From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from simark.ca by simark.ca with LMTP id ze4TEz15EWCeSAAAWB0awg (envelope-from ) for ; Wed, 27 Jan 2021 09:31:25 -0500 Received: by simark.ca (Postfix, from userid 112) id 3C2421EF80; Wed, 27 Jan 2021 09:31:25 -0500 (EST) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on simark.ca X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server2.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by simark.ca (Postfix) with ESMTPS id D064C1E590 for ; Wed, 27 Jan 2021 09:31:23 -0500 (EST) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 3CDCF3846405; Wed, 27 Jan 2021 14:31:23 +0000 (GMT) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by sourceware.org (Postfix) with ESMTPS id D8E7D3987C3A for ; Wed, 27 Jan 2021 14:31:19 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org D8E7D3987C3A Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=tdevries@suse.de X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id EFF09ABDA for ; Wed, 27 Jan 2021 14:31:18 +0000 (UTC) Date: Wed, 27 Jan 2021 15:31:17 +0100 From: Tom de Vries To: gdb-patches@sourceware.org Subject: [PATCH][gdb/breakpoints] Fix longjmp master breakpoint with separate debug info Message-ID: <20210127143115.GA11549@delia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gdb-patches-bounces@sourceware.org Sender: "Gdb-patches" Hi, When running test-case gdb.base/longjmp.exp with target board unix/-m32, we run into: ... (gdb) next^M Warning:^M Cannot insert breakpoint 0.^M Cannot access memory at address 0x7dbf7353^M ^M __libc_siglongjmp (env=0x804a040 , val=1) at longjmp.c:28^M 28 longjmps++;^M (gdb) FAIL: gdb.base/longjmp.exp: next over longjmp(1) ... The failure to access memory happens in i386_get_longjmp_target and is due to glibc having pointer encryption (aka "pointer mangling" or "pointer guard") of the long jump buffer. This is a known problem. In create_longjmp_master_breakpoint (which attempts to install a master longjmp breakpoint) a preference scheme is present, which installs a probe breakpoint if a libc:longjmp probe is present, and otherwise falls back to setting breakpoints at the names in the longjmp_names array. But in fact, both the probe breakpoint and the longjmp_names breakpoints are set. The latter ones are set when processing libc.so.debug, and the former one when processing libc.so. In other words, this is the longjmp variant of PR26881, which describes the same problem for master exception breakpoints. This problem only triggers when the glibc debug info package is installed, which is not due to the debug info itself in libc.so.debug, but due to the minimal symbols (because create_longjmp_master_breakpoint uses minimal symbols to translate the longjmp_names to addresses). The problem doesn't trigger for -m64, because there tdep->jb_pc_offset is not set. Fix this similar to commit 1940319c0ef (the fix for PR26881): only install longjmp_names breakpoints in libc.so/libc.so.debug if installing the libc:longjmp probe in libc.so failed. Tested on x86_64-linux. Any comments? Thanks, - Tom [gdb/breakpoints] Fix longjmp master breakpoint with separate debug info gdb/ChangeLog: 2021-01-27 Tom de Vries PR breakpoints/27205 * breakpoint.c (create_longjmp_master_breakpoint_probe) (create_longjmp_master_breakpoint_names): New function, factored out of ... (create_longjmp_master_breakpoint): ... here. Only try to install longjmp_names breakpoints in libc.so/libc.so.debug if installing probe breakpoint in libc.so failed. --- gdb/breakpoint.c | 187 +++++++++++++++++++++++++++++++++---------------------- 1 file changed, 113 insertions(+), 74 deletions(-) diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c index 70a4d0e1690..cdf647b44b2 100644 --- a/gdb/breakpoint.c +++ b/gdb/breakpoint.c @@ -3327,100 +3327,139 @@ create_overlay_event_breakpoint (void) } } -static void -create_longjmp_master_breakpoint (void) +/* Install a master longjmp breakpoint for OBJFILE using a probe. Return + true if a breakpoint was installed. */ + +static bool +create_longjmp_master_breakpoint_probe (objfile *objfile) { - scoped_restore_current_program_space restore_pspace; + struct gdbarch *gdbarch = objfile->arch (); + struct breakpoint_objfile_data *bp_objfile_data + = get_breakpoint_objfile_data (objfile); - for (struct program_space *pspace : program_spaces) + if (!bp_objfile_data->longjmp_searched) { - set_current_program_space (pspace); + std::vector ret + = find_probes_in_objfile (objfile, "libc", "longjmp"); - for (objfile *objfile : current_program_space->objfiles ()) + if (!ret.empty ()) { - int i; - struct gdbarch *gdbarch; - struct breakpoint_objfile_data *bp_objfile_data; + /* We are only interested in checking one element. */ + probe *p = ret[0]; - gdbarch = objfile->arch (); + if (!p->can_evaluate_arguments ()) + { + /* We cannot use the probe