On Mon, Feb 01, 2021 at 12:47:20PM +0000, Mark Rutland wrote:
> 1. copy reloc code into buffer
> 2. alter variables in copy of reloc code
> 3. branch to buffer
>
> ... which would avoid this class of problem too.
Yep, slightly messy to do though:
diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 5d84ad333f05..6058e0d3a40d 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -174,18 +174,27 @@ void machine_kexec(struct kimage *image)
reboot_code_buffer = page_address(image->control_code_page);
- /* Prepare parameters for reboot_code_buffer*/
- set_kernel_text_rw();
- kexec_start_address = image->start;
- kexec_indirection_page = page_list;
- kexec_mach_type = machine_arch_type;
- kexec_boot_atags = image->arch.kernel_r2;
-
/* copy our kernel relocation code to the control code page */
reboot_entry = fncpy(reboot_code_buffer,
&relocate_new_kernel,
relocate_new_kernel_size);
+#define set(what, val) \
+ do { \
+ uintptr_t __funcp_address; \
+ int __offset; \
+ void *__ptr; \
+ asm("" : "=r" (__funcp_address) : "0" (&relocate_new_kernel)); \
+ __offset = (uintptr_t)&(what) - (__funcp_address & ~1); \
+ __ptr = reboot_code_buffer + __offset; \
+ *(__typeof__(&(what)))__ptr = val; \
+ } while (0)
+
+ set(kexec_start_address, image->start);
+ set(kexec_indirection_page, page_list);
+ set(kexec_mach_type, machine_arch_type);
+ set(kexec_boot_atags, image->arch.kernel_r2);
+
/* get the identity mapping physical address for the reboot code */
reboot_entry_phys = virt_to_idmap(reboot_entry);
--
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