[PATCH 2/2] ld: Allow symbols from PROVIDE to be use in MEMORY regions
Andrew Burgess
andrew.burgess@embecosm.com
Thu Oct 15 12:58:10 GMT 2020
* Alan Modra <amodra@gmail.com> [2020-10-14 15:29:18 +1030]:
> On Mon, Oct 12, 2020 at 02:49:15PM +0100, Andrew Burgess wrote:
> > * ldlang.c (lang_process): Add extra call to lang_do_memory_regions, and pass
> > phase parameter.
> > (lang_do_memory_regions): Add parameter, only define origin and
> > length when we are not in the first phase. Reindent.
> > * testsuite/ld-scripts/provide-10.d: New file.
> > * testsuite/ld-scripts/provide-10.map: New file.
> > * testsuite/ld-scripts/provide-11.d: New file.
> > * testsuite/ld-scripts/provide-11.map: New file.
> > * testsuite/ld-scripts/provide-12.d: New file.
> > * testsuite/ld-scripts/provide-12.map: New file.
> > * testsuite/ld-scripts/provide-9.d: New file.
> > * testsuite/ld-scripts/provide-9.map: New file.
> > * testsuite/ld-scripts/provide-9.t: New file.
>
> OK, except I think it would be better in this case to omit the
> lang_do_memory_regions parameter and just test
> expld.phase != lang_first_phase_enum in lang_do_memory_regions.
Hi,
Thanks for the review.
I looked at making the change you suggested, but ran into a bit of a
problem. The two calls to lang_do_memory_regions appear in ldlang.c
like this:
/* A first pass through the memory regions ensures that if any region
references a symbol for its origin or length then this symbol will be
added to the symbol table. Having these symbols in the symbol table
means that when we call open_input_bfds PROVIDE statements will
trigger to provide any needed symbols. The regions origins and
lengths are not assigned as a result of this call. */
lang_do_memory_regions (...);
/* Create a bfd for each input file. */
current_target = default_target;
lang_statement_iteration++;
open_input_bfds (statement_list.head, OPEN_BFD_NORMAL);
/* Now that open_input_bfds has processed assignments and provide
statements we can give values to symbolic origin/length now. */
lang_do_memory_regions (...);
Now at the location of the first call expld.phase is indeed set to
lang_first_phase_enum, so that's not an issue. The problem is that
expld.phase is _still_ set to lang_first_phase_enum at the time of the
second call.
Now, sure, I can change its value, but what if some later call depends
on this being set to lang_first_phase_enum? OK, so I should change it
back again after. So now I have the second call like this:
/* Now that open_input_bfds has processed assignments and provide
statements we can give values to symbolic origin/length now. */
expld.phase = lang_final_phase_enum;
lang_do_memory_regions ();
expld.phase = lang_first_phase_enum;
That kind of feels like a really rubbish way to pass state to the
function call.
What I did do was move away from using the "phase" parameter, and
instead just passed a TRUE/FALSE 'update_regions_p' predicate.
Hopefully this removes possible confusion with "why a parameter and
not expld.phase?", but also avoids passing parameters through global
variables.
What do you think to this?
Thanks,
Andrew
---
commit 8c6592303d0dbd581fb779f50b4a22d477b3d647
Author: Andrew Burgess <andrew.burgess@embecosm.com>
Date: Wed Oct 7 14:27:56 2020 +0100
ld: Allow symbols from PROVIDE to be use in MEMORY regions
I wanted to write a linker script like this:
PROVIDE(mem_origin = 0x1000);
PROVIDE(mem_length = 0x1000);
MEMORY
{
REGION : ORIGIN = mem_origin, LENGTH = mem_length
}
....
Then when I link using this script I can optionally supply:
--defsym=mem_origin=..... --defsym=mem_length=....
to override the defaults.
And though passing `--defsym' does work, if I remove the use of
`--defsym' and just rely on the defaults I get an error:
ld-new: invalid origin for memory region REGION
Interestingly, if I make the above error non-fatal and dump a linker
map file I see that (a) REGION has origin 0x0, and length 0xffff...,
and (b) the symbol from the PROVIDE is provided.
An examination of ldlang.c:lang_process shows us what the issue is,
the origin and length of all memory regions are set as a result of a
single call to lang_do_memory_regions, this call is done after calling
open_input_bfds.
During the open_input_bfds call provide statements can be converted to
provided statements if we know that the assigned symbol is needed, but
for symbols that are only used in the memory regions we are unaware
that we need these symbols.
