Date: Tue, 7 Jul 2015 18:40:18 +0200 From: Alex <alexinbeijing@...il.com> To: musl@...ts.openwall.com Subject: Re: [PATCH v9] Build process uses script to add CFI directives to x86 asm On Tue, Jul 7, 2015 at 3:21 PM, Rich Felker <dalias@...c.org> wrote: > On Tue, Jul 07, 2015 at 07:45:34AM +0200, Alex wrote: >> On Tue, Jul 7, 2015 at 5:39 AM, Rich Felker <dalias@...c.org> wrote: >> > On Tue, Jun 23, 2015 at 09:18:08PM +0200, Alex Dowad wrote: >> >> Dear musl devs, >> >> >> >> ../configure now checks CFLAGS as well as CFLAGS_AUTO to see if generation of debug >> >> info was requested. >> >> >> >> The idea of removing duplication from the Makefile using a new AS_CMD variable has >> >> come up several times, but this will not work because the arguments need to be >> >> inserted in different places. I have tried using a Makefile 'define' instead. >> >> Please see whether you like the way this code reads or not. >> >> >> >> Subarch asm files are treated the same as other asm files. Please note that >> >> since I don't own the hardware, I can't test whether these Makefile rules work or not. >> > >> > I'm trying to test this and get it merged, but I'm not having any luck >> > getting gdb to backtrace when I interrupt a syscall with ^C. I've >> > tried pause() and syscall(SYS_pause) (cancellable and non-cancellable) >> > and the patch doesn't seem to help at all for the former, and only >> > helps mildly for the latter. Have you had better results than I did? >> >> I tested a different set of library calls, with my own test programs. >> Can you please send a copy of the test program you are using, and I >> will debug? Thanks, AD > > Here it is. Compile with -g -O0 to make a more interesting backtrace > (if it works). Thanks for the test program. I compiled it with: ./tools/musl-gcc -Xlinker -melf_i386 -m32 -o canbt canbt.c (That -Xlinker junk is because I am compiling to 32-bit code on a 64-bit machine.) And then: gdb ./canbt Set a breakpoint on pause(), single-stepped all the way into the innards of musl, and I was able to get a nice stack trace at each stop. Sample of what it looks like at one randomly chosen point: https://dl.dropboxusercontent.com/u/106217735/musl-debugging-pause.png Could you please 1) tell me the command-line invocation you are using to compile the test program and 2) send me a binary, so I can extract the DWARF data from it and see what it looks like? Thanks, AD
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