livepatch/arm: Add support for livepatch plt

euler inclusion
category: feature
bugzilla: 51923
CVE: N/A

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The offset of the direct jump under ARM is 32M. Longer jumps are
required to exceed this range.

First-- long jump for relocations

If the jump address exceeds the range in these relocation, it
needs to be implemented with a long jump. but there is no
function for us to modify its first LJMP_INSN_SIZE instructions
like enable livepatch do, we should use module plts to store
the information. so we need enough PLTS to store the symbol.

The .klp.rela.objname.secname section store all symbols that required
relocate by livepatch. For commit 425595a7 ("livepatch: reuse
module loader code to write relocations") merged, load_module can
create enough plt entries for livepatch by module_frob_arch_sections.

However, the module loader only use rel section, this is will be
fixed in the next commits and need adapter kpatch-build front-tools.

Second-- long jump for call new function

We modify several instructions from the beginning of the function
to jump instructions, thus completing the jump from the old
function to the new function. Unlike the relocation information,
there is no plt sections to use here, so use the LDT instruction
to complete the long jump using the LDT instruction.

[PC+0]: ldr PC [PC+8]
[PC+4]: nop
[PC+8]: new_addr_to_jump

Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
Reviewed-by: Bin Li <huawei.libin@huawei.com>
Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>

Signed-off-by: Dong Kai <dongkai11@huawei.com>

Signed-off-by: Ye Weihua <yeweihua4@huawei.com>
Reviewed-by: Yang Jihong <yangjihong1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>