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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>
This commit is contained in:
Will Deacon 2015-10-07 11:37:36 +01:00 committed by Catalin Marinas
parent 120798d2e7
commit 8f48c06290
1 changed files with 16 additions and 2 deletions
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18
arch/arm64/kernel/hw_breakpoint.c
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@ -163,6 +163,20 @@ enum hw_breakpoint_ops {
HW_BREAKPOINT_RESTORE
};
static int is_compat_bp(struct perf_event *bp)
{
struct task_struct *tsk = bp->hw.target;
/*
* tsk can be NULL for per-cpu (non-ptrace) breakpoints.
* In this case, use the native interface, since we don't have
* the notion of a "compat CPU" and could end up relying on
* deprecated behaviour if we use unaligned watchpoints in
* AArch64 state.
*/
return tsk && is_compat_thread(task_thread_info(tsk));
}
/**
* hw_breakpoint_slot_setup - Find and setup a perf slot according to
* operations
@ -420,7 +434,7 @@ static int arch_build_bp_info(struct perf_event *bp)
* Watchpoints can be of length 1, 2, 4 or 8 bytes.
*/
if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
if (is_compat_task()) {
if (is_compat_bp(bp)) {
if (info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
info->ctrl.len != ARM_BREAKPOINT_LEN_4)
return -EINVAL;
@ -477,7 +491,7 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
* AArch32 tasks expect some simple alignment fixups, so emulate
* that here.
*/
if (is_compat_task()) {
if (is_compat_bp(bp)) {
if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
alignment_mask = 0x7;
else