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arch: arm: support built-in stack protection in user mode for ARMv8m

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This commit extends the support of built-in thread stack
protection (i.e. based on the stack pointer limit registers)
in ARMv8-M, so that it works with user mode. The commit
does the following:
- enables and disables the stack limit checking on the
privileged stack, inside thread system calls, and upon
entering user mode,
- does not enable stack limit checking in context switch,
if the thread is in user mode.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
This commit is contained in:
Ioannis Glaropoulos 2018-10-08 15:48:49 +02:00 • committed by Andrew Boie
commit d04cec97d5
3 changed files with 67 additions and 8 deletions
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24
arch/arm/core/swap_helper.S
View file

@ -190,14 +190,6 @@ _thread_irq_disabled:
pop {r2, lr}
#endif /* CONFIG_MPU_STACK_GUARD */
#ifdef CONFIG_BUILTIN_STACK_GUARD
/* r2 contains k_thread */
add r0, r2, #0
push {r2, lr}
blx configure_builtin_stack_guard
pop {r2, lr}
#endif /* CONFIG_BUILTIN_STACK_GUARD */
#ifdef CONFIG_USERSPACE
/* restore mode */
ldr r0, [r2, #_thread_offset_to_mode]
@ -231,8 +223,24 @@ _thread_irq_disabled:
#error Unknown ARM architecture
#endif /* CONFIG_ARMV6_M_ARMV8_M_BASELINE */
#ifdef CONFIG_BUILTIN_STACK_GUARD
/* clear stack pointer limit before setting the PSP */
push {r3}
mov r3, #0
msr PSPLIM, r3
pop {r3}
#endif
msr PSP, ip
#ifdef CONFIG_BUILTIN_STACK_GUARD
/* r2 contains k_thread */
add r0, r2, #0
push {r2, lr}
blx configure_builtin_stack_guard
pop {r2, lr}
#endif /* CONFIG_BUILTIN_STACK_GUARD */
#ifdef CONFIG_EXECUTION_BENCHMARKING
stm sp!,{r0-r3} /* Save regs r0 to r4 on stack */
push {lr}