linux-toradex.git/arch/x86/lib/insn-eval.c, branch v6.11

x86/insn-eval: Fix function param name in get_eff_addr_sib()

2024-02-13T21:41:25+00:00

Change "regoff" to "base_offset" in 2 places in the kernel-doc comments to
prevent warnings:

  insn-eval.c:1152: warning: Function parameter or member 'base_offset' not described in 'get_eff_addr_sib'
  insn-eval.c:1152: warning: Excess function parameter 'regoff' description in 'get_eff_addr_sib'

Signed-off-by: Randy Dunlap 
Signed-off-by: Borislav Petkov (AMD) 
Link: https://lore.kernel.org/r/20240211062452.16411-1-rdunlap@infradead.org

x86/insn: Avoid namespace clash by separating instruction decoder MMIO type from MMIO trace type

2023-01-03T17:46:06+00:00

Both  and  define various MMIO_ enum constants,
whose namespace overlaps.

Rename the  ones to have a INSN_ prefix, so that the headers can be
used from the same source file.

Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Ingo Molnar 
Link: https://lore.kernel.org/r/20230101162910.710293-2-Jason@zx2c4.com

x86/32: Remove lazy GS macros

2022-04-14T12:09:43+00:00

GS is always a user segment now.

Signed-off-by: Brian Gerst 
Signed-off-by: Borislav Petkov 
Reviewed-by: Thomas Gleixner 
Acked-by: Andy Lutomirski 
Link: https://lore.kernel.org/r/20220325153953.162643-4-brgerst@gmail.com

Merge tag 'x86_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-01-13T00:31:19+00:00

Pull x86 core updates from Borislav Petkov:

 - Get rid of all the .fixup sections because this generates
   misleading/wrong stacktraces and confuse RELIABLE_STACKTRACE and
   LIVEPATCH as the backtrace misses the function which is being fixed
   up.

 - Add Straight Line Speculation mitigation support which uses a new
   compiler switch -mharden-sls= which sticks an INT3 after a RET or an
   indirect branch in order to block speculation after them. Reportedly,
   CPUs do speculate behind such insns.

 - The usual set of cleanups and improvements

* tag 'x86_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits)
  x86/entry_32: Fix segment exceptions
  objtool: Remove .fixup handling
  x86: Remove .fixup section
  x86/word-at-a-time: Remove .fixup usage
  x86/usercopy: Remove .fixup usage
  x86/usercopy_32: Simplify __copy_user_intel_nocache()
  x86/sgx: Remove .fixup usage
  x86/checksum_32: Remove .fixup usage
  x86/vmx: Remove .fixup usage
  x86/kvm: Remove .fixup usage
  x86/segment: Remove .fixup usage
  x86/fpu: Remove .fixup usage
  x86/xen: Remove .fixup usage
  x86/uaccess: Remove .fixup usage
  x86/futex: Remove .fixup usage
  x86/msr: Remove .fixup usage
  x86/extable: Extend extable functionality
  x86/entry_32: Remove .fixup usage
  x86/entry_64: Remove .fixup usage
  x86/copy_mc_64: Remove .fixup usage
  ...

x86/entry_32: Fix segment exceptions

2022-01-12T15:38:25+00:00

The LKP robot reported that commit in Fixes: caused a failure. Turns out
the ldt_gdt_32 selftest turns into an infinite loop trying to clear the
segment.

As discovered by Sean, what happens is that PARANOID_EXIT_TO_KERNEL_MODE
in the handle_exception_return path overwrites the entry stack data with
the task stack data, restoring the "bad" segment value.

Instead of having the exception retry the instruction, have it emulate
the full instruction. Replace EX_TYPE_POP_ZERO with EX_TYPE_POP_REG
which will do the equivalent of: POP %reg; MOV $imm, %reg.

In order to encode the segment registers, add them as registers 8-11 for
32-bit.

By setting regs->[defg]s the (nested) RESTORE_REGS will pop this value
at the end of the exception handler and by increasing regs->sp, it will
have skipped the stack slot.

This was debugged by Sean Christopherson .

 [ bp: Add EX_REG_GS too. ]

Fixes: aa93e2ad7464 ("x86/entry_32: Remove .fixup usage")
Reported-by: kernel test robot 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Borislav Petkov 
Link: https://lore.kernel.org/r/Yd1l0gInc4zRcnt/@hirez.programming.kicks-ass.net

x86/extable: Extend extable functionality

2021-12-11T08:09:46+00:00

In order to remove further .fixup usage, extend the extable
infrastructure to take additional information from the extable entry
sites.

