From cb5bf8fad2e653e44fcae8f4ba0ce6eb5f928cb3 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Tue, 2 May 2023 17:10:01 +0000 Subject: [PATCH] Implement LDPT_REGISTER_CLAIM_FILE_HOOK_V2 linker plugin hook [PR109128] 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. --- include/plugin-api.h | 16 ++++++++++++++++ lto-plugin/lto-plugin.c | 31 ++++++++++++++++++++++++++++--- 2 files changed, 44 insertions(+), 3 deletions(-) diff --git a/include/plugin-api.h b/include/plugin-api.h index 379828ba854..395d5bcc598 100644 --- a/include/plugin-api.h +++ b/include/plugin-api.h @@ -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; diff --git a/lto-plugin/lto-plugin.c b/lto-plugin/lto-plugin.c index cc512a463f3..ae87089b05d 100644 --- a/lto-plugin/lto-plugin.c +++ b/lto-plugin/lto-plugin.c @@ -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); -- 2.25.1