[ARM/FDPIC,v6,13/24,ARM] FDPIC: Force LSB bit for PC in Cortex-M architecture
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Message ID 20190909154526.11630-14-christophe.lyon@st.com
State New
Headers show
Series
  • FDPIC ABI for ARM
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Commit Message

Christophe Lyon Sept. 9, 2019, 3:44 p.m. UTC
From: Christophe Lyon <christophe.lyon@linaro.org>

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.lyon@st.com>
	Mickaël Guêné <mickael.guene@st.com>

	libgcc/
	* config/arm/unwind-arm.c (_Unwind_VRS_Set): Handle thumb-only
	architecture.

Change-Id: Ie84de548226bcf1751e19a09e8f091fb3013ccea

Patch
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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: