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Re: [ARM/FDPIC 13/21] [ARM] FDPIC: Support unwinding across thumb2 signal trampoline


Hi Christophe,

Similar comments to patch 11/21

On 25/05/18 09:03, Christophe Lyon wrote:
2018-XX-XX  Christophe Lyon <christophe.lyon@st.com>
        Mickaël Guêné <mickael.guene@st.com>

        libgcc/
        * unwind-arm-common.inc (FDPIC_T2_LDR_R12_WITH_FUNCDESC)
        (FDPIC_T2_LDR_R9_WITH_GOT, FDPIC_T2_LDR_PC_WITH_RESTORER): New.
        (__gnu_personality_sigframe_fdpic): Support Thumb address.
        (get_eit_entry): Support Thumb code.

Change-Id: I2bb8994e733e48a89c6f4e0682921186c086f8bc

diff --git a/libgcc/unwind-arm-common.inc b/libgcc/unwind-arm-common.inc
index 80d1e88..7de4033 100644
--- a/libgcc/unwind-arm-common.inc
+++ b/libgcc/unwind-arm-common.inc
@@ -38,6 +38,9 @@
 #define FDPIC_LDR_R12_WITH_FUNCDESC     0xe59fc004
 #define FDPIC_LDR_R9_WITH_GOT           0xe59c9004
 #define FDPIC_LDR_PC_WITH_RESTORER      0xe59cf000
+#define FDPIC_T2_LDR_R12_WITH_FUNCDESC  0xc008f8df
+#define FDPIC_T2_LDR_R9_WITH_GOT       0x9004f8dc
+#define FDPIC_T2_LDR_PC_WITH_RESTORER   0xf000f8dc
 #define FDPIC_FUNCDESC_OFFSET           12
 /* Signal frame offsets.  */
 #define ARM_NEW_RT_SIGFRAME_UCONTEXT    0x80
@@ -228,7 +231,7 @@ __gnu_personality_sigframe_fdpic (_Unwind_State state,
     _Unwind_VRS_Get (context, _UVRSC_CORE, R_SP, _UVRSD_UINT32, &sp);
     _Unwind_VRS_Get (context, _UVRSC_CORE, R_PC, _UVRSD_UINT32, &pc);

-    funcdesc = *(unsigned int *)(pc + FDPIC_FUNCDESC_OFFSET);
+    funcdesc = *(unsigned int *)((pc & ~1) + FDPIC_FUNCDESC_OFFSET);
     handler = *(unsigned int *)(funcdesc);
     first_handler_instruction = *(unsigned int *)(handler & ~1);

@@ -277,10 +280,13 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
           /* If we are unwinding a signal handler then perhaps we have
              reached a trampoline.  Try to detect jump to restorer
              sequence.  */
-         _uw *pc = (_uw *)((return_address+2) & ~3);
-         if (pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
-             && pc[1] == FDPIC_LDR_R9_WITH_GOT
-             && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
+         _uw *pc = (_uw *)((return_address+2) & ~1);
+         if ((pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
+              && pc[1] == FDPIC_LDR_R9_WITH_GOT
+              && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
+             || (pc[0] == FDPIC_T2_LDR_R12_WITH_FUNCDESC
+                 && pc[1] == FDPIC_T2_LDR_R9_WITH_GOT
+                 && pc[2] == FDPIC_T2_LDR_PC_WITH_RESTORER))
             {

This largely overwrites and extends code added in patch 11/21. Can't we just merge the two
patches into a final sane one?

Thanks,
Kyrill

               struct funcdesc_t *funcdesc = (struct funcdesc_t *)
                 &__gnu_personality_sigframe_fdpic;
@@ -309,13 +315,16 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
       /* If we are unwinding a signal handler then perhaps we have
          reached a trampoline.  Try to detect jump to restorer
          sequence.  */
-      _uw *pc = (_uw *)((return_address+2) & ~3);
-      if (pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
-         && pc[1] == FDPIC_LDR_R9_WITH_GOT
-         && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
+      _uw *pc = (_uw *)((return_address+2) & ~1);
+      if ((pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
+          && pc[1] == FDPIC_LDR_R9_WITH_GOT
+          && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
+         || (pc[0] == FDPIC_T2_LDR_R12_WITH_FUNCDESC
+             && pc[1] == FDPIC_T2_LDR_R9_WITH_GOT
+             && pc[2] == FDPIC_T2_LDR_PC_WITH_RESTORER))
         {
-         struct funcdesc_t *funcdesc = (struct funcdesc_t *)
-           &__gnu_personality_sigframe_fdpic;
+         struct funcdesc_t *funcdesc
+           = (struct funcdesc_t *) &__gnu_personality_sigframe_fdpic;

           UCB_PR_ADDR (ucbp) = funcdesc->ptr;
           UCB_PR_GOT (ucbp) = funcdesc->got;
@@ -335,13 +344,16 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
       /* If we are unwinding a signal handler then perhaps we have
          reached a trampoline.  Try to detect jump to restorer
          sequence.  */
-      _uw *pc = (_uw *)((return_address+2) & ~3);
-      if (pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
-         && pc[1] == FDPIC_LDR_R9_WITH_GOT
-         && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
+      _uw *pc = (_uw *)((return_address+2) & ~1);
+      if ((pc[0] == FDPIC_LDR_R12_WITH_FUNCDESC
+          && pc[1] == FDPIC_LDR_R9_WITH_GOT
+          && pc[2] == FDPIC_LDR_PC_WITH_RESTORER)
+         || (pc[0] == FDPIC_T2_LDR_R12_WITH_FUNCDESC
+             && pc[1] == FDPIC_T2_LDR_R9_WITH_GOT
+             && pc[2] == FDPIC_T2_LDR_PC_WITH_RESTORER))
         {
-         struct funcdesc_t *funcdesc = (struct funcdesc_t *)
-           &__gnu_personality_sigframe_fdpic;
+         struct funcdesc_t *funcdesc
+           = (struct funcdesc_t *) &__gnu_personality_sigframe_fdpic;

           UCB_PR_ADDR (ucbp) = funcdesc->ptr;
           UCB_PR_GOT (ucbp) = funcdesc->got;
--
2.6.3



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