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Date: Mon, 9 Oct 2017 19:39:34 +0200
From: Felix Hädicke <felixhaedicke@....de>
To: musl@...ts.openwall.com, Rich Felker <dalias@...c.org>
Subject: Re: SIGILL in setjmp() on ARM
On 10/09/17 07:06, Rich Felker wrote:
> On Sun, Oct 08, 2017 at 08:57:36PM +0200, Felix Hädicke wrote:
>> Hello,
>>
>> For the XCSoar open source software (https://xcsoar.org), we have a
>> version for Kobo eReader devices. We are currently using glibc for this,
>> but are trying to switch to musl.
>>
>> However, for optimized builds, the program crashes with SIGILL in
>> setjmp(), which is called by the freetype library, which is used in our
>> program.
>>
>> The following CFLAGS were used:
>> -march=armv7-a -mcpu=cortex-a8 -mfpu=neon -mfloat-abi=hard -mthumb
>> -fvisibility=hidden -Os -g
>>
>> Everything (including musl and freetype) is linked statically.
>>
>> Debian's "arm-linux-gnueabihf" toolchain is used for compiling, which
>> was configured with
>> --with-arch=armv7-a --with-fpu=vfpv3-d16 --with-float=hard --with-mode=thumb
>>
>> The Kobo Mini eReader which I use for testing, has a Freescale i.MX 5
>> (Cortex-A8). But the crash is reproducible on i.MX 6 based Kobo devices,
>> and even on QEMU, as well.
>>
>> Disabling optimisation (flag "-O0" instead of "-Os"), or disabling Thumb
>> (flag "-marm") for musl solves the problem. However, doing this for
>> compiling the setjmp.s file only does not make a difference. And using
>> "-O1" instead of "-Os" does not help.
>>
>> Find some GDB crash dump analysis below.
>>
>> Regards,
>> Felix
>>
>>
>>
>> Core was generated by `/mnt/onboard/xcsoar'.
>> Program terminated with signal SIGILL, Illegal instruction.
>> #0 setjmp () at
>> /home/felix/.tmp/xcsoar-merge-musl/output/src/musl-1.1.16/src/setjmp/arm/setjmp.s:35
>> 35 stcl p1, cr10, [ip], #8
>> [Current thread is 1 (LWP 820)]
>>
>> (gdb) bt
>> #0 setjmp () at
>> /home/felix/.tmp/xcsoar-merge-musl/output/src/musl-1.1.16/src/setjmp/arm/setjmp.s:35
>> #1 0x00135c04 in tt_face_build_cmaps (face=face@...ry=0x545880) at
>> /home/felix/.tmp/xcsoar-merge-musl/output/src/freetype-2.8/src/sfnt/ttcmap.c:3753
>> #2 0x00135f34 in sfnt_load_face (stream=<optimized out>, face=0x545880,
>> face_instance_index=<optimized out>, num_params=<optimized out>, params=0x0)
>> at
>> /home/felix/.tmp/xcsoar-merge-musl/output/src/freetype-2.8/src/sfnt/sfobjs.c:1470
>> #3 0x0012e7cc in tt_face_init (stream=<optimized out>, ttface=0x545880,
>> face_index=0, num_params=0, params=0x0) at
>> /home/felix/.tmp/xcsoar-merge-musl/output/src/freetype-2.8/src/truetype/ttobjs.c:596
>> #4 0x0012983e in open_face (driver=driver@...ry=0x5443b0,
>> astream=astream@...ry=0x7efdaaec,
>> external_stream=external_stream@...ry=0 '\000',
>> face_index=face_index@...ry=0, num_params=0, params=0x0,
>> aface=aface@...ry=0x7efdaaf0) at
>> /home/felix/.tmp/xcsoar-merge-musl/output/src/freetype-2.8/src/base/ftobjs.c:1195
>> #5 0x0012a34a in ft_open_face_internal (library=0x5442e0,
>> args=args@...ry=0x7efdac10, face_index=face_index@...ry=0,
>> aface=aface@...ry=0x7efdac3c, test_mac_fonts=test_mac_fonts@...ry=1 '\001')
>> at
>> /home/felix/.tmp/xcsoar-merge-musl/output/src/freetype-2.8/src/base/ftobjs.c:2267
>> #6 0x0012a686 in FT_New_Face (library=<optimized out>,
>> pathname=pathname@...ry=0x544710 "/opt/xcsoar/share/fonts/Vera.ttf",
>> face_index=face_index@...ry=0, aface=aface@...ry=0x7efdac3c)
>> at
>> /home/felix/.tmp/xcsoar-merge-musl/output/src/freetype-2.8/src/base/ftobjs.c:1258
