diff options
| -rw-r--r-- | target/arm/translate.c | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/target/arm/translate.c b/target/arm/translate.c index cfebd35d26..615859e23c 100644 --- a/target/arm/translate.c +++ b/target/arm/translate.c @@ -915,10 +915,27 @@ static inline void gen_bx(DisasContext *s, TCGv_i32 var) store_cpu_field(var, thumb); } -/* Set PC and Thumb state from var. var is marked as dead. +/* + * Set PC and Thumb state from var. var is marked as dead. * For M-profile CPUs, include logic to detect exception-return * branches and handle them. This is needed for Thumb POP/LDM to PC, LDR to PC, * and BX reg, and no others, and happens only for code in Handler mode. + * The Security Extension also requires us to check for the FNC_RETURN + * which signals a function return from non-secure state; this can happen + * in both Handler and Thread mode. + * To avoid having to do multiple comparisons in inline generated code, + * we make the check we do here loose, so it will match for EXC_RETURN + * in Thread mode. For system emulation do_v7m_exception_exit() checks + * for these spurious cases and returns without doing anything (giving + * the same behaviour as for a branch to a non-magic address). + * + * In linux-user mode it is unclear what the right behaviour for an + * attempted FNC_RETURN should be, because in real hardware this will go + * directly to Secure code (ie not the Linux kernel) which will then treat + * the error in any way it chooses. For QEMU we opt to make the FNC_RETURN + * attempt behave the way it would on a CPU without the security extension, + * which is to say "like a normal branch". That means we can simply treat + * all branches as normal with no magic address behaviour. */ static inline void gen_bx_excret(DisasContext *s, TCGv_i32 var) { @@ -926,10 +943,12 @@ static inline void gen_bx_excret(DisasContext *s, TCGv_i32 var) * s->base.is_jmp that we need to do the rest of the work later. */ gen_bx(s, var); +#ifndef CONFIG_USER_ONLY if (arm_dc_feature(s, ARM_FEATURE_M_SECURITY) || (s->v7m_handler_mode && arm_dc_feature(s, ARM_FEATURE_M))) { s->base.is_jmp = DISAS_BX_EXCRET; } +#endif } static inline void gen_bx_excret_final_code(DisasContext *s) |