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arch/arm/mps: Let user code run modules from the text and data heaps.

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In a protected build a module loaded by exec() runs as a user task, and
the loader puts it in the text and data heaps, which on this chip are
SRAM2.  Nothing gave user code access to SRAM2: the region that would have
done so, in arm_addregion(), exists only with CONFIG_MM_REGIONS > 1, and it
is built with mpu_user_intsram(), which on ARMv8-M is execute-never.  So
the module faulted on its first instruction.

The protected build now maps SRAM2 for user code to read, write and
execute when either heap is in use.  Privileged execution stays allowed,
since a kernel module loaded with insmod lands in the same heaps.

On mps3-an547:knsh under QEMU, with CONFIG_ELF, both heaps and the ROMFS
variant of examples/elf, errno faulted on its first instruction with an
instruction access violation at 0x21000001.  Now every module of the
example runs to the end.

Assisted-by: Claude Code:claude-opus-5-5
Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
This commit is contained in:
Marco Casaroli 2026-09-28 14:25:26 +02:00 • committed by Alan C. Assis
parent b960000dc8
commit 3297bbec44
1 changed files with 10 additions and 0 deletions
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10
arch/arm/src/mps/mps_allocateheap.c
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@ -164,6 +164,16 @@ void up_allocate_heap(void **heap_start, size_t *heap_size)
/* Allow user-mode access to the user heap memory */
mpu_user_intsram(ubase, usize);
# if defined(CONFIG_ARCH_USE_TEXT_HEAP) || defined(CONFIG_ARCH_USE_DATA_HEAP)
/* A module loaded for a user task runs out of the text and data heaps in
* SRAM2, so user code must be able to execute it as well as read and
* write it. mpu_user_intsram() would make it execute-never.
*/
mpu_configure_region(MPS_SRAM2_START, MPS_SRAM2_SIZE,
MPU_RBAR_AP_RWRW, MPU_RLAR_NONCACHEABLE);
# endif
#elif defined(CONFIG_BUILD_PIC)
/* Use different heap useful to debug */