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(interrupt): implement robust trap frame and state preservation

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This commit is contained in:
Liam Kerr 2026-02-11 22:56:25 +00:00
parent 43a26abe74
commit b48da838ec
3 changed files with 72 additions and 11 deletions
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23
src/boot/traps.S
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@ -4,11 +4,10 @@
.global trap_entry
trap_entry:
# 1. Create space on the stack for 32 registers (32 * 8 = 256 bytes)
# Create space on the stack for 32 registers (32 * 8 = 256 bytes)
addi sp, sp, -256
# 2. Save all General Purpose Registers (GPRs)
# We don't save x0 (zero) because it's always zero
# Save all General Purpose Registers (GPRs)
sd ra, 0(sp)
sd gp, 8(sp)
sd tp, 16(sp)
@ -40,11 +39,19 @@ trap_entry:
sd t5, 224(sp)
sd t6, 232(sp)
# 3. Call your C handler
# The CPU already put the cause in 'mcause', so C can read it
# Save mepc to the stack (using offset 240)
csrr t0, mepc
sd t0, 240(sp)
# Call trap handler
mv a0, sp # put the stack pointer to the first arg
call handle_trap
# 4. Restore all GPRs
# restore mepc
ld t0, 240(sp)
csrw mepc, t0
# Restore all GPRs
ld ra, 0(sp)
ld gp, 8(sp)
ld tp, 16(sp)
@ -76,8 +83,8 @@ trap_entry:
ld t5, 224(sp)
ld t6, 232(sp)
# 5. Shrink the stack back
# Shrink the stack back
addi sp, sp, 256
# 6. Return from Machine-mode trap
# Return from Machine-mode trap
mret