On 02/21/17 18:53, Anthony PERARD wrote: > On Tue, Feb 21, 2017 at 06:07:15PM +0100, Laszlo Ersek wrote: >> CC Rebecca & Konrad >> >> On 02/21/17 17:39, Anthony PERARD wrote:
[snip] >>> So, should I add EFIAPI to XenStoreVSPrint, as it is using VA_COPY? >>> >> >> Hm, please help me jog my memory... >> >> If I remember correctly, this is still a GCC bug, one that we suppressed for >> gcc-6.2 with your patch as follows: > > Yes. > >>> commit 432f1d83f77acf92d52ef18d2cee6dbf7c5b9b86 >>> Author: Anthony PERARD <anthony.per...@citrix.com> >>> Date: Tue Dec 6 12:03:25 2016 +0000 >>> >>> OvmfPkg/build.sh: Use GCC49 toolchains with GCC 6.[0-2] >>> >>> The goal of the patch is to avoid using -flto with GCC 6.0 to 6.2. >>> >>> This is to workaround a GCC bug: >>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70955 >>> >>> Contributed-under: TianoCore Contribution Agreement 1.0 >>> Signed-off-by: Anthony PERARD <anthony.per...@citrix.com> >>> Reviewed-by: Laszlo Ersek <ler...@redhat.com> >>> Regression-tested-by: Laszlo Ersek <ler...@redhat.com> >>> >>> diff --git a/OvmfPkg/build.sh b/OvmfPkg/build.sh >>> index 95fe8fb07647..b6e936056ca0 100755 >>> --- a/OvmfPkg/build.sh >>> +++ b/OvmfPkg/build.sh >>> @@ -102,7 +102,7 @@ case `uname` in >>> 4.8.*) >>> TARGET_TOOLS=GCC48 >>> ;; >>> - 4.9.*) >>> + 4.9.*|6.[0-2].*) >>> TARGET_TOOLS=GCC49 >>> ;; >>> *) >> >> Do I understand correctly that the gcc bug has not been fixed in >> gcc-6.3, and -- because we don't suppress it for gcc-6.3 as the >> above expression does not match -- it causes problems again? > > The bug describe in the GCC bugzilla is probably fix, but the > test-case does not make use of __builtin_ms_va_copy. :/ > >> You also mention gcc-5.4 as problematic. I think we haven't >> received such reports about gcc-5 versions up to and including >> gcc-5.3 (that's why GCC5 is the default selection in >> "OvmfPkg/build.sh"). Do you mean that the gcc bug has now been >> "backported" from the gcc-6 series to the gcc-5 series (starting >> with gcc-5.4)? > > I don't know the state of gcc-5.0 to gcc-5.3, I have never tested -flto > with gcc-5.x (until now), I would say they are also problematic until > proven otherwise. When we enabled GCC5, it definitely worked for at least one gcc release, with -flto. (-flto is the default for DEBUG and RELEASE builds with GCC5; NOOPT disables -Os and -flto.) > >> If that's the case, then I suggest flipping "OvmfPkg/build.sh" from >> black-listing gcc versions for -flto to white-listing. In other >> words, assume that -flto is generally broken with GCC, except for a >> few known versions: 5.0 through 5.3 inclusive. Those versions >> should trigger the use of the GCC5 toolchain, and everything else >> (5.4+, 6.*, 4.9.*) should use GCC49. >> >> I don't feel comfortable about adding EFIAPI to XenStoreVSPrint >> just because it takes a VA_LIST parameter -- note: it is *not* a >> varargs function itself! --; the same issue might hit elsewhere in >> the edk2 tree at any time, outside of OvmfPkg too. > > From the different tests I've done, I feel more like VA_COPY might be > the issue, but I don't know how __builtin_ms_va_* are supposed to be > used. If I recall correctly, from the upstream GCC bug, the problem is that __builtin_va_list does not track internally whether it was created in an msabi or sysvabi function, and therefore the va_* functions cannot be used transparently on it. Instead, when va_list is accessed, the accessor builtins seem to apply the currently executing function's calling convetion to va_list. (Even if the creation context of va_list was different.) > >> Would the gcc white-listing work for you? >> >> Note that the white-listing would practically undo Konrad's commit >> 2667ad40919a ("OvmfPkg/build.sh: Make GCC5 the default toolchain, >> catch GCC43 and earlier", 2016-11-23), but given the recent gcc >> developments (gcc-6.3 has not fixed the gcc bug, and the bug has >> even surfaced in gcc-5.4), I think it would be justified. > > Do be honnest, I don't think the toolchain GCC5 has ever been tested > with gcc-5.x and the module XenBusDxe. I think most people that want to > start OVMF under Xen are likely to build it with gcc-4.9 or already had > gcc-6.x when OVMF switch to the GCC5 toolchain by default. > Okay... I'm equally fine if we just say "given that GCC is broken like this, we hereby require all functions that take a variable argument list, *or* a VA_LIST parameter, to be EFIAPI". (The first part of the requirement already exists.) But in this case, the full edk2 codebase has to be grepped for VA_LIST-taking functions, and all of them must be flipped to EFIAPI, if they currently aren't EFIAPI. Covering just XenStoreVSPrint() seems incomplete. (Note: CryptoPkg/Library/OpensslLib is an exception.) Also, in this case, your commit 432f1d83f77a should likely be reverted. (Because we are ultimately giving in to the gcc bug.) Thanks Laszlo _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
