[PATCH v9 20/29] x86/insn-eval: Add wrapper function for 32 and 64-bit addresses

Ricardo Neri
2017-10-04T03:55:44Z

The function insn_get_addr_ref() is capable of handling only 64-bit
addresses. A previous commit introduced a function to handle 32-bit
addresses. Invoke these two functions from a third wrapper function that
calls the appropriate routine based on the address size specified in the
instruction structure (obtained by looking at the code segment default
address size and the address override prefix, if present).

While doing this, rename the original function insn_get_addr_ref() with
the more appropriate name get_addr_ref_64(), ensure it is only used
for 64-bit addresses.

Also, since 64-bit addresses are not possible in 32-bit builds, provide
a dummy function such case.

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: x86@kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
arch/x86/lib/insn-eval.c | 57 +++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 52 insertions(+), 5 deletions(-)

diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index 945c9b7..1d510a6 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -872,12 +872,28 @@ static void __user *get_addr_ref_32(struct insn *insn, struct pt_regs *regs)
return (void __user *)linear_addr;
}

-/*
- * return the address being referenced be instruction
- * for rm=3 returning the content of the rm reg
- * for rm!=3 calculates the address using SIB and Disp
+/**
+ * get_addr_ref_64() - Obtain a 64-bit linear address
+ * @insn: Instruction struct with ModRM and SIB bytes and displacement
+ * @regs: Structure with register values as seen when entering kernel mode
+ *
+ * This function is to be used with 64-bit address encodings to obtain the
+ * linear memory address referred by the instruction's ModRM, SIB,
+ * displacement bytes and segment base address, as applicable.
+ *
+ * Returns:
+ *
+ * Linear address referenced by instruction and registers on success.
+ *
+ * -1L on error.
*/
-void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
+#ifndef CONFIG_X86_64
+static void __user *get_addr_ref_64(struct insn *insn, struct pt_regs *regs)
+{
+ return (void __user *)-1L;
+}
+#else
+static void __user *get_addr_ref_64(struct insn *insn, struct pt_regs *regs)
{
int addr_offset, base_offset, indx_offset, seg_reg_indx;
unsigned long linear_addr = -1L, seg_base_addr;
@@ -888,6 +904,9 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
insn_get_sib(insn);
sib = insn->sib.value;

+ if (insn->addr_bytes != 8)
+ goto out;
+
if (X86_MODRM_MOD(insn->modrm.value) == 3) {
addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
if (addr_offset < 0)
@@ -971,3 +990,31 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
out:
return (void __user *)linear_addr;
}
+#endif /* CONFIG_X86_64 */
+
+/**
+ * insn_get_addr_ref() - Obtain the linear address referred by instruction
+ * @insn: Instruction structure containing ModRM byte and displacement
+ * @regs: Structure with register values as seen when entering kernel mode
+ *
+ * Obtain the linear address referred by the instruction's ModRM, SIB and
+ * displacement bytes, and segment base, as applicable. In protected mode,
+ * segment limits are enforced.
+ *
+ * Returns:
+ *
+ * Linear address referenced by instruction and registers on success.
+ *
+ * -1L on error.
+ */
+void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
+{
+ switch (insn->addr_bytes) {
+ case 4:
+ return get_addr_ref_32(insn, regs);
+ case 8:
+ return get_addr_ref_64(insn, regs);
+ default:
+ return (void __user *)-1L;
+ }
+}
--
2.7.4