We generally assume that calls into JavaScriptCore are made on an aligned stack. So, to my knowledge, our code does not usually do dynamic stack realignment. You should check the vmEntryToJavascript thunk - which gets called when you make a call into JS from native code - to see if it does dynamic realignment. You could add dynamic realignment code there if it isn't there already.
-Filip > On Jul 27, 2015, at 8:50 AM, Rodney Dowdall <rdowd...@cranksoftware.com> > wrote: > > Thanks for the response Michael. Where does the code that does the padding > live? It may be that I need to add something in there. I can try changing > what the stack alignment should be, but from what I understand the QNX OS > should align to 16. Maybe it is the exceptions that are causing the problem. > I could try building a 32 bit Linux build with exceptions on to see if I get > the same problem. > > Regards, > Rodney > >> On 07/27/2015 11:24 AM, Michael Saboff wrote: >> 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 _______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