>> #7 0x000c7a52 in FreeType::Load (path=path@...ry=0x544710
>> "/opt/xcsoar/share/fonts/Vera.ttf") at src/Screen/FreeType/Init.cpp:63
>> #8 0x000c757a in Font::LoadFile (this=0x52a27c <Fonts::map>,
>> file=0x544710 "/opt/xcsoar/share/fonts/Vera.ttf", ptsize=18,
>> bold=<optimized out>, italic=false) at src/Screen/FreeType/Font.cpp:157
>> #9 0x000c765a in Font::Load (this=this@...ry=0x52a27c <Fonts::map>,
>> d=...) at src/Screen/FreeType/Font.cpp:213
>> #10 0x00068eb8 in Fonts::Load (settings=...) at src/Look/GlobalFonts.cpp:36
>> #11 0x00068fe0 in Fonts::Initialize () at src/Look/DefaultFonts.cpp:52
>> #12 0x0006ae1c in MainWindow::Initialise (this=this@...ry=0x5451e0) at
>> src/MainWindow.cpp:196
>> #13 0x0006b8e4 in Startup () at src/Startup.cpp:231
>> #14 0x0001a800 in Main () at src/XCSoar.cpp:121
>> #15 main (argc=<optimized out>, argv=<optimized out>) at src/XCSoar.cpp:170
>>
>> (gdb) disassemble
>> Dump of assembler code for function setjmp:
>> 0x001968ce <+0>: mov r12, r0
>> 0x001968d0 <+2>: stmia.w r12!, {r4, r5, r6, r7, r8, r9, r10, r11}
>> 0x001968d4 <+6>: mov r2, sp
>> 0x001968d6 <+8>: stmia.w r12!, {r2, lr}
>> 0x001968da <+12>: mov.w r0, #0
>> 0x001968de <+16>: add r1, pc, #60 ; (adr r1, 0x19691c
>> <setjmp+78>)
>> 0x001968e0 <+18>: ldr r2, [pc, #60] ; (0x196920 <setjmp+82>)
>> 0x001968e2 <+20>: ldr r1, [r1, r2]
>> 0x001968e4 <+22>: tst.w r1, #608 ; 0x260
>> 0x001968e8 <+26>: beq.n 0x19691c <setjmp+78>
>> 0x001968ea <+28>: tst.w r1, #32
>> 0x001968ee <+32>: beq.n 0x1968f4 <setjmp+38>
>> 0x001968f0 <+34>: sfm f4, 4, [r12], #48 ; 0x30
>> 0x001968f4 <+38>: tst.w r1, #64 ; 0x40
>> 0x001968f8 <+42>: beq.n 0x1968fe <setjmp+48>
>> 0x001968fa <+44>: vstmia r12!, {d8-d15}
>> 0x001968fe <+48>: tst.w r1, #512 ; 0x200
>> 0x00196902 <+52>: beq.n 0x19691c <setjmp+78>
>> => 0x00196904 <+54>: stfp f2, [r12], #8
>> 0x00196908 <+58>: stfp f3, [r12], #8
>> 0x0019690c <+62>: stfp f4, [r12], #8
>> 0x00196910 <+66>: stfp f5, [r12], #8
>> 0x00196914 <+70>: stfp f6, [r12], #8
>> 0x00196918 <+74>: stfp f7, [r12], #8
>> 0x0019691c <+78>: bx lr
>> 0x0019691e <+80>: eorseq r7, r10, r2, ror #20
>> 0x00196922 <+84>: stmdbmi r4, {} ; <UNPREDICTABLE>
>> End of assembler dump.
>>
>> (gdb) info registers
>> r0 0x0 0
>> r1 0x27af4601 665798145
>> r2 0x3a 58
>> r3 0x10c 268
>> r4 0x7efda7c0 2130552768
>> r5 0xa59 2649
>> r6 0x1 1
>> r7 0x0 0
>> r8 0x0 0
>> r9 0x0 0
>> r10 0x0 0
>> r11 0x219cf4 2202868
>> r12 0x7efda7e8 2130552808
>> sp 0x7efda778 0x7efda778
>> lr 0x135c05 1268741
>> pc 0x196904 0x196904 <setjmp+54>
>> cpsr 0x30 48
> OK, this is a very subtle issue with the assembler and/or linker. For
> the adr pseudo-instruction above (setjmp+16), the assembler generates
> a 16-bit thumb add instruction which can only represent word-aligned
> addresses, despite not knowing the alignment of the label. When the
> setjmp function is assigned a non-multiple-of-4 address at link time
> (which is perturbed by your -O level, etc. of *other* object files,
> not setjmp itself) the load then loads from the wrong address
> (setjmp+78 rather than setjmp+80) and ends up reading nonsense instead
> of the value of __hwcap, thereby thinking you have IWMMX extensions
> and need to save/restore those registers.
>
> Try the attached patch and let me know if it fixes it for you.
>
> Rich
Your patch solves the problem! Tried with GCC5 and GCC7, with -fno-PIE
and with -fPIE. Everything compiled with -Os and -mthumb.
Regards,
Felix
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