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arm64: hw_breakpoint: use target state to determine ABI behaviour
The arm64 hw_breakpoint interface is slightly less flexible than its 32-bit counterpart, thanks to some changes in the architecture rendering unaligned watchpoint addresses obselete for AArch64. However, in a multi-arch environment (i.e. debugging a 32-bit target with a 64-bit GDB under a 64-bit kernel), we need to provide a feature compatible interface to GDB in order for debugging to function correctly. This patch adds a new helper, is_compat_bp, to our hw_breakpoint implementation which changes the interface behaviour based on the architecture of the debug target as opposed to the debugger itself. This allows debugged to function as expected for multi-arch configurations without relying on deprecated architectural behaviours when debugging native applications. Cc: Yao Qi <yao.qi@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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@ -163,6 +163,20 @@ enum hw_breakpoint_ops {
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HW_BREAKPOINT_RESTORE
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};
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static int is_compat_bp(struct perf_event *bp)
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{
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struct task_struct *tsk = bp->hw.target;
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/*
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* tsk can be NULL for per-cpu (non-ptrace) breakpoints.
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* In this case, use the native interface, since we don't have
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* the notion of a "compat CPU" and could end up relying on
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* deprecated behaviour if we use unaligned watchpoints in
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* AArch64 state.
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*/
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return tsk && is_compat_thread(task_thread_info(tsk));
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}
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/**
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* hw_breakpoint_slot_setup - Find and setup a perf slot according to
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* operations
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@ -420,7 +434,7 @@ static int arch_build_bp_info(struct perf_event *bp)
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* Watchpoints can be of length 1, 2, 4 or 8 bytes.
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*/
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if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
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if (is_compat_task()) {
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if (is_compat_bp(bp)) {
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if (info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
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info->ctrl.len != ARM_BREAKPOINT_LEN_4)
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return -EINVAL;
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@ -477,7 +491,7 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
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* AArch32 tasks expect some simple alignment fixups, so emulate
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* that here.
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*/
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if (is_compat_task()) {
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if (is_compat_bp(bp)) {
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if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
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alignment_mask = 0x7;
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else
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