[RFC PATCH v2 08/16] x86/kexec: Copy control page into place in machine_kexec_prepare()

[David Woodhouse]

From: David Woodhouse <d...@amazon.co.uk>

There's no need for this to wait until the actual machine_kexec() invocation;
a subsequent change will mark the control page ROX so all writes should be
completed earlier.

Signed-off-by: David Woodhouse <d...@amazon.co.uk>
---
 arch/x86/kernel/machine_kexec_64.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/machine_kexec_64.c 
b/arch/x86/kernel/machine_kexec_64.c
index 123e9544506b..60632a5a2a13 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -297,6 +297,8 @@ static void load_segments(void)
 int machine_kexec_prepare(struct kimage *image)
 {
        void *control_page = page_address(image->control_code_page) + PAGE_SIZE;
+       unsigned long reloc_start = (unsigned long)__relocate_kernel_start;
+       unsigned long reloc_end = (unsigned long)__relocate_kernel_end;
        unsigned long start_pgtable;
        int result;
 
@@ -308,6 +310,8 @@ int machine_kexec_prepare(struct kimage *image)
        if (result)
                return result;
 
+       __memcpy(control_page, __relocate_kernel_start, reloc_end - 
reloc_start);
+
        set_memory_x((unsigned long)control_page, 1);
 
        return 0;
@@ -334,7 +338,6 @@ void machine_kexec(struct kimage *image)
                                             unsigned int preserve_context,
                                             unsigned int host_mem_enc_active);
        unsigned long reloc_start = (unsigned long)__relocate_kernel_start;
-       unsigned long reloc_end = (unsigned long)__relocate_kernel_end;
        unsigned long page_list[PAGES_NR];
        unsigned int host_mem_enc_active;
        int save_ftrace_enabled;
@@ -372,7 +375,6 @@ void machine_kexec(struct kimage *image)
        }
 
        control_page = page_address(image->control_code_page) + PAGE_SIZE;
-       __memcpy(control_page, __relocate_kernel_start, reloc_end - 
reloc_start);
 
        page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page);
        page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;
-- 
2.47.0