On 7/12/22 08:28, Richard Biener wrote:
> On Mon, Jul 11, 2022 at 6:35 PM Alexander Monakov <amona...@ispras.ru> wrote:
>>
>> On Mon, 11 Jul 2022, Martin Liška wrote:
>>
>>> I've clarified that linker should return a value that is in range
>>> [minimal_api_supported, maximal_api_supported] and added an abort
>>> if it's not the case.
>>
>> I noticed that we are placing a trap for C++ consumers such as mold
>> by passing min/max_api_supported as enum values. Unlike C, C++ disallows
>> out-of-range enum values, so when mold does
>>
>> enum PluginLinkerAPIVersion {
>> LAPI_V0 = 0,
>> LAPI_V1,
>> };
>>
>> get_api_version(const char *plugin_identifier,
>> unsigned plugin_version,
>> PluginLinkerAPIVersion minimal_api_supported,
>> PluginLinkerAPIVersion maximal_api_supported,
>> const char **linker_identifier,
>> const char **linker_version) {
>>
>> checks such as 'min_api_supported > LAPI_V1' can be optimized out. Also,
>> if a future tool passes LAPI_V2, it will trigger Clang's UBSan (GCC
>> -fsanitize-undefined=enum instruments loads but not retrieval of function
>> arguments).
>>
>> I'd suggest to fix this on both sides by changing the arguments to plain
>> integer types.
>
> That's a good point - the enum itself is then also somewhat redundant
> if it just specifies symbolic names for 0, 1, ... but we can keep it for
> documentation purposes.
All right, here we go with the integer types.
May I install the version now?
Thanks,
Martin
>
>>
>> Alexander
From 8f7372bd2b3d76feeca84cdbb0d392d93569bd57 Mon Sep 17 00:00:00 2001
From: Martin Liska <mli...@suse.cz>
Date: Mon, 16 May 2022 14:01:52 +0200
Subject: [PATCH] lto-plugin: implement LDPT_GET_API_VERSION
include/ChangeLog:
* plugin-api.h (enum linker_api_version): New enum.
(ld_plugin_get_api_version): New.
(enum ld_plugin_tag): Add LDPT_GET_API_VERSION.
(struct ld_plugin_tv): Add tv_get_api_version.
lto-plugin/ChangeLog:
* lto-plugin.c (negotiate_api_version): New.
(onload): Negotiate API version.
* Makefile.am: Add -DBASE_VERSION.
* Makefile.in: Regenerate.
---
include/plugin-api.h | 33 +++++++++++++++++++++++++++++
lto-plugin/Makefile.am | 2 +-
lto-plugin/Makefile.in | 2 +-
lto-plugin/lto-plugin.c | 47 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 82 insertions(+), 2 deletions(-)
diff --git a/include/plugin-api.h b/include/plugin-api.h
index 8aebe2ff267..0b61cfc0443 100644
--- a/include/plugin-api.h
+++ b/include/plugin-api.h
@@ -483,6 +483,37 @@ enum ld_plugin_level
LDPL_FATAL
};
+/* Contract between a plug-in and a linker. */
+
+enum linker_api_version
+{
+ /* The linker/plugin do not implement any of the API levels below, the API
+ is determined solely via the transfer vector. */
+ LAPI_V0,
+
+ /* API level v1. The linker provides get_symbols_v3, add_symbols_v2,
+ the plugin will use that and not any lower versions.
+ claim_file is thread-safe on the plugin side and
+ add_symbols on the linker side. */
+ LAPI_V1
+};
+
+/* The linker's interface for API version negotiation. A plug-in calls
+ the function (with its IDENTIFIER and VERSION), plus minimal and maximal
+ version of linker_api_version is provided. Linker then returns selected
+ API version and provides its IDENTIFIER and VERSION. The returned value
+ by linker must be in range [MINIMAL_API_SUPPORTED, MAXIMAL_API_SUPPORTED].
+ Identifier pointers remain valid as long as the plugin is loaded. */
+
+typedef
+int
+(*ld_plugin_get_api_version) (const char *plugin_identifier,
+ const char *plugin_version,
+ int minimal_api_supported,
+ int maximal_api_supported,
+ const char **linker_identifier,
+ const char **linker_version);
+
/* Values for the tv_tag field of the transfer vector. */
enum ld_plugin_tag
@@ -521,6 +552,7 @@ enum ld_plugin_tag
LDPT_REGISTER_NEW_INPUT_HOOK,
LDPT_GET_WRAP_SYMBOLS,
LDPT_ADD_SYMBOLS_V2,
+ LDPT_GET_API_VERSION,
};
/* The plugin transfer vector. */
@@ -556,6 +588,7 @@ struct ld_plugin_tv
ld_plugin_get_input_section_size tv_get_input_section_size;
ld_plugin_register_new_input tv_register_new_input;
ld_plugin_get_wrap_symbols tv_get_wrap_symbols;
+ ld_plugin_get_api_version tv_get_api_version;
} tv_u;
};
diff --git a/lto-plugin/Makefile.am b/lto-plugin/Makefile.am
index 81362eafc36..482946e4dd5 100644
--- a/lto-plugin/Makefile.am
+++ b/lto-plugin/Makefile.am
@@ -8,7 +8,7 @@ target_noncanonical := @target_noncanonical@
libexecsubdir := $(libexecdir)/gcc/$(real_target_noncanonical)/$(gcc_version)$(accel_dir_suffix)
AM_CPPFLAGS = -I$(top_srcdir)/../include $(DEFS)
-AM_CFLAGS = @ac_lto_plugin_warn_cflags@ $(CET_HOST_FLAGS)
+AM_CFLAGS = @ac_lto_plugin_warn_cflags@ $(CET_HOST_FLAGS) -DBASE_VERSION='"$(gcc_version)"'
