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[PATCH] LTO: Properly handle wrapper symbols in IR
On Tue, Apr 2, 2019 at 4:12 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Tue, Apr 2, 2019 at 3:12 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > Change resolution from PREVAILING_DEF_IRONLY to LDPR_PREVAILING_DEF
> > for wrapper symbol.
> >
> > PR ld/24406
> > * ld.texi: Remove LTO warning from --wrap.
> > * plugin.c (get_symbols): Change resolution to LDPR_PREVAILING_DEF
> > for wrapper symbol.
> > * testsuite/ld-plugin/lto.exp: Run ld/24406 test.
> > * testsuite/ld-plugin/pr24406.c: New file.
>
> This patch is incomplete. I am working on it.
When a wrapper symbol, __wrap_FOO, is defined in IR, its resolution
should be LDPR_PREVAILING_DEF, not PREVAILING_DEF_IRONLY, since LTO
doesn't know that __wrap_FOO provides definition of FOO. And resolution
of FOO should be LDPR_RESOLVED_IR since it is resolved by __wrap_FOO in
IR.
--
H.J.
From 4f5116cc9b5fdd6f9a0c9be0bd0bf77ebd5d85c7 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Tue, 2 Apr 2019 15:06:10 -0700
Subject: [PATCH] LTO: Properly handle wrapper symbols in IR
When a wrapper symbol, __wrap_FOO, is defined in IR, its resolution
should be LDPR_PREVAILING_DEF, not PREVAILING_DEF_IRONLY, since LTO
doesn't know that __wrap_FOO provides definition of FOO. And resolution
of FOO should be LDPR_RESOLVED_IR since it is resolved by __wrap_FOO in
IR.
PR ld/24406
* ld.texi: Remove LTO warning from --wrap.
* plugin.c (get_symbols): Update resolution for wrapper and
wrapped symbols.
* testsuite/ld-plugin/lto.exp: Run ld/24406 tests.
* testsuite/ld-plugin/pr24406-1.c: New file.
* testsuite/ld-plugin/pr24406-2a.c: Likewise.
* testsuite/ld-plugin/pr24406-2b.c: Likewise.
---
ld/ld.texi | 3 ---
ld/plugin.c | 35 +++++++++++++++++++++++------
ld/testsuite/ld-plugin/lto.exp | 12 ++++++++++
ld/testsuite/ld-plugin/pr24406-1.c | 17 ++++++++++++++
ld/testsuite/ld-plugin/pr24406-2a.c | 17 ++++++++++++++
ld/testsuite/ld-plugin/pr24406-2b.c | 4 ++++
6 files changed, 78 insertions(+), 10 deletions(-)
create mode 100644 ld/testsuite/ld-plugin/pr24406-1.c
create mode 100644 ld/testsuite/ld-plugin/pr24406-2a.c
create mode 100644 ld/testsuite/ld-plugin/pr24406-2b.c
diff --git a/ld/ld.texi b/ld/ld.texi
index 0bcbec463f..f652740c04 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -2415,9 +2415,6 @@ g (void)
@}
@end smallexample
-Please keep in mind that with link-time optimization (LTO) enabled, your whole
-program may be a translation unit.
