Messages in this thread Patch in this message | | | From | Ricardo Neri <> | Subject | [PATCH v10 01/13] x86/insn-eval: Extend get_seg_base_addr() to also obtain segment limit | Date | Fri, 27 Oct 2017 16:51:38 -0700 |
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In protected mode, it is common to want to obtain the limit of a segment along with its base address. This is useful, for instance, to verify that an effective address lies within a segment before computing a linear address.
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> --- Up to this point, this library only computes linear addresses in long mode. Subsequent patches will include support for protected mode. Support to verify the segment limit will be needed. --- arch/x86/lib/insn-eval.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-)
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 1c23ec0..91f08aa 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -729,25 +729,29 @@ int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs) } /** - * get_seg_base_addr() - obtain base address of a segment + * get_seg_base_limit() - obtain base address and limit of a segment * @insn: Instruction. Must be valid. * @regs: Register values as seen when entering kernel mode * @regoff: Operand offset, in pt_regs, used to resolve segment descriptor * @base: Obtained segment base + * @limit: Obtained segment limit * - * Obtain the base address of the segment associated with the operand @regoff - * and, if any or allowed, override prefixes in @insn. This function is + * Obtain the base address and limit of the segment associated with the operand + * @regoff and, if any or allowed, override prefixes in @insn. This function is * different from insn_get_seg_base() as the latter does not resolve the segment - * associated with the instruction operand. + * associated with the instruction operand. If a limit is not needed (e.g., + * when running in long mode), @limit can be NULL. * * Returns: * - * 0 on success. @base will contain the base address of the resolved segment. + * 0 on success. @base and @limit will contain the base address and of the + * resolved segment, respectively. * * -EINVAL on error. */ -static int get_seg_base_addr(struct insn *insn, struct pt_regs *regs, - int regoff, unsigned long *base) +static int get_seg_base_limit(struct insn *insn, struct pt_regs *regs, + int regoff, unsigned long *base, + unsigned long *limit) { int seg_reg_idx; @@ -762,6 +766,13 @@ static int get_seg_base_addr(struct insn *insn, struct pt_regs *regs, if (*base == -1L) return -EINVAL; + if (!limit) + return 0; + + *limit = get_seg_limit(regs, seg_reg_idx); + if (!(*limit)) + return -EINVAL; + return 0; } @@ -843,7 +854,7 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) eff_addr += insn->displacement.value; } - ret = get_seg_base_addr(insn, regs, addr_offset, &seg_base); + ret = get_seg_base_limit(insn, regs, addr_offset, &seg_base, NULL); if (ret) goto out; -- 2.7.4
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