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6e0b52d406
sme_encrypt_execute() stashes the stack pointer on entry into %rbp
because it allocates a one-page stack in the non-encrypted area for the
encryption routine to use. When the latter is done, it restores it from
%rbp again, before returning.
However, it uses the FRAME_* macros partially but restores %rsp from
%rbp explicitly with a MOV. And this is fine as long as the macros
*actually* do something.
Unless, you do a !CONFIG_FRAME_POINTER build where those macros
are empty. Then, we still restore %rsp from %rbp but %rbp contains
*something* and this leads to a stack corruption. The manifestation
being a triple-fault during early boot when testing SME. Good luck to me
debugging this with the clumsy endless-loop-in-asm method and narrowing
it down gradually. :-(
So, long story short, open-code the frame macros so that there's no
monkey business and we avoid subtly breaking SME depending on the
.config.
Fixes: 6ebcb06071 ("x86/mm: Add support to encrypt the kernel in-place")
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Link: http://lkml.kernel.org/r/20170827163924.25552-1-bp@alien8.de
150 lines
4.4 KiB
ArmAsm
150 lines
4.4 KiB
ArmAsm
/*
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* AMD Memory Encryption Support
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*
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* Copyright (C) 2016 Advanced Micro Devices, Inc.
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*
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* Author: Tom Lendacky <thomas.lendacky@amd.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/linkage.h>
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#include <asm/pgtable.h>
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#include <asm/page.h>
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#include <asm/processor-flags.h>
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#include <asm/msr-index.h>
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.text
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.code64
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ENTRY(sme_encrypt_execute)
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/*
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* Entry parameters:
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* RDI - virtual address for the encrypted kernel mapping
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* RSI - virtual address for the decrypted kernel mapping
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* RDX - length of kernel
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* RCX - virtual address of the encryption workarea, including:
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* - stack page (PAGE_SIZE)
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* - encryption routine page (PAGE_SIZE)
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* - intermediate copy buffer (PMD_PAGE_SIZE)
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* R8 - physcial address of the pagetables to use for encryption
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*/
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push %rbp
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movq %rsp, %rbp /* RBP now has original stack pointer */
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/* Set up a one page stack in the non-encrypted memory area */
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movq %rcx, %rax /* Workarea stack page */
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leaq PAGE_SIZE(%rax), %rsp /* Set new stack pointer */
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addq $PAGE_SIZE, %rax /* Workarea encryption routine */
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push %r12
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movq %rdi, %r10 /* Encrypted kernel */
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movq %rsi, %r11 /* Decrypted kernel */
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movq %rdx, %r12 /* Kernel length */
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/* Copy encryption routine into the workarea */
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movq %rax, %rdi /* Workarea encryption routine */
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leaq __enc_copy(%rip), %rsi /* Encryption routine */
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movq $(.L__enc_copy_end - __enc_copy), %rcx /* Encryption routine length */
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rep movsb
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/* Setup registers for call */
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movq %r10, %rdi /* Encrypted kernel */
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movq %r11, %rsi /* Decrypted kernel */
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movq %r8, %rdx /* Pagetables used for encryption */
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movq %r12, %rcx /* Kernel length */
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movq %rax, %r8 /* Workarea encryption routine */
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addq $PAGE_SIZE, %r8 /* Workarea intermediate copy buffer */
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call *%rax /* Call the encryption routine */
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pop %r12
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movq %rbp, %rsp /* Restore original stack pointer */
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pop %rbp
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ret
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ENDPROC(sme_encrypt_execute)
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ENTRY(__enc_copy)
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/*
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* Routine used to encrypt kernel.
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* This routine must be run outside of the kernel proper since
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* the kernel will be encrypted during the process. So this
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* routine is defined here and then copied to an area outside
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* of the kernel where it will remain and run decrypted
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* during execution.
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*
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* On entry the registers must be:
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* RDI - virtual address for the encrypted kernel mapping
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* RSI - virtual address for the decrypted kernel mapping
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* RDX - address of the pagetables to use for encryption
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* RCX - length of kernel
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* R8 - intermediate copy buffer
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*
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* RAX - points to this routine
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*
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* The kernel will be encrypted by copying from the non-encrypted
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* kernel space to an intermediate buffer and then copying from the
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* intermediate buffer back to the encrypted kernel space. The physical
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* addresses of the two kernel space mappings are the same which
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* results in the kernel being encrypted "in place".
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*/
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/* Enable the new page tables */
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mov %rdx, %cr3
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/* Flush any global TLBs */
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mov %cr4, %rdx
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andq $~X86_CR4_PGE, %rdx
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mov %rdx, %cr4
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orq $X86_CR4_PGE, %rdx
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mov %rdx, %cr4
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/* Set the PAT register PA5 entry to write-protect */
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push %rcx
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movl $MSR_IA32_CR_PAT, %ecx
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rdmsr
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push %rdx /* Save original PAT value */
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andl $0xffff00ff, %edx /* Clear PA5 */
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orl $0x00000500, %edx /* Set PA5 to WP */
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wrmsr
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pop %rdx /* RDX contains original PAT value */
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pop %rcx
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movq %rcx, %r9 /* Save kernel length */
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movq %rdi, %r10 /* Save encrypted kernel address */
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movq %rsi, %r11 /* Save decrypted kernel address */
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wbinvd /* Invalidate any cache entries */
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/* Copy/encrypt 2MB at a time */
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1:
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movq %r11, %rsi /* Source - decrypted kernel */
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movq %r8, %rdi /* Dest - intermediate copy buffer */
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movq $PMD_PAGE_SIZE, %rcx /* 2MB length */
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rep movsb
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movq %r8, %rsi /* Source - intermediate copy buffer */
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movq %r10, %rdi /* Dest - encrypted kernel */
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movq $PMD_PAGE_SIZE, %rcx /* 2MB length */
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rep movsb
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addq $PMD_PAGE_SIZE, %r11
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addq $PMD_PAGE_SIZE, %r10
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subq $PMD_PAGE_SIZE, %r9 /* Kernel length decrement */
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jnz 1b /* Kernel length not zero? */
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/* Restore PAT register */
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push %rdx /* Save original PAT value */
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movl $MSR_IA32_CR_PAT, %ecx
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rdmsr
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pop %rdx /* Restore original PAT value */
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wrmsr
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ret
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.L__enc_copy_end:
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ENDPROC(__enc_copy)
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