search for: interpositioning

Hi everyone, Clang/LLVM's support for ELF interposition is in a confusing state, and I propose making a few (hopefully simple) adjustments in order to bring our model into a self-consistent state. The problem: On ELF systems, global symbols can be interposed. This means, for example, that calls to global functions in some (shared) library defined in that same library might end up being

I think that all makes sense. You're just adding the missing non-ODR conterpart of 'external' linkage. I could imagine having "external / external_odr" linkage for example. That said, do you think we should take the opportunity to split out a bit for interposability so that we can kill off the *_odr linkage variants? Today's non-ODR weak functions would look more like

----- Original Message ----- > From: "James Y Knight" <jyknight at google.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Sanjoy Das" <sanjoy at playingwithpointers.com>, "llvm-dev" > <llvm-dev at lists.llvm.org> > Sent: Monday, February 29, 2016 9:31:24 AM > Subject: Re: [llvm-dev] Possible soundness issue with

You present a good case for not using "protected" visibility in ELF, despite it being exactly what it is supposed to mean. >From what http://www.airs.com/blog/archives/307 says, it sounds like the *correctness* issue with protected visibility is because LLVM is doing it wrong -- not an intrinsic property of protected visibility in ELF, or even ELF/x86. The blog says that the compiler

> On Mar 11, 2016, at 12:16 PM, Rafael Espíndola <rafael.espindola at gmail.com> wrote: > On 11 March 2016 at 14:58, John McCall <rjmccall at apple.com> wrote: >>> On Mar 11, 2016, at 11:26 AM, Rafael Espíndola <rafael.espindola at gmail.com> wrote: >>>> Now, there are a number of things about linkage that are kindof orthogonal, >>>> and it

On Feb 26, 2016 8:50 PM, "Hal Finkel" <hfinkel at anl.gov> wrote: > *From: *"James Y Knight via llvm-dev" <llvm-dev at lists.llvm.org> > *To: *"Sanjoy Das" <sanjoy at playingwithpointers.com> > *Cc: *"llvm-dev" <llvm-dev at lists.llvm.org> > *Sent: *Thursday, February 25, 2016 1:41:43 PM > *Subject: *Re: [llvm-dev]

----- Original Message ----- > From: "Eric Christopher" <echristo at gmail.com> > To: "Reid Kleckner" <rnk at google.com>, "Hal Finkel" <hfinkel at anl.gov> > Cc: "llvm-dev" <llvm-dev at lists.llvm.org> > Sent: Tuesday, November 29, 2016 11:34:56 AM > Subject: Re: [llvm-dev] RFC: Add an "interposible" linkage

+kledzik at apple.com The dynamic runtime is using dylib interposition (google for "__DATA,__interpose). If I'm understanding correctly (Nick, can you please confirm this?) this allows to interpose the function regardless of the two-level namespace. The support for dynamic runtime in ASan is almost there. But the new interposition method has revealed some issues with the allocator which

> On Mar 11, 2016, at 9:56 AM, Reid Kleckner <rnk at google.com> wrote: > > On Fri, Mar 11, 2016 at 9:41 AM, John McCall <rjmccall at apple.com <mailto:rjmccall at apple.com>> wrote: > Okay, so, it sounds to me like LLVM basically treats strong definitions as protected, then. Should we just formalize that? > > I guess the proposal here would be: > 1.

On Tue, Dec 04, 2012 at 09:46:09AM -0800, Alexander Potapenko wrote: > +kledzik at apple.com > The dynamic runtime is using dylib interposition (google for > "__DATA,__interpose). > If I'm understanding correctly (Nick, can you please confirm this?) > this allows to interpose the function regardless of the two-level > namespace. > The support for dynamic runtime in

> On Mar 11, 2016, at 8:33 AM, Reid Kleckner <rnk at google.com> wrote: > On Thu, Mar 10, 2016 at 10:32 PM, John McCall via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote: > I mean, I’ve never really liked ELF’s stance on symbol interposition, but taking it as given, I’m not sure I agree that it’s reasonable to carve out virtual functions

Currently the replacement of allocation routines is based on creating a new malloc zone and a new CFAllocator (because the allocator replacement is done later than it could be, we must have both). This makes us depend on CoreFoundation to call CFAllocatorSetDefault. Because of some bugs in CF which start firing after CFAllocatorSetDefault, we have to add several hacks to circumvent the effects of

> On Mar 11, 2016, at 11:26 AM, Rafael Espíndola <rafael.espindola at gmail.com> wrote: >> Now, there are a number of things about linkage that are kindof orthogonal, >> and it would be nice to model them more orthogonally. That would be a major >> change in representation, though. Absent the will to do that, I propose >> that we: >> - remove/deprecate

On 30 November 2012 13:32, Alexander Potapenko <glider at google.com> wrote: > No, we are not going to use mach_inject. This isn't portable and may > be even harder to set up than mach_override. > The new ASan runtime will use the dylib interposition and will in fact > require DYLD_INSERT_LIBRARIES to work. However ASan already handles it > correctly itself: if the

On Wed, Dec 18, 2019 at 3:38 AM Iurii Gribov via llvm-dev < llvm-dev at lists.llvm.org> wrote: > (Readding Hal) > > > Are you suggesting that we should be more aggressive by default (i.e. > without -fvisibility=hidden or any new options)? > > I believe that will be too aggressive for class LTO visibility. > > It is common to override a virtual functions across

On Tue, Dec 04, 2012 at 10:36:18AM -0800, Alexander Potapenko wrote: > Currently the replacement of allocation routines is based on creating > a new malloc zone and a new CFAllocator (because the allocator > replacement is done later than it could be, we must have both). This > makes us depend on CoreFoundation to call CFAllocatorSetDefault. > Because of some bugs in CF which start

> On Mar 11, 2016, at 1:40 PM, Rafael Espíndola <rafael.espindola at gmail.com> wrote: >>> And you can't also just produce STV_PROTECTED for every symbol. I >>> would love for that to be the case, but while most ELF systems support >>> copy relocations and related PLT hacks for functions it is not >>> practical to do it. >> >> I’m

> Are you suggesting that we should be more aggressive by default (i.e. without -fvisibility=hidden or any new options)? > I believe that will be too aggressive for class LTO visibility. > It is common to override a virtual functions across shared library boundaries I'm myself a fan of GCC's conservative approach so I'd agree with you on that. But regardless of my personal

----- Original Message ----- > From: "James Y Knight via llvm-dev" <llvm-dev at lists.llvm.org> > To: "Sanjoy Das" <sanjoy at playingwithpointers.com> > Cc: "llvm-dev" <llvm-dev at lists.llvm.org> > Sent: Thursday, February 25, 2016 1:41:43 PM > Subject: Re: [llvm-dev] Possible soundness issue with > available_externally (split

No, we are not going to use mach_inject. This isn't portable and may be even harder to set up than mach_override. The new ASan runtime will use the dylib interposition and will in fact require DYLD_INSERT_LIBRARIES to work. However ASan already handles it correctly itself: if the corresponding env var is missing the app is just re-execed. Dylib interposition is supported by Apple and should