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x86/mm: Clean up register saving in the __enc_copy() assembly code

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Clean up the use of PUSH and POP and when registers are saved in the
__enc_copy() assembly function in order to improve the readability of the code.

Move parameter register saving into general purpose registers earlier
in the code and move all the pushes to the beginning of the function
with corresponding pops at the end.

We do this to prepare fixes.

Tested-by: Gabriel Craciunescu <nix.or.die@gmail.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180110192556.6026.74187.stgit@tlendack-t1.amdoffice.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Tom Lendacky 2018-01-10 13:25:56 -06:00 committed by Ingo Molnar
parent 327867faa4
commit 1303880179
1 changed files with 12 additions and 12 deletions
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24
arch/x86/mm/mem_encrypt_boot.S
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@ -103,21 +103,20 @@ ENTRY(__enc_copy)
orq $X86_CR4_PGE, %rdx
mov %rdx, %cr4
/* Set the PAT register PA5 entry to write-protect */
push %rcx
movl $MSR_IA32_CR_PAT, %ecx
rdmsr
push %rdx /* Save original PAT value */
andl $0xffff00ff, %edx /* Clear PA5 */
orl $0x00000500, %edx /* Set PA5 to WP */
wrmsr
pop %rdx /* RDX contains original PAT value */
pop %rcx
push %r15
movq %rcx, %r9 /* Save kernel length */
movq %rdi, %r10 /* Save encrypted kernel address */
movq %rsi, %r11 /* Save decrypted kernel address */
/* Set the PAT register PA5 entry to write-protect */
movl $MSR_IA32_CR_PAT, %ecx
rdmsr
mov %rdx, %r15 /* Save original PAT value */
andl $0xffff00ff, %edx /* Clear PA5 */
orl $0x00000500, %edx /* Set PA5 to WP */
wrmsr
wbinvd /* Invalidate any cache entries */
/* Copy/encrypt 2MB at a time */
@ -138,12 +137,13 @@ ENTRY(__enc_copy)
jnz 1b /* Kernel length not zero? */
/* Restore PAT register */
push %rdx /* Save original PAT value */
movl $MSR_IA32_CR_PAT, %ecx
rdmsr
pop %rdx /* Restore original PAT value */
mov %r15, %rdx /* Restore original PAT value */
wrmsr
pop %r15
ret
.L__enc_copy_end:
ENDPROC(__enc_copy)