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-rw-r--r--arch/x86/include/asm/insn-eval.h1
-rw-r--r--arch/x86/lib/insn-eval.c114
2 files changed, 115 insertions, 0 deletions
diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h
index 7e8c9633a377..25d6e44dcbfc 100644
--- a/arch/x86/include/asm/insn-eval.h
+++ b/arch/x86/include/asm/insn-eval.h
@@ -13,5 +13,6 @@
void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs);
int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs);
+unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx);
#endif /* _ASM_X86_INSN_EVAL_H */
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index d85e84091ddc..89d5c8902f42 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -526,6 +526,120 @@ static struct desc_struct *get_desc(unsigned short sel)
}
/**
+ * insn_get_seg_base() - Obtain base address of segment descriptor.
+ * @regs: Register values as seen when entering kernel mode
+ * @seg_reg_idx: Index of the segment register pointing to seg descriptor
+ *
+ * Obtain the base address of the segment as indicated by the segment descriptor
+ * pointed by the segment selector. The segment selector is obtained from the
+ * input segment register index @seg_reg_idx.
+ *
+ * Returns:
+ *
+ * In protected mode, base address of the segment. Zero in long mode,
+ * except when FS or GS are used. In virtual-8086 mode, the segment
+ * selector shifted 4 bits to the right.
+ *
+ * -1L in case of error.
+ */
+unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx)
+{
+ struct desc_struct *desc;
+ short sel;
+
+ sel = get_segment_selector(regs, seg_reg_idx);
+ if (sel < 0)
+ return -1L;
+
+ if (v8086_mode(regs))
+ /*
+ * Base is simply the segment selector shifted 4
+ * bits to the right.
+ */
+ return (unsigned long)(sel << 4);
+
+ if (user_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)
+ rdmsrl(MSR_FS_BASE, base);
+ 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
+ base = 0;
+ return base;
+ }
+
+ /* In protected mode the segment selector cannot be null. */
+ if (!sel)
+ return -1L;
+
+ desc = get_desc(sel);
+ if (!desc)
+ return -1L;
+
+ return get_desc_base(desc);
+}
+
+/**
+ * get_seg_limit() - Obtain the limit of a segment descriptor
+ * @regs: Register values as seen when entering kernel mode
+ * @seg_reg_idx: Index of the segment register pointing to seg descriptor
+ *
+ * Obtain the limit of the segment as indicated by the segment descriptor
+ * pointed by the segment selector. The segment selector is obtained from the
+ * input segment register index @seg_reg_idx.
+ *
+ * Returns:
+ *
+ * In protected mode, the limit of the segment descriptor in bytes.
+ * In long mode and virtual-8086 mode, segment limits are not enforced. Thus,
+ * limit is returned as -1L to imply a limit-less segment.
+ *
+ * Zero is returned on error.
+ */
+static unsigned long get_seg_limit(struct pt_regs *regs, int seg_reg_idx)
+{
+ struct desc_struct *desc;
+ unsigned long limit;
+ short sel;
+
+ sel = get_segment_selector(regs, seg_reg_idx);
+ if (sel < 0)
+ return 0;
+
+ if (user_64bit_mode(regs) || v8086_mode(regs))
+ return -1L;
+
+ if (!sel)
+ return 0;
+
+ desc = get_desc(sel);
+ if (!desc)
+ return 0;
+
+ /*
+ * If the granularity bit is set, the limit is given in multiples
+ * of 4096. This also means that the 12 least significant bits are
+ * not tested when checking the segment limits. In practice,
+ * this means that the segment ends in (limit << 12) + 0xfff.
+ */
+ limit = get_desc_limit(desc);
+ if (desc->g)
+ limit = (limit << 12) + 0xfff;
+
+ return limit;
+}
+
+/**
* insn_get_modrm_rm_off() - Obtain register in r/m part of the ModRM byte
* @insn: Instruction containing the ModRM byte
* @regs: Register values as seen when entering kernel mode