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

Masami Hiramatsu
2016-12-25T06:17:50Z

Hi Ricado,

On Fri, 23 Dec 2016 17:37:41 -0800
Ricardo Neri <ricardo.neri-calderon@linux.intel.com> wrote:

> 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.

Thank you for your great work! :)

> ---
> 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);

Could you also rename this to add "insn_" prefix?

Other part looks good to me :)
(btw, I saw a kbuild bot warning, would you also test it with
CONFIG_X86_DECODER_SELFTEST=y?)

Thanks again!

>
> /* 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
>

--
Masami Hiramatsu <mhiramat@kernel.org>