From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-x341.google.com (mail-ot1-x341.google.com [IPv6:2607:f8b0:4864:20::341]) by sourceware.org (Postfix) with ESMTPS id 5F4D5385E82C for ; Mon, 16 Mar 2020 18:17:17 +0000 (GMT) Received: by mail-ot1-x341.google.com with SMTP id r2so3433069otn.6 for ; Mon, 16 Mar 2020 11:17:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=rtKq0sG/q6atF7fzBJHtF5VJnazO3hqEBQ+FYpU/rmU=; b=XLD7rxSEVcaTUbuDtfeaN9rljzgViB8UqKbmJbAlC0Smzmt8ld6C+qPVua5nJNzbum iGfEjPXVEI6yMIv2V2W+jlAx8gL7TW/1IuCRGvNLbQJQ3maD+S89e8JmWj6oRJnK+rV2 5v9ifP8Lmx5GqWwvnC7GHc0bORb9p0+DkGw1qTDfRYj8BLNoKLbYvtGOO4y94ukfRVxX nn6PAfYJc9/pz6Sk6U282W0yBxH7lxRB+k4qVYDHP21K5SPns7QE3QEHe0t1dbtf7xPz jxXeJiDUaADSEn0hAFXaxWiHMmY9dSrlnrlLESwpD1tqiAzf4aNO27WjIZgaSdm3VJFF AdHg== X-Gm-Message-State: ANhLgQ1GBygoGJRFKW0WQTTUHbEzX0HSS1tQK1rlgXyKwU+Yu+J9F9Wp I7AM1IoSJ4LVsKf7ZxXhbueD1N+E9RtKtVFKHVIKZ83s X-Google-Smtp-Source: ADFU+vu1pQYa0zBNK4tba/eaMrepKCp47eA2rMAN7nE3c/hsfmGts+h7qzn0/Njbr7F2yTthx9LeOJVQVlee6LoOLrM= X-Received: by 2002:a9d:6b1a:: with SMTP id g26mr452385otp.2.1584382636180; Mon, 16 Mar 2020 11:17:16 -0700 (PDT) MIME-Version: 1.0 References: <20200316170845.184386-1-simon.marchi@polymtl.ca> <20200316170845.184386-7-simon.marchi@polymtl.ca> In-Reply-To: <20200316170845.184386-7-simon.marchi@polymtl.ca> From: Christian Biesinger Date: Mon, 16 Mar 2020 13:16:39 -0500 Message-ID: Subject: Re: [PATCH 6/7] gdb: select "Cygwin" OS ABI for Cygwin binaries To: Simon Marchi Cc: gdb-patches , Jon Turney , Simon Marchi Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-40.7 required=5.0 tests=DKIMWL_WL_MED, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, ENV_AND_HDR_SPF_MATCH, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, USER_IN_DEF_DKIM_WL, USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org 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: , X-List-Received-Date: Mon, 16 Mar 2020 18:17:19 -0000 On Mon, Mar 16, 2020 at 12:09 PM Simon Marchi via Gdb-patches wrote: > > From: Simon Marchi > > Before this patch, the "Windows" OS ABI is selected for all Windows > executables, including Cygwin ones. This patch makes GDB differentiate > Cygwin binaries from non-Cygwin ones, and selects the "Cygwin" OS ABI > for the Cygwin ones. > > To check whether a Windows PE executable is a Cygwin one, we check the > library list in the .idata section, see if it contains "cygwin1.dll". > > I had to add code to parse the .idata section, because BFD doesn't seem > to expose this information. BFD does parse this information, but only > to print it in textual form (function pe_print_idata): > > https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=bfd/peXXigen.c;h=e42d646552a0ca1e856e082256cd3d943b54ddf0;hb=HEAD#l1261 > > Here's the relevant portion of the PE format documentation: > > https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#the-idata-section > > This page was also useful: > > https://blog.kowalczyk.info/articles/pefileformat.html#9ccef823-67e7-4372-9172-045d7b1fb006 > > With this patch applied, this is what I get: > > (gdb) file some_mingw_x86_64_binary.exe > Reading symbols from some_mingw_x86_64_binary.exe... > (gdb) show osabi > The current OS ABI is "auto" (currently "Windows"). > The default OS ABI is "GNU/Linux". > > (gdb) file