diff --git a/arch/x86/include/asm/mpx.h b/arch/x86/include/asm/mpx.h
index 7d7c5f54cc5f4f07d0d0be3d1d60b778fef903af..35bcb1cddf40b0b01727ed3688879ac762cb15d5 100644
--- a/arch/x86/include/asm/mpx.h
+++ b/arch/x86/include/asm/mpx.h
@@ -3,6 +3,7 @@
#include <linux/types.h>
#include <asm/ptrace.h>
+#include <asm/insn.h>
#ifdef CONFIG_X86_64
@@ -33,4 +34,15 @@
#define MPX_BNDSTA_ERROR_CODE 0x3
+#ifdef CONFIG_X86_INTEL_MPX
+siginfo_t *mpx_generate_siginfo(struct pt_regs *regs,
+ struct xsave_struct *xsave_buf);
+#else
+static inline siginfo_t *mpx_generate_siginfo(struct pt_regs *regs,
+ struct xsave_struct *xsave_buf)
+{
+ return NULL;
+}
+#endif /* CONFIG_X86_INTEL_MPX */
+
#endif /* _ASM_X86_MPX_H */
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 72d13b0779a29f938c4ce6ac40012495a4a66c91..9009e094d6863eac5accf86d6071da85402e0149 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -6,6 +6,7 @@
* Dave Hansen <dave.hansen@intel.com>
*/
#include <linux/kernel.h>
+#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/sched/sysctl.h>
@@ -84,3 +85,239 @@ static unsigned long mpx_mmap(unsigned long len)
up_write(&mm->mmap_sem);
return ret;
}
+
+enum reg_type {
+ REG_TYPE_RM = 0,
+ REG_TYPE_INDEX,
+ REG_TYPE_BASE,
+};
+
+static unsigned long 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) == 1)
+ regno += 8;
+ break;
+
+ case REG_TYPE_INDEX:
+ regno = X86_SIB_INDEX(insn->sib.value);
+ if (X86_REX_X(insn->rex_prefix.value) == 1)
+ regno += 8;
+ break;
+
+ case REG_TYPE_BASE:
+ regno = X86_SIB_BASE(insn->sib.value);
+ if (X86_REX_B(insn->rex_prefix.value) == 1)
+ 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, addr_offset;
+ unsigned long base, base_offset;
+ unsigned long indx, 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);
+ indx = regs_get_register(regs, indx_offset);
+ 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)
+{
+ unsigned char buf[MAX_INSN_SIZE];
+ int x86_64 = !test_thread_flag(TIF_IA32);
+ int not_copied;
+ int nr_copied;
+
+ not_copied = copy_from_user(buf, (void __user *)regs->ip, sizeof(buf));
+ nr_copied = sizeof(buf) - not_copied;
+ /*
+ * The decoder _should_ fail nicely if we pass it a short buffer.
+ * But, let's not depend on that implementation detail. If we
+ * did not get anything, just error out now.
+ */
+ if (!nr_copied)
+ return -EFAULT;
+ insn_init(insn, buf, nr_copied, x86_64);
+ insn_get_length(insn);
+ /*
+ * copy_from_user() tries to get as many bytes as we could see in
+ * the largest possible instruction. If the instruction we are
+ * after is shorter than that _and_ we attempt to copy from
+ * something unreadable, we might get a short read. This is OK
+ * as long as the read did not stop in the middle of the
+ * instruction. Check to see if we got a partial instruction.
+ */
+ if (nr_copied < insn->length)
+ return -EFAULT;
+
+ insn_get_opcode(insn);
+ /*
+ * We only _really_ need to decode bndcl/bndcn/bndcu
+ * Error out on anything else.
+ */
+ if (insn->opcode.bytes[0] != 0x0f)
+ goto bad_opcode;
+ if ((insn->opcode.bytes[1] != 0x1a) &&
+ (insn->opcode.bytes[1] != 0x1b))
+ goto bad_opcode;
+
+ return 0;
+bad_opcode:
+ return -EINVAL;
+}
+
+/*
+ * If a bounds overflow occurs then a #BR is generated. This
+ * function decodes MPX instructions to get violation address
+ * and set this address into extended struct siginfo.
+ *
+ * Note that this is not a super precise way of doing this.
+ * Userspace could have, by the time we get here, written
+ * anything it wants in to the instructions. We can not
+ * trust anything about it. They might not be valid
+ * instructions or might encode invalid registers, etc...
+ *
+ * The caller is expected to kfree() the returned siginfo_t.
+ */
+siginfo_t *mpx_generate_siginfo(struct pt_regs *regs,
+ struct xsave_struct *xsave_buf)
+{
+ struct insn insn;
+ uint8_t bndregno;
+ int err;
+ siginfo_t *info;
+
+ err = mpx_insn_decode(&insn, regs);
+ if (err)
+ goto err_out;
+
+ /*
+ * We know at this point that we are only dealing with
+ * MPX instructions.
+ */
+ insn_get_modrm(&insn);
+ bndregno = X86_MODRM_REG(insn.modrm.value);
+ if (bndregno > 3) {
+ err = -EINVAL;
+ goto err_out;
+ }
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ /*
+ * The registers are always 64-bit, but the upper 32
+ * bits are ignored in 32-bit mode. Also, note that the
+ * upper bounds are architecturally represented in 1's
+ * complement form.
+ *
+ * The 'unsigned long' cast is because the compiler
+ * complains when casting from integers to different-size
+ * pointers.
+ */
+ info->si_lower = (void __user *)(unsigned long)
+ (xsave_buf->bndreg[bndregno].lower_bound);
+ info->si_upper = (void __user *)(unsigned long)
+ (~xsave_buf->bndreg[bndregno].upper_bound);
+ info->si_addr_lsb = 0;
+ info->si_signo = SIGSEGV;
+ info->si_errno = 0;
+ info->si_code = SEGV_BNDERR;
+ info->si_addr = mpx_get_addr_ref(&insn, regs);
+ /*
+ * We were not able to extract an address from the instruction,
+ * probably because there was something invalid in it.
+ */
+ if (info->si_addr == (void *)-1) {
+ err = -EINVAL;
+ goto err_out;
+ }
+ return info;
+err_out:
+ return ERR_PTR(err);
+}