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Re: [PATCH 2/2] ld: Don't evaluate unneeded PROVIDE expressions.
- From: Andrew Burgess <andrew dot burgess at embecosm dot com>
- To: binutils at sourceware dot org
- Cc: Hans-Peter Nilsson <hp at bitrange dot com>
- Date: Thu, 8 Jan 2015 10:17:56 +0000
- Subject: Re: [PATCH 2/2] ld: Don't evaluate unneeded PROVIDE expressions.
- Authentication-results: sourceware.org; auth=none
- References: <cover dot 1420631791 dot git dot andrew dot burgess at embecosm dot com> <3d30f0e7bfaf420b6a4d64a818db85700c4fc083 dot 1420631791 dot git dot andrew dot burgess at embecosm dot com> <alpine dot BSF dot 2 dot 02 dot 1501072022030 dot 57687 at arjuna dot pair dot com>
* Hans-Peter Nilsson <hp@bitrange.com> [2015-01-07 20:25:49 -0500]:
> Having not looked at the rest, I just spotted:
Thanks for the review. I've fixed the issues you pointed out, and
attached an updated patch.
Andrew
---
When creating a linker mapfile (using -Map=MAPFILE), we previously would
always try to evaluate the expression from a PROVIDE statement.
However, this is not always safe, consider:
PROVIDE (foo = 0x10);
PROVIDE (bar = foo);
In this example, if neither 'foo' or 'bar' is needed, then while
generating the linker mapfile evaluating the expression for 'foo' is
harmless (just the value 0x10). However, evaluating the expression for
'bar' requires the symbol 'foo', which is undefined. This used to cause
a fatal error.
This patch changes the behaviour, so that when the destination of the
PROVIDE is not defined (that is the PROVIDE is not going to provide
anything) the expression is not evaluated, and instead a special string
is displayed to indicate that the linker is discarding the PROVIDE
statement.
This change not only fixes the spurious undefined symbol error, but also
means that a user can now tell if a PROVIDE statement has provided
anything by inspecting the linker mapfile, something that could not be
done before.
ld/ChangeLog:
* ldlang.c (print_assignment): Only evaluate the expression for a
PROVIDE'd assignment when the destination is being defined.
Display a special message for PROVIDE'd symbols that are not being
provided.
ld/testsuite/ChangeLog:
* ld-scripts/provide-4.d: New file.
* ld-scripts/provide-4-map.d: New file.
* ld-scripts/provide-4.t: New file.
* ld-scripts/provide.exp: Run the provide-4.d test.
---
ld/ChangeLog | 7 +++++++
ld/ldlang.c | 14 ++++++++++++--
ld/testsuite/ChangeLog | 7 +++++++
ld/testsuite/ld-scripts/provide-4-map.d | 26 ++++++++++++++++++++++++++
ld/testsuite/ld-scripts/provide-4.d | 10 ++++++++++
ld/testsuite/ld-scripts/provide-4.t | 16 ++++++++++++++++
ld/testsuite/ld-scripts/provide.exp | 1 +
7 files changed, 79 insertions(+), 2 deletions(-)
create mode 100644 ld/testsuite/ld-scripts/provide-4-map.d
create mode 100644 ld/testsuite/ld-scripts/provide-4.d
create mode 100644 ld/testsuite/ld-scripts/provide-4.t
diff --git a/ld/ChangeLog b/ld/ChangeLog
index be4617f..fab597e 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,10 @@
+2015-01-07 Andrew Burgess <andrew.burgess@embecosm.com>
+
+ * ldlang.c (print_assignment): Only evaluate the expression for a
+ PROVIDE'd assignment when the destination is being defined.
+ Display a special message for PROVIDE'd symbols that are not being
+ provided.
+
2015-01-01 Alan Modra <amodra@gmail.com>
* ldver.c (ldversion): Just print current year.
