[v2 3/7] x86/mpx, x86/insn: Relocate insn util functions to a new insn-utils

Ricardo Neri
2016-12-24T01:37:41Z

Other kernel submodules can benefit from using the utility functions
defined in mpx.c to obtain the addresses and values of operands contained
in the general purpose registers. An instance of this is the emulation code
used for instructions protected by the Intel User-Mode Instruction
Prevention feature.

Thus, these functions are relocated to a new insn-utils.c file. The reason
to not relocate these utilities for insn.c is that the latter solely
analyses instructions given by a struct insn. The file insn-utils.c intends
to be used when, for instance, determining addresses from the contents
of the general purpose registers.

To avoid creating a new insn-utils.h, insn.h is used. One caveat, however,
is that several #include's were needed by the utility functions.

Functions are simply relocated. There are not functional or indentation
changes.

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/include/asm/insn.h | 6 ++
arch/x86/lib/Makefile | 2 +-
arch/x86/lib/insn-utils.c | 148 ++++++++++++++++++++++++++++++++++++++++++++
arch/x86/mm/mpx.c | 136 +---------------------------------------
4 files changed, 156 insertions(+), 136 deletions(-)
create mode 100644 arch/x86/lib/insn-utils.c

diff --git a/arch/x86/include/asm/insn.h b/arch/x86/include/asm/insn.h
index b3e32b0..9dc9d42 100644
--- a/arch/x86/include/asm/insn.h
+++ b/arch/x86/include/asm/insn.h
@@ -22,6 +22,10 @@

/* insn_attr_t is defined in inat.h */
#include <asm/inat.h>
+#include <linux/compiler.h>
+#include <linux/bug.h>
+#include <linux/err.h>
+#include <asm/ptrace.h>

struct insn_field {
union {
@@ -106,6 +110,8 @@ extern void insn_get_sib(struct insn *insn);
extern void insn_get_displacement(struct insn *insn);
extern void insn_get_immediate(struct insn *insn);
extern void insn_get_length(struct insn *insn);
+extern void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs);
+extern int get_reg_offset_rm(struct insn *insn, struct pt_regs *regs);

/* Attribute will be determined after getting ModRM (for opcode groups) */
static inline void insn_get_attribute(struct insn *insn)
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 34a7413..0d01d82 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -23,7 +23,7 @@ lib-y := delay.o misc.o cmdline.o cpu.o
lib-y += usercopy_$(BITS).o usercopy.o getuser.o putuser.o
lib-y += memcpy_$(BITS).o
lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
-lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o
+lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o insn-utils.o
lib-$(CONFIG_RANDOMIZE_BASE) += kaslr.o

obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o
diff --git a/arch/x86/lib/insn-utils.c b/arch/x86/lib/insn-utils.c
new file mode 100644
index 0000000..598bbd6
--- /dev/null
+++ b/arch/x86/lib/insn-utils.c
@@ -0,0 +1,148 @@
+/*
+ * Utility functions for x86 operand and address decoding
+ *
+ * Copyright (C) Intel Corporation 2016
+ */
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <asm/inat.h>
+#include <asm/insn.h>
+
+enum reg_type {
+ REG_TYPE_RM = 0,
+ REG_TYPE_INDEX,
+ REG_TYPE_BASE,
+};
+
+static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
+ enum reg_type type)
+{
+ int regno = 0;
+
+ static const int regoff[] = {
+ offsetof(struct pt_regs, ax),
+ offsetof(struct pt_regs, cx),
+ offsetof(struct pt_regs, dx),
+ offsetof(struct pt_regs, bx),
+ offsetof(struct pt_regs, sp),
+ offsetof(struct pt_regs, bp),
+ offsetof(struct pt_regs, si),
+ offsetof(struct pt_regs, di),
+#ifdef CONFIG_X86_64
+ offsetof(struct pt_regs, r8),
+ offsetof(struct pt_regs, r9),
+ offsetof(struct pt_regs, r10),
+ offsetof(struct pt_regs, r11),
+ offsetof(struct pt_regs, r12),
+ offsetof(struct pt_regs, r13),
+ offsetof(struct pt_regs, r14),
+ offsetof(struct pt_regs, r15),
+#endif
+ };
+ int nr_registers = ARRAY_SIZE(regoff);
+ /*
+ * Don't possibly decode a 32-bit instructions as
+ * reading a 64-bit-only register.
+ */
+ if (IS_ENABLED(CONFIG_X86_64) && !insn->x86_64)
+ nr_registers -= 8;
+
+ switch (type) {
+ case REG_TYPE_RM:
+ regno = X86_MODRM_RM(insn->modrm.value);
+ if (X86_REX_B(insn->rex_prefix.value))
+ regno += 8;
+ break;
+
+ case REG_TYPE_INDEX:
+ regno = X86_SIB_INDEX(insn->sib.value);
+ if (X86_REX_X(insn->rex_prefix.value))
+ regno += 8;
+ /*
+ * If mod !=3, SP is not used as index. Check is done after
+ * looking at REX.X This is because R12 can be used as an
+ * index.
+ */
+ if (regno == 4 && X86_MODRM_RM(insn->modrm.value) != 3)
+ return 0;
+ break;
+
+ case REG_TYPE_BASE:
+ regno = X86_SIB_BASE(insn->sib.value);
+ if (regno == 5 && X86_MODRM_RM(insn->modrm.value) == 0) {
+ WARN_ONCE(1, "An explicit displacement is required when %sBP used as SIB base.",
+ (IS_ENABLED(CONFIG_X86_64) && insn->x86_64) ?
+ "R13 or R" : "E");
+ return -EINVAL;
+ }
+
+ if (X86_REX_B(insn->rex_prefix.value))
+ regno += 8;
+ break;
+
+ default:
+ pr_err("invalid register type");
+ BUG();
+ break;
+ }
+
+ if (regno >= nr_registers) {
+ WARN_ONCE(1, "decoded an instruction with an invalid register");
+ return -EINVAL;
+ }
+ return regoff[regno];
+}
+
+int get_reg_offset_rm(struct insn *insn, struct pt_regs *regs)
+{
+ return get_reg_offset(insn, regs, REG_TYPE_RM);
+}
+
+/*
+ * 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
+ */
+void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
+{
+ unsigned long addr, base, indx;
+ int addr_offset, base_offset, indx_offset;
+ insn_byte_t sib;
+
+ insn_get_modrm(insn);
+ insn_get_sib(insn);
+ sib = insn->sib.value;
+
+ if (X86_MODRM_MOD(insn->modrm.value) == 3) {
+ addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
+ if (addr_offset < 0)
+ goto out_err;
+ addr = regs_get_register(regs, addr_offset);
+ } else {
+ if (insn->sib.nbytes) {
+ base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE);
+ if (base_offset < 0)
+ goto out_err;
+
+ indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX);
+ if (indx_offset < 0)
+ goto out_err;
+
+ base = regs_get_register(regs, base_offset);
+ if (indx_offset)
+ indx = regs_get_register(regs, indx_offset);
+ else
+ indx = 0;
+ addr = base + indx * (1 << X86_SIB_SCALE(sib));
+ } else {
+ addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
+ if (addr_offset < 0)
+ goto out_err;
+ addr = regs_get_register(regs, addr_offset);
+ }
+ addr += insn->displacement.value;
+ }
+ return (void __user *)addr;
+out_err:
+ return (void __user *)-1;
+}
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 71681d0..32ba342 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -59,140 +59,6 @@ static unsigned long mpx_mmap(unsigned long len)
return addr;
}

