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From:   Lai Jiangshan <laijs@linux.alibaba.com>
To:     linux-kernel@vger.kernel.org
Cc:     Lai Jiangshan <laijs@linux.alibaba.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Alexandre Chartre <alexandre.chartre@oracle.com>
Subject: [RFC PATCH V2 1/7] x86/hw_breakpoint: add within_area() to check data breakpoints
Date:   Tue, 26 May 2020 01:42:15 +0000
Message-Id: <20200526014221.2119-2-laijs@linux.alibaba.com>
In-Reply-To: <20200526014221.2119-1-laijs@linux.alibaba.com>
References: <20200525152517.GY325280@hirez.programming.kicks-ass.net>
 <20200526014221.2119-1-laijs@linux.alibaba.com>
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within_area() is added for checking if the data breakpoints overlap
with cpu_entry_area, and will be used for checking if the data
breakpoints overlap with GDT, IDT, or TSS in places other than
cpu_entry_area next patches.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
 arch/x86/kernel/hw_breakpoint.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index 9ddf441ccaa8..c149c7b29ac3 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -227,14 +227,23 @@ int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
 	return (va >= TASK_SIZE_MAX) || ((va + len - 1) >= TASK_SIZE_MAX);
 }
 
+/*
+ * Checks whether the range [addr, end], overlaps the area [base, base + size).
+ */
+static inline bool within_area(unsigned long addr, unsigned long end,
+			       unsigned long base, unsigned long size)
+{
+	return end >= base && addr < (base + size);
+}
+
 /*
  * Checks whether the range from addr to end, inclusive, overlaps the CPU
  * entry area range.
  */
 static inline bool within_cpu_entry_area(unsigned long addr, unsigned long end)
 {
-	return end >= CPU_ENTRY_AREA_BASE &&
-	       addr < (CPU_ENTRY_AREA_BASE + CPU_ENTRY_AREA_TOTAL_SIZE);
+	return within_area(addr, end, CPU_ENTRY_AREA_BASE,
+			   CPU_ENTRY_AREA_TOTAL_SIZE);
 }
 
 static int arch_build_bp_info(struct perf_event *bp,
-- 
2.20.1