llext: disable ELF buffer reuse on MPU/MMU builds

This PR adds a new CONFIG_LLEXT_HW_MEMORY_CHECKS hidden option to the
LLEXT Kconfig, which is enabled by default on builds where memory is
managed by an MPU, MMU or RISC-V PMP, and which may impose additional
alignment or access restrictions to the LLEXT memory regions.

This is used to disable the optimization that allows reuse of the ELF
buffer on such builds, since the ELF sections would certainly not be
aligned properly.

Signed-off-by: Luca Burelli <[email protected]>

Author: pillo79

subsys/llext/Kconfig

@@ -10,6 +10,10 @@ menuconfig LLEXT
 
 if LLEXT
 
+config LLEXT_HW_MEMORY_CHECKS
+	bool
+	default y if MPU || MMU || RISCV_PMP
+
 choice LLEXT_BINARY_TYPE
 	prompt "Binary object type for llext"
 	default LLEXT_TYPE_ELF_OBJECT if ARM || ARM64

subsys/llext/llext_mem.c

@@ -70,6 +70,7 @@ static int llext_copy_region(struct llext_loader *ldr, struct llext *ext,
 	ext->mem_size[mem_idx] = region->sh_size;
 
 	if (region->sh_type != SHT_NOBITS &&
+	    !IS_ENABLED(CONFIG_LLEXT_HW_MEMORY_CHECKS) &&
 	    IS_ENABLED(CONFIG_LLEXT_STORAGE_WRITABLE)) {
 		/* Directly use data from the ELF buffer if peek() is supported */
 		ext->mem[mem_idx] = llext_peek(ldr, region->sh_offset);