some_mingw_i386_binary.exe > Reading symbols from some_mingw_i386_binary.exe... > (gdb) show osabi > The current OS ABI is "auto" (currently "Windows"). > The default OS ABI is "GNU/Linux". > > (gdb) file some_cygwin_x86_64_binary.exe > Reading symbols from some_cygwin_x86_64_binary.exe... > (gdb) show osabi > The current OS ABI is "auto" (currently "Cygwin"). > The default OS ABI is "GNU/Linux". > > gdb/ChangeLog: > > * windows-tdep.h (is_linked_with_cygwin_dll): New declaration. > * windows-tdep.c (CYGWIN_DLL_NAME): New. > (pe_import_directory_entry): New struct type. > (is_linked_with_cygwin_dll): New function. > * amd64-windows-tdep.c (amd64_windows_osabi_sniffer): Select > GDB_OSABI_CYGWIN if the BFD is linked with the Cygwin DLL. > * i386-windows-tdep.c (i386_windows_osabi_sniffer): Likewise. > --- > gdb/amd64-windows-tdep.c | 9 ++-- > gdb/i386-windows-tdep.c | 9 ++-- > gdb/windows-tdep.c | 101 +++++++++++++++++++++++++++++++++++++++ > gdb/windows-tdep.h | 6 +++ > 4 files changed, 119 insertions(+), 6 deletions(-) > > diff --git a/gdb/amd64-windows-tdep.c b/gdb/amd64-windows-tdep.c > index 88ff794abcb6..e0346f8628fe 100644 > --- a/gdb/amd64-windows-tdep.c > +++ b/gdb/amd64-windows-tdep.c > @@ -1249,10 +1249,13 @@ amd64_windows_osabi_sniffer (bfd *abfd) > { > const char *target_name = bfd_get_target (abfd); > > - if (strcmp (target_name, "pei-x86-64") == 0) > - return GDB_OSABI_WINDOWS; > + if (!streq (target_name, "pei-x86-64")) > + return GDB_OSABI_UNKNOWN; > > - return GDB_OSABI_UNKNOWN; > + if (is_linked_with_cygwin_dll (abfd)) > + return GDB_OSABI_CYGWIN; > + > + return GDB_OSABI_WINDOWS; > } > > void _initialize_amd64_windows_tdep (); > diff --git a/gdb/i386-windows-tdep.c b/gdb/i386-windows-tdep.c > index a71ceda781f8..bd6107b02f1f 100644 > --- a/gdb/i386-windows-tdep.c > +++ b/gdb/i386-windows-tdep.c > @@ -232,10 +232,13 @@ i386_windows_osabi_sniffer (bfd *abfd) > { > const char *target_name = bfd_get_target (abfd); > > - if (strcmp (target_name, "pei-i386") == 0) > - return GDB_OSABI_WINDOWS; > + if (!streq (target_name, "pei-i386")) > + return GDB_OSABI_UNKNOWN; > > - return GDB_OSABI_UNKNOWN; > + if (is_linked_with_cygwin_dll (abfd)) > + return GDB_OSABI_CYGWIN; > + > + return GDB_OSABI_WINDOWS; > } > > static enum gdb_osabi > diff --git a/gdb/windows-tdep.c b/gdb/windows-tdep.c > index e02b1ceed387..32e551bcb175 100644 > --- a/gdb/windows-tdep.c > +++ b/gdb/windows-tdep.c > @@ -38,6 +38,8 @@ > #include "libcoff.h" > #include "solist.h" > > +#define CYGWIN_DLL_NAME "cygwin1.dll" > + > /* Windows signal numbers differ between MinGW flavors and between > those and Cygwin. The below enumeration was gleaned from the > respective headers; the ones marked with MinGW64/Cygwin are defined > @@ -898,6 +900,105 @@ static const struct internalvar_funcs tlb_funcs = > NULL > }; > > +/* Layout of an element of a PE's Import Directory Table. Based on: > + > + https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-directory-table > + */ > + > +struct pe_import_directory_entry > +{ > + uint32_t import_lookup_table_rva; > + uint32_t timestamp; > + uint32_t forwarder_chain; > + uint32_t name_rva; > + uint32_t import_address_table_rva; > +}; > + > +gdb_static_assert (sizeof (pe_import_directory_entry) == 20); > + > +/* Return true