable)
+void __init efi_multiboot2(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE
*SystemTable)
{
EFI_GRAPHICS_OUTPUT_PROTOCOL *gop;
UINTN cols, gop_mode = ~0, rows;
@@ -698,9 +698,6 @@ paddr_t __init efi_multiboot2(EFI_HANDLE ImageHandle,
EFI_SYSTEM_TABLE *SystemTa
efi_set_gop_mode(gop, gop_mode);
efi_exit_boot(ImageHandle, SystemTable);
-
- /* Return trampoline address. */
- return trampoline_phys;
}
/*
diff --git a/xen/arch/x86/efi/stub.c b/xen/arch/x86/efi/stub.c
index 8df9ba2..2127cce 100644
--- a/xen/arch/x86/efi/stub.c
+++ b/xen/arch/x86/efi/stub.c
@@ -17,11 +17,11 @@
* efi_multiboot2() is an exception. Please look below for more details.
*/
-paddr_t __init noreturn efi_multiboot2(EFI_HANDLE ImageHandle,
- EFI_SYSTEM_TABLE *SystemTable)
+void __init noreturn efi_multiboot2(EFI_HANDLE ImageHandle,
+ EFI_SYSTEM_TABLE *SystemTable)
{
static const CHAR16 __initconst err[] =
- L"(XEN) Xen does not have EFI code build in!\r\n(XEN) System
halted!\r\n";
+ L"Xen does not have EFI code build in!\r\nSystem halted!\r\n";
SIMPLE_TEXT_OUTPUT_INTERFACE *StdErr;
StdErr = SystemTable->StdErr ? SystemTable->StdErr : SystemTable->ConOut;
@@ -37,7 +37,7 @@ paddr_t __init noreturn efi_multiboot2(EFI_HANDLE ImageHandle,
" call *%2 \n"
"0: hlt \n"
" jmp 0b \n"
- : "+c" (StdErr), "+d" (err) : "rm" (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 addf2ef..76e18ab 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) < TRAMPOLINE_SPACE,
- "not enough room for trampoline")
+ASSERT((trampoline_end - trampoline_start) < TRAMPOLINE_SPACE - MBI_SPACE_MIN,
+ "not enough room for trampoline and mbi data")
diff --git a/xen/include/asm-x86/config.h b/xen/include/asm-x86/config.h
index 9cd05a2..b9a6d94 100644
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -76,6 +76,8 @@
#define TRAMPOLINE_STACK_SPACE PAGE_SIZE
#define TRAMPOLINE_SPACE (KB(64) - TRAMPOLINE_STACK_SPACE)
+#define MBI_SPACE_MIN (2 * PAGE_SIZE)
+
/* Primary stack is restricted to 8kB by guard pages. */
#define PRIMARY_STACK_SIZE 8192
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