What I propose in this patch is to make two calls to
lang_do_memory_regions, in the first call we process the expressions
for the origin and length fields of each region, however, errors,
especially undefined symbols, will be ignored. The origin and length
values are not updated. However, by evaluating the expressions any
symbols we need will be added to the symbol table.
Now when we call open_input_bfds, when we process the provide
statements, we will see that the assigned symbol is needed add its new
value to the symbol table.
Finally we reach the original call to lang_do_memory_regions, in
this (now second) call we again process the expressions, and this time
update the origin and length values. Any errors encountered now are
reported to the user.
ld/ChangeLog:
* ldlang.c (lang_process): Add extra call to
lang_do_memory_regions, and pass parameter.
(lang_do_memory_regions): Add parameter, only define origin and
length when requested. Reindent.
* testsuite/ld-scripts/provide-10.d: New file.
* testsuite/ld-scripts/provide-10.map: New file.
* testsuite/ld-scripts/provide-11.d: New file.
* testsuite/ld-scripts/provide-11.map: New file.
* testsuite/ld-scripts/provide-12.d: New file.
* testsuite/ld-scripts/provide-12.map: New file.
* testsuite/ld-scripts/provide-9.d: New file.
* testsuite/ld-scripts/provide-9.map: New file.
* testsuite/ld-scripts/provide-9.t: New file.
diff --git a/ld/ldlang.c b/ld/ldlang.c
index 4249b3a045d..2073ac09ce4 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -98,7 +98,7 @@ static void lang_record_phdrs (void);
static void lang_do_version_exports_section (void);
static void lang_finalize_version_expr_head
(struct bfd_elf_version_expr_head *);
-static void lang_do_memory_regions (void);
+static void lang_do_memory_regions (bfd_boolean);
/* Exported variables. */
const char *output_target;
@@ -7909,13 +7909,22 @@ lang_process (void)
if (!bfd_section_already_linked_table_init ())
einfo (_("%F%P: can not create hash table: %E\n"));
+ /* A first pass through the memory regions ensures that if any region
+ references a symbol for its origin or length then this symbol will be
+ added to the symbol table. Having these symbols in the symbol table
+ means that when we call open_input_bfds PROVIDE statements will
+ trigger to provide any needed symbols. The regions origins and
+ lengths are not assigned as a result of this call. */
+ lang_do_memory_regions (FALSE);
+
/* Create a bfd for each input file. */
current_target = default_target;
lang_statement_iteration++;
open_input_bfds (statement_list.head, OPEN_BFD_NORMAL);
- /* open_input_bfds also handles assignments, so we can give values
- to symbolic origin/length now. */
- lang_do_memory_regions ();
+
+ /* Now that open_input_bfds has processed assignments and provide
+ statements we can give values to symbolic origin/length now. */
+ lang_do_memory_regions (TRUE);
#if BFD_SUPPORTS_PLUGINS
if (link_info.lto_plugin_active)
@@ -9373,10 +9382,16 @@ lang_do_version_exports_section (void)
lang_new_vers_node (greg, lreg), NULL);
}
-/* Evaluate LENGTH and ORIGIN parts of MEMORY spec */
+/* Evaluate LENGTH and ORIGIN parts of MEMORY spec. This is initially
+ called with UPDATE_REGIONS_P set to FALSE, in this case no errors are
+ thrown, however, references to symbols in the origin and length fields
+ will be pushed into the symbol table, this allows PROVIDE statements to
+ then provide these symbols. This function is called a second time with
+ UPDATE_REGIONS_P set to TRUE, this time the we update the actual region
+ data structures, and throw errors if missing symbols are encountered. */
static void
-lang_do_memory_regions (void)
+lang_do_memory_regions (bfd_boolean update_regions_p)
{
lang_memory_region_type *r = lang_memory_region_list;
@@ -9385,24 +9400,30 @@ lang_do_memory_regions (void)
if (r->origin_exp)
{
exp_fold_tree_no_dot (r->origin_exp);
- if (expld.result.valid_p)
- {
- r->origin = expld.result.value;
- r->current = r->origin;
- }
- else
- einfo (_("%F%P: invalid origin for memory region %s\n"),
- r->name_list.name);
+ if (update_regions_p)
+ {
+ if (expld.result.valid_p)
+ {
+ r->origin = expld.result.value;
+ r->current = r->origin;
+ }
+ else
+ einfo (_("%P: invalid origin for memory region %s\n"),
+ r->name_list.name);
+ }
}
if (r->length_exp)
{
exp_fold_tree_no_dot (r->length_exp);
- if (expld.result.valid_p)
- r->length = expld.result.value;
- else
- einfo (_("%F%P: invalid length for memory region %s\n"),
- r->name_list.name);
- }
+ if (update_regions_p)
+ {
+ if (expld.result.valid_p)
+ r->length = expld.result.value;
+ else
+ einfo (_("%P: invalid length for memory region %s\n"),
+ r->name_list.name);
+ }
+ }
}
}
diff --git a/ld/testsuite/ld-scripts/provide-10.d b/ld/testsuite/ld-scripts/provide-10.d
new file mode 100644
index 00000000000..7481a92bbbd
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-10.d
@@ -0,0 +1,3 @@
+#source: provide-5.s
+#ld: --defsym=mem_origin=0x300 --defsym=mem_length=0x400 -T provide-9.t
+#map: provide-10.map
diff --git a/ld/testsuite/ld-scripts/provide-10.map b/ld/testsuite/ld-scripts/provide-10.map
new file mode 100644
index 00000000000..022b962b2d8
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-10.map
@@ -0,0 +1,6 @@
+#...