diff --git a/ld/ldlang.c b/ld/ldlang.c
index 9f3d209..a99febe 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -3983,7 +3983,14 @@ print_assignment (lang_assignment_statement_type *assignment,
osec = output_section->bfd_section;
if (osec == NULL)
osec = bfd_abs_section_ptr;
- exp_fold_tree (tree, osec, &print_dot);
+
+ if (assignment->exp->type.node_class != etree_provide
+ || bfd_link_hash_lookup (link_info.hash,
+ assignment->exp->assign.dst,
+ FALSE, FALSE, TRUE) != NULL)
+ exp_fold_tree (tree, osec, &print_dot);
+ else
+ expld.result.valid_p = FALSE;
if (expld.result.valid_p)
{
bfd_vma value;
@@ -4021,7 +4028,10 @@ print_assignment (lang_assignment_statement_type *assignment,
}
else
{
- minfo ("*undef* ");
+ if (assignment->exp->type.node_class == etree_provide)
+ minfo ("[!provide]");
+ else
+ minfo ("*undef* ");
#ifdef BFD64
minfo (" ");
#endif
diff --git a/ld/testsuite/ChangeLog b/ld/testsuite/ChangeLog
index 266e996..521c819 100644
--- a/ld/testsuite/ChangeLog
+++ b/ld/testsuite/ChangeLog
@@ -1,5 +1,12 @@
2015-01-07 Andrew Burgess <andrew.burgess@embecosm.com>
+ * ld-scripts/provide-4.d: New file.
+ * ld-scripts/provide-4-map.d: New file.
+ * ld-scripts/provide-4.t: New file.
+ * ld-scripts/provide.exp: Run the provide-4.d test.
+
+2015-01-07 Andrew Burgess <andrew.burgess@embecosm.com>
+
* ld-scripts/overlay-size.d: Add 'map' option.
* ld-scripts/overlay-size.exp: Remove manual check of mapfile.
* lib/ld-lib.exp (run_dump_test): Add support for new 'map'
diff --git a/ld/testsuite/ld-scripts/provide-4-map.d b/ld/testsuite/ld-scripts/provide-4-map.d
new file mode 100644
index 0000000..da2ff66
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-4-map.d
@@ -0,0 +1,26 @@
+#...
+Linker script and memory map
+
+ 0x0+1 PROVIDE \(foo, 0x1\)
+ \[!provide\] PROVIDE \(bar, 0x2\)
+ 0x0+3 PROVIDE \(baz, 0x3\)
+
+\.text 0x0+ 0x0
+ \.text 0x0+ 0x0 tmpdir/dump0\.o
+
+\.iplt 0x0+ 0x0
+ \.iplt 0x0+ 0x0 tmpdir/dump0\.o
+
+\.rela\.dyn 0x0+ 0x0
+ \.rela\.iplt 0x0+ 0x0 tmpdir/dump0\.o
+ \.rela\.data 0x0+ 0x0 tmpdir/dump0\.o
+
+\.data 0x0+2000 0x10
+ \*\(\.data\)
+ \.data 0x0+2000 0x10 tmpdir/dump0\.o
+ 0x0+2000 foo
+ \[!provide\] PROVIDE \(loc1, ALIGN \(\., 0x10\)\)
+ 0x0+2010 PROVIDE \(loc2, ALIGN \(\., 0x10\)\)
+ \[!provide\] PROVIDE \(loc3, \(loc1 \+ 0x20\)\)
+ 0x0+2030 loc4 = \(loc2 \+ 0x20\)
+#...
diff --git a/ld/testsuite/ld-scripts/provide-4.d b/ld/testsuite/ld-scripts/provide-4.d
new file mode 100644
index 0000000..78482ea
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-4.d
@@ -0,0 +1,10 @@
+#source: provide-2.s
+#ld: -T provide-4.t
+#PROG: nm
+#map: provide-4-map.d
+
+0000000000000003 A baz
+0000000000002000 D foo
+0000000000002010 D loc2
+0000000000002030 A loc4
+
diff --git a/ld/testsuite/ld-scripts/provide-4.t b/ld/testsuite/ld-scripts/provide-4.t
new file mode 100644
index 0000000..424c238
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-4.t
@@ -0,0 +1,16 @@
+SECTIONS
+{
+ PROVIDE (foo = 1);
+ PROVIDE (bar = 2);
+ PROVIDE (baz = 3);
+ .data 0x2000 :
+ {
+ *(.data)
+
+ PROVIDE (loc1 = ALIGN (., 0x10));
+ PROVIDE (loc2 = ALIGN (., 0x10));
+ }
+
+ PROVIDE (loc3 = loc1 + 0x20);
+ loc4 = loc2 + 0x20;
+}
diff --git a/ld/testsuite/ld-scripts/provide.exp b/ld/testsuite/ld-scripts/provide.exp
index 7f45e58..baba0a4 100644
--- a/ld/testsuite/ld-scripts/provide.exp
+++ b/ld/testsuite/ld-scripts/provide.exp
@@ -40,5 +40,6 @@ run_dump_test provide-1
run_dump_test provide-2
setup_xfail *-*-*
run_dump_test provide-3
+run_dump_test provide-4
set LDFLAGS "$saved_LDFLAGS"
--
1.9.3