LoongArch: Simplify the processing of jumping new kernel for KASLR

Modified relocate_kernel() doesn't return new kernel's entry point but
the random_offset. In this way we share the start_kernel() processing
with the normal kernel, which avoids calling 'jr a0' directly and allows
some other operations (e.g, kasan_early_init) before start_kernel() when
KASLR (CONFIG_RANDOMIZE_BASE) is turned on.

Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/include/asm/setup.h
index 7c68b43..a0bc159 100644 (file)
--- a/arch/loongarch/include/asm/setup.h
+++ b/arch/loongarch/include/asm/setup.h
@@ -34,7 +34,7 @@ extern long __la_abs_end;
 extern long __rela_dyn_begin;
 extern long __rela_dyn_end;
 
-extern void * __init relocate_kernel(void);
+extern unsigned long __init relocate_kernel(void);
 
 #endif
 

diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index 5e828a8..5743fef 100644 (file)
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -95,13 +95,14 @@ SYM_CODE_START(kernel_entry)                        # kernel entry point
        PTR_LI          sp, (_THREAD_SIZE - PT_SIZE)
        PTR_ADD         sp, sp, tp
        set_saved_sp    sp, t0, t1
-#endif
 
-       /* relocate_kernel() returns the new kernel entry point */
-       jr              a0
-       ASM_BUG()
+       /* Jump to the new kernel: new_pc = current_pc + random_offset */
+       pcaddi          t0, 0
+       add.d           t0, t0, a0
+       jirl            zero, t0, 0xc
+#endif /* CONFIG_RANDOMIZE_BASE */
 
-#endif
+#endif /* CONFIG_RELOCATABLE */
 
        bl              start_kernel
        ASM_BUG()

diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
index 01f94d1..6c3eff9 100644 (file)
--- a/arch/loongarch/kernel/relocate.c
+++ b/arch/loongarch/kernel/relocate.c
@@ -157,12 +157,11 @@ static inline void __init update_reloc_offset(unsigned long *addr, long random_o
        *new_addr = (unsigned long)reloc_offset;
 }
 
-void * __init relocate_kernel(void)
+unsigned long __init relocate_kernel(void)
 {
        unsigned long kernel_length;
        unsigned long random_offset = 0;
        void *location_new = _text; /* Default to original kernel start */
-       void *kernel_entry = start_kernel; /* Default to original kernel entry point */
        char *cmdline = early_ioremap(fw_arg1, COMMAND_LINE_SIZE); /* Boot command line is passed in fw_arg1 */
 
        strscpy(boot_command_line, cmdline, COMMAND_LINE_SIZE);
@@ -190,9 +189,6 @@ void * __init relocate_kernel(void)
 
                reloc_offset += random_offset;
 
-               /* Return the new kernel's entry point */
-               kernel_entry = RELOCATED_KASLR(start_kernel);
-
                /* The current thread is now within the relocated kernel */
                __current_thread_info = RELOCATED_KASLR(__current_thread_info);
 
@@ -204,7 +200,7 @@ void * __init relocate_kernel(void)
 
        relocate_absolute(random_offset);
 
-       return kernel_entry;
+       return random_offset;
 }
 
 /*