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Author SHA1 Message Date
Ricardo Neri
4efea85fb5 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 <bp@suse.de>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: ricardo.neri@intel.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Garnier <thgarnie@google.com>
Link: https://lkml.kernel.org/r/1509135945-13762-17-git-send-email-ricardo.neri-calderon@linux.intel.com
 2017-11-01 21:50:12 +01:00
Ricardo Neri
bd5a410a5d x86/insn-eval: Add utility functions to get segment descriptor base address and limit 
With segmentation, the base address of the segment is needed to compute a
linear address. This base address is obtained from the applicable segment
descriptor. Such segment descriptor is referenced from a segment selector.
These new functions obtain the segment base and limit of the segment
selector indicated by segment register index given as argument. This index
is any of the INAT_SEG_REG_* family of #define's.

The logic to obtain the segment selector is wrapped in the function
get_segment_selector() with the inputs described above. Once the selector
is known, the base address is determined. In protected mode, the selector
is used to obtain the segment descriptor and then its base address. In
long mode, the segment base address is zero except when FS or GS are used.
In virtual-8086 mode, the base address is computed as the value of the
segment selector shifted 4 positions to the left.

In protected mode, segment limits are enforced. Thus, a function to
determine the limit of the segment is added. Segment limits are not
enforced in long or virtual-8086. For the latter, addresses are limited
to 20 bits; address size will be handled when computing the linear
address.

Improvements-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: ricardo.neri@intel.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Garnier <thgarnie@google.com>
Link: https://lkml.kernel.org/r/1509135945-13762-16-git-send-email-ricardo.neri-calderon@linux.intel.com
 2017-11-01 21:50:12 +01:00
Ricardo Neri
670f928ba0 x86/insn-eval: Add utility function to get segment descriptor 
The segment descriptor contains information that is relevant to how linear
addresses need to be computed. It contains the default size of addresses
as well as the base address of the segment. Thus, given a segment
selector, we ought to look at segment descriptor to correctly calculate
the linear address.

In protected mode, the segment selector might indicate a segment
descriptor from either the global descriptor table or a local descriptor
table. Both cases are considered in this function.

This function is a prerequisite for functions in subsequent commits that
will obtain the aforementioned attributes of the segment descriptor.

Improvements-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: ricardo.neri@intel.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Garnier <thgarnie@google.com>
Link: https://lkml.kernel.org/r/1509135945-13762-15-git-send-email-ricardo.neri-calderon@linux.intel.com
 2017-11-01 21:50:12 +01:00
Ricardo Neri
32d0b95300 x86/insn-eval: Add utility functions to get segment selector 
When computing a linear address and segmentation is used, we need to know
the base address of the segment involved in the computation. In most of
the cases, the segment base address will be zero as in USER_DS/USER32_DS.
However, it may be possible that a user space program defines its own
segments via a local descriptor table. In such a case, the segment base
address may not be zero. Thus, the segment base address is needed to
calculate correctly the linear address.

If running in protected mode, the segment selector to be used when
computing a linear address is determined by either any of segment override
prefixes in the instruction or inferred from the registers involved in the
computation of the effective address; in that order. Also, there are cases
when the segment override prefixes shall be ignored (i.e., code segments
are always selected by the CS segment register; string instructions always
use the ES segment register when using rDI register as operand). In long
mode, segment registers are ignored, except for FS and GS. In these two
cases, base addresses are obtained from the respective MSRs.

For clarity, this process can be split into four steps (and an equal
number of functions): determine if segment prefixes overrides can be used;
parse the segment override prefixes, and use them if found; if not found
or cannot be used, use the default segment registers associated with the
operand registers. Once the segment register to use has been identified,
read its value to obtain the segment selector.

The method to obtain the segment selector depends on several factors. In
32-bit builds, segment selectors are saved into a pt_regs structure
when switching to kernel mode. The same is also true for virtual-8086
mode. In 64-bit builds, segmentation is mostly ignored, except when
running a program in 32-bit legacy mode. In this case, CS and SS can be
obtained from pt_regs. DS, ES, FS and GS can be read directly from
the respective segment registers.

