[tip: x86/entry] x86/hw_breakpoint: Add within_area() to check data breakpoints

tip-bot2 for Lai Jiangshan
2020-05-30T09:57:37Z

The following commit has been merged into the x86/entry branch of tip:

Commit-ID: 83f7a80367e99cca0023be95538635abacec07ae
Gitweb: https://git.kernel.org/tip/83f7a80367e99cca0023be95538635abacec07ae
Author: Lai Jiangshan <laijs@linux.alibaba.com>
AuthorDate: Fri, 29 May 2020 23:27:29 +02:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sat, 30 May 2020 10:00:05 +02:00

x86/hw_breakpoint: Add within_area() to check data breakpoints

Add a within_area() helper to checking whether the data breakpoints overlap
with cpu_entry_area.

It will be used to completely prevent data breakpoints on GDT, IDT, or TSS.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200526014221.2119-2-laijs@linux.alibaba.com
Link: https://lkml.kernel.org/r/20200529213320.784524504@infradead.org

---
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 9ddf441..c149c7b 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -228,13 +228,22 @@ int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
}

/*
+ * 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,