| Message ID | 20200428133411.44092-1-vincenzo.frascino@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: vdso: Add -fasynchronous-unwind-tables to cflags | expand |
On Tue, Apr 28, 2020 at 02:34:11PM +0100, Vincenzo Frascino wrote: > On arm64 linux gcc uses -fasynchronous-unwind-tables -funwind-tables > by default since gcc-8, so now the de facto platform ABI is to allow > unwinding from async signal handlers. > > However on bare metal targets (aarch64-none-elf), and on old gcc, > async and sync unwind tables are not enabled by default to avoid > runtime memory costs. > > This means if linux is built with a baremetal toolchain the vdso.so > may not have unwind tables which breaks the gcc platform ABI guarantee > in userspace. > > Add -fasynchronous-unwind-tables explicitly to the vgettimeofday.o > cflags to address the ABI change. > > Cc: Will Deacon <will@kernel.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Reported-by: Szabolcs Nagy <szabolcs.nagy@arm.com> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> > --- > arch/arm64/kernel/vdso/Makefile | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile > index 331290a0cead..b388ce4c6d5f 100644 > --- a/arch/arm64/kernel/vdso/Makefile > +++ b/arch/arm64/kernel/vdso/Makefile > @@ -33,7 +33,8 @@ KCOV_INSTRUMENT := n > CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny > > ifneq ($(c-gettimeofday-y),) > - CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y) > + CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y) \ > + -fasynchronous-unwind-tables Minor comment, but why is this inside the conditional block and not part of the CFLAGS_vgettimeofday.o directly above it? Anyway, Szabolcs -- please can you confirm this fixes the problem for you? Thanks, Will
On 4/29/20 3:54 PM, Will Deacon wrote: > On Tue, Apr 28, 2020 at 02:34:11PM +0100, Vincenzo Frascino wrote: >> On arm64 linux gcc uses -fasynchronous-unwind-tables -funwind-tables >> by default since gcc-8, so now the de facto platform ABI is to allow >> unwinding from async signal handlers. >> >> However on bare metal targets (aarch64-none-elf), and on old gcc, >> async and sync unwind tables are not enabled by default to avoid >> runtime memory costs. >> >> This means if linux is built with a baremetal toolchain the vdso.so >> may not have unwind tables which breaks the gcc platform ABI guarantee >> in userspace. >> >> Add -fasynchronous-unwind-tables explicitly to the vgettimeofday.o >> cflags to address the ABI change. >> >> Cc: Will Deacon <will@kernel.org> >> Cc: Catalin Marinas <catalin.marinas@arm.com> >> Reported-by: Szabolcs Nagy <szabolcs.nagy@arm.com> >> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> >> --- >> arch/arm64/kernel/vdso/Makefile | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile >> index 331290a0cead..b388ce4c6d5f 100644 >> --- a/arch/arm64/kernel/vdso/Makefile >> +++ b/arch/arm64/kernel/vdso/Makefile >> @@ -33,7 +33,8 @@ KCOV_INSTRUMENT := n >> CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny >> >> ifneq ($(c-gettimeofday-y),) >> - CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y) >> + CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y) \ >> + -fasynchronous-unwind-tables > > Minor comment, but why is this inside the conditional block and not part > of the CFLAGS_vgettimeofday.o directly above it? > Because I rushed the patch out without rechecking it, sorry. Going to send v2. > Anyway, Szabolcs -- please can you confirm this fixes the problem for you? > > Thanks, > > Will >
diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile index 331290a0cead..b388ce4c6d5f 100644 --- a/arch/arm64/kernel/vdso/Makefile +++ b/arch/arm64/kernel/vdso/Makefile @@ -33,7 +33,8 @@ KCOV_INSTRUMENT := n CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny ifneq ($(c-gettimeofday-y),) - CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y) + CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y) \ + -fasynchronous-unwind-tables endif # Clang versions less than 8 do not support -mcmodel=tiny
On arm64 linux gcc uses -fasynchronous-unwind-tables -funwind-tables by default since gcc-8, so now the de facto platform ABI is to allow unwinding from async signal handlers. However on bare metal targets (aarch64-none-elf), and on old gcc, async and sync unwind tables are not enabled by default to avoid runtime memory costs. This means if linux is built with a baremetal toolchain the vdso.so may not have unwind tables which breaks the gcc platform ABI guarantee in userspace. Add -fasynchronous-unwind-tables explicitly to the vgettimeofday.o cflags to address the ABI change. Cc: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Reported-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> --- arch/arm64/kernel/vdso/Makefile | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)