In order to identify the segment registers, a new set of #defines is
introduced. It also includes two special identifiers. One of them
indicates when the default segment register associated with instruction
operands shall be used. Another one indicates that the contents of the
segment register shall be ignored; this identifier is used when in long
mode.

Improvements-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: ricardo.neri@intel.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Garnier <thgarnie@google.com>
Link: https://lkml.kernel.org/r/1509135945-13762-14-git-send-email-ricardo.neri-calderon@linux.intel.com
 2017-11-01 21:50:11 +01:00
Ricardo Neri
536b815388 x86/insn-eval: Add utility function to identify string instructions 
String instructions are special because, in protected mode, the linear
address is always obtained via the ES segment register in operands that
use the (E)DI register; the DS segment register in operands that use
the (E)SI register. Furthermore, segment override prefixes are ignored
when calculating a linear address involving the (E)DI register; segment
override prefixes can be used when calculating linear addresses involving
the (E)SI register.

It follows that linear addresses are calculated differently for the case of
string instructions. The purpose of this utility function is to identify
such instructions for callers to determine a linear address correctly.

Note that this function only identifies string instructions; it does not
determine what segment register to use in the address computation. That is
left to callers. A subsequent commmit introduces a function to determine
the segment register to use given the instruction, operands and
segment override prefixes.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: ricardo.neri@intel.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Garnier <thgarnie@google.com>
Link: https://lkml.kernel.org/r/1509135945-13762-13-git-send-email-ricardo.neri-calderon@linux.intel.com
 2017-11-01 21:50:11 +01:00
Ricardo Neri
e5e45f1111 x86/insn-eval: Add a utility function to get register offsets 
The function get_reg_offset() returns the offset to the register the
argument specifies as indicated in an enumeration of type offset. Callers
of this function would need the definition of such enumeration. This is
not needed. Instead, add helper functions for this purpose. These functions
are useful in cases when, for instance, the caller needs to decide whether
the operand is a register or a memory location by looking at the rm part
of the ModRM byte. As of now, this is the only helper function that is
needed.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: ricardo.neri@intel.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Garnier <thgarnie@google.com>
Link: https://lkml.kernel.org/r/1509135945-13762-12-git-send-email-ricardo.neri-calderon@linux.intel.com
 2017-11-01 21:50:11 +01:00
Ricardo Neri
ed594e4ba5 x86/insn-eval: Do not BUG on invalid register type 
We are not in a critical failure path. The invalid register type is caused
when trying to decode invalid instruction bytes from a user-space program.
Thus, simply print an error message. To prevent this warning from being
abused from user space programs, use the rate-limited variant of pr_err().
along with a descriptive prefix.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: ricardo.neri@intel.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Garnier <thgarnie@google.com>
Link: https://lkml.kernel.org/r/1509135945-13762-11-git-send-email-ricardo.neri-calderon@linux.intel.com
 2017-11-01 21:50:10 +01:00
Ricardo Neri
32542ee295 x86/mpx, x86/insn: Relocate insn util functions to a new insn-eval file 
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-eval.c file. The reason
to not relocate these utilities into insn.c is that the latter solely
analyses instructions given by a struct insn without any knowledge of the
meaning of the values of instruction operands. This new utility insn-
eval.c aims to be used to resolve userspace linear addresses based on
the contents of the instruction operands as well as the contents of pt_regs
structure.

These utilities come with a separate header. This is to avoid taking insn.c
out of sync from the instructions decoders under tools/obj and tools/perf.
This also avoids adding cumbersome #ifdef's for the #include'd files
required to decode instructions in a kernel context.

Functions are simply relocated. There are not functional or indentation
changes.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: ricardo.neri@intel.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Garnier <thgarnie@google.com>
Link: https://lkml.kernel.org/r/1509135945-13762-10-git-send-email-ricardo.neri-calderon@linux.intel.com
 2017-11-01 21:50:10 +01:00