Specifically add _ASM_EXTABLE_TYPE_REG() and EX_TYPE_IMM_REG that
extend the existing _ASM_EXTABLE_TYPE() by taking an additional
register argument and encoding that and an s16 immediate into the
existing s32 type field. This limits the actual types to the first
byte, 255 seem plenty.

Also add a few flags into the type word, specifically CLEAR_AX and
CLEAR_DX which clear the return and extended return register.

Notes:
 - due to the % in our register names it's hard to make it more
   generally usable as arm64 did.
 - the s16 is far larger than used in these patches, future extentions
   can easily shrink this to get more bits.
 - without the bitfield fix this will not compile, because: 0xFF > -1
   and we can't even extract the TYPE field.

[nathanchance: Build fix for clang-lto builds:
 https://lkml.kernel.org/r/20211210234953.3420108-1-nathan@kernel.org
]

Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Josh Poimboeuf 
Reviewed-by: Nick Desaulniers 
Tested-by: Nick Desaulniers 
Link: https://lore.kernel.org/r/20211110101325.303890153@infradead.org

x86/insn-eval: Introduce insn_decode_mmio()

2021-11-30T22:53:19+00:00

In preparation for sharing MMIO instruction decode between SEV-ES and
TDX, factor out the common decode into a new insn_decode_mmio() helper.

For regular virtual machine, MMIO is handled by the VMM and KVM
emulates instructions that caused MMIO. But, this model doesn't work
for a secure VMs (like SEV or TDX) as VMM doesn't have access to the
guest memory and register state. So, for TDX or SEV VMM needs
assistance in handling MMIO. It induces exception in the guest. Guest
has to decode the instruction and handle it on its own.

The code is based on the current SEV MMIO implementation.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Dave Hansen 
Reviewed-by: Andi Kleen 
Reviewed-by: Tony Luck 
Tested-by: Joerg Roedel 
Acked-by: Tom Lendacky 
Link: https://lkml.kernel.org/r/20211130184933.31005-4-kirill.shutemov@linux.intel.com

x86/insn-eval: Introduce insn_get_modrm_reg_ptr()

2021-11-30T22:53:04+00:00

The helper returns a pointer to the register indicated by
ModRM byte.

It's going to replace vc_insn_get_reg() in the SEV MMIO
implementation. TDX MMIO implementation will also use it.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Dave Hansen 
Reviewed-by: Andi Kleen 
Reviewed-by: Tony Luck 
Tested-by: Joerg Roedel 
Acked-by: Tom Lendacky 
Link: https://lkml.kernel.org/r/20211130184933.31005-3-kirill.shutemov@linux.intel.com

x86/insn-eval: Handle insn_get_opcode() failure

2021-11-30T22:52:26+00:00

is_string_insn() calls insn_get_opcode() that can fail, but does not
handle the failure.

is_string_insn() interface does not allow to communicate an error to the
caller.

Push insn_get_opcode() to the only non-static user of is_string_insn()
and fail it early if insn_get_opcode() fails.

[ dhansen: fix tabs-versus-spaces breakage ]

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Dave Hansen 
Tested-by: Joerg Roedel 
Acked-by: Tom Lendacky 
Link: https://lkml.kernel.org/r/20211130184933.31005-2-kirill.shutemov@linux.intel.com

x86/iopl: Fake iopl(3) CLI/STI usage

2021-09-21T11:52:18+00:00

Since commit c8137ace5638 ("x86/iopl: Restrict iopl() permission
scope") it's possible to emulate iopl(3) using ioperm(), except for
the CLI/STI usage.

Userspace CLI/STI usage is very dubious (read broken), since any
exception taken during that window can lead to rescheduling anyway (or
worse). The IOPL(2) manpage even states that usage of CLI/STI is highly
discouraged and might even crash the system.

Of course, that won't stop people and HP has the dubious honour of
being the first vendor to be found using this in their hp-health
package.

In order to enable this 'software' to still 'work', have the #GP treat
the CLI/STI instructions as NOPs when iopl(3). Warn the user that
their program is doing dubious things.

Fixes: a24ca9976843 ("x86/iopl: Remove legacy IOPL option")
Reported-by: Ondrej Zary 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Thomas Gleixner 
Cc: stable@kernel.org # v5.5+
Link: https://lkml.kernel.org/r/20210918090641.GD5106@worktop.programming.kicks-ass.net