# The plug-in depends on pthreads.
AM_LDFLAGS = -pthread @ac_lto_plugin_ldflags@
AM_LIBTOOLFLAGS = --tag=disable-static
diff --git a/lto-plugin/Makefile.in b/lto-plugin/Makefile.in
index 2033dd9b7c2..9453bc7d607 100644
--- a/lto-plugin/Makefile.in
+++ b/lto-plugin/Makefile.in
@@ -343,7 +343,7 @@ AUTOMAKE_OPTIONS = no-dependencies
gcc_version := $(shell @get_gcc_base_ver@ $(top_srcdir)/../gcc/BASE-VER)
libexecsubdir := $(libexecdir)/gcc/$(real_target_noncanonical)/$(gcc_version)$(accel_dir_suffix)
AM_CPPFLAGS = -I$(top_srcdir)/../include $(DEFS)
-AM_CFLAGS = @ac_lto_plugin_warn_cflags@ $(CET_HOST_FLAGS)
+AM_CFLAGS = @ac_lto_plugin_warn_cflags@ $(CET_HOST_FLAGS) -DBASE_VERSION='"$(gcc_version)"'
# The plug-in depends on pthreads.
AM_LDFLAGS = -pthread @ac_lto_plugin_ldflags@
AM_LIBTOOLFLAGS = --tag=disable-static
diff --git a/lto-plugin/lto-plugin.c b/lto-plugin/lto-plugin.c
index 7927dca60a4..e9afd2fb76d 100644
--- a/lto-plugin/lto-plugin.c
+++ b/lto-plugin/lto-plugin.c
@@ -180,6 +180,10 @@ static ld_plugin_add_input_file add_input_file;
static ld_plugin_add_input_library add_input_library;
static ld_plugin_message message;
static ld_plugin_add_symbols add_symbols, add_symbols_v2;
+static ld_plugin_get_api_version get_api_version;
+
+/* By default, use version LAPI_V0 if there is not negotiation. */
+static enum linker_api_version api_version = LAPI_V0;
static struct plugin_file_info *claimed_files = NULL;
static unsigned int num_claimed_files = 0;
@@ -1428,6 +1432,43 @@ process_option (const char *option)
verbose = verbose || debug;
}
+/* Negotiate linker API version. */
+
+static void
+negotiate_api_version (void)
+{
+ const char *linker_identifier;
+ const char *linker_version;
+
+ enum linker_api_version supported_api = LAPI_V0;
+#if HAVE_PTHREAD_LOCKING
+ supported_api = LAPI_V1;
+#endif
+
+ api_version = get_api_version ("GCC", BASE_VERSION, LAPI_V0,
+ supported_api, &linker_identifier, &linker_version);
+ if (api_version > supported_api)
+ {
+ fprintf (stderr, "requested an unsupported API version (%d)\n", api_version);
+ abort ();
+ }
+
+ switch (api_version)
+ {
+ case LAPI_V0:
+ break;
+ case LAPI_V1:
+ check (get_symbols_v3, LDPL_FATAL,
+ "get_symbols_v3 required for API version 1");
+ check (add_symbols_v2, LDPL_FATAL,
+ "add_symbols_v2 required for API version 1");
+ break;
+ default:
+ fprintf (stderr, "unsupported API version (%d)\n", api_version);
+ abort ();
+ }
+}
+
/* Called by a linker after loading the plugin. TV is the transfer vector. */
enum ld_plugin_status
@@ -1496,12 +1537,18 @@ onload (struct ld_plugin_tv *tv)
/* We only use this to make user-friendly temp file names. */
link_output_name = p->tv_u.tv_string;
break;
+ case LDPT_GET_API_VERSION:
+ get_api_version = p->tv_u.tv_get_api_version;
+ break;
default:
break;
}
p++;
}
+ if (get_api_version)
+ negotiate_api_version ();
+
check (register_claim_file, LDPL_FATAL, "register_claim_file not found");
check (add_symbols, LDPL_FATAL, "add_symbols not found");
status = register_claim_file (claim_file_handler);
--
2.37.0
