linux-kernel - [PATCH 17/30] x86, kaiser: map debug IDT tables

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Date:   Fri, 10 Nov 2017 11:31:38 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, dave.hansen@...ux.intel.com,
        moritz.lipp@...k.tugraz.at, daniel.gruss@...k.tugraz.at,
        michael.schwarz@...k.tugraz.at, richard.fellner@...dent.tugraz.at,
        luto@...nel.org, torvalds@...ux-foundation.org,
        keescook@...gle.com, hughd@...gle.com, x86@...nel.org
Subject: [PATCH 17/30] x86, kaiser: map debug IDT tables


From: Dave Hansen <dave.hansen@...ux.intel.com>

The IDT is another structure which the CPU references via 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@...ux.intel.com>
Cc: Moritz Lipp <moritz.lipp@...k.tugraz.at>
Cc: Daniel Gruss <daniel.gruss@...k.tugraz.at>
Cc: Michael Schwarz <michael.schwarz@...k.tugraz.at>
Cc: Richard Fellner <richard.fellner@...dent.tugraz.at>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Kees Cook <keescook@...gle.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: x86@...nel.org
---

 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	2017-11-10 11:22:14.332244936 -0800
+++ b/arch/x86/mm/kaiser.c	2017-11-10 11:22:14.336244936 -0800
@@ -286,6 +286,14 @@ 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
@@ -374,6 +382,10 @@ void __init kaiser_init(void)
 				  sizeof(gate_desc) * NR_VECTORS,
 				  __PAGE_KERNEL_RO | _PAGE_GLOBAL);
 
+	kaiser_user_map_ptr_early(&debug_idt_table,
+				  sizeof(gate_desc) * NR_VECTORS,
+				  __PAGE_KERNEL | _PAGE_GLOBAL);
+
 	/*
 	 * We could theoretically do this in setup_fixmap_gdt().
 	 * But, we would need to rewrite the above page table
_