Re: malloc() call somehow calling the rtld malloc() implementaion

On 27 Jan, Alexander Kabaev wrote:
> On Fri, 27 Jan 2017 00:31:30 -0800 (PST)
> Don Lewis <truckman_at_FreeBSD.org> wrote:

>> If I create a simple test program that calls malloc() and set a
>> breakpoint in malloc(), the breakpoint gets set in the rtld version,
>> but the the libc version of malloc is what gets called.
>> 
>> What the heck is going on here, and how can I fix it?
>> 
> 
> rtld on my system does not have malloc exposed as dynamic symbol, it
> cannot possibly be used for symbol resolution by any outside module.

Same here, but gdb at least seems to find it anyway.

12.0-CURRENT r311765M

%nm /libexec/ld-elf.so.1
nm: /libexec/ld-elf.so.1: no symbols

%elfdump -s /libexec/ld-elf.so.1 | grep st_name | sort
	st_name: 
	st_name: 
	st_name: FBSD_1.0
	st_name: FBSD_1.1
	st_name: FBSD_1.2
	st_name: FBSD_1.3
	st_name: FBSD_1.4
	st_name: FBSD_1.5
	st_name: FBSDprivate_1.0
	st_name: __tls_get_addr
	st_name: _r_debug_postinit
	st_name: _rtld_addr_phdr
	st_name: _rtld_allocate_tls
	st_name: _rtld_atfork_post
	st_name: _rtld_atfork_pre
	st_name: _rtld_error
	st_name: _rtld_free_tls
	st_name: _rtld_get_stack_prot
	st_name: _rtld_is_dlopened
	st_name: _rtld_thread_init
	st_name: dl_iterate_phdr
	st_name: dladdr
	st_name: dlclose
	st_name: dlerror
	st_name: dlfunc
	st_name: dlinfo
	st_name: dllockinit
	st_name: dlopen
	st_name: dlsym
	st_name: dlvsym
	st_name: fdlopen
	st_name: r_debug_state

%cd /tmp
zipper:/tmp 508%cat malloctest.c 
#include <stdlib.h>
volatile void *p;
int
main(void) {
	p = malloc(16);
}
%cc -g malloctest.c
%gdb a.out
GNU gdb 6.1.1 [FreeBSD]
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "amd64-marcel-freebsd"...
(gdb) break main
Breakpoint 1 at 0x40076b: file malloctest.c, line 5.
(gdb) run
Starting program: /tmp/a.out 

Breakpoint 1, main () at malloctest.c:5
5		p = malloc(16);
Current language:  auto; currently minimal
(gdb) break malloc
Breakpoint 2 at 0x80060e9a4: file /usr/src/libexec/rtld-elf/malloc.c, line 163.
(gdb) cont
Continuing.

Program exited normally.
(gdb) quit

Ports gdb finds both the rtld malloc() and the libc malloc():

%/usr/local/bin/gdb a.out
GNU gdb (GDB) 7.12 [GDB v7.12 for FreeBSD]
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-portbld-freebsd12.0".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from a.out...done.
(gdb) break main
Breakpoint 1 at 0x40076b: file malloctest.c, line 5.
(gdb) run
Starting program: /tmp/a.out 

Breakpoint 1, main () at malloctest.c:5
5		p = malloc(16);
(gdb) break malloc
Breakpoint 2 at 0x80060e9a4: malloc. (2 locations)
(gdb) cont
Continuing.

Breakpoint 2, __malloc (size=16) at jemalloc_jemalloc.c:1636
1636		size_t usize JEMALLOC_CC_SILENCE_INIT(0);