Re: [patch] Implement qXfer:libraries for Linux/gdbserver

[Paul Pluzhnikov <ppluzhnikov at google dot com>]

On Tue, Aug 9, 2011 at 2:06 AM, Jan Kratochvil
<jan.kratochvil@redhat.com> wrote:

> On Tue, 09 Aug 2011 01:49:49 +0200, Paul Pluzhnikov wrote:
>> --- gdbserver/linux-low.c ? ? 21 Jul 2011 23:46:12 -0000 ? ? ?1.173
>> +++ gdbserver/linux-low.c ? ? 8 Aug 2011 23:34:10 -0000
>> @@ -4755,6 +4755,289 @@ linux_emit_ops (void)
> [...]
>> +static CORE_ADDR
>> +get_dynamic (const int pid, const int is_elf64)
>> +{
>> + ?CORE_ADDR phdr_memaddr;
>> + ?int num_phdr, i;
>> + ?unsigned char *phdr_buf;
>> + ?const int phdr_size = is_elf64 ? sizeof (Elf64_Phdr) : sizeof (Elf32_Phdr);
>> +
>> +
>
> Two empty lines, should be one.

Fixed here and elsewhere ...

>> + ?if (get_phdr_phnum_from_proc_auxv (pid, is_elf64, &phdr_memaddr, &num_phdr))
>> + ? ?return 0;
>> +
>> + ?gdb_assert (num_phdr < 100); ?/* Basic sanity check. ?*/
>> + ?phdr_buf = alloca (num_phdr * phdr_size);
>> +
>> + ?if (linux_read_memory (phdr_memaddr, phdr_buf, num_phdr * phdr_size))
>> + ? ?return 0;
>> +
>> + ?for (i = 0; i < num_phdr; i++)
>> + ? ?{
>> + ? ? ?if (is_elf64)
>> + ? ? {
>> + ? ? ? Elf64_Phdr *const p = (Elf64_Phdr *) (phdr_buf + i * phdr_size);
>> +
>> + ? ? ? if (p->p_type == PT_DYNAMIC)
>> + ? ? ? ? return p->p_vaddr;
>
> This does not work for -fPIE -pie executables such as those on Chromebook.
> One needs to relocate A_VAL as it is the in-file (0-based) address while
> in-memory address is shifted by X. ?X is calculated by solib-svr4.c
> svr4_exec_displacement.
>
> One can find here X probably most easily by subtracting PT_PHDR->P_VADDR from
> PHDR_MEMADDR.

Done.

>
> There is also a bug in it in solib-svr4.c scan_dyntag_auxv
> ? ? ? ?[rfc] Use auxillary vector to retrieve .dynamic/.interp sections
> ? ? ? ?http://sourceware.org/ml/gdb-patches/2008-08/msg00360.html
> but one would need to patch the code around to get the fix applicable first.
>
>
>> + ? ? }
>> + ? ? ?else
>> + ? ? {
>> + ? ? ? Elf32_Phdr *const p = (Elf32_Phdr *) (phdr_buf + i * phdr_size);
>> +
>> + ? ? ? if (p->p_type == PT_DYNAMIC)
>> + ? ? ? ? return p->p_vaddr;
>
> Here too.

Ditto.

>> + ? ? ?/* Not checking for error because reading may stop before
>> + ? ? ?we've got PATH_MAX worth of characters. ?*/
>> + ? ? ?libname[0] = '\0';
>> + ? ? ?linux_read_memory (l_name, libname, sizeof (libname));
>> + ? ? ?if (libname[0] != '\0')
>> + ? ? loaded_dll ((const char *) libname, l_addr);
>
> Unprotected against inferior string longer than PATH_MAX, this is a regression
> against solib-svr4.c.

Fixed.

Side note: SO_NAME_MAX_PATH_SIZE == 512 in solist.h is wrong for Linux;
I am surprised this hasn't bitten anyone yet. Why doesn't it use PATH_MAX ?

Thanks,
-- 
Paul Pluzhnikov

2011-08-09  Paul Pluzhnikov  <ppluzhnikov@google.com>

	* solib-svr4.c (library_list_start_segment): New function.
	(library_list_start_library, library_list_end_library): Likewise.
	(library_list_start_list): Likewise.
	(segment_attributes, library_children): New variables.
	(library_attributes, library_list_children): Likewise.
	(library_list_attributes, library_list_elements): Likewise.
	(svr4_free_so): Moved to here.
	(svr4_free_library_list, svr4_parse_libraries): New functions.
	(svr4_current_sos_via_xfer_libraries): Likewise.
	(svr4_current_sos): Adjust.

gdbserver/ChangeLog:

2011-08-09  Paul Pluzhnikov  <ppluzhnikov@google.com>
           Jan Kratochvil  <jan.kratochvil@redhat.com>

	* inferiors.c (clear_all_dlls): New function.
	(clear_inferiors): Move there the code from here, call it here.
	* linux-low.c (linux_add_process): Adjust.
	(get_phdr_phnum_from_proc_auxv, get_dynamic): New functions.
	(get_r_debug, read_one_ptr): Likewise.
	(struct link_map_offsets): New struct decl.
	(linux_refresh_libraries): New function.
	(struct linux_target_ops): Adjust.
	(struct process_info_private): New member.
	(handle_qxfer_libraries): Adjust.
	(struct target_ops): New member.
	* server.c (handle_qxfer_libraries): Adjust.
	* server.h (clear_all_dlls): New prototype.
	* target.h (struct target_ops): New member.

Attachment: gdb-solib-list-20110809.txt
Description: Text document