The version 2.00 of LoongArch ELF ABI specification introduced new
relocation types, and the development tree of Binutils and GCC has
started to use them. If the kernel is built with the latest snapshot of
Binutils or GCC, it will fail to load the modules because of unrecognized
relocation types in modules.
Add support for GOT and new relocation types for the module loader, so
the kernel (with modules) can be built with the "normal" code model and
function properly.
Tested by building the kernel with Binutils & GCC master branch,
running the kernel with 35 in-tree modules loaded, and loading one
module with 20 GOT loads (both old SOP_PUSH_GPREL and new
GOT_PC_HI20/GOT_PC_LO12 relocations tested, and loaded addresses
verified by comparing with /proc/kallsyms).
Link: https://github.com/loongson/LoongArch-Documentation/pull/57
Link: https://gcc.gnu.org/r13-1834
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f09482a
Changes from v1 to v2:
- Fix a stupid programming error (confusion between the number of PLT
entries and the number of GOT entries). (Bug spotted by Youling).
- Synthesize the _GLOBAL_OFFSET_TABLE_ symbol with module.lds, instead
of faking it at runtime. The 3rd patch from V1 is now merged into
the 1st patch because it would be a one-line change. (Suggested by
Jinyang).
- Keep reloc_rela_handlers[] ordered by the relocation type ID.
(Suggested by Youling).
- Remove -fplt along with -Wa,-mla-* options because it's the default.
(Suggested by Youling).
Xi Ruoyao (4):
LoongArch: Add section of GOT for kernel module
LoongArch: Support R_LARCH_SOP_PUSH_GPREL relocation type in kernel
module
LoongArch: Stop using undocumented assembler options
LoongArch: Support modules with new relocation types
arch/loongarch/Makefile | 4 --
arch/loongarch/include/asm/elf.h | 37 ++++++++++
arch/loongarch/include/asm/module.h | 23 ++++++
arch/loongarch/include/asm/module.lds.h | 1 +
arch/loongarch/kernel/head.S | 10 +--
arch/loongarch/kernel/module-sections.c | 51 ++++++++++++--
arch/loongarch/kernel/module.c | 94 +++++++++++++++++++++++++
7 files changed, 207 insertions(+), 13 deletions(-)
--
2.37.0
Now we can handle GOT and GOT-based relocations properly, remove the
undocumented `-Wa,-mla-{global,local}-with-{pcrel,abs}` assembler hacks.
And, -fplt is the default of all supported compilers (GCC, and maybe
Clang in the future), so it can be removed as well.
Adjust assembly code to explicitly use "la.pcrel" where necessary.
Signed-off-by: Xi Ruoyao <[email protected]>
---
arch/loongarch/Makefile | 4 ----
arch/loongarch/kernel/head.S | 10 +++++-----
2 files changed, 5 insertions(+), 9 deletions(-)
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index 039dcc4fe1f3..800349ea9310 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile
@@ -40,10 +40,6 @@ endif
cflags-y += -G0 -pipe -msoft-float
LDFLAGS_vmlinux += -G0 -static -n -nostdlib
-KBUILD_AFLAGS_KERNEL += -Wa,-mla-global-with-pcrel
-KBUILD_CFLAGS_KERNEL += -Wa,-mla-global-with-pcrel
-KBUILD_AFLAGS_MODULE += -Wa,-mla-global-with-abs
-KBUILD_CFLAGS_MODULE += -fplt -Wa,-mla-global-with-abs,-mla-local-with-abs
cflags-y += -ffreestanding
cflags-y += $(call cc-option, -mno-check-zero-division)
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index 74ea7bf6c8d6..193329ed6e8c 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -60,17 +60,17 @@ SYM_CODE_START(kernel_entry) # kernel entry point
la.abs t0, 0f
jirl zero, t0, 0
0:
- la t0, __bss_start # clear .bss
+ la.pcrel t0, __bss_start # clear .bss
st.d zero, t0, 0
- la t1, __bss_stop - LONGSIZE
+ la.pcrel t1, __bss_stop - LONGSIZE
1:
addi.d t0, t0, LONGSIZE
st.d zero, t0, 0
bne t0, t1, 1b
- la t0, fw_arg0
+ la.pcrel t0, fw_arg0
st.d a0, t0, 0 # firmware arguments
- la t0, fw_arg1
+ la.pcrel t0, fw_arg1
st.d a1, t0, 0
/* KSave3 used for percpu base, initialized as 0 */
@@ -78,7 +78,7 @@ SYM_CODE_START(kernel_entry) # kernel entry point
/* GPR21 used for percpu base (runtime), initialized as 0 */
or u0, zero, zero
- la tp, init_thread_union
+ la.pcrel tp, init_thread_union
/* Set the SP after an empty pt_regs. */
PTR_LI sp, (_THREAD_SIZE - 32 - PT_SIZE)
PTR_ADD sp, sp, tp
--
2.37.0