Commit-ID: 4efea85fb56fa1691b79af1eea4c1425660cf4e3 Gitweb: https://git.kernel.org/tip/4efea85fb56fa1691b79af1eea4c1425660cf4e3 Author: Ricardo Neri <ricardo.neri-calde...@linux.intel.com> AuthorDate: Fri, 27 Oct 2017 13:25:43 -0700 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Wed, 1 Nov 2017 21:50:12 +0100
x86/insn-eval: Add function to get default params of code segment Obtain the default values of the address and operand sizes as specified in the D and L bits of the the segment descriptor selected by the register CS. The function can be used for both protected and long modes. For virtual-8086 mode, the default address and operand sizes are always 2 bytes. The returned parameters are encoded in a signed 8-bit data type. Auxiliar macros are provided to encode and decode such values. Improvements-by: Borislav Petkov <b...@suse.de> Signed-off-by: Ricardo Neri <ricardo.neri-calde...@linux.intel.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Reviewed-by: Borislav Petkov <b...@suse.de> Cc: "Michael S. Tsirkin" <m...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Dave Hansen <dave.han...@linux.intel.com> Cc: ricardo.n...@intel.com Cc: Adrian Hunter <adrian.hun...@intel.com> Cc: Paul Gortmaker <paul.gortma...@windriver.com> Cc: Huang Rui <ray.hu...@amd.com> Cc: Qiaowei Ren <qiaowei....@intel.com> Cc: Shuah Khan <sh...@kernel.org> Cc: Kees Cook <keesc...@chromium.org> Cc: Jonathan Corbet <cor...@lwn.net> Cc: Jiri Slaby <jsl...@suse.cz> Cc: Dmitry Vyukov <dvyu...@google.com> Cc: "Ravi V. Shankar" <ravi.v.shan...@intel.com> Cc: Chris Metcalf <cmetc...@mellanox.com> Cc: Brian Gerst <brge...@gmail.com> Cc: Arnaldo Carvalho de Melo <a...@redhat.com> Cc: Andy Lutomirski <l...@kernel.org> Cc: Colin Ian King <colin.k...@canonical.com> Cc: Chen Yucong <sla...@gmail.com> Cc: Adam Buchbinder <adam.buchbin...@gmail.com> Cc: Vlastimil Babka <vba...@suse.cz> Cc: Lorenzo Stoakes <lstoa...@gmail.com> Cc: Masami Hiramatsu <mhira...@kernel.org> Cc: Paolo Bonzini <pbonz...@redhat.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Thomas Garnier <thgar...@google.com> Link: https://lkml.kernel.org/r/1509135945-13762-17-git-send-email-ricardo.neri-calde...@linux.intel.com --- arch/x86/include/asm/insn-eval.h | 5 ++++ arch/x86/lib/insn-eval.c | 64 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 69 insertions(+) diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h index 25d6e44..e1d3b4c 100644 --- a/arch/x86/include/asm/insn-eval.h +++ b/arch/x86/include/asm/insn-eval.h @@ -11,8 +11,13 @@ #include <linux/err.h> #include <asm/ptrace.h> +#define INSN_CODE_SEG_ADDR_SZ(params) ((params >> 4) & 0xf) +#define INSN_CODE_SEG_OPND_SZ(params) (params & 0xf) +#define INSN_CODE_SEG_PARAMS(oper_sz, addr_sz) (oper_sz | (addr_sz << 4)) + 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); +char insn_get_code_seg_params(struct pt_regs *regs); #endif /* _ASM_X86_INSN_EVAL_H */ diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 89d5c89..01e36bd 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -640,6 +640,70 @@ static unsigned long get_seg_limit(struct pt_regs *regs, int seg_reg_idx) } /** + * insn_get_code_seg_params() - Obtain code segment parameters + * @regs: Structure with register values as seen when entering kernel mode + * + * Obtain address and operand sizes of the code segment. It is obtained from the + * selector contained in the CS register in regs. In protected mode, the default + * address is determined by inspecting the L and D bits of the segment + * descriptor. In virtual-8086 mode, the default is always two bytes for both + * address and operand sizes. + * + * Returns: + * + * A signed 8-bit value containing the default parameters on success. + * + * -EINVAL on error. + */ +char insn_get_code_seg_params(struct pt_regs *regs) +{ + struct desc_struct *desc; + short sel; + + if (v8086_mode(regs)) + /* Address and operand size are both 16-bit. */ + return INSN_CODE_SEG_PARAMS(2, 2); + + sel = get_segment_selector(regs, INAT_SEG_REG_CS); + if (sel < 0) + return sel; + + desc = get_desc(sel); + if (!desc) + return -EINVAL; + + /* + * The most significant byte of the Type field of the segment descriptor + * determines whether a segment contains data or code. If this is a data + * segment, return error. + */ + if (!(desc->type & BIT(3))) + return -EINVAL; + + switch ((desc->l << 1) | desc->d) { + case 0: /* + * Legacy mode. CS.L=0, CS.D=0. Address and operand size are + * both 16-bit. + */ + return INSN_CODE_SEG_PARAMS(2, 2); + case 1: /* + * Legacy mode. CS.L=0, CS.D=1. Address and operand size are + * both 32-bit. + */ + return INSN_CODE_SEG_PARAMS(4, 4); + case 2: /* + * IA-32e 64-bit mode. CS.L=1, CS.D=0. Address size is 64-bit; + * operand size is 32-bit. + */ + return INSN_CODE_SEG_PARAMS(4, 8); + case 3: /* Invalid setting. CS.L=1, CS.D=1 */ + /* fall through */ + default: + return -EINVAL; + } +} + +/** * 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
