From 1ec78cfedd16abb0095f9e77f2700af24522345d Mon Sep 17 00:00:00 2001 From: Tim Newsome Date: Thu, 9 Jun 2016 10:18:32 -0700 Subject: [PATCH] Fix 2 bugs in Debug ROM: (#52) 1. Debug ROM wasn't actually writing 0xffffffff to the last word in Debug RAM after an exception happened. 2. Fix a race where debug interrupts were cleared before that write would have happened, so a debugger (gdbserver.cc in this case) might get the wrong idea about whether an exception happened or not. Why wasn't this wreaking havoc before? --- debug_rom/debug_rom.S | 12 +++++++----- debug_rom/debug_rom.h | 10 +++++----- 2 files changed, 12 insertions(+), 10 deletions(-) diff --git a/debug_rom/debug_rom.S b/debug_rom/debug_rom.S index 9e83098..b0be7fc 100755 --- a/debug_rom/debug_rom.S +++ b/debug_rom/debug_rom.S @@ -30,9 +30,6 @@ exception: _resume: li s0, 0 _resume2: - # Clear debug interrupt. - csrr s1, CSR_MHARTID - sw s1, CLEARDEBINT(zero) fence # Restore s1. @@ -40,21 +37,26 @@ _resume2: bltz s1, restore_not_32 restore_32: lw s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 4)(zero) - j check_halt + j finish_restore restore_not_32: slli s1, s1, 1 bltz s1, restore_128 restore_64: ld s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 8)(zero) - j check_halt + j finish_restore restore_128: nop #lq s1, (DEBUG_RAM + DEBUG_RAM_SIZE - 16)(zero) +finish_restore: # s0 contains ~0 if we got here through an exception, and 0 otherwise. # Store this to the last word in Debug RAM so the debugger can tell if # an exception occurred. sw s0, (DEBUG_RAM + DEBUG_RAM_SIZE - 4)(zero) + # Clear debug interrupt. + csrr s0, CSR_MHARTID + sw s0, CLEARDEBINT(zero) + check_halt: csrr s0, CSR_DCSR andi s0, s0, DCSR_HALT diff --git a/debug_rom/debug_rom.h b/debug_rom/debug_rom.h index a929a27..b4ee2dd 100644 --- a/debug_rom/debug_rom.h +++ b/debug_rom/debug_rom.h @@ -1,10 +1,10 @@ static const unsigned char debug_rom_raw[] = { 0x6f, 0x00, 0x00, 0x06, 0x6f, 0x00, 0xc0, 0x00, 0x13, 0x04, 0xf0, 0xff, - 0x6f, 0x00, 0x80, 0x00, 0x13, 0x04, 0x00, 0x00, 0xf3, 0x24, 0x40, 0xf1, - 0x23, 0x20, 0x90, 0x10, 0x0f, 0x00, 0xf0, 0x0f, 0xf3, 0x24, 0x00, 0xf1, - 0x63, 0xc6, 0x04, 0x00, 0x83, 0x24, 0xc0, 0x43, 0x6f, 0x00, 0xc0, 0x01, - 0x93, 0x94, 0x14, 0x00, 0x63, 0xc6, 0x04, 0x00, 0x83, 0x34, 0x80, 0x43, - 0x6f, 0x00, 0xc0, 0x00, 0x13, 0x00, 0x00, 0x00, 0x23, 0x2e, 0x80, 0x42, + 0x6f, 0x00, 0x80, 0x00, 0x13, 0x04, 0x00, 0x00, 0x0f, 0x00, 0xf0, 0x0f, + 0xf3, 0x24, 0x00, 0xf1, 0x63, 0xc6, 0x04, 0x00, 0x83, 0x24, 0xc0, 0x43, + 0x6f, 0x00, 0x80, 0x01, 0x93, 0x94, 0x14, 0x00, 0x63, 0xc6, 0x04, 0x00, + 0x83, 0x34, 0x80, 0x43, 0x6f, 0x00, 0x80, 0x00, 0x13, 0x00, 0x00, 0x00, + 0x23, 0x2e, 0x80, 0x42, 0x73, 0x24, 0x40, 0xf1, 0x23, 0x20, 0x80, 0x10, 0x73, 0x24, 0x00, 0x7b, 0x13, 0x74, 0x84, 0x00, 0x63, 0x04, 0x04, 0x00, 0x6f, 0x00, 0x80, 0x05, 0x73, 0x24, 0x20, 0x7b, 0x73, 0x00, 0x20, 0x7b, 0x73, 0x10, 0x24, 0x7b, 0x73, 0x24, 0x00, 0x7b, 0x13, 0x74, 0x04, 0x1c, -- 2.30.2