interface here, + because it does not know how to evaluate + arguments. */ + ret.clear (); + } + } + bp_objfile_data->longjmp_probes = ret; + bp_objfile_data->longjmp_searched = 1; + } - bp_objfile_data = get_breakpoint_objfile_data (objfile); + if (bp_objfile_data->longjmp_probes.empty ()) + return false; - if (!bp_objfile_data->longjmp_searched) - { - std::vector ret - = find_probes_in_objfile (objfile, "libc", "longjmp"); + for (probe *p : bp_objfile_data->longjmp_probes) + { + struct breakpoint *b; - if (!ret.empty ()) - { - /* We are only interested in checking one element. */ - probe *p = ret[0]; + b = create_internal_breakpoint (gdbarch, + p->get_relocated_address (objfile), + bp_longjmp_master, + &internal_breakpoint_ops); + b->location = new_probe_location ("-probe-stap libc:longjmp"); + b->enable_state = bp_disabled; + } - if (!p->can_evaluate_arguments ()) - { - /* We cannot use the probe interface here, - because it does not know how to evaluate - arguments. */ - ret.clear (); - } - } - bp_objfile_data->longjmp_probes = ret; - bp_objfile_data->longjmp_searched = 1; - } + return true; +} - if (!bp_objfile_data->longjmp_probes.empty ()) - { - for (probe *p : bp_objfile_data->longjmp_probes) - { - struct breakpoint *b; - - b = create_internal_breakpoint (gdbarch, - p->get_relocated_address (objfile), - bp_longjmp_master, - &internal_breakpoint_ops); - b->location = new_probe_location ("-probe-stap libc:longjmp"); - b->enable_state = bp_disabled; - } +/* Install master longjmp breakpoints for OBJFILE using longjmp_names. + Return true if at least one breakpoint was installed. */ + +static bool +create_longjmp_master_breakpoint_names (objfile *objfile) +{ + struct gdbarch *gdbarch = objfile->arch (); + if (!gdbarch_get_longjmp_target_p (gdbarch)) + return false; + + struct breakpoint_objfile_data *bp_objfile_data + = get_breakpoint_objfile_data (objfile); + unsigned int installed_bp = 0; + for (int i = 0; i < NUM_LONGJMP_NAMES; i++) + { + struct breakpoint *b; + const char *func_name; + CORE_ADDR addr; + struct explicit_location explicit_loc; + + if (msym_not_found_p (bp_objfile_data->longjmp_msym[i].minsym)) + continue; + + func_name = longjmp_names[i]; + if (bp_objfile_data->longjmp_msym[i].minsym == NULL) + { + struct bound_minimal_symbol m; + + m = lookup_minimal_symbol_text (func_name, objfile); + if (m.minsym == NULL) + { + /* Prevent future lookups in this objfile. */ + bp_objfile_data->longjmp_msym[i].minsym = &msym_not_found; continue; } + bp_objfile_data->longjmp_msym[i] = m; + } - if (!gdbarch_get_longjmp_target_p (gdbarch)) - continue; + addr = BMSYMBOL_VALUE_ADDRESS (bp_objfile_data->longjmp_msym[i]); + b = create_internal_breakpoint (gdbarch, addr, bp_longjmp_master, + &internal_breakpoint_ops); + initialize_explicit_location (&explicit_loc); + explicit_loc.function_name = ASTRDUP (func_name); + b->location = new_explicit_location (&explicit_loc); + b->enable_state = bp_disabled; + installed_bp++; + } - for (i = 0; i < NUM_LONGJMP_NAMES; i++) - { - struct breakpoint *b; - const char *func_name; - CORE_ADDR addr; - struct explicit_location explicit_loc; + return installed_bp > 0; +} - if (msym_not_found_p (bp_objfile_data->longjmp_msym[i].minsym)) - continue; +/* Create a master longjmp breakpoint. */ - func_name = longjmp_names[i]; - if (bp_objfile_data->longjmp_msym[i].minsym == NULL) - { - struct bound_minimal_symbol m; +static void +create_longjmp_master_breakpoint (void) +{ + scoped_restore_current_program_space restore_pspace; - m = lookup_minimal_symbol_text (func_name, objfile); - if (m.minsym == NULL) - { - /* Prevent future lookups in this objfile. */ - bp_objfile_data->longjmp_msym[i].minsym = &msym_not_found; - continue; - } - bp_objfile_data->longjmp_msym[i] = m; - } + for (struct program_space *pspace : program_spaces) + { + set_current_program_space (pspace); - addr = BMSYMBOL_VALUE_ADDRESS (bp_objfile_data->longjmp_msym[i]); - b = create_internal_breakpoint (gdbarch, addr, bp_longjmp_master, - &internal_breakpoint_ops); - initialize_explicit_location (&explicit_loc); - explicit_loc.function_name = ASTRDUP (func_name); - b->location = new_explicit_location (&explicit_loc); - b->enable_state = bp_disabled; - } + for (objfile *obj : current_program_space->objfiles ()) + { + /* Skip separate debug object. */ + if (obj->separate_debug_objfile_backlink) + continue; + + /* Try a probe kind breakpoint. */ + if (create_longjmp_master_breakpoint_probe (obj)) + continue; + + /* Try longjmp_names kind breakpoints. */ + if (create_longjmp_master_breakpoint_names (obj)) + continue; + + /* Iterate over separate debug objects and try longjmp_names + kind breakpoints. */ + for (objfile *sepdebug = obj->separate_debug_objfile; + sepdebug != nullptr; sepdebug = sepdebug->separate_debug_objfile) + if (create_longjmp_master_breakpoint_names (sepdebug)) + break; } } }