Date: Fri, 27 Oct 2017 15:21:54 +0000 From: Brooks Davis <brooks@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: mmel@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: <20171027152154.GA31598@spindle.one-eyed-alien.net> In-Reply-To: <20171027150841.GH2566@kib.kiev.ua> 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>
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On Fri, Oct 27, 2017 at 06:08:41PM +0300, Konstantin Belousov wrote:
> On Fri, Oct 27, 2017 at 02:53:26PM +0200, Michal Meloun wrote:
> > Sorry for top posting
> > That's pity, we have clear problem in rtld code :(
> > See:
> > -----------------------------------------------------
> > RESCUE WITHOUT JEMALLOC_ALIGNED(16);
> > -----------------------------------------------------
> > Program Headers:
> > TLS 0xa732b0 0x00a832b0 0x00a832b0 0x00b40 0x011bc R 0x8
> > Section Headers:
> > 04 .tdata .tbss .init_array .fini_array .jcr .got
> > Dump:
> > 00a832b0 <__je_tsd_tls+0xa832b0>:
> > a832b0: 00000005
> >
> > GDB
> > (gdb) b tsd_fetch_impl
> > Breakpoint 1 at 0x7c4c08: tsd_fetch_impl. (6 locations)
> > (gdb) r
> > Starting program: /usr/src/rescue.noalign sh
> >
> > Breakpoint 1, tsd_fetch_impl (init=true, minimal=false) at
> > /usr/src/contrib/jemalloc/include/jemalloc/internal/tsd.h:261
> > 261 tsd_t *tsd = tsd_get(init);
> > (gdb) n
> > 263 if (!init && tsd_get_allocates() && tsd == NULL) {
> >
> > (gdb) p tsd
> > $1 = (tsd_t *) 0x20c83008
> >
> > (gdb) p *tsd
> > $2 = {state = 5 '\005', ....
> >
> > (gdb) p *((tsd_t *)0x00a832b0)
> > $3 = {state = 5 '\005', ...
> >
> >
> >
> > -----------------------------------------------------
> > RESCUE WITH JEMALLOC_ALIGNED(16);
> > -----------------------------------------------------
> > Program Headers:
> > TLS 0xa732b0 0x00a832b0 0x00a832b0 0x00b40 0x011bc R 0x10
> > Section Headers:
> > 04 .tdata .tbss .init_array .fini_array .jcr .got
> > Dump:
> > 00a832b0 <__je_tsd_tls+0xa832b0>:
> > a832b0: 00000005
> >
> > GDB
> > (gdb) b tsd_fetch_impl
> > Breakpoint 1 at 0x7c4c08: tsd_fetch_impl. (6 locations)
> > (gdb) r
> > Starting program: /usr/obj/usr/src/rescue/rescue/rescue sh
> > Breakpoint 1, tsd_fetch_impl (init=true, minimal=false) at
> > /usr/src/contrib/jemalloc/include/jemalloc/internal/tsd.h:261
> > 261 tsd_t *tsd = tsd_get(init);
> > (gdb) n
> > 263 if (!init && tsd_get_allocates() && tsd == NULL) {
> >
> > (gdb) p tsd
> > $1 = (tsd_t *) 0x20c83010
> >
> > (gdb) p *tsd
> > $2 = {state = 0 '\000', ...
> >
> > (gdb) p *((tsd_t *)0x00a832b0)
> > $3 = {state = 5 '\005', ...
> >
> > !!!! BUT p *(tsd - 8 bytes) !!!!!!!!!!
> > (gdb) p *((tsd_t *)0x20c83008)
> > $4 = {state = 5 '\005', ...
> >
> > -----------------------------------------------------
> > So it's clear that:
> >
> > - both binaries are valid, .tdata section have valid data.
> > - requested alignment is propagated to binary.
> > - .tdata section is properly loaded to memory because
> > p *((tsd_t *)0x00a832b0) is {state = 5 '\005'
> > in both cases
> >
> > - a per thread copy of .tdata respect requested alignment
> > but the original data was copied to unaligned address.
> > because for aligned binary
> > p *tsd is {state = 0 '\000', ...
> > p *(tsd - 8 bytes) is {state = 5 '\005'
> >
> > I'm right?
> > Kib, please, can you help us?
>
> Does it happen for rescue binary ?
>
> Note that the binary is linked static, so the problem is in lib/libc/gen/tls.c
> and not in rtld. There, I do not see any real use of the phdr' p_align
> value.
>
> BTW, is rescue linked to libthr ?
There isn't alignment support for TLS in static binaries. I've fixed
this in CheriBSD and am planning to upstream the fixes at some point.
The fix for variant I is in:
https://github.com/CTSRD-CHERI/cheribsd/commit/3cfb124ebb9fdb545dad8436a04dd58c05b33f4b
-- Brooks
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