[ARM] __cxa_end_cleanup: avoid clobbering r4 am: c0a6edcf3b am: 00928ed8ee am: 4b96903904t_frc_odp_330442040t_frc_odp_330442000t_frc_ase_330444010android-13.0.0_r83android-13.0.0_r82android-13.0.0_r81android-13.0.0_r80android-13.0.0_r79android-13.0.0_r78android-13.0.0_r77android-13.0.0_r76android-13.0.0_r75android-13.0.0_r74android-13.0.0_r73android-13.0.0_r72android-13.0.0_r71android-13.0.0_r70android-13.0.0_r69android-13.0.0_r68android-13.0.0_r67android-13.0.0_r66android-13.0.0_r65android-13.0.0_r64android-13.0.0_r63android-13.0.0_r62android-13.0.0_r61android-13.0.0_r60android-13.0.0_r59android-13.0.0_r58android-13.0.0_r57android-13.0.0_r56android-13.0.0_r54android-13.0.0_r53android-13.0.0_r52android-13.0.0_r51android-13.0.0_r50android-13.0.0_r49android-13.0.0_r48android-13.0.0_r47android-13.0.0_r46android-13.0.0_r45android-13.0.0_r44android-13.0.0_r43android-13.0.0_r42android-13.0.0_r41android-13.0.0_r40android-13.0.0_r39android-13.0.0_r38android-13.0.0_r37android-13.0.0_r36android-13.0.0_r35android-13.0.0_r34android-13.0.0_r33android-13.0.0_r32aml_go_odp_330912000aml_go_ads_330915100aml_go_ads_330915000aml_go_ads_330913000main-16k-with-phonesmain-16kandroid13-qpr3-s9-releaseandroid13-qpr3-s8-releaseandroid13-qpr3-s7-releaseandroid13-qpr3-s6-releaseandroid13-qpr3-s5-releaseandroid13-qpr3-s4-releaseandroid13-qpr3-s3-releaseandroid13-qpr3-s2-releaseandroid13-qpr3-s14-releaseandroid13-qpr3-s13-releaseandroid13-qpr3-s12-releaseandroid13-qpr3-s11-releaseandroid13-qpr3-s10-releaseandroid13-qpr3-s1-releaseandroid13-qpr3-releaseandroid13-qpr3-c-s8-releaseandroid13-qpr3-c-s7-releaseandroid13-qpr3-c-s6-releaseandroid13-qpr3-c-s5-releaseandroid13-qpr3-c-s4-releaseandroid13-qpr3-c-s3-releaseandroid13-qpr3-c-s2-releaseandroid13-qpr3-c-s12-releaseandroid13-qpr3-c-s11-releaseandroid13-qpr3-c-s10-releaseandroid13-qpr3-c-s1-releaseandroid13-qpr2-s9-releaseandroid13-qpr2-s8-releaseandroid13-qpr2-s7-releaseandroid13-qpr2-s6-releaseandroid13-qpr2-s5-releaseandroid13-qpr2-s3-releaseandroid13-qpr2-s2-releaseandroid13-qpr2-s12-releaseandroid13-qpr2-s11-releaseandroid13-qpr2-s10-releaseandroid13-qpr2-s1-releaseandroid13-qpr2-releaseandroid13-qpr2-b-s1-releaseandroid13-mainline-go-adservices-releaseandroid13-frc-odp-releaseandroid13-devandroid13-d4-s2-releaseandroid13-d4-s1-releaseandroid13-d4-releaseandroid13-d3-s1-release

Original change: https://android-review.googlesource.com/c/platform/external/libcxxabi/+/2024827

Change-Id: Ibd8610f45ae3983ee130a0ea4eb75fc9b11d8c3a

1 files changed, 23 insertions, 10 deletions

diff --git a/src/cxa_exception.cpp b/src/cxa_exception.cpp
index 8d30e5c..9e650b5 100644
--- a/src/cxa_exception.cpp
+++ b/src/cxa_exception.cpp
@@ -343,8 +343,11 @@ unwinding with _Unwind_Resume.
 According to ARM EHABI 8.4.1, __cxa_end_cleanup() should not clobber any
 register, thus we have to write this function in assembly so that we can save
 {r1, r2, r3}.  We don't have to save r0 because it is the return value and the
-first argument to _Unwind_Resume().  In addition, we are saving r4 in order to
-align the stack to 16 bytes, even though it is a callee-save register.
+first argument to _Unwind_Resume().  The function also saves/restores r4 to
+keep the stack aligned and to provide a temp register.  _Unwind_Resume never
+returns and we need to keep the original lr so just branch to it.  When
+targeting bare metal, the function also clobbers ip/r12 to hold the address of
+_Unwind_Resume, which may be too far away for an ordinary branch.
 */
 __attribute__((used)) static _Unwind_Exception *
 __cxa_end_cleanup_impl()
@@ -374,20 +377,30 @@ __cxa_end_cleanup_impl()
     return &exception_header->unwindHeader;
 }
 
-asm (
-    "	.pushsection	.text.__cxa_end_cleanup,\"ax\",%progbits\n"
+asm("	.pushsection	.text.__cxa_end_cleanup,\"ax\",%progbits\n"
     "	.globl	__cxa_end_cleanup\n"
     "	.type	__cxa_end_cleanup,%function\n"
     "__cxa_end_cleanup:\n"
+#if defined(__ARM_FEATURE_BTI_DEFAULT)
+    "	bti\n"
+#endif
     "	push	{r1, r2, r3, r4}\n"
+    "	mov	r4, lr\n"
     "	bl	__cxa_end_cleanup_impl\n"
+    "	mov	lr, r4\n"
+#if defined(LIBCXXABI_BAREMETAL)
+    "	ldr	r4,	=_Unwind_Resume\n"
+    "	mov	ip,	r4\n"
+#endif
     "	pop	{r1, r2, r3, r4}\n"
-    "	bl	_Unwind_Resume\n"
-    "	bl	abort\n"
-    "	.popsection"
-);
-#endif  // defined(_LIBCXXABI_ARM_EHABI)
-    
+#if defined(LIBCXXABI_BAREMETAL)
+    "	bx	ip\n"
+#else
+    "	b	_Unwind_Resume\n"
+#endif
+    "	.popsection");
+#endif // defined(_LIBCXXABI_ARM_EHABI)
+
 /*
 This routine can catch foreign or native exceptions.  If native, the exception
 can be a primary or dependent variety.  This routine may remain blissfully