Date: Fri, 27 Oct 2017 21:34:34 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: mmel@freebsd.org Cc: Brooks Davis <brooks@freebsd.org>, Dimitry Andric <dim@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org, kib@freebsd.org Subject: Re: svn commit: r324938 - head/contrib/jemalloc/include/jemalloc/internal Message-ID: <20171027183434.GK2566@kib.kiev.ua> In-Reply-To: <d75bb1fc-60c8-c9b8-eef8-fc36750dca18@freebsd.org> References: <201710232131.v9NLV4Rb068825@repo.freebsd.org> <38db6f4e-72b8-6ffd-4529-f15ca32bad54@freebsd.org> <6FD27DFB-5039-4E33-B131-EF5391DD1630@FreeBSD.org> <6eff6e66-4987-8753-105f-b6a5b8234ff3@freebsd.org> <20171027150841.GH2566@kib.kiev.ua> <20171027152154.GA31598@spindle.one-eyed-alien.net> <d75bb1fc-60c8-c9b8-eef8-fc36750dca18@freebsd.org>
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On Fri, Oct 27, 2017 at 07:48:43PM +0200, Michal Meloun wrote:
> But there is something what's still missing me.
> The rescue binary is statically linked, so whole program have only one
> TLS section and full TLS layout is determined by linker.
> The problematic structure, tsd_tls, is first one in TLS section group:
>
> readelf -a /usr/obj/usr/src/rescue/rescue/rescue | grep TLS
> 518961: 0000000000000000 2880 TLS GLOBAL DEFAULT 9 __je_tsd_tls
> and
>
> objdump -d -j .tdata /usr/obj/usr/src/rescue/rescue/rescue
> 00a832b0 <__je_tsd_tls+0xa832b0>:
> a832b0: 00000005
>
> but disassembled code expect it at TLS ptr + 0x8 (for code without
> JEMALLOC_ALIGNED) or at TLS ptr + 0x10 (for code with JEMALLOC_ALIGNED)
>
> [without JEMALLOC_ALIGNED]
> 7c4d90: e59f0014 ldr r0, [pc, #20] ; 7c4dac
> <tsd_get+0x80>
> 7c4d94: e58d0004 str r0, [sp, #4]
> 7c4d98: eb031d14 bl 88c1f0 <__aeabi_read_tp>
> 7c4d9c: e59dc004 ldr ip, [sp, #4]
> 7c4da0: e080000c add r0, r0, ip
> 7c4da4: e1a0d00b mov sp, fp
> 7c4da8: e8bd8800 pop {fp, pc}
> 7c4dac: 00000008 .word 0x00000008 [0x10 for code
> with JEMALLOC_ALIGNED]
>
> so someone other allocates at least one byte from start of TLS and
> linker is aware about this. But again, .data is first member of TLS
> and tsd_tls is first of .tdata and the 0x5 is value of first member of
> tsd_tls structure (.state = tsd_state_uninitialized).
>
> So who consumes the first bytes in TLS ????
Hack the makefile to pass the -M option to linker, like -Wl,-M
>/some/path/file.map. The file.map provides the data about sections
assembly.
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