gdb/testsuite/gdb.arch/amd64-init-x87-values.exp

# Copyright 2018-2021 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# This file is part of the gdb testsuite.

# Test initial values of x87 control registers, before any x87
# instructions have been executed in the inferior.

if ![is_amd64_regs_target] then {
    return
}

standard_testfile .S

set options [list debug \
		 additional_flags=-static \
		 additional_flags=-nostartfiles]
if { [build_executable "failed to prepare" ${testfile} ${srcfile} $options] } {
    return -1
}

# Start the test file, and check the x87 control registers (and
# mxcsr), we expect the default values in all registers.
#
# Step forward until the x87 unit is enabled, recheck the register
# values; they should still have the default values.
#
# Finally, step forward until the x87 state has changed, and then
# recheck the register state to view the changes.
proc_with_prefix check_x87_regs_around_init {} {
    global binfile

    clean_restart ${binfile}

    # Get things started.
    if ![runto_main] then {
	return 0
    }

    # Check initial values of x87 control registers.  The MXCSR isn't part
    # of the x87 set, it belongs with SSE/AVX, however we test it here
    # too, it should have its default value in both cases.
    foreach {regname regvalue} { "fctrl" "0x37f" \
				 "fstat" "0x0" \
				 "ftag" "0xffff" \
				 "fiseg" "0x0" \
				 "fioff" "0x0" \
				 "foseg" "0x0" \
				 "fooff" "0x0" \
				 "fop" "0x0" \
				 "mxcsr" "0x1f80"} {
	gdb_test "p/x \$${regname}" " = ${regvalue}"  "check initial value of \$${regname}"
    }

    # No x87 instructions have been executed yet.  Step up to FWAIT
    # instruction.  Executing this instruction will enable the x87 unit,
    # causing the kernel to place the default values into all registers.
    # After this GDB will no longer supply the default values itself but
    # will instread read the values out of the xsave buffer.
    gdb_test "stepi" "fwait" "step to FWAIT instruction"
    gdb_test "stepi" "nop" "step past FWAIT instruction"

    # The x87 unit is now enabled, but the register values should be
    # unchanged.
    foreach {regname regvalue} { "fctrl" "0x37f" \
				 "fstat" "0x0" \
				 "ftag" "0xffff" \
				 "fiseg" "0x0" \
				 "fioff" "0x0" \
				 "foseg" "0x0" \
				 "fooff" "0x0" \
				 "fop" "0x0" \
				 "mxcsr" "0x1f80"} {
	gdb_test "p/x \$${regname}" " = ${regvalue}"  "check post FWAIT value of \$${regname}"
    }

    # Now step to an x87 instruction that modifies some state.
    gdb_test "stepi" "fld1" "step to FLD1 instruction"

    # Grab the address of this instruction, it will appear in later
    # results.
    set addr [get_hexadecimal_valueof "\$pc" "0"]

    # Step past the FLD1 instruction.
    gdb_test "stepi" "nop" "step past FLD1 instruction"

    # Check new values of x87 control registers (and MXCSR).
    foreach {regname regvalue} [list "fctrl" "0x37f" \
				     "fstat" "0x3800" \
				     "ftag" "0x3fff" \
				     "fiseg" "0x0" \
				     "fioff" $addr \
				     "foseg" "0x0" \
				     "fooff" "0x0" \
				     "fop" "0x0" \
				     "mxcsr" "0x1f80" ] {
	gdb_test "p/x \$${regname}" " = ${regvalue}"  "check post FLD1 value of \$${regname}"
    }
}

# Start the test file, all FP features will be disabled.  Set a new
# value into the MXCSR register, then step forward one instruction (a
# nop that does not enable any FP features).  Finally check that the
# mxcsr register still has the value we set.
proc_with_prefix check_setting_mxcsr_before_enable {} {
    global binfile gdb_prompt

    clean_restart ${binfile}

    if ![runto_main] then {
	return 0
    }

    gdb_test_no_output "set \$mxcsr=0x9f80" "set a new value for MXCSR"
    gdb_test "stepi" "fwait" "step forward one instruction for mxcsr test"

    set test "check new value of MXCSR is still in place"
    set pass_pattern " = 0x9f80"
    # Pre-4.14 kernels have a bug (fixed by commit 0852b374173b "x86/fpu:
    # Add FPU state copying quirk to handle XRSTOR failure on Intel Skylake
    # CPUs") that causes mxcsr not to be copied, in which case we get 0 instead of
    # the just saved value.
    set xfail_pattern " = 0x0"
    gdb_test_multiple "p/x \$mxcsr" $test {
	-re "\[\r\n\]*(?:$pass_pattern)\[\r\n\]+$gdb_prompt $" {
	    pass $test
	}
	-re "\[\r\n\]*(?:$xfail_pattern)\[\r\n\]+$gdb_prompt $" {
	    xfail $test
	}
    }
}

# Start the test file, all FP features will be disabled.  Set new
# values into the x87 control-registers, then step forward one
# instruction (a nop that does not enable any FP features).  Finally
# check that all the x87 control-registers still have the values we
# set.
proc_with_prefix check_setting_x87_regs_before_enable {} {
    global binfile

    clean_restart ${binfile}

    if ![runto_main] then {
	return 0
    }

    foreach {regname regvalue} [list "fctrl" "0x37f" \
				    "fstat" "0x3800" \
				    "ftag" "0x7777" \
				    "fiseg" "0x12" \
				    "fioff" "0x2418" \
				    "foseg" "0x24" \
				    "fooff" "0x36" \
				    "fop" "0x100" ] {
	gdb_test_no_output "set \$$regname=$regvalue" "set a new value for $regname"
    }

    gdb_test "stepi" "fwait" "step forward one instruction for x87 test"

    foreach {regname regvalue} [list "fctrl" "0x37f" \
				    "fstat" "0x3800" \
				    "ftag" "0x7777" \
				    "fiseg" "0x12" \
				    "fioff" "0x2418" \
				    "foseg" "0x24" \
				    "fooff" "0x36" \
				    "fop" "0x100" ] {
	gdb_test "p/x \$$regname" "= $regvalue" "check new value of $regname"
    }
}

check_x87_regs_around_init
check_setting_mxcsr_before_enable
check_setting_x87_regs_before_enable