@@ -79,6 +79,9 @@ FEXPORT(__kernel_entry)
j kernel_entry
#endif /* CONFIG_BOOT_RAW */
+#define PC_REGION_SHIFT 28
+#define PC_REGION_MASK (~(1 << PC_REGION_SHIFT - 1))
+
__REF
NESTED(kernel_entry, 16, sp) # kernel entry point
@@ -89,9 +92,17 @@ NESTED(kernel_entry, 16, sp) # kernel entry point
/* We might not get launched at the address the kernel is linked to,
so we jump there. */
- PTR_LA t0, 0f
- jr t0
-0:
+ PTR_LA t0, 1f
+ bal 1f
+1: move t1, ra
+ PTR_LI t2, PC_REGION_MASK
+ and t0, t2
+ PTR_LI t2, ~PC_REGION_MASK
+ and t1, t2
+ or t0, t1
+ PTR_ADDIU t0, 2f-1b
+ jr t0
+2:
PTR_LA t0, __bss_start # clear .bss
LONG_S zero, (t0)
Commit 15ad838d281b ("[MIPS] Always do the ARC64_TWIDDLE_PC thing.") gives the kernel a chance to jump to the address the kernel is linked to. It can be seen from the old records that this situation is usually a jump from XPHYS to KSEG0. For example, kdump operation, kexec_start_address is usually in XPHYS on Loongson64 platform. Jumping from XPHYS to KSEG0 is a big jump. With the relocation, there may be small jumps. As follows, +-----------+ | | |___________| | | | _kernel | | | |_\0: | | jr t0 |---+ | la t0, \0 | | |___________| | | | | | | | |___________| | | | | | kernel | | | | | |\0: |<--+ | jr t0 | | la t0, \0 | | | |___________| | | +-----------+ _kernel is same as kernel, only the loaded address is different. They are all in KSEG0. For kernel, `jr t0` is right operation and PC will jump to \0. For _kernel, `jr t0` is dangerous operation and PC will not jump to _\0 because `la t0, \0` target address is not PC relative. This patch get the PC address by fixed `1:` (t0) and dynamic ra at `1:` (t1). t0 determines the PC Region of the address where the kernel is linked to. t1 determines the offset relative to the PC Region. Signed-off-by: Jinyang He <hejinyang@loongson.cn> --- arch/mips/kernel/head.S | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)