From: David Woodhouse <dwmw@xxxxxxxxxxxx>
The swap_pages function expects the swap page to be in %r10, but there
was no documentation to that effect. Once upon a time the setup code
used to load its value from a kernel virtual address and save it to an
address which is accessible in the identity-mapped page tables, and
*happened* to use %r10 to do so, with no comment that it was left there
on *purpose* instead of just being a scratch register. Once that was no
longer necessary, %r10 just holds whatever the kernel happened to leave
in it.
Now that the original value passed by the kernel is accessible via
%rip-relative addressing, load directly from there instead of using %r10
for it. But document the other parameters that the swap_pages function
*does* expect in registers.
Fixes: b3adabae8a96 ("x86/kexec: Drop page_list argument from relocate_kernel()")
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
arch/x86/kernel/relocate_kernel_64.S | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 1a52e4339c1d..0d6fce1e0a32 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -264,6 +264,10 @@ SYM_CODE_END(virtual_mapped)
/* Do the copies */
SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
UNWIND_HINT_END_OF_STACK
+ /*
+ * %rdi indirection page
+ * %r11 preserve_context
+ */
movq %rdi, %rcx /* Put the indirection_page in %rcx */
xorl %edi, %edi
xorl %esi, %esi
@@ -302,7 +306,7 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
jz .Lnoswap
/* copy source page to swap page */
- movq %r10, %rdi
+ movq kexec_pa_swap_page(%rip), %rdi
movl $512, %ecx
rep ; movsq
@@ -314,7 +318,7 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
/* copy swap page to destination page */
movq %rdx, %rdi
- movq %r10, %rsi
+ movq kexec_pa_swap_page(%rip), %rsi
.Lnoswap:
movl $512, %ecx
rep ; movsq
--
2.47.0
