diff options
Diffstat (limited to 'arch/x86/lib')
| -rw-r--r-- | arch/x86/lib/insn-eval.c | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 6a902b155f5d..d85e84091ddc 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -6,9 +6,13 @@ #include <linux/kernel.h> #include <linux/string.h> #include <linux/ratelimit.h> +#include <linux/mmu_context.h> +#include <asm/desc_defs.h> +#include <asm/desc.h> #include <asm/inat.h> #include <asm/insn.h> #include <asm/insn-eval.h> +#include <asm/ldt.h> #include <asm/vm86.h> #undef pr_fmt @@ -469,6 +473,59 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs, } /** + * get_desc() - Obtain pointer to a segment descriptor + * @sel: Segment selector + * + * Given a segment selector, obtain a pointer to the segment descriptor. + * Both global and local descriptor tables are supported. + * + * Returns: + * + * Pointer to segment descriptor on success. + * + * NULL on error. + */ +static struct desc_struct *get_desc(unsigned short sel) +{ + struct desc_ptr gdt_desc = {0, 0}; + unsigned long desc_base; + +#ifdef CONFIG_MODIFY_LDT_SYSCALL + if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT) { + struct desc_struct *desc = NULL; + struct ldt_struct *ldt; + + /* Bits [15:3] contain the index of the desired entry. */ + sel >>= 3; + + mutex_lock(¤t->active_mm->context.lock); + ldt = current->active_mm->context.ldt; + if (ldt && sel < ldt->nr_entries) + desc = &ldt->entries[sel]; + + mutex_unlock(¤t->active_mm->context.lock); + + return desc; + } +#endif + native_store_gdt(&gdt_desc); + + /* + * Segment descriptors have a size of 8 bytes. Thus, the index is + * multiplied by 8 to obtain the memory offset of the desired descriptor + * from the base of the GDT. As bits [15:3] of the segment selector + * contain the index, it can be regarded as multiplied by 8 already. + * All that remains is to clear bits [2:0]. + */ + desc_base = sel & ~(SEGMENT_RPL_MASK | SEGMENT_TI_MASK); + + if (desc_base > gdt_desc.size) + return NULL; + + return (struct desc_struct *)(gdt_desc.address + desc_base); +} + +/** * 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 |