On Thu, 29 Aug 2019 at 17:32, Kyrill Tkachov
<kyrylo.tkac...@foss.arm.com> wrote:
>
> Hi Christophe,
>
> On 5/15/19 1:39 PM, Christophe Lyon wrote:
> > Without this, when we are unwinding across a signal frame we can jump
> > to an even address which leads to an exception.
> >
> > This is needed in __gnu_persnality_sigframe_fdpic() when restoring the
> > PC from the signal frame since the PC saved by the kernel has the LSB
> > bit set to zero.
> >
> > 2019-XX-XX Christophe Lyon <christophe.l...@st.com>
> > Mickaël Guêné <mickael.gu...@st.com>
> >
> > libgcc/
> > * config/arm/unwind-arm.c (_Unwind_VRS_Set): Handle v7m
> > architecture.
> >
> > Change-Id: Ie84de548226bcf1751e19a09e8f091fb3013ccea
> >
> > diff --git a/libgcc/config/arm/unwind-arm.c
> > b/libgcc/config/arm/unwind-arm.c
> > index 9ba73e7..ba47150 100644
> > --- a/libgcc/config/arm/unwind-arm.c
> > +++ b/libgcc/config/arm/unwind-arm.c
> > @@ -199,6 +199,11 @@ _Unwind_VRS_Result _Unwind_VRS_Set
> > (_Unwind_Context *context,
> > return _UVRSR_FAILED;
> >
> > vrs->core.r[regno] = *(_uw *) valuep;
> > +#if defined(__ARM_ARCH_7M__)
> > + /* Force LSB bit since we always run thumb code. */
> > + if (regno == 15)
> > + vrs->core.r[regno] |= 1;
> > +#endif
>
> Hmm, this looks quite specific. There are other architectures that are
> thumb-only too (6-M, 7E-M etc).
>
> Would checking for __thumb__ be better?
>
Right.
The attached updated patch also uses R_PC instead of 15.
Christophe
> Thanks,
>
> Kyrill
>
>
> > return _UVRSR_OK;
> >
> > case _UVRSC_VFP:
> > --
> > 2.6.3
> >
commit d50dfb233059bc5a110117047fe8f60d6580f095
Author: Christophe Lyon <christophe.l...@linaro.org>
Date: Thu Feb 8 14:52:02 2018 +0100
[ARM] FDPIC: Force LSB bit for PC in Cortex-M architecture
Without this, when we are unwinding across a signal frame we can jump
to an even address which leads to an exception.
This is needed in __gnu_persnality_sigframe_fdpic() when restoring the
PC from the signal frame since the PC saved by the kernel has the LSB
bit set to zero.
2019-XX-XX Christophe Lyon <christophe.l...@st.com>
Mickaël Guêné <mickael.gu...@st.com>
libgcc/
* config/arm/unwind-arm.c (_Unwind_VRS_Set): Handle thumb-only
architecture.
Change-Id: Ie84de548226bcf1751e19a09e8f091fb3013ccea
diff --git a/libgcc/config/arm/unwind-arm.c b/libgcc/config/arm/unwind-arm.c
index 9ba73e7..8313ee0 100644
--- a/libgcc/config/arm/unwind-arm.c
+++ b/libgcc/config/arm/unwind-arm.c
@@ -199,6 +199,11 @@ _Unwind_VRS_Result _Unwind_VRS_Set (_Unwind_Context *context,
return _UVRSR_FAILED;
vrs->core.r[regno] = *(_uw *) valuep;
+#if defined(__thumb__)
+ /* Force LSB bit since we always run thumb code. */
+ if (regno == R_PC)
+ vrs->core.r[regno] |= 1;
+#endif
return _UVRSR_OK;
case _UVRSC_VFP:
