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x86: misc boot/link tweaking
* Introduce symbols bounding the multiboot1 header, which helps clarify that
it is data and not code corruption when viewing the disassembly.
* Move the __high_start symbol to its implementation, and declare it
correctly as ENTRY()
* Move the l1_identmap construction to be with all the other pagetables, and
within __page_tables_{start,end}. This won't affect the EFI relocation
algorithm, as l1_identmap contains no relocations.
* Move the cpu0_stack alignment check to the linker. Chances are very good
that a binary with a misaligned stack won't get as far as the test.
* Use MB() in linker script.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
This commit is contained in:
Andrew Cooper authored and 
Jan Beulich committed
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@@ -23,7 +23,7 @@ ENTRY(start)
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jmp __start
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.align 4
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/*** MULTIBOOT HEADER ****/
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multiboot1_header_start: /*** MULTIBOOT1 HEADER ****/
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#define MULTIBOOT_HEADER_FLAGS (MULTIBOOT_HEADER_MODS_ALIGNED | \
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MULTIBOOT_HEADER_WANT_MEMORY)
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/* Magic number indicating a Multiboot header. */
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@@ -32,6 +32,7 @@ ENTRY(start)
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.long MULTIBOOT_HEADER_FLAGS
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/* Checksum: must be the negated sum of the first two fields. */
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.long -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
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multiboot1_header_end:
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.section .init.rodata, "a", @progbits
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.align 4
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@@ -212,27 +213,4 @@ ENTRY(trampoline_start)
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#include "trampoline.S"
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GLOBAL(trampoline_end)
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.text
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__high_start:
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#include "x86_64.S"
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.section .data.page_aligned, "aw", @progbits
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.p2align PAGE_SHIFT
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/*
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* Mapping of first 2 megabytes of memory. This is mapped with 4kB mappings
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* to avoid type conflicts with fixed-range MTRRs covering the lowest megabyte
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* of physical memory. In any case the VGA hole should be mapped with type UC.
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*/
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GLOBAL(l1_identmap)
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pfn = 0
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.rept L1_PAGETABLE_ENTRIES
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/* VGA hole (0xa0000-0xc0000) should be mapped UC. */
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.if pfn >= 0xa0 && pfn < 0xc0
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.long (pfn << PAGE_SHIFT) | PAGE_HYPERVISOR_NOCACHE | MAP_SMALL_PAGES
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.else
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.long (pfn << PAGE_SHIFT) | PAGE_HYPERVISOR | MAP_SMALL_PAGES
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.endif
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.long 0
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pfn = pfn + 1
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.endr
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.size l1_identmap, . - l1_identmap
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@@ -1,5 +1,7 @@
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.text
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.code64
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ENTRY(__high_start)
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/* Install relocated data selectors. */
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lgdt gdt_descr(%rip)
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mov $(__HYPERVISOR_DS64),%ecx
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@@ -80,6 +82,24 @@ GLOBAL(boot_cpu_compat_gdt_table)
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.align PAGE_SIZE, 0
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GLOBAL(__page_tables_start)
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/*
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* Mapping of first 2 megabytes of memory. This is mapped with 4kB mappings
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* to avoid type conflicts with fixed-range MTRRs covering the lowest megabyte
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* of physical memory. In any case the VGA hole should be mapped with type UC.
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*/
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GLOBAL(l1_identmap)
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pfn = 0
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.rept L1_PAGETABLE_ENTRIES
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/* VGA hole (0xa0000-0xc0000) should be mapped UC. */
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.if pfn >= 0xa0 && pfn < 0xc0
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.long (pfn << PAGE_SHIFT) | PAGE_HYPERVISOR_NOCACHE | MAP_SMALL_PAGES
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.else
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.long (pfn << PAGE_SHIFT) | PAGE_HYPERVISOR | MAP_SMALL_PAGES
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.endif
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.long 0
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pfn = pfn + 1
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.endr
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.size l1_identmap, . - l1_identmap
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/* Mapping of first 16 megabytes of memory. */
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GLOBAL(l2_identmap)
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@@ -674,9 +674,6 @@ void __init noreturn __start_xen(unsigned long mbi_p)
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if ( !(mbi->flags & MBI_MODULES) || (mbi->mods_count == 0) )
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panic("dom0 kernel not specified. Check bootloader configuration.");
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if ( ((unsigned long)cpu0_stack & (STACK_SIZE-1)) != 0 )
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panic("Misaligned CPU0 stack.");
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if ( efi_enabled )
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{
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set_pdx_range(xen_phys_start >> PAGE_SHIFT,
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@@ -38,7 +38,7 @@ SECTIONS
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. = __XEN_VIRT_START;
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__image_base__ = .;
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#endif
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. = __XEN_VIRT_START + 0x100000;
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. = __XEN_VIRT_START + MB(1);
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_start = .;
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.text : {
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_stext = .; /* Text and read-only data */
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@@ -187,7 +187,7 @@ SECTIONS
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/* Trick the linker into setting the image size to exactly 16Mb. */
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. = ALIGN(__section_alignment__);
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.pad : {
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. = ALIGN(0x1000000);
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. = ALIGN(MB(16));
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} :text
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#else
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efi = .;
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@@ -221,3 +221,4 @@ ASSERT(__image_base__ > XEN_VIRT_START ||
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_end <= XEN_VIRT_END - NR_CPUS * PAGE_SIZE,
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"Xen image overlaps stubs area")
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ASSERT(kexec_reloc_size - kexec_reloc <= PAGE_SIZE, "kexec_reloc is too large")
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ASSERT((cpu0_stack & (STACK_SIZE - 1)) == 0, "cpu0_stack misaligned")
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