Rodney, JavaScriptCore assumes that the stack is 16 byte aligned. This may be more restrictive than some OS / ABIs, but there is code to pad appropriately for some platforms. You didn’t say what OS you are running on, but maybe there needs to be a code added for your OS. Turning on C++ exceptions could be responsible, as that could be changing stack layout. I don’t know of any platform that turns on C++ exceptions, so you may be in uncharted waters.
Your build is 2 months old, the current revision is 187434. You could also try a more recent build. - Michael > On Jul 27, 2015, at 8:07 AM, Rodney Dowdall <rdowd...@cranksoftware.com> > wrote: > > Hello > > I am seeing a SIGTRAP generated in the LLINT code when I try and load up a > page. It happens as soon as the page tries to execute JavaScript. The > target is an 32 bit x86 machine. The SIGTRAP appears to happen when it is > checking the stack alignment. I have tried compiling the code with the gcc > option -mstackrealign and without it. The SIGTRAP is generated in the same > spot with or without the option. C++ exceptions are turned on (they have to > be with this particular compiler. The compiler is gcc based). The version > of Webkit that I am building from is 184845. > > > Here is the assembly execution that causes the SIGTRAP: > > vmEntryToJavaScript: > b9a80ef7: push %ebp > b9a80ef8: mov %esp,%ebp > b9a80efa: push %esi > b9a80efb: push %edi > b9a80efc: push %ebx > b9a80efd: mov 0xc(%ebp),%ebx > b9a80f00: mov 0x8(%ebp),%edi > b9a80f03: mov %ebp,%esp > b9a80f05: sub $0x20,%esp > b9a80f08: mov %ebx,(%esp) > b9a80f0b: mov 0x1498(%ebx),%edx > b9a80f11: mov %edx,0x4(%esp) > b9a80f15: mov 0x1494(%ebx),%edx > b9a80f1b: mov %edx,0x8(%esp) > b9a80f1f: mov 0x10(%ebp),%esi > b9a80f22: mov 0x20(%esi),%edx > b9a80f25: add $0x4,%edx > b9a80f28: shl $0x3,%edx > b9a80f2b: mov %esp,%eax > b9a80f2d: sub %edx,%eax > b9a80f2f: cmp 0x2384(%ebx),%eax > b9a80f35: jae 0xb9a80f71 <vmEntryToJavaScript+122> > > b9a80f71: mov %eax,%esp > b9a80f73: mov $0x4,%eax > b9a80f78: sub $0x1,%eax > b9a80f7b: mov 0x4(%esi,%eax,8),%ecx > b9a80f7f: mov %ecx,0xc(%esp,%eax,8) > b9a80f83: mov (%esi,%eax,8),%ecx > b9a80f86: mov %ecx,0x8(%esp,%eax,8) > b9a80f8a: test %eax,%eax > b9a80f8c: jne 0xb9a80f78 <vmEntryToJavaScript+129> > > b9a80f9e: sub $0x1,%ecx > b9a80fa1: movl $0xfffffffc,0x2c(%esp,%ecx,8) > b9a80fa9: movl $0x0,0x28(%esp,%ecx,8) > b9a80fb1: cmp %ecx,%edx > b9a80fb3: jne 0xb9a80f9e <vmEntryToJavaScript+167> > b9a80fb5: mov 0x28(%esi),%eax > b9a80fb8: test %edx,%edx > b9a80fba: je 0xb9a80fd0 <vmEntryToJavaScript+217> > > b9a80f78: sub $0x1,%eax > b9a80f7b: mov 0x4(%esi,%eax,8),%ecx > b9a80f7f: mov %ecx,0xc(%esp,%eax,8) > b9a80f83: mov (%esi,%eax,8),%ecx > b9a80f86: mov %ecx,0x8(%esp,%eax,8) > b9a80f8a: test %eax,%eax > b9a80f8c: jne 0xb9a80f78 <vmEntryToJavaScript+129> > > b9a80f78: sub $0x1,%eax > b9a80f7b: mov 0x4(%esi,%eax,8),%ecx > b9a80f7f: mov %ecx,0xc(%esp,%eax,8) > b9a80f83: mov (%esi,%eax,8),%ecx > b9a80f86: mov %ecx,0x8(%esp,%eax,8) > b9a80f8a: test %eax,%eax > b9a80f8c: jne 0xb9a80f78 <vmEntryToJavaScript+129> > > b9a80f78: sub $0x1,%eax > b9a80f7b: mov 0x4(%esi,%eax,8),%ecx > b9a80f7f: mov %ecx,0xc(%esp,%eax,8) > b9a80f83: mov (%esi,%eax,8),%ecx > b9a80f86: mov %ecx,0x8(%esp,%eax,8) > b9a80f8a: test %eax,%eax > b9a80f8c: jne 0xb9a80f78 <vmEntryToJavaScript+129> > b9a80f8e: mov 0x10(%esi),%edx > b9a80f91: sub $0x1,%edx > b9a80f94: mov 0x20(%esi),%ecx > b9a80f97: sub $0x1,%ecx > b9a80f9a: cmp %ecx,%edx > b9a80f9c: je 0xb9a80fb5 <vmEntryToJavaScript+190> > > b9a80fd0: mov %esp,0x1498(%ebx) > b9a80fd6: mov %ebp,0x1494(%ebx) > b9a80fdc: add $0x8,%esp > b9a80fdf: mov %esp,%ecx > b9a80fe1: and $0xf,%ecx > b9a80fe4: test %ecx,%ecx > b9a80fe6: je 0xb9a80fee <vmEntryToJavaScript+247> > b9a80fe8: mov $0xbad0dc02,%ecx > b9a80fed: int3 > > So using the LLintAssembly.h I tracked this too: > > "\tjz " > LOCAL_LABEL_STRING(_offlineasm_doVMEntry__makeCall__checkStackPointerAlignment__stackPointerOkay > > Which leads me to believe that the alignment on my stack is wrong. The value > of esp is 0x7db9284. The value of ecx after the and is 4, so that looks > right. > > I don't have a lot of experience with the LLINT, so I was wondering if there > was a specific place I should start to look to see why this error is beign > generated. > > Thanks, > Rodney > > _______________________________________________ > webkit-dev mailing list > webkit-dev@lists.webkit.org > https://lists.webkit.org/mailman/listinfo/webkit-dev _______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
