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diff --git a/subx/052kernel-string-equal.subx b/subx/052kernel-string-equal.subx
new file mode 100644
index 00000000..67e9695e
--- /dev/null
+++ b/subx/052kernel-string-equal.subx
@@ -0,0 +1,260 @@
+# Checking null-terminated ascii strings.
+#
+# By default we create strings with a 4-byte length prefix rather than a null suffix.
+# However we still need null-prefixed strings when interacting with the Linux
+# kernel in a few places. This layer implements a function for comparing
+# a null-terminated 'kernel string' with a length-prefixed 'SubX string'.
+#
+# To run (from the subx directory):
+#   $ ./subx translate 05[0-2]*.subx -o /tmp/tmp52
+#   $ ./subx run /tmp/tmp52  # runs a series of tests
+#   ......  # all tests pass
+#
+# (We can't yet run the tests when given a "test" commandline argument,
+# because checking for it would require the function being tested! Breakage
+# would cause tests to not run, rather than to fail as we'd like.)
+
+== code
+#   instruction                     effective address                                                   register    displacement    immediate
+# . op          subop               mod             rm32          base        index         scale       r32
+# . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
+
+# main:
+    e8/call  run-tests/disp32  # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
+    # syscall(exit, Num-test-failures)
+    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/EBX   Num-test-failures/disp32          # copy *Num-test-failures to EBX
+    b8/copy-to-EAX  1/imm32/exit
+    cd/syscall  0x80/imm8
+
+# compare a null-terminated ascii string with a more idiomatic length-prefixed byte array
+# reason for the name: the only place we should have null-terminated ascii strings is from commandline args
+kernel-string-equal:  # s : null-terminated ascii string, benchmark : length-prefixed ascii string -> EAX : boolean
+    # . prolog
+    55/push-EBP
+    89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
+    # . save registers
+    51/push-ECX
+    52/push-EDX
+    53/push-EBX
+    56/push-ESI
+    57/push-EDI
+
+    # pseudocode:
+    #   initialize n = b->length
+    #   initialize s1 = s
+    #   initialize s2 = b->data
+    #   i = 0
+    #   for (i = 0; i < n; ++n)
+    #     c1 = *s1
+    #     c2 = *s2
+    #     if c1 == 0
+    #       return false
+    #     if c1 != c2
+    #       return false
+    #   return *s1 == 0
+    #
+    # initialize s into EDI
+    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           7/r32/EDI   8/disp8         .                 # copy *(EBP+8) to EDI
+    # initialize benchmark length n into EDX
+    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           2/r32/EDX   0xc/disp8       .                 # copy *(EBP+12) to EDX
+    8b/copy                         0/mod/indirect  2/rm32/EDX    .           .             .           2/r32/EDX   .               .                 # copy *EDX to EDX
+    # initialize benchmark data into ESI
+    8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           6/r32/ESI   0xc/disp8       .                 # copy *(EBP+12) to ESI
+    81          0/subop/add         3/mod/direct    6/rm32/ESI    .           .             .           .           .               4/imm32           # add to ESI
+    # initialize loop counter i into ECX
+    b9/copy-to-ECX  0/imm32/exit
+    # while (i/ECX < n/EDX)
+$kernel-string-equal:loop:
+    39/compare                      3/mod/direct    1/rm32/ECX    .           .             .           2/r32/EDX   .               .                 # compare ECX with EDX
+    74/jump-if-equal  $kernel-string-equal:break/disp8
+    # c1/EAX, c2/EBX = *s, *benchmark
+    b8/copy-to-EAX  0/imm32
+    8a/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           0/r32/EAX   .               .                 # copy byte at *EDI to lower byte of EAX
+    bb/copy-to-EBX  0/imm32
+    8a/copy                         0/mod/indirect  6/rm32/ESI    .           .             .           3/r32/EBX   .               .                 # copy byte at *ESI to lower byte of EBX
+    # if (c1 == 0) return false
+    3d/compare-EAX  0/imm32
+    74/jump-if-equal  $kernel-string-equal:false/disp8
+    # if (c1 != c2) return false
+    39/compare                      3/mod/direct    0/rm32/EAX    .           .             .           3/r32/EBX   .               .                 # compare EAX with EBX
+    75/jump-if-not-equal  $kernel-string-equal:false/disp8
+    # ++s1, ++s2, ++i
+    41/inc-ECX
+    46/inc-ESI
+    47/inc-EDI
+    # end while
+    eb/jump  $kernel-string-equal:loop/disp8
