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authorAlan Modra <amodra@gmail.com>2017-10-03 08:46:39 +1030
committerAlan Modra <amodra@gmail.com>2017-10-03 09:36:26 +1030
commitdef5c83c02fcc1c91d3f0da21005e0503b8ec881 (patch)
tree62286854efdd097cc76cc52d5931e476ab3405cc
parent45320ffa0450b27e232d933d2a1c6a09d94ac18b (diff)
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ld -z relro documentation
* ld.texinfo (-z relro): Expand description. (DATA_SEGMENT_ALIGN): Note that -z relro is not effective when running with system page size larger than commonpagesize. (DATA_SEGMENT_RELRO_END): Be explicit about the alignment.
-rw-r--r--ld/ChangeLog7
-rw-r--r--ld/ld.texinfo17
2 files changed, 18 insertions, 6 deletions
diff --git a/ld/ChangeLog b/ld/ChangeLog
index 5beae41..068715e 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,10 @@
+2017-10-03 Alan Modra <amodra@gmail.com>
+
+ * ld.texinfo (-z relro): Expand description.
+ (DATA_SEGMENT_ALIGN): Note that -z relro is not effective when
+ running with system page size larger than commonpagesize.
+ (DATA_SEGMENT_RELRO_END): Be explicit about the alignment.
+
2017-10-01 Alan Modra <amodra@gmail.com>
PR 21970
diff --git a/ld/ld.texinfo b/ld/ld.texinfo
index 90a745a..b67a715 100644
--- a/ld/ld.texinfo
+++ b/ld/ld.texinfo
@@ -1219,7 +1219,10 @@ first called.
Marks the object may contain $ORIGIN.
@item relro
-Create an ELF @code{PT_GNU_RELRO} segment header in the object.
+Create an ELF @code{PT_GNU_RELRO} segment header in the object. This
+specifies a memory segment that should be made read-only after
+relocation, if supported. Specifying @samp{common-page-size} smaller
+than the system page size will render this protection ineffective.
@item max-page-size=@var{value}
Set the emulation maximum page size to @var{value}.
@@ -6363,8 +6366,10 @@ bytes in the on-disk file.
This expression can only be used directly in @code{SECTIONS} commands, not in
any output section descriptions and only once in the linker script.
@var{commonpagesize} should be less or equal to @var{maxpagesize} and should
-be the system page size the object wants to be optimized for (while still
-working on system page sizes up to @var{maxpagesize}).
+be the system page size the object wants to be optimized for while still
+running on system page sizes up to @var{maxpagesize}. Note however
+that @samp{-z relro} protection will not be effective if the system
+page size is larger than @var{commonpagesize}.
@noindent
Example:
@@ -6387,9 +6392,9 @@ This defines the end of the @code{PT_GNU_RELRO} segment when
@samp{-z relro} option is used.
When @samp{-z relro} option is not present, @code{DATA_SEGMENT_RELRO_END}
does nothing, otherwise @code{DATA_SEGMENT_ALIGN} is padded so that
-@var{exp} + @var{offset} is aligned to the most commonly used page
-boundary for particular target. If present in the linker script,
-it must always come in between @code{DATA_SEGMENT_ALIGN} and
+@var{exp} + @var{offset} is aligned to the @var{commonpagesize}
+argument given to @code{DATA_SEGMENT_ALIGN}. If present in the linker
+script, it must be placed between @code{DATA_SEGMENT_ALIGN} and
@code{DATA_SEGMENT_END}. Evaluates to the second argument plus any
padding needed at the end of the @code{PT_GNU_RELRO} segment due to
section alignment.