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* [PATCH v3 1/4] x86/insn-eval: Add support for 64-bit kernel mode
@ 2019-11-20 10:36 Jann Horn
  2019-11-20 10:36 ` [PATCH v3 2/4] x86/traps: Print non-canonical address on #GP Jann Horn
                   ` (2 more replies)
  0 siblings, 3 replies; 19+ messages in thread
From: Jann Horn @ 2019-11-20 10:36 UTC (permalink / raw)
  To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, H. Peter Anvin,
	x86, Andrey Ryabinin, Alexander Potapenko, Dmitry Vyukov,
	kasan-dev, jannh
  Cc: linux-kernel, Andrey Konovalov, Andy Lutomirski,
	Sean Christopherson, Andi Kleen

To support evaluating 64-bit kernel mode instructions:

Replace existing checks for user_64bit_mode() with a new helper that
checks whether code is being executed in either 64-bit kernel mode or
64-bit user mode.

Select the GS base depending on whether the instruction is being
evaluated in kernel mode.

Signed-off-by: Jann Horn <jannh@google.com>
---

Notes:
    v2:
      no changes
    v3:
      no changes

 arch/x86/include/asm/ptrace.h | 13 +++++++++++++
 arch/x86/lib/insn-eval.c      | 26 +++++++++++++++-----------
 2 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 5057a8ed100b..ac45b06941a5 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -159,6 +159,19 @@ static inline bool user_64bit_mode(struct pt_regs *regs)
 #endif
 }
 
+/*
+ * Determine whether the register set came from any context that is running in
+ * 64-bit mode.
+ */
+static inline bool any_64bit_mode(struct pt_regs *regs)
+{
+#ifdef CONFIG_X86_64
+	return !user_mode(regs) || user_64bit_mode(regs);
+#else
+	return false;
+#endif
+}
+
 #ifdef CONFIG_X86_64
 #define current_user_stack_pointer()	current_pt_regs()->sp
 #define compat_user_stack_pointer()	current_pt_regs()->sp
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index 306c3a0902ba..31600d851fd8 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -155,7 +155,7 @@ static bool check_seg_overrides(struct insn *insn, int regoff)
  */
 static int resolve_default_seg(struct insn *insn, struct pt_regs *regs, int off)
 {
-	if (user_64bit_mode(regs))
+	if (any_64bit_mode(regs))
 		return INAT_SEG_REG_IGNORE;
 	/*
 	 * Resolve the default segment register as described in Section 3.7.4
@@ -266,7 +266,7 @@ static int resolve_seg_reg(struct insn *insn, struct pt_regs *regs, int regoff)
 	 * which may be invalid at this point.
 	 */
 	if (regoff == offsetof(struct pt_regs, ip)) {
-		if (user_64bit_mode(regs))
+		if (any_64bit_mode(regs))
 			return INAT_SEG_REG_IGNORE;
 		else
 			return INAT_SEG_REG_CS;
@@ -289,7 +289,7 @@ static int resolve_seg_reg(struct insn *insn, struct pt_regs *regs, int regoff)
 	 * In long mode, segment override prefixes are ignored, except for
 	 * overrides for FS and GS.
 	 */
-	if (user_64bit_mode(regs)) {
+	if (any_64bit_mode(regs)) {
 		if (idx != INAT_SEG_REG_FS &&
 		    idx != INAT_SEG_REG_GS)
 			idx = INAT_SEG_REG_IGNORE;
@@ -646,23 +646,27 @@ unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx)
 		 */
 		return (unsigned long)(sel << 4);
 
-	if (user_64bit_mode(regs)) {
+	if (any_64bit_mode(regs)) {
 		/*
 		 * Only FS or GS will have a base address, the rest of
 		 * the segments' bases are forced to 0.
 		 */
 		unsigned long base;
 
-		if (seg_reg_idx == INAT_SEG_REG_FS)
+		if (seg_reg_idx == INAT_SEG_REG_FS) {
 			rdmsrl(MSR_FS_BASE, base);
-		else if (seg_reg_idx == INAT_SEG_REG_GS)
+		} else if (seg_reg_idx == INAT_SEG_REG_GS) {
 			/*
 			 * swapgs was called at the kernel entry point. Thus,
 			 * MSR_KERNEL_GS_BASE will have the user-space GS base.
 			 */
-			rdmsrl(MSR_KERNEL_GS_BASE, base);
-		else
+			if (user_mode(regs))
+				rdmsrl(MSR_KERNEL_GS_BASE, base);
+			else
+				rdmsrl(MSR_GS_BASE, base);
+		} else {
 			base = 0;
+		}
 		return base;
 	}
 
@@ -703,7 +707,7 @@ static unsigned long get_seg_limit(struct pt_regs *regs, int seg_reg_idx)
 	if (sel < 0)
 		return 0;
 
-	if (user_64bit_mode(regs) || v8086_mode(regs))
+	if (any_64bit_mode(regs) || v8086_mode(regs))
 		return -1L;
 
 	if (!sel)
@@ -948,7 +952,7 @@ static int get_eff_addr_modrm(struct insn *insn, struct pt_regs *regs,
 	 * following instruction.
 	 */
 	if (*regoff == -EDOM) {
-		if (user_64bit_mode(regs))
+		if (any_64bit_mode(regs))
 			tmp = regs->ip + insn->length;
 		else
 			tmp = 0;
@@ -1250,7 +1254,7 @@ static void __user *get_addr_ref_32(struct insn *insn, struct pt_regs *regs)
 	 * After computed, the effective address is treated as an unsigned
 	 * quantity.
 	 */
-	if (!user_64bit_mode(regs) && ((unsigned int)eff_addr > seg_limit))
+	if (!any_64bit_mode(regs) && ((unsigned int)eff_addr > seg_limit))
 		goto out;
 
 	/*
-- 
2.24.0.432.g9d3f5f5b63-goog


^ permalink raw reply	[flat|nested] 19+ messages in thread

end of thread, other threads:[~2019-11-20 17:37 UTC | newest]

Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-11-20 10:36 [PATCH v3 1/4] x86/insn-eval: Add support for 64-bit kernel mode Jann Horn
2019-11-20 10:36 ` [PATCH v3 2/4] x86/traps: Print non-canonical address on #GP Jann Horn
2019-11-20 11:18   ` Ingo Molnar
2019-11-20 11:24     ` Borislav Petkov
2019-11-20 12:25       ` Jann Horn
2019-11-20 12:41         ` Borislav Petkov
2019-11-20 13:16         ` Ingo Molnar
2019-11-20 13:23           ` Jann Horn
2019-11-20 14:05             ` Ingo Molnar
2019-11-20 12:14     ` Jann Horn
2019-11-20 12:30       ` Ingo Molnar
2019-11-20 12:39         ` Borislav Petkov
2019-11-20 12:42           ` Jann Horn
2019-11-20 13:28           ` Ingo Molnar
2019-11-20 13:39             ` Borislav Petkov
2019-11-20 16:21               ` Sean Christopherson
2019-11-20 17:37                 ` Borislav Petkov
2019-11-20 10:36 ` [PATCH v3 3/4] x86/dumpstack: Split out header line printing from __die() Jann Horn
2019-11-20 10:36 ` [PATCH v3 4/4] x86/kasan: Print original address on #GP Jann Horn

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