+$kernel-string-equal:break:
+    # if (*s/EDI == 0) return true
+    b8/copy-to-EAX  0/imm32
+    8a/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           0/r32/EAX   .               .                 # copy byte at *EDI to lower byte of EAX
+    3d/compare-EAX  0/imm32
+    75/jump-if-not-equal  $kernel-string-equal:false/disp8
+$kernel-string-equal:true:
+    b8/copy-to-EAX  1/imm32
+    eb/jump  $kernel-string-equal:end/disp8
+    # return false
+$kernel-string-equal:false:
+    b8/copy-to-EAX  0/imm32
+$kernel-string-equal:end:
+    # . restore registers
+    5f/pop-to-EDI
+    5e/pop-to-ESI
+    5b/pop-to-EBX
+    5a/pop-to-EDX
+    59/pop-to-ECX
+    # . epilog
+    89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
+    5d/pop-to-EBP
+    c3/return
+
+# - tests
+
+test-compare-null-kernel-string-with-empty-array:
+    # EAX = kernel-string-equal(Null-kernel-string, "")
+    # . . push args
+    68/push  ""/imm32
+    68/push  Null-kernel-string/imm32
+    # . . call
+    e8/call  kernel-string-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
+    # check-ints-equal(EAX, 1, msg)
+    # . . push args
+    68/push  "F - test-compare-null-kernel-string-with-empty-array"/imm32
+    68/push  1/imm32/true
+    50/push-EAX
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    c3/return
+
+test-compare-null-kernel-string-with-non-empty-array:
+    # EAX = kernel-string-equal(Null-kernel-string, "Abc")
+    # . . push args
+    68/push  "Abc"/imm32
+    68/push  Null-kernel-string/imm32
+    # . . call
+    e8/call  kernel-string-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
+    # check-ints-equal(EAX, 0, msg)
+    # . . push args
+    68/push  "F - test-compare-null-kernel-string-with-non-empty-array"/imm32
+    68/push  0/imm32/false
+    50/push-EAX
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    c3/return
+
+test-compare-kernel-string-with-equal-array:
+    # EAX = kernel-string-equal(Abc-kernel-string, "Abc")
+    # . . push args
+    68/push  "Abc"/imm32
+    68/push  Abc-kernel-string/imm32
+    # . . call
+    e8/call  kernel-string-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
+    # check-ints-equal(EAX, 1, msg)
+    # . . push args
+    68/push  "F - test-compare-kernel-string-with-equal-array"/imm32
+    68/push  1/imm32/true
+    50/push-EAX
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    c3/return
+
+test-compare-kernel-string-with-inequal-array:
+    # EAX = kernel-string-equal(Abc-kernel-string, "Adc")
+    # . . push args
+    68/push  "Adc"/imm32
+    68/push  Abc-kernel-string/imm32
+    # . . call
+    e8/call  kernel-string-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
+    # check-ints-equal(EAX, 0, msg)
+    # . . push args
+    68/push  "F - test-compare-kernel-string-with-equal-array"/imm32
+    68/push  0/imm32/false
+    50/push-EAX
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    c3/return
+
+test-compare-kernel-string-with-empty-array:
+    # EAX = kernel-string-equal(Abc-kernel-string, "")
+    # . . push args
+    68/push  ""/imm32
+    68/push  Abc-kernel-string/imm32
+    # . . call
+    e8/call  kernel-string-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
+    # check-ints-equal(EAX, 0, msg)
+    # . . push args
+    68/push  "F - test-compare-kernel-string-with-equal-array"/imm32
+    68/push  0/imm32/false
+    50/push-EAX
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    c3/return
+
+test-compare-kernel-string-with-shorter-array:
+    # EAX = kernel-string-equal(Abc-kernel-string, "Ab")
+    # . . push args
+    68/push  "Ab"/imm32
+    68/push  Abc-kernel-string/imm32
+    # . . call
+    e8/call  kernel-string-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
+    # check-ints-equal(EAX, 0, msg)
+    # . . push args
+    68/push  "F - test-compare-kernel-string-with-shorter-array"/imm32
+    68/push  0/imm32/false
+    50/push-EAX
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    c3/return
+
+test-compare-kernel-string-with-longer-array:
+    # EAX = kernel-string-equal(Abc-kernel-string, "Abcd")
+    # . . push args
+    68/push  "Abcd"/imm32
+    68/push  Abc-kernel-string/imm32
+    # . . call
+    e8/call  kernel-string-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
+    # check-ints-equal(EAX, 0, msg)
+    # . . push args
+    68/push  "F - test-compare-kernel-string-with-longer-array"/imm32
+    68/push  0/imm32/false
+    50/push-EAX
+    # . . call
+    e8/call  check-ints-equal/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
+    c3/return
+
+== data
+
+Null-kernel-string:
+    00/null
+Abc-kernel-string:
+    41/A 62/b 63/c 00/null
+
+# . . vim:nowrap:textwidth=0