uprobes: Introduce arch_uprobe->ixol

Currently xol_get_insn_slot() assumes that we should simply copy
arch_uprobe->insn[] which is (ignoring arch_uprobe_analyze_insn)
just the copy of the original insn.

This is not true for arm which needs to create another insn to
execute it out-of-line.

So this patch simply adds the new member, ->ixol into the union.
This doesn't make any difference for x86 and powerpc, but arm
can divorce insn/ixol and initialize the correct xol insn in
arch_uprobe_analyze_insn().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

3 files changed, 7 insertions, 2 deletions

diff --git a/arch/powerpc/include/asm/uprobes.h b/arch/powerpc/include/asm/uprobes.h
index b6fc3178372a..75c6ecdb8f37 100644
--- a/arch/powerpc/include/asm/uprobes.h
+++ b/arch/powerpc/include/asm/uprobes.h
@@ -37,6 +37,7 @@ typedef ppc_opcode_t uprobe_opcode_t;
 struct arch_uprobe {
         union {
                 u8      insn[MAX_UINSN_BYTES];
+                u8      ixol[MAX_UINSN_BYTES];
                 u32     ainsn;
         };
 };
diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index b20b4d68b934..3087ea9c5f2e 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -35,7 +35,10 @@ typedef u8 uprobe_opcode_t;
 
 struct arch_uprobe {
         u16                             fixups;
-        u8                              insn[MAX_UINSN_BYTES];
+        union {
+                u8                      insn[MAX_UINSN_BYTES];
+                u8                      ixol[MAX_UINSN_BYTES];
+        };
 #ifdef CONFIG_X86_64
         unsigned long                   rip_rela_target_address;
 #endif
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 0012c8ebb098..fbcff61b5099 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1264,7 +1264,8 @@ static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
                 return 0;
 
         /* Initialize the slot */
-        copy_to_page(area->page, xol_vaddr, uprobe->arch.insn, MAX_UINSN_BYTES);
+        copy_to_page(area->page, xol_vaddr,
+                        uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
         /*
          * We probably need flush_icache_user_range() but it needs vma.
          * This should work on supported architectures too.