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

[tip-bot2 for Lai Jiangshan]

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@xxxxxxxxxxxxxxxxx>
AuthorDate:    Fri, 29 May 2020 23:27:29 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200526014221.2119-2-laijs@xxxxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20200529213320.784524504@xxxxxxxxxxxxx

---
 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,