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Implement LDPT_REGISTER_CLAIM_FILE_HOOK_V2 linker plugin hook [PR109128]

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This is one part of the fix for PR109128, along with a corresponding
binutils's linker change.  Without this patch, what happens in the
linker, when an unused object in a .a file has offload data, is that
elf_link_is_defined_archive_symbol calls bfd_link_plugin_object_p,
which ends up calling the plugin's claim_file_handler, which then
records the object as one with offload data. That is, the linker never
decides to use the object in the first place, but use of this _p
interface (called as part of trying to decide whether to use the
object) results in the plugin deciding to use its offload data (and a
consequent mismatch in the offload data present at runtime).

The new hook allows the linker plugin to distinguish calls to
claim_file_handler that know the object is being used by the linker
(from ldmain.c:add_archive_element), from calls that don't know it's
being used by the linker (from elf_link_is_defined_archive_symbol); in
the latter case, the plugin should avoid recording the object as one
with offload data.

	PR middle-end/109128

	include/
	* plugin-api.h (ld_plugin_claim_file_handler_v2)
	(ld_plugin_register_claim_file_v2)
	(LDPT_REGISTER_CLAIM_FILE_HOOK_V2): New.
	(struct ld_plugin_tv): Add tv_register_claim_file_v2.

	lto-plugin/
	* lto-plugin.c (register_claim_file_v2): New.
	(claim_file_handler_v2): New.
	(claim_file_handler): Wrap claim_file_handler_v2.
	(onload): Handle LDPT_REGISTER_CLAIM_FILE_HOOK_V2.
This commit is contained in:
Joseph Myers 2023-05-11 10:07:00 +02:00 committed by Tobias Burnus
parent 5e05361e2f
commit c49d51fa81
2 changed files with 44 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
include/plugin-api.h
View File

@ -260,6 +260,13 @@ enum ld_plugin_status
(*ld_plugin_claim_file_handler) (
const struct ld_plugin_input_file *file, int *claimed);
/* The plugin library's "claim file" handler, version 2. */
typedef
enum ld_plugin_status
(*ld_plugin_claim_file_handler_v2) (
const struct ld_plugin_input_file *file, int *claimed, int known_used);
/* The plugin library's "all symbols read" handler. */
typedef
@ -278,6 +285,13 @@ typedef
enum ld_plugin_status
(*ld_plugin_register_claim_file) (ld_plugin_claim_file_handler handler);
/* The linker's interface for registering the "claim file" handler,
version 2. */
typedef
enum ld_plugin_status
(*ld_plugin_register_claim_file_v2) (ld_plugin_claim_file_handler_v2 handler);
/* The linker's interface for registering the "all symbols read" handler. */
typedef
@ -553,6 +567,7 @@ enum ld_plugin_tag
LDPT_GET_WRAP_SYMBOLS,
LDPT_ADD_SYMBOLS_V2,
LDPT_GET_API_VERSION,
LDPT_REGISTER_CLAIM_FILE_HOOK_V2
};
/* The plugin transfer vector. */
@ -565,6 +580,7 @@ struct ld_plugin_tv
int tv_val;
const char *tv_string;
ld_plugin_register_claim_file tv_register_claim_file;
ld_plugin_register_claim_file_v2 tv_register_claim_file_v2;
ld_plugin_register_all_symbols_read tv_register_all_symbols_read;
ld_plugin_register_cleanup tv_register_cleanup;
ld_plugin_add_symbols tv_add_symbols;

31
lto-plugin/lto-plugin.c
View File

@ -173,6 +173,7 @@ static pthread_mutex_t plugin_lock;
static char *arguments_file_name;
static ld_plugin_register_claim_file register_claim_file;
static ld_plugin_register_claim_file_v2 register_claim_file_v2;
static ld_plugin_register_all_symbols_read register_all_symbols_read;
static ld_plugin_get_symbols get_symbols, get_symbols_v2, get_symbols_v3;
static ld_plugin_register_cleanup register_cleanup;
@ -1191,10 +1192,15 @@ process_offload_section (void *data, const char *name, off_t offset, off_t len)
}
/* Callback used by a linker to check if the plugin will claim FILE. Writes
the result in CLAIMED. */
the result in CLAIMED. If KNOWN_USED, the object is known by the linker
to be used, or an older API version is in use that does not provide that
information; otherwise, the linker is only determining whether this is
a plugin object and it should not be registered as having offload data if
not claimed by the plugin. */
static enum ld_plugin_status
claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
claim_file_handler_v2 (const struct ld_plugin_input_file *file, int *claimed,
int known_used)
{
enum ld_plugin_status status;
struct plugin_objfile obj;
@ -1307,7 +1313,7 @@ claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
if (*claimed && !obj.offload && offload_files_last_lto == NULL)
offload_files_last_lto = offload_files_last;
if (obj.offload)
if (obj.offload && (known_used || obj.found > 0))
{
/* Add file to the list. The order must be exactly the same as the final
order after recompilation and linking, otherwise host and target tables
@ -1372,6 +1378,15 @@ claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
return LDPS_OK;
}
/* Callback used by a linker to check if the plugin will claim FILE. Writes
the result in CLAIMED. */
static enum ld_plugin_status
claim_file_handler (const struct ld_plugin_input_file *file, int *claimed)
{
return claim_file_handler_v2 (file, claimed, true);
}
/* Parse the plugin options. */
static void
@ -1496,6 +1511,9 @@ onload (struct ld_plugin_tv *tv)
case LDPT_REGISTER_CLAIM_FILE_HOOK:
register_claim_file = p->tv_u.tv_register_claim_file;
break;
case LDPT_REGISTER_CLAIM_FILE_HOOK_V2:
register_claim_file_v2 = p->tv_u.tv_register_claim_file_v2;
break;
case LDPT_ADD_SYMBOLS_V2:
add_symbols_v2 = p->tv_u.tv_add_symbols;
break;
@ -1555,6 +1573,13 @@ onload (struct ld_plugin_tv *tv)
check (status == LDPS_OK, LDPL_FATAL,
"could not register the claim_file callback");
if (register_claim_file_v2)
{
status = register_claim_file_v2 (claim_file_handler_v2);
check (status == LDPS_OK, LDPL_FATAL,
"could not register the claim_file_v2 callback");
}
if (register_cleanup)
{
status = register_cleanup (cleanup_handler);