On Fri, May 05, 2017 at 11:17:11AM -0700, Ricardo Neri wrote:
This function returns the default values of the address and operand sizes as specified in the segment descriptor. This information is determined from the D and L bits. Hence, it can be used for both IA-32e 64-bit and 32-bit legacy modes. For virtual-8086 mode, the default address and operand sizes are always 2 bytes.
The D bit is only meaningful for code segments. Thus, these functions always use the code segment selector contained in regs.
Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Adam Buchbinder adam.buchbinder@gmail.com Cc: Colin Ian King colin.king@canonical.com Cc: Lorenzo Stoakes lstoakes@gmail.com Cc: Qiaowei Ren qiaowei.ren@intel.com Cc: Arnaldo Carvalho de Melo acme@redhat.com Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Adrian Hunter adrian.hunter@intel.com Cc: Kees Cook keescook@chromium.org Cc: Thomas Garnier thgarnie@google.com Cc: Peter Zijlstra peterz@infradead.org Cc: Borislav Petkov bp@suse.de Cc: Dmitry Vyukov dvyukov@google.com Cc: Ravi V. Shankar ravi.v.shankar@intel.com Cc: x86@kernel.org Signed-off-by: Ricardo Neri ricardo.neri-calderon@linux.intel.com
arch/x86/include/asm/insn-eval.h | 6 ++++ arch/x86/lib/insn-eval.c | 65 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 71 insertions(+)
diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h index 7f3c7fe..9ed1c88 100644 --- a/arch/x86/include/asm/insn-eval.h +++ b/arch/x86/include/asm/insn-eval.h @@ -11,9 +11,15 @@ #include <linux/err.h> #include <asm/ptrace.h>
+struct insn_code_seg_defaults {
A whole struct for a function which gets called only once?
Bah, that's a bit too much, if you ask me.
So you're returning two small unsigned integers - i.e., you can just as well return a single u8 and put address and operand sizes in there:
ret = oper_sz | addr_sz << 4;
No need for special structs for that.
- unsigned char address_bytes;
- unsigned char operand_bytes;
+};
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, struct insn *insn, int regoff); +struct insn_code_seg_defaults insn_get_code_seg_defaults(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 c77ed80..693e5a8 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -603,6 +603,71 @@ static unsigned long get_seg_limit(struct pt_regs *regs, struct insn *insn, }
/**
- insn_get_code_seg_defaults() - Obtain code segment default parameters
- @regs: Structure with register values as seen when entering kernel mode
- Obtain the default parameters of the code segment: address and operand sizes.
- The code segment 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.
- Return: A populated insn_code_seg_defaults structure on success. The
- structure contains only zeros on failure.
s/failure/error/
- */
+struct insn_code_seg_defaults insn_get_code_seg_defaults(struct pt_regs *regs) +{
- struct desc_struct *desc;
- struct insn_code_seg_defaults defs;
- unsigned short sel;
- /*
* The most significant byte of AR_TYPE_MASK determines whether a* segment contains data or code.*/- unsigned int type_mask = AR_TYPE_MASK & (1 << 11);
- memset(&defs, 0, sizeof(defs));
- if (v8086_mode(regs)) {
defs.address_bytes = 2;defs.operand_bytes = 2;return defs;- }
- sel = (unsigned short)regs->cs;
- desc = get_desc(sel);
- if (!desc)
return defs;- /* if data segment, return */
- if (!(desc->b & type_mask))
return defs;
So you can simplify that into:
/* A code segment? */ if (!(desc->b & BIT(11))) return defs;
and remove that type_mask thing.