x86/boot/compressed/32: Save the output address instead of recalculating it
In preparation for being able to decompress into a buffer starting at a different address than startup_32, save the calculated output address instead of recalculating it later. We now keep track of three addresses: %edx: startup_32 as we were loaded by bootloader %ebx: new location of compressed kernel %ebp: start of decompression buffer Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200303221205.4048668-2-nivedita@alum.mit.edu Link: https://lore.kernel.org/r/20200308080859.21568-16-ardb@kernel.org
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arch/x86/boot/compressed
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@ -75,11 +75,11 @@ SYM_FUNC_START(startup_32)
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*/
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leal (BP_scratch+4)(%esi), %esp
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call 1f
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1: popl %ebp
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subl $1b, %ebp
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1: popl %edx
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subl $1b, %edx
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/* Load new GDT */
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leal gdt(%ebp), %eax
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leal gdt(%edx), %eax
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movl %eax, 2(%eax)
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lgdt (%eax)
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@ -92,13 +92,14 @@ SYM_FUNC_START(startup_32)
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movl %eax, %ss
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/*
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* %ebp contains the address we are loaded at by the boot loader and %ebx
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* %edx contains the address we are loaded at by the boot loader and %ebx
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* contains the address where we should move the kernel image temporarily
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* for safe in-place decompression.
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* for safe in-place decompression. %ebp contains the address that the kernel
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* will be decompressed to.
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*/
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#ifdef CONFIG_RELOCATABLE
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movl %ebp, %ebx
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movl %edx, %ebx
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movl BP_kernel_alignment(%esi), %eax
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decl %eax
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addl %eax, %ebx
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@ -110,10 +111,10 @@ SYM_FUNC_START(startup_32)
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movl $LOAD_PHYSICAL_ADDR, %ebx
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1:
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movl %ebx, %ebp // Save the output address for later
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/* Target address to relocate to for decompression */
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movl BP_init_size(%esi), %eax
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subl $_end, %eax
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addl %eax, %ebx
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addl BP_init_size(%esi), %ebx
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subl $_end, %ebx
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/* Set up the stack */
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leal boot_stack_end(%ebx), %esp
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@ -127,7 +128,7 @@ SYM_FUNC_START(startup_32)
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* where decompression in place becomes safe.
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*/
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pushl %esi
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leal (_bss-4)(%ebp), %esi
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leal (_bss-4)(%edx), %esi
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leal (_bss-4)(%ebx), %edi
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movl $(_bss - startup_32), %ecx
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shrl $2, %ecx
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@ -196,9 +197,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
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/* push arguments for extract_kernel: */
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pushl $z_output_len /* decompressed length, end of relocs */
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leal _end(%ebx), %eax
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subl BP_init_size(%esi), %eax
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pushl %eax /* output address */
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pushl %ebp /* output address */
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pushl $z_input_len /* input_len */
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leal input_data(%ebx), %eax
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