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32-bit and 64-bit address encodings are identical. Thus, the same logic could be used to resolve the effective address. However, there are two key differences: address size and enforcement of segment limits. If running a 32-bit process on a 64-bit kernel, it is best to perform the address calculation using 32-bit data types. In this manner hardware is used for the arithmetic, including handling of signs and overflows. 32-bit addresses are generally used in protected mode; segment limits are enforced in this mode. This implementation obtains the limit of the segment associated with the instruction operands and prefixes. If the computed address is outside the segment limits, an error is returned. It is also possible to use 32-bit address in long mode and virtual-8086 mode by using an address override prefix. In such cases, segment limits are not enforced. Support to use 32-bit arithmetic is added to the utility functions that compute effective addresses. However, the end result is stored in a variable of type long (which has a width of 8 bytes in 64-bit builds). Hence, once a 32-bit effective address is computed, the 4 most significant bytes are masked out to avoid sign extension. The newly added function get_addr_ref_32() is almost identical to the existing function insn_get_addr_ref() (used for 64-bit addresses). The only difference is that it verifies that the effective address is within the limits of the segment. Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Adam Buchbinder <adam.buchbinder@gmail.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Chen Yucong <slaoub@gmail.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Colin Ian King <colin.king@canonical.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Huang Rui <ray.huang@amd.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Qiaowei Ren <qiaowei.ren@intel.com> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Thomas Garnier <thgarnie@google.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: ricardo.neri@intel.com Link: http://lkml.kernel.org/r/1509935277-22138-3-git-send-email-ricardo.neri-calderon@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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