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List: qemu-arm
Subject: [PATCH 3/5] target/arm: Suppress debug exceptions when OS Lock set
From: Peter Maydell <peter.maydell () linaro ! org>
Date: 2022-06-30 19:41:14
Message-ID: 20220630194116.3438513-4-peter.maydell () linaro ! org
[Download RAW message or body]
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(+)
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 {
--
2.25.1
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