From a9431a03f70c8c711a870d4c1a0439bdbb4703cf Mon Sep 17 00:00:00 2001 From: Mark Cave-Ayland Date: Mon, 8 Mar 2021 12:11:55 +0000 Subject: [PATCH] target/m68k: add M68K_FEATURE_UNALIGNED_DATA feature According to the M68040UM Appendix D the requirement for data accesses to be word aligned is only for the 68000, 68008 and 68010 CPUs. Later CPUs from the 68020 onwards will allow unaligned data accesses but at the cost of being less efficient. Add a new M68K_FEATURE_UNALIGNED_DATA feature to specify that data accesses are not required to be word aligned, and don't perform the alignment on the stack pointer when taking an exception if this feature is not selected. This is required because the MacOS DAFB driver attempts to call an A-trap with a byte-aligned stack pointer during initialisation and without this the stack pointer is off by one when the A-trap returns. Signed-off-by: Mark Cave-Ayland Reviewed-by: Laurent Vivier Reviewed-by: Richard Henderson Message-Id: <20210308121155.2476-4-mark.cave-ayland@ilande.co.uk> Signed-off-by: Laurent Vivier --- target/m68k/cpu.c | 1 + target/m68k/cpu.h | 2 ++ target/m68k/op_helper.c | 5 ++++- 3 files changed, 7 insertions(+), 1 deletion(-) diff --git a/target/m68k/cpu.c b/target/m68k/cpu.c index 37d2ed9dc7..a14874b4da 100644 --- a/target/m68k/cpu.c +++ b/target/m68k/cpu.c @@ -161,6 +161,7 @@ static void m68020_cpu_initfn(Object *obj) m68k_set_feature(env, M68K_FEATURE_CAS); m68k_set_feature(env, M68K_FEATURE_CHK2); m68k_set_feature(env, M68K_FEATURE_MSP); + m68k_set_feature(env, M68K_FEATURE_UNALIGNED_DATA); } /* diff --git a/target/m68k/cpu.h b/target/m68k/cpu.h index ce558e9b03..402c86c876 100644 --- a/target/m68k/cpu.h +++ b/target/m68k/cpu.h @@ -527,6 +527,8 @@ enum m68k_features { M68K_FEATURE_MOVEP, /* MOVEC insn. (from 68010) */ M68K_FEATURE_MOVEC, + /* Unaligned data accesses (680[2346]0) */ + M68K_FEATURE_UNALIGNED_DATA, }; static inline int m68k_feature(CPUM68KState *env, int feature) diff --git a/target/m68k/op_helper.c b/target/m68k/op_helper.c index 5f981e5bf6..46ff81acc9 100644 --- a/target/m68k/op_helper.c +++ b/target/m68k/op_helper.c @@ -348,7 +348,10 @@ static void m68k_interrupt_all(CPUM68KState *env, int is_hw) cpu_m68k_set_sr(env, sr); sp = env->aregs[7]; - sp &= ~1; + if (!m68k_feature(env, M68K_FEATURE_UNALIGNED_DATA)) { + sp &= ~1; + } + if (cs->exception_index == EXCP_ACCESS) { if (env->mmu.fault) { cpu_abort(cs, "DOUBLE MMU FAULT\n");