From: Kevin Buettner Date: Thu, 24 Apr 2025 04:39:28 +0000 (-0700) Subject: Don't attempt to find TLS address when target has no registers X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8b87fe90e81f933b7c88e1ea25b02426ee3f58eb;p=thirdparty%2Fbinutils-gdb.git Don't attempt to find TLS address when target has no registers This commit fixes two bugs, one of which is Bug 25807, which occurs when target_translate_tls_address() is called from language_defn::read_var_value in findvar.c. I found it while testing on aarch64; it turned a KFAIL for gdb.threads/tls.exp: print a_thread_local into a FAIL due to a GDB internal error. Now, with this commit in place, the KFAIL/FAIL turns into a PASS. In addition to the existing test just noted, I've also added a test to the new test case gdb.base/tls-nothreads.exp. It'll be tested, using different scenarios, up to 8 times: PASS: gdb.base/tls-nothreads.exp: default: force_internal_tls=false: after exit: print tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: default: force_internal_tls=true: after exit: print tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: static: force_internal_tls=false: after exit: print tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: static: force_internal_tls=true: after exit: print tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: pthreads: force_internal_tls=false: after exit: print tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: pthreads: force_internal_tls=true: after exit: print tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: pthreads-static: force_internal_tls=false: after exit: print tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: pthreads-static: force_internal_tls=true: after exit: print tls_tbss_1 There is a related problem that occurs when target_translate_tls_address is called from find_minsym_type_and_address() in minsyms.c. It can be observed when debugging a program without debugging symbols when the program is not executing. I've written a new test for this, but it's (also) included in the new test case gdb.base/tls-nothreads.exp, found later in this series. Depending on the target, it can run up to 8 times using different scenarios. E.g., on aarch64, I'm seeing these PASSes, all of which test this change: PASS: gdb.base/tls-nothreads.exp: default: force_internal_tls=false: stripped: after exit: print (int) tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: default: force_internal_tls=true: stripped: after exit: print (int) tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: static: force_internal_tls=false: stripped: after exit: print (int) tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: static: force_internal_tls=true: stripped: after exit: print (int) tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: pthreads: force_internal_tls=false: stripped: after exit: print (int) tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: pthreads: force_internal_tls=true: stripped: after exit: print (int) tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: pthreads-static: force_internal_tls=false: stripped: after exit: print (int) tls_tbss_1 PASS: gdb.base/tls-nothreads.exp: pthreads-static: force_internal_tls=true: stripped: after exit: print (int) tls_tbss_1 In an earlier version of this commit (v4), I was checking whether the target has registers in language_defn::read_var_value in findvar.c and in find_minsym_type_and_address in minsyms.c, printing suitable error messages in each case. In his review of this commit for the v4 series, Tom Tromey asked whether it would be better to do this check in target_translate_tls_address. I had considered doing that for the v4 (and earlier) series, but I wanted to print slightly different messages at each check. Also, read_var_value in findvar.c was already printing a message in some cases and I had arranged for the later check in that function to match the original message. However, while I had added a target-has-registers check at two of the call sites for target_translate_tls_address, I hadn't added it at the third call site which is in dwarf_expr_context::execute_stack_op() in dwarf2/expr.c. I believe that in most cases, this is handled by the early check in language_defn::read_var_value... else if (sym_need == SYMBOL_NEEDS_REGISTERS && !target_has_registers ()) error (_("Cannot read `%s' without registers"), var->print_name ()); ...but it's entirely possible that dwarf_expr_context::execute_stack_op() might get called in some other context. So it makes sense to do the