From c7169a96c46be8580613c67801ffb48e21231c8b Mon Sep 17 00:00:00 2001
From: Christian Cunningham <cc@localhost>
Date: Tue, 1 Feb 2022 18:26:33 -0700
Subject: Preserve CPSR
Fixed syscall bug
---
include/sys/schedule.h | 1 +
src/sys/schedule.S | 6 +++++-
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/include/sys/schedule.h b/include/sys/schedule.h
index 8a68e05..4d331a6 100644
--- a/include/sys/schedule.h
+++ b/include/sys/schedule.h
@@ -32,6 +32,7 @@ struct Thread {
unsigned char priority;
unsigned char preempt;
unsigned short status;
+ unsigned long cpsr;
};
struct ThreadRotBuffer {
diff --git a/src/sys/schedule.S b/src/sys/schedule.S
index c8dcaa2..aa55ac2 100644
--- a/src/sys/schedule.S
+++ b/src/sys/schedule.S
@@ -10,9 +10,11 @@
push {lr}
ldr r3, =scheduler // struct Scheduler
ldr r2, [r3, #0] // struct Thread* rthread
- str lr, [r2, #0] // svc_lr -> void* pc
str sp, [r2, #4] // svc_lr -> void* sp
+ mrs r1, cpsr
+ str r1, [r2, #0xc] // preserve cpsr
cps #0x13 // Svc mode
+ str lr, [r2, #0] // svc_lr -> void* pc
.endm
.macro restore_ctx
@@ -20,7 +22,9 @@
ldr r2, [r3, #0] // struct Thread* rthread
ldr lr, [r2, #0] // void* pc -> lr_svc
ldr r0, [r2, #4] // void* sp -> r0
+ ldr r1, [r2, #0xc] // restore cpsr
cps #0x1f // Sys mode
+ msr cpsr, r1
mov sp, r0 // Set stack pointer
// Restore Usr regs
pop {lr}
--
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