[PATCH v2 1/2] LoongArch: Expand module virtual address space to 2GB

[Tiezhu Yang]

The current 256MB module virtual address space is easily exhausted
when loading massive graphics drivers such as amdgpu along with the
large unstripped symbol tables, resulting in allocation failures of
"execmem: unable to allocate memory".

Thus, expand the module virtual address space to 2GB while keeping
the current normal code model '-mcmodel=normal', rather than using
the medium code model '-mcmodel=medium'. This approach avoids the
extra performance overhead and larger binary size of forcing every
function call into a 2-instruction sequence of 'pcaddu18i + jirl'.

Given that individual module code segments rarely exceed 128MB, most
jumps remain fast direct calls by using the bl instruction. For the
long-distance jumps exceeding the 128MB limit, apply_r_larch_b26()
emits PLT entries, while signed_imm_check() guarantees the run-time
safety by rejecting any out-of-bound instruction offsets.

Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
 arch/loongarch/include/asm/pgtable.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
index 223528c04d73..e5952ecd6a73 100644
--- a/arch/loongarch/include/asm/pgtable.h
+++ b/arch/loongarch/include/asm/pgtable.h
@@ -96,7 +96,7 @@ struct vm_area_struct;
 #ifdef CONFIG_64BIT
 
 #define MODULES_VADDR	(vm_map_base + PCI_IOSIZE + (2 * PAGE_SIZE))
-#define MODULES_END	(MODULES_VADDR + SZ_256M)
+#define MODULES_END	(MODULES_VADDR + SZ_2G)
 
 #ifdef CONFIG_KFENCE
 #define KFENCE_AREA_SIZE	(((CONFIG_KFENCE_NUM_OBJECTS + 1) * 2 + 2) * PAGE_SIZE)
-- 
2.42.0