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authorChristian Cunningham <cc@localhost>2022-03-16 22:28:33 -0700
committerChristian Cunningham <cc@localhost>2022-03-16 22:28:33 -0700
commita9f63b8cdb930d079cc69d492fe44dc8224c1e03 (patch)
treec97c9f84f5caa2b0cc77850c21f33b9f5cefaecb /src/exceptions/svc.S
parenta3732c11ad3bcd2c01a36d0a82a6f310fe8557af (diff)
More comments
Diffstat (limited to 'src/exceptions/svc.S')
-rw-r--r--src/exceptions/svc.S12
1 files changed, 9 insertions, 3 deletions
diff --git a/src/exceptions/svc.S b/src/exceptions/svc.S
index 3fb534e..7c8a9cc 100644
--- a/src/exceptions/svc.S
+++ b/src/exceptions/svc.S
@@ -3,8 +3,10 @@
svc:
cpsid aif
stmfd sp!, {r0-r12,lr}
+ // Get the SVC Exception #
ldr r0, [lr, #-4]
bic r0, #0xFF000000
+ // Jump to the appropriate Call
cmp r0, #5
bgt svc_exit
beq svc_000005
@@ -18,11 +20,11 @@ svc:
beq svc_000001
cmp r0, #0
beq svc_000000
-svc_000000:
+svc_000000: // SYS_YIELD
bl yield
ldmfd sp!, {r0-r12,lr}
b schedule
-svc_000001: // Get time
+svc_000001: // SYS_TIME
mov r2, #0x3004
movt r2, #0x3F00
ldr r0, [r2, #4] // <- SYS_TIMER_CLO
@@ -50,13 +52,15 @@ svc_000004: // Lock Lock (usr_r0 = struct Lock*)
1: clrex
ldrex r2, [r0, #0]
cmp r2, #0
+ // If it is not available, wait-queue the thread
bne svc_000004_delay_mutex
+ // Otherwise lock it
strexeq r2, r1, [r0, #0]
teq r2, #0
bne 1b
dmb
b svc_exit
-svc_000004_delay_mutex:
+svc_000004_delay_mutex: // Wait-queue the current thread
// r0 = struct Lock* m
bl sched_mutex_yield
ldmfd sp!, {r0-r12,lr}
@@ -65,9 +69,11 @@ svc_000005: // Release Lock
ldr r0, [sp, #0] // struct Lock* m
mov r1, #0
dmb
+ // Unlock
str r1, [r0, #0]
dsb
sev
+ // Awake any threads waiting for this lock
bl sched_mutex_resurrect
ldmfd sp!, {r0-r12,lr}
b schedule