LoongArch: module: set section addresses to 0x0

These got*, plt* and .text.ftrace_trampoline sections specified for
LoongArch have non-zero addressses. Non-zero section addresses in a
relocatable ELF would confuse GDB when it tries to compute the section
offsets and it ends up printing wrong symbol addresses. Therefore, set
them to zero, which mirrors the change in commit 5d8591bc0fbaeb6ded
("arm64 module: set plt* section addresses to 0x0").

Cc: stable@vger.kernel.org
Reviewed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Chong Qiao <qiaochong@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: modules/ftrace: Initialize PLT at load time

This patch implements ftrace trampolines through plt entry.

Tested by forcing ftrace_make_call() to use the module PLT, and then
loading up a module after setting up ftrace with:

| echo ":mod:<module-name>" > set_ftrace_filter;
| echo function > current_tracer;
| modprobe <module-name>

Since FTRACE_ADDR/FTRACE_REGS_ADDR is only defined when CONFIG_DYNAMIC_
FTRACE is selected, we wrap their usage in module_init_ftrace_plt() with
ifdeffery rather than using IS_ENABLED().

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

LoongArch: Support R_LARCH_GOT_PC_{LO12,HI20} in modules

GCC >= 13 and GNU assembler >= 2.40 use these relocations to address
external symbols, so we need to add them.

Let the module loader emit GOT entries for data symbols so we would be
able to handle GOT relocations. The GOT entry is just the data's symbol
address.

In module.lds, emit a stub .got section for a section header entry. The
actual content of the section entry will be filled at runtime by module_
frob_arch_sections().

Tested-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

LoongArch: Add ELF and module support

Add ELF-related definition and module relocation code for basic
LoongArch support.

Cc: Jessica Yu <jeyu@kernel.org>
Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>