-
@kindex --eh-frame-hdr
@kindex --no-eh-frame-hdr
@item --eh-frame-hdr
diff --git a/ld/plugin.c b/ld/plugin.c
index a76e44c79f..9d86c771f1 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -744,13 +744,32 @@ get_symbols (const void *handle, int nsyms, struct ld_plugin_symbol *syms,
struct bfd_link_hash_entry *blhe;
asection *owner_sec;
int res;
+ struct bfd_link_hash_entry *h
+ = bfd_link_hash_lookup (link_info.hash, syms[n].name,
+ FALSE, FALSE, TRUE);
+ enum { wrap_none, wrapper, wrapped } wrap_status = wrap_none;
- if (syms[n].def != LDPK_UNDEF)
- blhe = bfd_link_hash_lookup (link_info.hash, syms[n].name,
- FALSE, FALSE, TRUE);
+ if (syms[n].def != LDPK_UNDEF && syms[n].def != LDPK_WEAKUNDEF)
+ {
+ blhe = h;
+ if (blhe)
+ {
+ /* Check if a symbol is a wrapper symbol. */
+ struct bfd_link_hash_entry *unwrap
+ = unwrap_hash_lookup (&link_info, (bfd *) abfd, blhe);
+ if (unwrap && unwrap != h)
+ wrap_status = wrapper;
+ }
+ }
else
- blhe = bfd_wrapped_link_hash_lookup (link_info.output_bfd, &link_info,
- syms[n].name, FALSE, FALSE, TRUE);
+ {
+ blhe = bfd_wrapped_link_hash_lookup (link_info.output_bfd,
+ &link_info, syms[n].name,
+ FALSE, FALSE, TRUE);
+ /* Check if a symbol is a wrapped symbol. */
+ if (blhe && blhe != h)
+ wrap_status = wrapped;
+ }
if (!blhe)
{
/* The plugin is called to claim symbols in an archive element
@@ -836,9 +855,11 @@ get_symbols (const void *handle, int nsyms, struct ld_plugin_symbol *syms,
/* We need to know if the sym is referenced from non-IR files. Or
even potentially-referenced, perhaps in a future final link if
this is a partial one, perhaps dynamically at load-time if the
- symbol is externally visible. */
- if (blhe->non_ir_ref_regular)
+ symbol is externally visible. Also check for wrapper symbol. */
+ if (blhe->non_ir_ref_regular || wrap_status == wrapper)
res = LDPR_PREVAILING_DEF;
+ else if (wrap_status == wrapped)
+ res = LDPR_RESOLVED_IR;
else if (is_visible_from_outside (&syms[n], blhe))
res = def_ironly_exp;
}
diff --git a/ld/testsuite/ld-plugin/lto.exp b/ld/testsuite/ld-plugin/lto.exp
index ce57705f46..c828ca5ab9 100644
--- a/ld/testsuite/ld-plugin/lto.exp
+++ b/ld/testsuite/ld-plugin/lto.exp
@@ -246,6 +246,9 @@ set lto_link_tests [list \
{pr23958.c} \
"" \
"libpr23958.so"] \
+ [list "Build pr24406-2b.o" \
+ "" "-O2 -fno-lto" \
+ {pr24406-2b.c}] \
]
if { [at_least_gcc_version 4 7] } {
@@ -461,6 +464,15 @@ set lto_run_tests [list \
"-O2 -flto" "" \
{dummy.c} "pr22751" "pass.out" "-flto -O2" "c" "" \
"-Wl,--whole-archive tmpdir/pr22751.a -Wl,--no-whole-archive"] \
+ [list "Run pr24406-1" \
+ "-O2 -flto" "" \
+ {pr24406-1.c} "pr24406-1" "pass.out" "-flto -O2" "c" "" \
+ "-Wl,--wrap=read"] \
+ [list "Run pr24406-2" \
+ "-O2 -flto" "" \
+ {pr24406-2a.c} "pr24406-2" "pass.out" \
+ "-flto -O2" "c" "" \
+ "tmpdir/pr24406-2b.o -Wl,--wrap=cook"] \
]
if { [at_least_gcc_version 4 7] } {
diff --git a/ld/testsuite/ld-plugin/pr24406-1.c b/ld/testsuite/ld-plugin/pr24406-1.c
new file mode 100644
index 0000000000..43995bdb07
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr24406-1.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <unistd.h>
+
+ssize_t
+__wrap_read (int fd, void *buffer, size_t count)
+{
+ puts ("PASS");
+ return fd + count + sizeof (buffer);
+}
+
+
+int
+main ()
+{
+ int i = read (1, "abc", 5);
+ return i == 0;
+}
diff --git a/ld/testsuite/ld-plugin/pr24406-2a.c b/ld/testsuite/ld-plugin/pr24406-2a.c
new file mode 100644
index 0000000000..14f54ba0ea
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr24406-2a.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+
+extern int cook(void);
+
+int __wrap_cook(void)
+{
+ puts ("PASS");
+ return 0;
+}
+
+int main()
+{
+ if (cook () == -1)
+ __builtin_abort ();
+
+ return 0;
+}
diff --git a/ld/testsuite/ld-plugin/pr24406-2b.c b/ld/testsuite/ld-plugin/pr24406-2b.c
new file mode 100644
index 0000000000..bfb69dfe51
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr24406-2b.c
@@ -0,0 +1,4 @@
+int cook(void)
+{
+ return -1;
+}
--
2.20.1