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target/arm: trap DCC access in user mode emulation

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Accessing EL0-accessible Debug Communication Channel (DCC) registers in
user mode emulation is currently enabled.  However, it does not match
Linux behavior as Linux sets MDSCR_EL1.TDCC on startup to disable EL0
access to DCC (see __cpu_setup() in arch/arm64/mm/proc.S).

This patch fixes access_tdcc() to check MDSCR_EL1.TDCC for EL0 and sets
MDSCR_EL1.TDCC for user mode emulation to match Linux.

Signed-off-by: Zhuojia Shen <chaosdefinition@hotmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: DS7PR12MB630905198DD8E69F6817544CAC4EA@DS7PR12MB6309.namprd12.prod.outlook.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Zhuojia Shen 2023-06-06 10:19:40 +01:00 • committed by Peter Maydell
parent c81e4ab370
commit f9ac778898
2 changed files with 7 additions and 0 deletions
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2
target/arm/cpu.c
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@ -289,6 +289,8 @@ static void arm_cpu_reset_hold(Object *obj)
* This is not yet exposed from the Linux kernel in any way.
*/
env->cp15.sctlr_el[1] |= SCTLR_TSCXT;
/* Disable access to Debug Communication Channel (DCC). */
env->cp15.mdscr_el1 |= 1 << 12;
#else
/* Reset into the highest available EL */
if (arm_feature(env, ARM_FEATURE_EL3)) {