From patchwork Tue Apr 10 21:54:03 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pedro Alves X-Patchwork-Id: 26681 Received: (qmail 115827 invoked by alias); 10 Apr 2018 21:54:09 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 115813 invoked by uid 89); 10 Apr 2018 21:54:09 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-24.0 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_STOCKGEN autolearn=ham version=3.3.2 spammy=refreshed X-HELO: mx1.redhat.com Received: from mx3-rdu2.redhat.com (HELO mx1.redhat.com) (66.187.233.73) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 10 Apr 2018 21:54:06 +0000 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 700BB406804A; Tue, 10 Apr 2018 21:54:05 +0000 (UTC) Received: from [127.0.0.1] (ovpn04.gateway.prod.ext.ams2.redhat.com [10.39.146.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id AC5342026DFD; Tue, 10 Apr 2018 21:54:04 +0000 (UTC) Subject: Re: [PATCH v2 03/15] Calling ifunc functions when target has no debug info but resolver has To: Simon Marchi , gdb-patches@sourceware.org References: <20180325191943.8246-1-palves@redhat.com> <20180325191943.8246-4-palves@redhat.com> <805a18bb-d85d-f115-2e27-970ac8e8523c@simark.ca> <6914cfea-6c6d-44c2-ff5d-2acc6c378016@redhat.com> From: Pedro Alves Message-ID: <538e0eea-fe63-556c-201b-fb7e217bd85d@redhat.com> Date: Tue, 10 Apr 2018 22:54:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <6914cfea-6c6d-44c2-ff5d-2acc6c378016@redhat.com> On 04/10/2018 10:48 PM, Pedro Alves wrote: > > Here's what I'm squashing into the patch locally. And here's the result. I've also pushed the refreshed patches to users/palves/ifunc. From 7a6a9fdd7504b3098e9a7019dff945e579bde371 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Tue, 10 Apr 2018 22:48:46 +0100 Subject: [PATCH] Calling ifunc functions when target has no debug info but resolver has After the previous patch, on Fedora 27 (glibc 2.26), if you try calling strlen in the inferior, you now get: (top-gdb) p strlen ("hello") '__strlen_avx2' has unknown return type; cast the call to its declared return type This is correct, because __strlen_avx2 is written in assembly. We can improve on this though -- if the final ifunc resolved/target function has no debug info, but the ifunc _resolver_ does have debug info, we can try extracting the final function's type from the type that the resolver returns. E.g.,: typedef size_t (*strlen_t) (const char*); size_t my_strlen (const char *) { /* some implementation */ } strlen_t strlen_resolver (unsigned long hwcap) { return my_strlen; } extern size_t strlen (const char *s); __typeof (strlen) strlen __attribute__ ((ifunc ("strlen_resolver"))); In the strlen example above, the resolver returns strlen_t, which is a typedef for pointer to a function that returns size_t. "strlen_t" is the type of both the user-visible "strlen", and of the the target function that implements it. This patch teaches GDB to extract that type. This is done for actual inferior function calls (in infcall.c), and for ptype (in eval_call). By the time we get to either of these places, we've already lost the original symbol/minsym, and only have values and types to work with. Hence the changes to c-exp.y and evaluate_var_msym_value, to ensure that we propagate the ifunc minsymbol's info. The change to make ifunc symbols have no/unknown return type exposes a latent problem -- gdb.compile/compile-ifunc.exp calls a no-debug-info function, but we did not warn about it. The test is fixed by this commit too. gdb/ChangeLog: yyyy-mm-dd Pedro Alves * blockframe.c (find_gnu_ifunc_target_type): New function. (find_function_type): New. * eval.c (evaluate_var_msym_value): For