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authorWill Deacon <will.deacon@arm.com>2013-12-17 17:09:08 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2013-12-19 17:41:25 +0000
commitcdc27c27843248ae7eb0df5fc261dd004eaa5670 (patch)
tree202d38bcf449e2a9edb9e2e8da9384078b1af660
parent319e2e3f63c348a9b66db4667efa73178e18b17d (diff)
downloadlinux-cdc27c27843248ae7eb0df5fc261dd004eaa5670.tar.gz
arm64: ptrace: avoid using HW_BREAKPOINT_EMPTY for disabled events
Commit 8f34a1da35ae ("arm64: ptrace: use HW_BREAKPOINT_EMPTY type for disabled breakpoints") fixed an issue with GDB trying to zero breakpoint control registers. The problem there is that the arch hw_breakpoint code will attempt to create a (disabled), execute breakpoint of length 0. This will fail validation and report unexpected failure to GDB. To avoid this, we treated disabled breakpoints as HW_BREAKPOINT_EMPTY, but that seems to have broken with recent kernels, causing watchpoints to be treated as TYPE_INST in the core code and returning ENOSPC for any further breakpoints. This patch fixes the problem by prioritising the `enable' field of the breakpoint: if it is cleared, we simply update the perf_event_attr to indicate that the thing is disabled and don't bother changing either the type or the length. This reinforces the behaviour that the breakpoint control register is essentially read-only apart from the enable bit when disabling a breakpoint. Cc: <stable@vger.kernel.org> Reported-by: Aaron Liu <liucy214@gmail.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
-rw-r--r--arch/arm64/kernel/ptrace.c38
1 files changed, 18 insertions, 20 deletions
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 6777a2192b83..6a8928bba03c 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -214,31 +214,29 @@ static int ptrace_hbp_fill_attr_ctrl(unsigned int note_type,
{
int err, len, type, disabled = !ctrl.enabled;
- if (disabled) {
- len = 0;
- type = HW_BREAKPOINT_EMPTY;
- } else {
- err = arch_bp_generic_fields(ctrl, &len, &type);
- if (err)
- return err;
-
- switch (note_type) {
- case NT_ARM_HW_BREAK:
- if ((type & HW_BREAKPOINT_X) != type)
- return -EINVAL;
- break;
- case NT_ARM_HW_WATCH:
- if ((type & HW_BREAKPOINT_RW) != type)
- return -EINVAL;
- break;
- default:
+ attr->disabled = disabled;
+ if (disabled)
+ return 0;
+
+ err = arch_bp_generic_fields(ctrl, &len, &type);
+ if (err)
+ return err;
+
+ switch (note_type) {
+ case NT_ARM_HW_BREAK:
+ if ((type & HW_BREAKPOINT_X) != type)
return -EINVAL;
- }
+ break;
+ case NT_ARM_HW_WATCH:
+ if ((type & HW_BREAKPOINT_RW) != type)
+ return -EINVAL;
+ break;
+ default:
+ return -EINVAL;
}
attr->bp_len = len;
attr->bp_type = type;
- attr->disabled = disabled;
return 0;
}