| Message ID | 20220630194116.3438513-4-peter.maydell@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | target/arm: Implement (or don't) OS Lock and DoubleLock properly | expand |
On 7/1/22 01:11, Peter Maydell wrote: > The "OS Lock" in the Arm debug architecture is a way for software > to suppress debug exceptions while it is trying to power down > a CPU and save the state of the breakpoint and watchpoint > registers. In QEMU we implemented the support for writing > the OS Lock bit via OSLAR_EL1 and reading it via OSLSR_EL1, > but didn't implement the actual behaviour. > > The required behaviour with the OS Lock set is: > * debug exceptions (apart from BKPT insns) are suppressed > * some MDSCR_EL1 bits allow write access to the corresponding > EDSCR external debug status register that they shadow > (we can ignore this because we don't implement external debug) > * similarly with the OSECCR_EL1 which shadows the EDECCR > (but we don't implement OSECCR_EL1 anyway) > > Implement the missing behaviour of suppressing debug > exceptions. > > Signed-off-by: Peter Maydell<peter.maydell@linaro.org> > --- > target/arm/debug_helper.c | 3 +++ > 1 file changed, 3 insertions(+) Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
diff --git a/target/arm/debug_helper.c b/target/arm/debug_helper.c index 9a78c1db966..691b9b74c4a 100644 --- a/target/arm/debug_helper.c +++ b/target/arm/debug_helper.c @@ -142,6 +142,9 @@ static bool aa32_generate_debug_exceptions(CPUARMState *env) */ bool arm_generate_debug_exceptions(CPUARMState *env) { + if (env->cp15.oslsr_el1 & 1) { + return false; + } if (is_a64(env)) { return aa64_generate_debug_exceptions(env); } else {
The "OS Lock" in the Arm debug architecture is a way for software to suppress debug exceptions while it is trying to power down a CPU and save the state of the breakpoint and watchpoint registers. In QEMU we implemented the support for writing the OS Lock bit via OSLAR_EL1 and reading it via OSLSR_EL1, but didn't implement the actual behaviour. The required behaviour with the OS Lock set is: * debug exceptions (apart from BKPT insns) are suppressed * some MDSCR_EL1 bits allow write access to the corresponding EDSCR external debug status register that they shadow (we can ignore this because we don't implement external debug) * similarly with the OSECCR_EL1 which shadows the EDECCR (but we don't implement OSECCR_EL1 anyway) Implement the missing behaviour of suppressing debug exceptions. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- target/arm/debug_helper.c | 3 +++ 1 file changed, 3 insertions(+)