1 files changed, 29 insertions, 5 deletions

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 26bc2e24e9e3..ca9012930ce7 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -173,6 +173,20 @@ bool __weak is_swbp_insn(uprobe_opcode_t *insn)
         return *insn == UPROBE_SWBP_INSN;
 }
 
+/**
+ * is_trap_insn - check if instruction is breakpoint instruction.
+ * @insn: instruction to be checked.
+ * Default implementation of is_trap_insn
+ * Returns true if @insn is a breakpoint instruction.
+ *
+ * This function is needed for the case where an architecture has multiple
+ * trap instructions (like powerpc).
+ */
+bool __weak is_trap_insn(uprobe_opcode_t *insn)
+{
+        return is_swbp_insn(insn);
+}
+
 static void copy_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *opcode)
 {
         void *kaddr = kmap_atomic(page);
@@ -185,6 +199,15 @@ static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t
         uprobe_opcode_t old_opcode;
         bool is_swbp;
 
+        /*
+         * Note: We only check if the old_opcode is UPROBE_SWBP_INSN here.
+         * We do not check if it is any other 'trap variant' which could
+         * be conditional trap instruction such as the one powerpc supports.
+         *
+         * The logic is that we do not care if the underlying instruction
+         * is a trap variant; uprobes always wins over any other (gdb)
+         * breakpoint.
+         */
         copy_opcode(page, vaddr, &old_opcode);
         is_swbp = is_swbp_insn(&old_opcode);
 
@@ -204,7 +227,7 @@ static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t
  * Expect the breakpoint instruction to be the smallest size instruction for
  * the architecture. If an arch has variable length instruction and the
  * breakpoint instruction is not of the smallest length instruction
- * supported by that architecture then we need to modify is_swbp_at_addr and
+ * supported by that architecture then we need to modify is_trap_at_addr and
  * write_opcode accordingly. This would never be a problem for archs that
  * have fixed length instructions.
  */
@@ -550,7 +573,7 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
                 goto out;
 
         ret = -ENOTSUPP;
-        if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
+        if (is_trap_insn((uprobe_opcode_t *)uprobe->arch.insn))
                 goto out;
 
         ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
@@ -1431,7 +1454,7 @@ static void mmf_recalc_uprobes(struct mm_struct *mm)
         clear_bit(MMF_HAS_UPROBES, &mm->flags);
 }
 
-static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
+static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
 {
         struct page *page;
         uprobe_opcode_t opcode;
@@ -1452,7 +1475,8 @@ static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
         copy_opcode(page, vaddr, &opcode);
         put_page(page);
  out:
-        return is_swbp_insn(&opcode);
+        /* This needs to return true for any variant of the trap insn */
+        return is_trap_insn(&opcode);
 }
 
 static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
@@ -1472,7 +1496,7 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
                 }
 
                 if (!uprobe)
-                        *is_swbp = is_swbp_at_addr(mm, bp_vaddr);
+                        *is_swbp = is_trap_at_addr(mm, bp_vaddr);
         } else {
                 *is_swbp = -EFAULT;
         }