-enum reg_type {
- REG_TYPE_RM = 0,
- REG_TYPE_INDEX,
- REG_TYPE_BASE,
-};
-
-static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
- enum reg_type type)
-{
- int regno = 0;
-
- static const int regoff[] = {
- offsetof(struct pt_regs, ax),
- offsetof(struct pt_regs, cx),
- offsetof(struct pt_regs, dx),
- offsetof(struct pt_regs, bx),
- offsetof(struct pt_regs, sp),
- offsetof(struct pt_regs, bp),
- offsetof(struct pt_regs, si),
- offsetof(struct pt_regs, di),
-#ifdef CONFIG_X86_64
- offsetof(struct pt_regs, r8),
- offsetof(struct pt_regs, r9),
- offsetof(struct pt_regs, r10),
- offsetof(struct pt_regs, r11),
- offsetof(struct pt_regs, r12),
- offsetof(struct pt_regs, r13),
- offsetof(struct pt_regs, r14),
- offsetof(struct pt_regs, r15),
-#endif
- };
- int nr_registers = ARRAY_SIZE(regoff);
- /*
- * Don't possibly decode a 32-bit instructions as
- * reading a 64-bit-only register.
- */
- if (IS_ENABLED(CONFIG_X86_64) && !insn->x86_64)
- nr_registers -= 8;
-
- switch (type) {
- case REG_TYPE_RM:
- regno = X86_MODRM_RM(insn->modrm.value);
- if (X86_REX_B(insn->rex_prefix.value))
- regno += 8;
- break;
-
- case REG_TYPE_INDEX:
- regno = X86_SIB_INDEX(insn->sib.value);
- if (X86_REX_X(insn->rex_prefix.value))
- regno += 8;
- /*
- * If mod !=3, SP is not used as index. Check is done after
- * looking at REX.X This is because R12 can be used as an
- * index.
- */
- if (regno == 4 && X86_MODRM_RM(insn->modrm.value) != 3)
- return 0;
- break;
-
- case REG_TYPE_BASE:
- regno = X86_SIB_BASE(insn->sib.value);
- if (regno == 5 && X86_MODRM_RM(insn->modrm.value) == 0) {
- WARN_ONCE(1, "An explicit displacement is required when %sBP used as SIB base.",
- (IS_ENABLED(CONFIG_X86_64) && insn->x86_64) ?
- "R13 or R" : "E");
- return -EINVAL;
- }
-
- if (X86_REX_B(insn->rex_prefix.value))
- regno += 8;
- break;
-
- default:
- pr_err("invalid register type");
- BUG();
- break;
- }
-
- if (regno >= nr_registers) {
- WARN_ONCE(1, "decoded an instruction with an invalid register");
- return -EINVAL;
- }
- return regoff[regno];
-}
-
-/*
- * 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
- */
-static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs)
-{
- unsigned long addr, base, indx;
- int addr_offset, base_offset, indx_offset;
- insn_byte_t sib;
-
- insn_get_modrm(insn);
- insn_get_sib(insn);
- sib = insn->sib.value;
-
- if (X86_MODRM_MOD(insn->modrm.value) == 3) {
- addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
- if (addr_offset < 0)
- goto out_err;
- addr = regs_get_register(regs, addr_offset);
- } else {
- if (insn->sib.nbytes) {
- base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE);
- if (base_offset < 0)
- goto out_err;
-
- indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX);
- if (indx_offset < 0)
- goto out_err;
-
- base = regs_get_register(regs, base_offset);
- if (indx_offset)
- indx = regs_get_register(regs, indx_offset);
- else
- indx = 0;
- addr = base + indx * (1 << X86_SIB_SCALE(sib));
- } else {
- addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
- if (addr_offset < 0)
- goto out_err;
- addr = regs_get_register(regs, addr_offset);
- }
- addr += insn->displacement.value;
- }
- return (void __user *)addr;
-out_err:
- return (void __user *)-1;
-}
-
static int mpx_insn_decode(struct insn *insn,
struct pt_regs *regs)
{
@@ -305,7 +171,7 @@ siginfo_t *mpx_generate_siginfo(struct pt_regs *regs)
info->si_signo = SIGSEGV;
info->si_errno = 0;
info->si_code = SEGV_BNDERR;
- info->si_addr = mpx_get_addr_ref(&insn, regs);
+ info->si_addr = insn_get_addr_ref(&insn, regs);
/*
* We were not able to extract an address from the instruction,
* probably because there was something invalid in it.
--
2.9.3