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ld: =fillexp different behaviors for hexidecimal literal

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PR 30865
  * ld.texi: Update description of the FILL command.
  * testsuite/ld-scripts/fill2.d: New test.
  * testsuite/ld-scripts/fill2.t: New test source.
  * testsuite/ld-scripts/data.exp: Run the new test.
This commit is contained in:
Nick Clifton
2023-11-06 13:59:53 +00:00
parent f005d22941
commit f1837d9c3f
5 changed files with 89 additions and 1 deletions
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ld/ChangeLog
+8
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@@ -1,3 +1,11 @@
2023-11-06 Nick Clifton <nickc@redhat.com>
PR 30865
* ld.texi: Update description of the FILL command.
* testsuite/ld-scripts/fill2.d: New test.
* testsuite/ld-scripts/fill2.t: New test source.
* testsuite/ld-scripts/data.exp: Run the new test.
2023-11-02 Nick Clifton <nickc@redhat.com>
* testsuite/ld-x86-64/property-3.r: Update regexp to allow for
ld/ld.texi
+39 -1
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@@ -5552,6 +5552,36 @@ entire section. If both are used, the @code{FILL} command takes
precedence. @xref{Output Section Fill}, for details on the fill
expression.
Note - normally the value of @code{expression} is zero extended to 4
bytes when used to fill gaps. Thus @samp{FILL(144)} will fill a
region with repeats of the pattern @samp{0 0 0 144}. The value is
treated as a big-endian number, so for example
@samp{FILL(22 * 256 + 23)} will fill the region with repeats of the
pattern @samp {0 0 22 23}. If the expression results in a value with
more than 4 significant bytes only the least 4 bytes of the value will
be used.
The above rules do not apply when the @code{expression} is a simple
hexadecimal number. In this case zero extension is not performed and
all bytes are significant. So @samp{FILL(0x90)} will fill a region with
repeats of @samp{0x90} with no zero bytes, and @samp{FILL(0x9192)}
will fill the region with repeats of @samp{0x91 0x92}. Zero bytes
in a hexadecimal expression are significant even at the start, so
@samp{FILL(0x0090)} will fill a region with repeats of @samp{0x00 0x90}.
Hexadecimal numbers can be longer than 4 bytes, and all of the bytes
are significant, so @samp{FILL(0x123456789a)} will fill a region with
repeats of the 5 byte sequence @samp{0x12 0x34 0x56 0x78 0x9a}.
Excess bytes in a hexadecimal value beyond the size of a region will
be silently ignored.
The above only applies to hexadecimal numbers specified as
@samp{0x[0-9][a-f][A-F]}. Hexadecimal numbers specified with a
@samp{$} prefix, or a @samp{h}, @samp{H}, @samp{x} or @samp{X} suffix
will follow the normal fill value rules. This also applies to
expressions that involve hexadecimal numbers, and hexadecimal numbers
that have a magnitude suffix.
@kindex LINKER_VERSION
@cindex LINKER_VERSION
The @code{LINKER_VERSION} command inserts a string containing the
@@ -5966,7 +5996,15 @@ an arbitrarily long sequence of hex digits can be used to specify the
fill pattern; Leading zeros become part of the pattern too. For all
other cases, including extra parentheses or a unary @code{+}, the fill
pattern is the four least significant bytes of the value of the
expression. In all cases, the number is big-endian.
expression. If the value is less than four bytes in size then it will
be zero extended to four bytes. In all cases, the number is big-endian.
@smallexample
Fill Value Fill Pattern
0x90 90 90 90 90
0x0090 00 90 00 90
144 00 00 00 90
@end smallexample
You can also change the fill value with a @code{FILL} command in the
output section commands; (@pxref{Output Section Data}).
ld/testsuite/ld-scripts/data.exp
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@@ -29,6 +29,7 @@ if { [is_pecoff_format] } then {
run_dump_test data
run_dump_test fill
run_dump_test fill16
run_dump_test fill2
run_dump_test pr27100
set LDFLAGS $old_LDFLAGS
ld/testsuite/ld-scripts/fill2.d
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@@ -0,0 +1,12 @@
#source: fill_0.s
#ld: -T fill2.t
#readelf: -x.foo
#notarget: ![is_elf_format]
# See PR 30865 - a fill value expressed as a simple hexadecimal
# number behaves differently from other fill values.
Hex dump of section '.foo':
0x00000000 00000000 00000090 91919191 00000092 ................
0x00000010 00000093 00025000 00969500 00000097 ................
0x00000020 00010203 04050607 04050607 04050607 ................
0x00000030 08090a0b ffffffff .*
ld/testsuite/ld-scripts/fill2.t
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@@ -0,0 +1,29 @@
SECTIONS {
.foo :
{
. += 4;
FILL (144) # Decimal values zero extend to 4 bytes. Fills with: 00 00 00 90
. += 4;
FILL (0x91) # Hex values do not zero extend. Fills with: 91 91 91 91
. += 4;
FILL ($92) # A dollar prefix indicates a hex values that does zero extend. Fills with: 00 00 00 92
. += 4;
FILL (93H) # An H suffix does the same. Fills with: 00 00 00 93
. += 4;
FILL (0x94K) # A hex value with a manitude suffix zero extends. Fills with: 00 02 50 00
. += 4;
FILL (0x009695) # Zeros in hex values are significant. Values are big-endian. Fills with: 00 96 95 00
. += 4;
FILL (0x90+0x7) # An expression containing hex values also zero extends. Fills with: 00 00 00 97
. += 4;
FILL (0x0001020304050607) # Hex values can be used to specify fills with more than 4 bytes. Fills with: 00 01 02 03 04 05 06 07
. += 8;
FILL ($0001020304050607) # But non-hex or $-hex or suffix-hex values cannot. Fills with 04 05 06 07 04 05 06 07
. += 8;
FILL (0x08090a0b0c0d0e0f) # Extra bytes at the end of a value are silently ignored. Fills with 08 09 0a 0b
. += 4;
LONG(0xffffffff)
} =0
/DISCARD/ : { *(*) }
}