From 00ac85d3751b763155adb4e9d15dd134399b4e77 Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Thu, 16 Apr 2020 15:46:03 -0400 Subject: [PATCH] gdb: is_linked_with_cygwin_dll: handle import table not at beginning of .idata section When loading the file C:\Windows\SysWOW64\msvcrt.dll, taken from a Windows 10 system, into GDB, we get the following warning: warning: Failed to parse .idata section: name's virtual address (0x0) is outside .idata section's range [0xb82b8, 0xb97f0[. This uncovers an issue with how we parse the import table, part of the .idata section. Right now, we assume that the import table is located at the beginning of the section. That was the case in everything I had tried so far, but this file is an example where that's not true. We need to compute the offset of the import table within the .idata section, and start there, instead of at the beginning of the .idata section. Using the file mentioned above, this is the values we have to work with: A) bfd_section_vma (idata_section) 101b8000 B) Import table's virtual address b82b8 C) Image base 10100000 The virtual address that BFD returns us for the section has the image base applied, so we need to subtract it first. The offset of the table in the section is therefore: B - (A - C) This patch implements that. gdb/ChangeLog: * windows-tdep.c (is_linked_with_cygwin_dll): Consider case where import table is not at beginning of .idata section. --- gdb/ChangeLog | 5 +++++ gdb/windows-tdep.c | 47 +++++++++++++++++++++++++++++++++------------- 2 files changed, 39 insertions(+), 13 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 6c280e3f49..ebba52faef 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2020-04-16 Simon Marchi + + * windows-tdep.c (is_linked_with_cygwin_dll): Consider case where + import table is not at beginning of .idata section. + 2020-04-16 Pedro Alves * inferior.c (delete_inferior): Use delete operator directly diff --git a/gdb/windows-tdep.c b/gdb/windows-tdep.c index d1894ca088..50bb9591f9 100644 --- a/gdb/windows-tdep.c +++ b/gdb/windows-tdep.c @@ -999,11 +999,32 @@ is_linked_with_cygwin_dll (bfd *abfd) 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; + bfd_size_type idata_section_size = bfd_section_size (idata_section); + internal_extra_pe_aouthdr *pe_extra = &pe_data (abfd)->pe_opthdr; + bfd_vma import_table_va = pe_extra->DataDirectory[PE_IMPORT_TABLE].VirtualAddress; + bfd_vma idata_section_va = bfd_section_vma (idata_section); + + /* The section's virtual address as reported by BFD has the image base applied, + remove it. */ + gdb_assert (idata_section_va >= pe_extra->ImageBase); + idata_section_va -= pe_extra->ImageBase; + + bfd_vma idata_section_end_va = idata_section_va + idata_section_size; + + /* Make sure that the import table is indeed within the .idata section's range. */ + if (import_table_va < idata_section_va + || import_table_va >= idata_section_end_va) + { + warning (_("\ +%s: import table's virtual address (0x%" BFD_VMA_FMT "x) is outside .idata \ +section's range [0x%" BFD_VMA_FMT "x, 0x%" BFD_VMA_FMT "x[."), + bfd_get_filename (abfd), import_table_va, idata_section_va, + idata_section_end_va); + return false; + } + + /* The import table starts at this offset into the .idata section. */ + bfd_vma import_table_offset_in_sect = import_table_va - idata_section_va; /* Get the section's data. */ gdb::byte_vector idata_contents; @@ -1013,9 +1034,10 @@ is_linked_with_cygwin_dll (bfd *abfd) return false; } - size_t idata_size = idata_contents.size (); - const gdb_byte *iter = idata_contents.data (); - const gdb_byte *end = idata_contents.data () + idata_size; + gdb_assert (idata_contents.size () == idata_section_size); + + const gdb_byte *iter = idata_contents.data () + import_table_offset_in_sect; + const gdb_byte *end = idata_contents.data () + idata_section_size; const pe_import_directory_entry null_dir_entry = { 0 }; /* Iterate through all directory entries. */ @@ -1036,21 +1058,20 @@ is_linked_with_cygwin_dll (bfd *abfd) sizeof (pe_import_directory_entry)) == 0) break; - bfd_vma name_addr = dir_entry->name_rva; + bfd_vma name_va = 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)) + if (name_va < idata_section_va || name_va >= idata_section_end_va) { 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); + name_va, idata_section_va, idata_section_end_va); break; } - const gdb_byte *name = &idata_contents[name_addr - idata_addr]; + const gdb_byte *name = &idata_contents[name_va - idata_section_va]; /* Make sure we don't overshoot the end of the section with the streq. */ if (name + sizeof (CYGWIN_DLL_NAME) > end) -- 2.34.1