if the Portable Executable behind ABFD uses the Cygwin dll > + (cygwin1.dll). */ > +/* See windows-tdep.h. */ Remove the first of these two comments? > + > +bool > +is_linked_with_cygwin_dll (bfd *abfd) > +{ > + /* The list of DLLs a PE is linked to is in the .idata section. See: > + > + https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#the-idata-section > + */ > + asection *idata_section = bfd_get_section_by_name (abfd, ".idata"); > + if (idata_section == nullptr) > + return false; > + > + /* Find the virtual address of the .idata section. We must subtract this > + from the RVAs (relative virtual addresses) to obtain an offset in the > + section. */ > + bfd_vma idata_addr = > + pe_data (abfd)->pe_opthdr.DataDirectory[PE_IMPORT_TABLE].VirtualAddress; > + > + /* Map the section's data. */ > + bfd_size_type idata_size; > + const gdb_byte *const idata_contents > + = gdb_bfd_map_section (idata_section, &idata_size); > + if (idata_contents == nullptr) > + { > + warning (_("Failed to get content of .idata section.")); > + return false; > + } > + > + const gdb_byte *iter = idata_contents; > + const gdb_byte *end = idata_contents + idata_size; > + const pe_import_directory_entry null_dir_entry = { 0 }; > + > + /* Iterate through all directory entries. */ > + while (true) > + { > + /* Is there enough space left in the section for another entry? */ > + if (iter + sizeof (pe_import_directory_entry) > end) > + { > + warning (_("Failed to parse .idata section: unexpected end of " > + ".idata section.")); > + break; > + } > + > + pe_import_directory_entry *dir_entry = (pe_import_directory_entry *) iter; > + > + /* Is it the end of list marker? */ > + if (memcmp (dir_entry, &null_dir_entry, > + sizeof (pe_import_directory_entry)) == 0) > + break; > + > + bfd_vma name_addr = dir_entry->name_rva; > + > + /* If the name's virtual address is smaller than the section's virtual > + address, there's a problem. */ > + if (name_addr < idata_addr > + || name_addr >= (idata_addr + idata_size)) > + { > + warning (_("\ > +Failed to parse .idata section: name's virtual address (0x%" BFD_VMA_FMT "x) \ > +is outside .idata section's range [0x%" BFD_VMA_FMT "x, 0x%" BFD_VMA_FMT "x[."), > + name_addr, idata_addr, idata_addr + idata_size); > + break; > + } > + > + const gdb_byte *name = &idata_contents[name_addr - idata_addr]; > + > + /* Make sure we don't overshoot the end of the section with the streq. */ > + if (name + sizeof(CYGWIN_DLL_NAME) > end) > + continue; > + > + /* Finally, check if this is the dll name we are looking for. */ > + if (streq ((const char *) name, CYGWIN_DLL_NAME)) > + return true; > + > + iter += sizeof(pe_import_directory_entry); > + } > + > + return false; > +} > + > void _initialize_windows_tdep (); > void > _initialize_windows_tdep () > diff --git a/gdb/windows-tdep.h b/gdb/windows-tdep.h > index 34474f259c2a..f2dc4260469d 100644 > --- a/gdb/windows-tdep.h > +++ b/gdb/windows-tdep.h > @@ -33,4 +33,10 @@ extern void windows_xfer_shared_library (const char* so_name, > > extern void windows_init_abi (struct gdbarch_info info, > struct gdbarch *gdbarch); > + > +/* Return true if the Portable Executable behind ABFD uses the Cygwin dll > + (cygwin1.dll). */ > + > +extern bool is_linked_with_cygwin_dll (bfd *abfd); > + > #endif > -- > 2.25.1 >