The format of the task state segment is governed by bit 3 in the
descriptor type field. On a task switch, the format for saving
is given by the current value of TR's type field, while the
format for loading is given by the new descriptor.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
According to the manual, the high 16-bit of the registers are preserved
when switching to a 16-bit task. Implement this in switch_tss_ra.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The TSS offsets in the manuals have only 2-byte slots for the
segment registers. QEMU incorrectly uses 4-byte slots, so
that SS overlaps the LDT selector.
Resolves: #382
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The we never allow i/o from user-only, and the tss check
that helper_check_io does will always fail. Use an ifdef
within gen_check_io and return false, indicating that an
exception is known to be raised.
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210514151342.384376-50-richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Drop helper_check_io[bwl] and expose their common
subroutine to tcg directly.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210514151342.384376-49-richard.henderson@linaro.org>
smm is only really useful for sysemu, split in two modules
around the CONFIG_USER_ONLY, in order to remove the ifdef
and use the build system instead.
add cpu_abort() when detecting attempts to enter SMM mode via
SMI interrupt in user-mode, and assert that the cpu is not
in SMM mode while translating RSM instructions.
Signed-off-by: Claudio Fontana <cfontana@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210322132800.7470-12-cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
env->error_code is only 32-bits wide, so the high 32 bits of EXITINFO1
are being lost. However, even though saving guest state and restoring
host state must be delayed to do_vmexit, because they might take tb_lock,
it is always possible to write to the VMCB. So do this for the exit
code and EXITINFO1, just like it is already being done for EXITINFO2.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Use the dedicated X86Seg enum type for segment registers.
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210109233427.749748-1-f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When the 'int N' instruction is executed in protected mode, the
pseudocode in the architecture manual specifies that we need to check:
* vector number within IDT limits
* selected IDT descriptor is a valid type (interrupt, trap or task gate)
* if this was a software interrupt then gate DPL < CPL
The way we had structured the code meant that the privilege check for
software interrupts ended up not in the code path taken for task gate
handling, because all of the task gate handling code was in the 'case 5'
of the switch which was checking "is this descriptor a valid type".
Move the task gate handling code out of that switch (so that it is now
purely doing the "valid type?" check) and below the software interrupt
privilege check.
The effect of this missing check was that in a guest userspace binary
executing 'int 8' would cause a guest kernel panic rather than the
userspace binary being handed a SEGV.
This is essentially the same bug fixed in VirtualBox in 2012:
https://www.halfdog.net/Security/2012/VirtualBoxSoftwareInterrupt0x8GuestCrash/
Note that for QEMU this is not a security issue because it is only
present when using TCG.
Fixes: https://bugs.launchpad.net/qemu/+bug/1813201
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20201121224445.16236-1-peter.maydell@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
to do this, we need to take code out of cpu.c and helper.c,
and also move some prototypes from cpu.h, for code that is
needed in tcg/xxx_helper.c, and which in turn is part of the
callbacks registered by the class initialization.
Therefore, do some shuffling of the parts of cpu.h that
are only relevant for tcg/, and put them in tcg/helper-tcg.h
For FT0 and similar macros, put them in tcg/fpu-helper.c
since they are used only there.
Signed-off-by: Claudio Fontana <cfontana@suse.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20201212155530.23098-8-cfontana@suse.de>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