target-has-registers check for that case too. And rather than add yet another check at that call site, I decided that moving the check and error message to target_translate_tls_address makes sense. I had to make the error messages that it prints somewhat more generic. In particular, when called from language_defn::read_var_value, the message printed by target_translate_tls_address no longer matches the earlier message that could be printed (as shown above). That meant that the test cases which check for this message, gdb.threads/tls.exp, and gdb.base/tls-nothreads.exp had to be adjusted to account for the new message. Also, I think it's valuable to the user to know (if possible) the name of the variable that caused the error, so I've added an optional parameter to target_translate_tls_address, providing the name of the variable, if it's known. Therefore, the message that's printed when the target-has-registers test fails is one of the following: When the TLS variable isn't known (due to being called from dwarf_expr_context::execute_stack_op): "Cannot translate TLS address without registers" When the TLS variable is known (from either of the other two call sites for target_translate_tls_address): "Cannot find address of TLS symbol `%s' without registers" Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=25807 Tested-By: Luis Machado Approved-By: Luis Machado --- diff --git a/gdb/findvar.c b/gdb/findvar.c index 29389313f94..9da5c4831a6 100644 --- a/gdb/findvar.c +++ b/gdb/findvar.c @@ -485,7 +485,8 @@ language_defn::read_var_value (struct symbol *var, /* Determine address of TLS variable. */ if (obj_section && (obj_section->the_bfd_section->flags & SEC_THREAD_LOCAL) != 0) - addr = target_translate_tls_address (obj_section->objfile, addr); + addr = target_translate_tls_address (obj_section->objfile, addr, + var->print_name ()); } break; diff --git a/gdb/minsyms.c b/gdb/minsyms.c index 649a9f17c3e..9ac3145cb62 100644 --- a/gdb/minsyms.c +++ b/gdb/minsyms.c @@ -1688,7 +1688,8 @@ find_minsym_type_and_address (minimal_symbol *msymbol, { /* Skip translation if caller does not need the address. */ if (address_p != NULL) - *address_p = target_translate_tls_address (objfile, addr); + *address_p = target_translate_tls_address + (objfile, addr, bound_msym.minsym->print_name ()); return builtin_type (objfile)->nodebug_tls_symbol; } diff --git a/gdb/target.c b/gdb/target.c index 4a1964e664b..522bed8e939 100644 --- a/gdb/target.c +++ b/gdb/target.c @@ -1250,11 +1250,21 @@ generic_tls_error (void) _("Cannot find thread-local variables on this target")); } -/* Using the objfile specified in OBJFILE, find the address for the - current thread's thread-local storage with offset OFFSET. */ +/* See target.h. */ + CORE_ADDR -target_translate_tls_address (struct objfile *objfile, CORE_ADDR offset) +target_translate_tls_address (struct objfile *objfile, CORE_ADDR offset, + const char *name) { + if (!target_has_registers ()) + { + if (name == nullptr) + error (_("Cannot translate TLS address without registers")); + else + error (_("Cannot find address of TLS symbol `%s' without registers"), + name); + } + volatile CORE_ADDR addr = 0; struct target_ops *target = current_inferior ()->top_target (); gdbarch *gdbarch = current_inferior ()->arch (); diff --git a/gdb/target.h b/gdb/target.h index 004494dc3c4..2d3bac77bd2 100644 --- a/gdb/target.h +++ b/gdb/target.h @@ -2472,8 +2472,14 @@ extern void target_pre_inferior (); extern void target_preopen (int); +/* Using the objfile specified in OBJFILE, find the address for the + current thread's thread-local storage with offset OFFSET. If it's + provided, NAME might be used to indicate the relevant variable + in an error message. */ + extern CORE_ADDR target_translate_tls_address (struct objfile *objfile, - CORE_ADDR offset); + CORE_ADDR offset, + const char *name = nullptr); /* Return the "section" containing the specified address. */ const struct target_section *target_section_by_addr (struct target_ops *target, diff --git a/gdb/testsuite/gdb.threads/tls.exp b/gdb/testsuite/gdb.threads/tls.exp index 1bc5df26233..73fada7bcd1 100644 --- a/gdb/testsuite/gdb.threads/tls.exp +++ b/gdb/testsuite/gdb.threads/tls.exp @@ -159,7 +159,7 @@ gdb_test_multiple "print a_thread_local" "" { -re -wrap "Cannot find thread-local variables on this target" { kfail "gdb/25807" $gdb_test_name } - -re -wrap "Cannot read .a_thread_local. without registers" { + -re -wrap "Cannot (?:read|find address of TLS symbol) .a_thread_local. without registers" { pass $gdb_test_name } }