GNU ifunc types, always return a value with a memory address. (eval_call): For calls to GNU ifunc functions, try to find the type of the target function from the type that the resolver returns. * gdbtypes.c (objfile_type): Don't install a return type for ifunc symbols. * infcall.c (find_function_return_type): Delete. (find_function_addr): Add 'function_type' parameter. For calls to GNU ifunc functions, try to find the type of the target function from the type that the resolver returns, and return it via FUNCTION_TYPE. (call_function_by_hand_dummy): Adjust to use the function type returned by find_function_addr. (find_function_addr): Add 'function_type' parameter and move description here. * symtab.h (find_function_type, find_gnu_ifunc_target_type): New declarations. gdb/testsuite/ChangeLog: yyyy-mm-dd Pedro Alves * gdb.compile/compile-ifunc.exp: Also expect "function has unknown return type" warnings. --- gdb/blockframe.c | 39 +++++++++++++++++ gdb/eval.c | 25 ++++++----- gdb/gdbtypes.c | 4 -- gdb/infcall.c | 66 +++++++++++++++-------------- gdb/infcall.h | 9 +++- gdb/symtab.h | 11 +++++ gdb/testsuite/gdb.compile/compile-ifunc.exp | 9 ++-- 7 files changed, 112 insertions(+), 51 deletions(-) diff --git a/gdb/blockframe.c b/gdb/blockframe.c index 9be8871f756..e6938a341ae 100644 --- a/gdb/blockframe.c +++ b/gdb/blockframe.c @@ -323,6 +323,45 @@ find_pc_partial_function (CORE_ADDR pc, const char **name, CORE_ADDR *address, return find_pc_partial_function_gnu_ifunc (pc, name, address, endaddr, NULL); } +/* See symtab.h. */ + +struct type * +find_function_type (CORE_ADDR pc) +{ + struct symbol *sym = find_pc_function (pc); + + if (sym != NULL && BLOCK_START (SYMBOL_BLOCK_VALUE (sym)) == pc) + return SYMBOL_TYPE (sym); + + return NULL; +} + +/* See symtab.h. */ + +struct type * +find_gnu_ifunc_target_type (CORE_ADDR resolver_funaddr) +{ + struct type *resolver_type = find_function_type (resolver_funaddr); + if (resolver_type != NULL) + { + /* Get the return type of the resolver. */ + struct type *resolver_ret_type + = check_typedef (TYPE_TARGET_TYPE (resolver_type)); + + /* If we found a pointer to function, then the resolved type + is the type of the pointed-to function. */ + if (TYPE_CODE (resolver_ret_type) == TYPE_CODE_PTR) + { + struct type *resolved_type + = TYPE_TARGET_TYPE (resolver_ret_type); + if (TYPE_CODE (check_typedef (resolved_type)) == TYPE_CODE_FUNC) + return resolved_type; + } + } + + return NULL; +} + /* Return the innermost stack frame that is executing inside of BLOCK and is at least as old as the selected frame. Return NULL if there is no such frame. If BLOCK is NULL, just return NULL. */ diff --git a/gdb/eval.c b/gdb/eval.c index b6fbfcf6c95..ad66f7c32c1 100644 --- a/gdb/eval.c +++ b/gdb/eval.c @@ -734,17 +734,13 @@ value * evaluate_var_msym_value (enum noside noside, struct objfile *objfile, minimal_symbol *msymbol) { - if (noside == EVAL_AVOID_SIDE_EFFECTS) - { - type *the_type = find_minsym_type_and_address (msymbol, objfile, NULL); - return value_zero (the_type, not_lval); - } + CORE_ADDR address; + type *the_type = find_minsym_type_and_address (msymbol, objfile, &address); + + if (noside == EVAL_AVOID_SIDE_EFFECTS && !TYPE_GNU_IFUNC (the_type)) + return value_zero (the_type, not_lval); else - { - CORE_ADDR address; - type *the_type = find_minsym_type_and_address (msymbol, objfile, &address); - return value_at_lazy (the_type, address); - } + return value_at_lazy (the_type, address); } /* Helper for returning a value when handling EVAL_SKIP. */ @@ -797,6 +793,15 @@ eval_call (expression *exp, enum noside noside, else if (TYPE_CODE (ftype) == TYPE_CODE_FUNC || TYPE_CODE (ftype) == TYPE_CODE_METHOD) { + if (TYPE_GNU_IFUNC (ftype)) + { + CORE_ADDR address = value_address (argvec[0]); + type *resolved_type = find_gnu_ifunc_target_type (address); + + if (resolved_type != NULL) + ftype = resolved_type; + } + type *return_type = TYPE_TARGET_TYPE (ftype); if (return_type == NULL) diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c index b3a037971e0..2efd1264ff8 100644 --- a/gdb/gdbtypes.c +++ b/gdb/gdbtypes.c @@ -5443,10 +5443,6 @@ objfile_type (struct objfile *objfile) objfile_type->nodebug_text_gnu_ifunc_symbol = init_type (objfile, TYPE_CODE_FUNC, TARGET_CHAR_BIT, ""); - /* Ifunc resolvers return a function address. */ - TYPE_TARGET_TYPE (objfile_type->nodebug_text_gnu_ifunc_symbol) - = init_integer_type (objfile, gdbarch_addr_bit (gdbarch), 1, - "__IFUNC_RESOLVER_RET"); TYPE_GNU_IFUNC (objfile_type->nodebug_text_gnu_ifunc_symbol) = 1; objfile_type->nodebug_got_plt_symbol = init_pointer_type (objfile, gdbarch_addr_bit (gdbarch), diff --git a/gdb/infcall.c b/gdb/infcall.c index 9f02674bdf2..b233e369f27 100644 --- a/gdb/infcall.c +++ b/gdb/infcall.c @@ -229,26 +229,12 @@ value_arg_coerce (struct gdbarch *gdbarch, struct value *arg, return value_cast (type, arg); } -/* Return the return type of a function with its first instruction exactly at - the PC address. Return NULL otherwise. */ - -static struct type * -find_function_return_type (CORE_ADDR pc) -{ - struct symbol *sym = find_pc_function (pc); - - if (sym != NULL && BLOCK_START (SYMBOL_BLOCK_VALUE (sym)) == pc - && SYMBOL_TYPE (sym) != NULL) - return TYPE_TARGET_TYPE (SYMBOL_TYPE (sym)); - - return NULL; -} - -/* Determine a function's address and its return type from its value. - Calls error() if the function is not valid for calling. */ +/* See infcall.h. */ CORE_ADDR -find_function_addr (struct value *function, struct type **retval_type) +find_function_addr (struct value *function, + struct type **retval_type, + struct type **function_type) { struct type *ftype = check_typedef (value_type (function)); struct gdbarch *gdbarch = get_type_arch (ftype); @@ -275,17 +261,33 @@ find_function_addr (struct value *function, struct type **retval_type) if (TYPE_CODE (ftype) == TYPE_CODE_FUNC || TYPE_CODE (ftype) == TYPE_CODE_METHOD) { - value_type = TYPE_TARGET_TYPE (ftype); - if (TYPE_GNU_IFUNC (ftype)) { - funaddr = gnu_ifunc_resolve_addr (gdbarch, funaddr); + CORE_ADDR resolver_addr = funaddr; - /* Skip querying the function symbol if no RETVAL_TYPE has been - asked for. */ - if (retval_type) - value_type = find_function_return_type (funaddr); + /* Resolve the ifunc. Note this may call the resolver + function in the inferior. */ + funaddr = gnu_ifunc_resolve_addr (gdbarch, resolver_addr); + + /* Skip querying the function symbol if no RETVAL_TYPE or + FUNCTION_TYPE have been asked for. */ + if (retval_type != NULL || function_type != NULL) + { + type *target_ftype = find_function_type (funaddr); + /* If we don't have debug info for the target function, + see if we can instead extract the target function's + type from the type that the resolver returns. */ + if (target_ftype == NULL) + target_ftype = find_gnu_ifunc_target_type (resolver_addr); + if (target_ftype != NULL) + { + value_type = TYPE_TARGET_TYPE (check_typedef (target_ftype)); + ftype = target_ftype; + } + } } + else + value_type = TYPE_TARGET_TYPE (ftype); } else if (TYPE_CODE (ftype) == TYPE_CODE_INT) { @@ -320,6 +322,8 @@ find_function_addr (struct value *function, struct type **retval_type) if (retval_type != NULL) *retval_type = value_type; + if (function_type != NULL) + *function_type = ftype; return funaddr + gdbarch_deprecated_function_start_offset (gdbarch); } @@ -719,15 +723,13 @@ call_function_by_hand_dummy (struct value *function, void *dummy_dtor_data) { CORE_ADDR sp; - struct type *values_type, *target_values_type; + struct type *target_values_type; unsigned char struct_return = 0, hidden_first_param_p = 0; CORE_ADDR struct_addr = 0; struct infcall_control_state *inf_status; struct cleanup *inf_status_cleanup; struct infcall_suspend_state *caller_state; - CORE_ADDR funaddr; CORE_ADDR real_pc; - struct type *ftype = check_typedef (value_type (function)); CORE_ADDR bp_addr; struct frame_id dummy_id; struct frame_info *frame; @@ -738,9 +740,6 @@ call_function_by_hand_dummy (struct value *function, char name_buf[RAW_FUNCTION_ADDRESS_SIZE]; bool stack_temporaries = thread_stack_temporaries_enabled_p (inferior_ptid); - if (TYPE_CODE (ftype) == TYPE_CODE_PTR) - ftype = check_typedef (TYPE_TARGET_TYPE (ftype)); - if (!target_has_execution) noprocess (); @@ -864,7 +863,10 @@ call_function_by_hand_dummy (struct value *function, } } - funaddr = find_function_addr (function, &values_type); + type *ftype; + type *values_type; + CORE_ADDR funaddr = find_function_addr (function, &values_type, &ftype); + if (values_type == NULL) values_type = default_return_type; if (values_type == NULL) diff --git a/gdb/infcall.h b/gdb/infcall.h index a3861fb1bf3..8b2195019c9 100644 --- a/gdb/infcall.h +++ b/gdb/infcall.h @@ -25,8 +25,15 @@ struct value; struct type; +/* Determine a function's address and its return type from its value. + If the function is a GNU ifunc, then return the address of the + target function, and set *FUNCTION_TYPE to the target function's + type, and *RETVAL_TYPE to the target function's return type. + Calls error() if the function is not valid for calling. */ + extern CORE_ADDR find_function_addr (struct value *function, - struct type **retval_type); + struct type **retval_type, + struct type **function_type = NULL); /* Perform a function call in the inferior. diff --git a/gdb/symtab.h b/gdb/symtab.h index f9d52e76979..83ff6f226d8 100644 --- a/gdb/symtab.h +++ b/gdb/symtab.h @@ -1675,6 +1675,17 @@ extern int find_pc_partial_function_gnu_ifunc (CORE_ADDR pc, const char **name, extern int find_pc_partial_function (CORE_ADDR, const char **, CORE_ADDR *, CORE_ADDR *); +/* Return the type of a function with its first instruction exactly at + the PC address. Return NULL otherwise. */ + +extern struct type *find_function_type (CORE_ADDR pc); + +/* See if we can figure out the function's actual type from the type + that the resolver returns. RESOLVER_FUNADDR is the address of the + ifunc resolver. */ + +extern struct type *find_gnu_ifunc_target_type (CORE_ADDR resolver_funaddr); + extern void clear_pc_function_cache (void); /* Expand symtab containing PC, SECTION if not already expanded. */ diff --git a/gdb/testsuite/gdb.compile/compile-ifunc.exp b/gdb/testsuite/gdb.compile/compile-ifunc.exp index ed700e416bb..979e39147e7 100644 --- a/gdb/testsuite/gdb.compile/compile-ifunc.exp +++ b/gdb/testsuite/gdb.compile/compile-ifunc.exp @@ -37,7 +37,9 @@ with_test_prefix "nodebug" { } gdb_test "compile code resultvar = gnu_ifunc (10);" \ - "warning: variable has unknown type; assuming int" + [multi_line \ + "warning: variable has unknown type; assuming int" \ + "warning: function has unknown return type; assuming int"] gdb_test "p (int) resultvar" " = 11" @@ -52,10 +54,9 @@ with_test_prefix "debug" { if ![runto_main] { return -1 } - # gnu_ifunc (10): error: too many arguments to function 'gnu_ifunc' - gdb_test_no_output "compile code resultvar = gnu_ifunc_alias (10);" - + gdb_test "compile code resultvar = gnu_ifunc_alias (10);" \ + "warning: function has unknown return type; assuming int" gdb_test "p resultvar" " = 11" }