Messages in this thread Patch in this message | | | Date | Fri, 23 Jan 2015 17:50:39 +0000 | From | Will Deacon <> | Subject | Re: arm64 -- psci tell the compiler in which registers we are expecting arguments |
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Hi Andy,
Thanks for the patch.
On Fri, Jan 23, 2015 at 05:31:54PM +0000, Andy Whitcroft wrote: > When compiling the kernel with very recent gcc-4.9 compilers we see the > following errors: > > /tmp/ccEayz7S.s: Assembler messages: > /tmp/ccEayz7S.s:41: Error: .err encountered > /tmp/ccEayz7S.s:42: Error: .err encountered > /tmp/ccEayz7S.s:43: Error: .err encountered > /tmp/ccEayz7S.s:101: Error: .err encountered > /tmp/ccEayz7S.s:102: Error: .err encountered > /tmp/ccEayz7S.s:103: Error: .err encountered > > This is due to assumptions about the register assignments made by gcc on > function entry. The errors above occur when these assignments are not > as expected. It turns out that when you enable mcount preables (-pg) > these are altered and the compilation failed. > > Inform the compiler of these register requirements. > > BugLink: http://bugs.launchpad.net/bugs/1414002 > Signed-off-by: Andy Whitcroft <apw@canonical.com> > --- > arch/arm64/kernel/psci.c | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c > index f1dbca7..425cf78 100644 > --- a/arch/arm64/kernel/psci.c > +++ b/arch/arm64/kernel/psci.c > @@ -113,9 +113,14 @@ static void psci_power_state_unpack(u32 power_state, > * The following two functions are invoked via the invoke_psci_fn pointer > * and will not be inlined, allowing us to piggyback on the AAPCS. > */ > -static noinline int __invoke_psci_fn_hvc(u64 function_id, u64 arg0, u64 arg1, > - u64 arg2) > +static noinline int __invoke_psci_fn_hvc(u64 _function_id, u64 _arg0, > + u64 _arg1, u64 _arg2) > { > + register u64 function_id asm("x0") = _function_id; > + register u64 arg0 asm("x1") = _arg0; > + register u64 arg1 asm("x2") = _arg1; > + register u64 arg2 asm("x3") = _arg2; > +
Given that we've already been bitten by the compiler, I think we should just bite the bullet and implement these two functions in assembly in a separate file rather than rely on register variables doing what we want.
Will
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