[PATCH 16/23] x86, kaiser: map debug IDT tables

[Dave Hansen]

The IDT table it references are another structure where the
CPU references a virtual address.  It also obviously needs these
to handle an interrupt in userspace, so these need to be mapped into
the user copy of the page tables.

Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Moritz Lipp <moritz.lipp@xxxxxxxxxxxxxx>
Cc: Daniel Gruss <daniel.gruss@xxxxxxxxxxxxxx>
Cc: Michael Schwarz <michael.schwarz@xxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
---

 b/arch/x86/mm/kaiser.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff -puN arch/x86/mm/kaiser.c~kaiser-user-map-trace-and-debug-idt arch/x86/mm/kaiser.c
--- a/arch/x86/mm/kaiser.c~kaiser-user-map-trace-and-debug-idt	2017-10-31 15:03:57.365444956 -0700
+++ b/arch/x86/mm/kaiser.c	2017-10-31 15:03:57.368445098 -0700
@@ -250,6 +250,14 @@ int kaiser_add_user_map_ptrs(const void
 				   flags);
 }
 
+static int kaiser_user_map_ptr_early(const void *start_addr, unsigned long size,
+				 unsigned long flags)
+{
+	int ret = kaiser_add_user_map(start_addr, size, flags);
+	WARN_ON(ret);
+	return ret;
+}
+
 /*
  * Ensure that the top level of the (shadow) page tables are
  * entirely populated.  This ensures that all processes that get
@@ -331,6 +339,10 @@ void __init kaiser_init(void)
 				  sizeof(gate_desc) * NR_VECTORS,
 				  __PAGE_KERNEL_RO);
 
+	kaiser_user_map_ptr_early(&debug_idt_table,
+				  sizeof(gate_desc) * NR_VECTORS,
+				  __PAGE_KERNEL);
+
 	/*
 	 * We could theoretically do this in setup_fixmap_gdt().
 	 * But, we would need to rewrite the above page table
_