When the .elf file is loaded from disk, the kernel must be given write
access to the allocated .text section in the task's address environment.
The access is removed after the elf is loaded and relocations are done.
NOTE:
The reason this works for the ARM implementation, is that the ARM MMU
can be configured to give write access for the privileged mode, but
revoke write access for the user mode.
Regardless, it would be smart to revoke write access even for the
kernel, when the kernel does not need it. This framework allows doing
that, if someone wishes to take up the task.
Basically, mirror the following two commits from modlib.
It's shame we have two copies of elf loaders.
```
commit 51490bad55
Author: YAMAMOTO Takashi <yamamoto@midokura.com>
Date: Wed Apr 14 17:07:39 2021 +0900
modlib: Implement sh_addralign handling
I've seen a module with 16 bytes .rodata alignment for xmm operations.
It was getting SEGV on sim/Linux because of the alignment issue.
The same module binary seems working fine after applying this patch.
Also, tested on sim/macOS and esp32 on qemu,
using a module with an artificially large alignment. (64 bytes)
```
```
commit 418e11b8b3
Author: YAMAMOTO Takashi <yamamoto@midokura.com>
Date: Thu Apr 15 11:33:48 2021 +0900
modlib: Always use separate allocation for text and data
Pros:
* Reduce code differences
* Smaller allocations for !CONFIG_ARCH_USE_MODULE_TEXT
Cons:
* Likely to use more memory for !CONFIG_ARCH_USE_MODULE_TEXT in total
Tested with:
* sim:module on macOS
* esp32-devkit:nsh + CONFIG_MODULE on qemu
* lm3s6965-ek:qemu-protected + CONFIG_EXAMPLES_SOTEST on qemu
```
Summary:
- This commit introduces a separate text memory for ELF
- The logic is similar to modlib
Impact:
- None
Testing:
- Tested with spresense:elf
- NOTE: needs separate commits
Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>
