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riscv: pmp: Add support for custom user-defined PMP entry #96241

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riscv: pmp: Add support for custom user-defined PMP entry #96241

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0672ac2
riscv: pmp: Rename PMP stackguard functions to kernelmode
fsammoura1980 Oct 14, 2025
8dfc483
riscv: Add CONFIG_PMP_KERNEL_MODE_DYNAMIC
fsammoura1980 Oct 24, 2025
d03b87c
riscv: pmp: Support custom entries from Device Tree for memory attrib…
fsammoura1980 Sep 18, 2025
3d6fca6
riscv: pmp: Extract region address calculation to helper function
fsammoura1980 Oct 24, 2025
da86356
tests: riscv: Implement unit tests for PMP memattr configuration and …
fsammoura1980 Oct 14, 2025
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8 changes: 8 additions & 0 deletions arch/riscv/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -361,6 +361,7 @@ config RISCV_PMP
select THREAD_LOCAL_STORAGE if USERSPACE
select ARCH_MEM_DOMAIN_SUPPORTS_ISOLATED_STACKS
select MEM_DOMAIN_ISOLATED_STACKS
select PMP_KERNEL_MODE_DYNAMIC if MEM_ATTR
help
MCU implements Physical Memory Protection.

Expand Down Expand Up @@ -414,6 +415,7 @@ endif #RISCV_PMP
config PMP_STACK_GUARD
def_bool y
depends on HW_STACK_PROTECTION
select PMP_KERNEL_MODE_DYNAMIC if MULTITHREADING

config PMP_STACK_GUARD_MIN_SIZE
int "Stack Guard area size"
Expand All @@ -430,6 +432,12 @@ config PMP_STACK_GUARD_MIN_SIZE
wiggle room to accommodate the eventual overflow exception
stack usage.

config PMP_KERNEL_MODE_DYNAMIC
bool
help
Enable this to dynamically reconfigure and activate PMP entries for
Machine mode when switching between kernel (ISR, syscall) and threads.

# Implement the null pointer detection using the Physical Memory Protection
# (PMP) Unit.
config NULL_POINTER_EXCEPTION_DETECTION_PMP
Expand Down
4 changes: 2 additions & 2 deletions arch/riscv/core/fatal.c
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Expand Up @@ -221,12 +221,12 @@ void z_riscv_fault(struct arch_esf *esf)
unsigned int reason = K_ERR_CPU_EXCEPTION;

if (bad_stack_pointer(esf)) {
#ifdef CONFIG_PMP_STACK_GUARD
#if defined(CONFIG_PMP_STACK_GUARD) && defined(CONFIG_MULTITHREADING)
/*
* Remove the thread's PMP setting to prevent triggering a stack
* overflow error again due to the previous configuration.
*/
z_riscv_pmp_stackguard_disable();
z_riscv_pmp_kernelmode_disable();
#endif /* CONFIG_PMP_STACK_GUARD */
reason = K_ERR_STACK_CHK_FAIL;
}
Expand Down
26 changes: 13 additions & 13 deletions arch/riscv/core/isr.S
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Original file line number Diff line number Diff line change
Expand Up @@ -368,19 +368,19 @@ no_fp: /* increment _current->arch.exception_depth */
li t1, RISCV_EXC_ECALLU
beq t0, t1, is_user_syscall

#if defined(CONFIG_PMP_STACK_GUARD) && defined(CONFIG_MULTITHREADING)
#ifdef CONFIG_PMP_KERNEL_MODE_DYNAMIC
/*
* Determine if we come from user space. If so, reconfigure the PMP for
* kernel mode stack guard.
* kernel mode configuration.
*/
csrr t0, mstatus
li t1, MSTATUS_MPP
and t0, t0, t1
bnez t0, 1f
lr a0, ___cpu_t_current_OFFSET(s0)
call z_riscv_pmp_stackguard_enable
call z_riscv_pmp_kernelmode_enable
1:
#endif /* CONFIG_PMP_STACK_GUARD */
#endif /* CONFIG_PMP_KERNEL_MODE_DYNAMIC */

#endif /* CONFIG_USERSPACE */

Expand Down Expand Up @@ -422,7 +422,7 @@ is_kernel_syscall:
addi t0, t0, 4
sr t0, __struct_arch_esf_mepc_OFFSET(sp)

#if defined(CONFIG_PMP_STACK_GUARD) && defined(CONFIG_MULTITHREADING)
#ifdef CONFIG_PMP_KERNEL_MODE_DYNAMIC
/* Re-activate PMP for m-mode */
li t1, MSTATUS_MPP
csrc mstatus, t1
Expand Down Expand Up @@ -515,13 +515,13 @@ do_irq_offload:
#ifdef CONFIG_USERSPACE
is_user_syscall:

#if defined(CONFIG_PMP_STACK_GUARD) && defined(CONFIG_MULTITHREADING)
#ifdef CONFIG_PMP_KERNEL_MODE_DYNAMIC
/*
* We came from userspace and need to reconfigure the
* PMP for kernel mode stack guard.
* PMP for kernel mode configuration.
*/
lr a0, ___cpu_t_current_OFFSET(s0)
call z_riscv_pmp_stackguard_enable
call z_riscv_pmp_kernelmode_enable
#endif

/* It is safe to re-enable IRQs now */
Expand Down Expand Up @@ -585,18 +585,18 @@ valid_syscall_id:

is_interrupt:

#if defined(CONFIG_PMP_STACK_GUARD) && defined(CONFIG_MULTITHREADING)
#ifdef CONFIG_PMP_KERNEL_MODE_DYNAMIC
#ifdef CONFIG_USERSPACE
/*
* If we came from userspace then we need to reconfigure the
* PMP for kernel mode stack guard.
* PMP for kernel mode configuration.
*/
lr t0, __struct_arch_esf_mstatus_OFFSET(sp)
li t1, MSTATUS_MPP
and t0, t0, t1
bnez t0, 1f
lr a0, ___cpu_t_current_OFFSET(s0)
call z_riscv_pmp_stackguard_enable
call z_riscv_pmp_kernelmode_enable
j 2f
#endif /* CONFIG_USERSPACE */
1: /* Re-activate PMP for m-mode */
Expand Down Expand Up @@ -769,8 +769,8 @@ fp_trap_exit:
and t0, t2, t1
bnez t0, 1f

#if defined(CONFIG_PMP_STACK_GUARD) && defined(CONFIG_MULTITHREADING)
/* Remove kernel stack guard and Reconfigure PMP for user mode */
#ifdef CONFIG_PMP_KERNEL_MODE_DYNAMIC
/* Remove kernel mode configuration and Reconfigure PMP for user mode */
lr a0, ___cpu_t_current_OFFSET(s0)
call z_riscv_pmp_usermode_enable
#endif
Expand Down
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