+Memory Configuration
+
+Name Origin Length Attributes
+FOO 0x[0-9a-f]+300 +0x[0-9a-f]+400
+#pass
diff --git a/ld/testsuite/ld-scripts/provide-11.d b/ld/testsuite/ld-scripts/provide-11.d
new file mode 100644
index 00000000000..79bcfa62162
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-11.d
@@ -0,0 +1,3 @@
+#source: provide-5.s
+#ld: --defsym=mem_length=0x400 -T provide-9.t
+#map: provide-11.map
diff --git a/ld/testsuite/ld-scripts/provide-11.map b/ld/testsuite/ld-scripts/provide-11.map
new file mode 100644
index 00000000000..71763123123
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-11.map
@@ -0,0 +1,6 @@
+#...
+Memory Configuration
+
+Name Origin Length Attributes
+FOO 0x[0-9a-f]+100 +0x[0-9a-f]+400
+#pass
diff --git a/ld/testsuite/ld-scripts/provide-12.d b/ld/testsuite/ld-scripts/provide-12.d
new file mode 100644
index 00000000000..41d95900fd3
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-12.d
@@ -0,0 +1,3 @@
+#source: provide-5.s
+#ld: --defsym=mem_origin=0x300 -T provide-9.t
+#map: provide-12.map
diff --git a/ld/testsuite/ld-scripts/provide-12.map b/ld/testsuite/ld-scripts/provide-12.map
new file mode 100644
index 00000000000..e76654b10fd
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-12.map
@@ -0,0 +1,6 @@
+#...
+Memory Configuration
+
+Name Origin Length Attributes
+FOO 0x[0-9a-f]+300 +0x[0-9a-f]+200
+#pass
diff --git a/ld/testsuite/ld-scripts/provide-9.d b/ld/testsuite/ld-scripts/provide-9.d
new file mode 100644
index 00000000000..94dc02949b7
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-9.d
@@ -0,0 +1,3 @@
+#source: provide-5.s
+#ld: -T provide-9.t
+#map: provide-9.map
diff --git a/ld/testsuite/ld-scripts/provide-9.map b/ld/testsuite/ld-scripts/provide-9.map
new file mode 100644
index 00000000000..e35e3e25157
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-9.map
@@ -0,0 +1,6 @@
+#...
+Memory Configuration
+
+Name Origin Length Attributes
+FOO 0x[0-9a-f]+100 +0x[0-9a-f]+200
+#pass
diff --git a/ld/testsuite/ld-scripts/provide-9.t b/ld/testsuite/ld-scripts/provide-9.t
new file mode 100644
index 00000000000..00d906aa80a
--- /dev/null
+++ b/ld/testsuite/ld-scripts/provide-9.t
@@ -0,0 +1,25 @@
+PROVIDE (mem_origin = 0x100);
+PROVIDE (mem_length = 0x200);
+
+MEMORY
+{
+ FOO : ORIGIN = mem_origin, LENGTH = mem_length
+}
+
+SECTIONS
+{
+ .data : {
+ *(.data .data.*)
+ } >FOO
+
+ .text : {
+ *(.text .text.*)
+ } >FOO
+
+ .bss : {
+ *(.bss .bss.*)
+ } >FOO
+
+ /DISCARD/ : { *(.*) }
+}
+
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