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Re: [ARM/FDPIC 06/21] [ARM] FDPIC: Add support for c++ exceptions


Hi Christophe,

On 25/05/18 09:03, Christophe Lyon wrote:
When restoring a function address, we also have to restore the FDPIC
register value (r9).

2018-XX-XX  Christophe Lyon  <christophe.lyon@st.com>
        Mickaël Guêné <mickael.guene@st.com>

        gcc/
        * ginclude/unwind-arm-common.h (unwinder_cache): Add reserved5
        field.

        libgcc/
        * config/arm/linux-atomic.c (__ARM_ARCH__): Define.
        (__kernel_cmpxchg): Add FDPIC support.
        (__kernel_dmb): Likewise.
        (__fdpic_cmpxchg): New function.
        (__fdpic_dmb): New function.
        * config/arm/unwind-arm.h (gnu_Unwind_Find_got): New function.
        (_Unwind_decode_typeinfo_ptr): Add FDPIC support.
        * unwindo-arm-common.inc (UCB_PR_GOT): New.
        (funcdesc_t): New struct.
        (get_eit_entry): Add FDPIC support.
        (unwind_phase2): Likewise.
        (unwind_phase2_forced): Likewise.
        (__gnu_Unwind_RaiseException): Likewise.
        (__gnu_Unwind_Resume): Likewise.
        (__gnu_Unwind_Backtrace): Likewise.
        * unwind-pe.h (read_encoded_value_with_base): Likewise.

        libstdc++/
        * libsupc++/eh_personality.cc (get_ttype_entry): Add FDPIC
        support.

Change-Id: Ic0841eb3d7bfb0b3f6d187cd52a660b8fd394d85

diff --git a/gcc/ginclude/unwind-arm-common.h b/gcc/ginclude/unwind-arm-common.h
index 8a1a919..150bd0f 100644
--- a/gcc/ginclude/unwind-arm-common.h
+++ b/gcc/ginclude/unwind-arm-common.h
@@ -91,7 +91,7 @@ extern "C" {
           _uw reserved2;  /* Personality routine address */
           _uw reserved3;  /* Saved callsite address */
           _uw reserved4;  /* Forced unwind stop arg */
-         _uw reserved5;
+         _uw reserved5;  /* Personality routine GOT value in FDPIC mode.  */
         }
       unwinder_cache;
       /* Propagation barrier cache (valid after phase 1): */
diff --git a/libgcc/config/arm/linux-atomic.c b/libgcc/config/arm/linux-atomic.c
index d334c58..a20ad94 100644
--- a/libgcc/config/arm/linux-atomic.c
+++ b/libgcc/config/arm/linux-atomic.c
@@ -23,13 +23,99 @@ a copy of the GCC Runtime Library Exception along with this program;
 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
 <http://www.gnu.org/licenses/>. */

+#if defined(__ARM_ARCH_2__)
+# define __ARM_ARCH__ 2
+#endif
+
+#if defined(__ARM_ARCH_3__)
+# define __ARM_ARCH__ 3
+#endif
+
+#if defined(__ARM_ARCH_3M__) || defined(__ARM_ARCH_4__) \
+  || defined(__ARM_ARCH_4T__)
+/* We use __ARM_ARCH__ set to 4 here, but in reality it's any processor with
+   long multiply instructions.  That includes v3M.  */
+# define __ARM_ARCH__ 4
+#endif
+

Support for __ARM_ARCH_2__, __ARM_ARCH_3__, __ARM_ARCH_3M__ has been removed in GCC 9
so this code is dead.

I notice that in the removal I've missed out an occurrence of these in config/arm/lib1funcs.S.
If you want to remove those occurrences as a separate patch that would be preapproved.

Thanks,
Kyrill

+#if defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5T__) \
+  || defined(__ARM_ARCH_5E__) || defined(__ARM_ARCH_5TE__) \
+  || defined(__ARM_ARCH_5TEJ__)
+# define __ARM_ARCH__ 5
+#endif
+
+#if defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) \
+  || defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6Z__) \
+  || defined(__ARM_ARCH_6ZK__) || defined(__ARM_ARCH_6T2__) \
+  || defined(__ARM_ARCH_6M__)
+# define __ARM_ARCH__ 6
+#endif
+
+#if defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) \
+  || defined(__ARM_ARCH_7R__) || defined(__ARM_ARCH_7M__) \
+  || defined(__ARM_ARCH_7EM__)
+# define __ARM_ARCH__ 7
+#endif
+
+#ifndef __ARM_ARCH__
+#error Unable to determine architecture.
+#endif
+
 /* Kernel helper for compare-and-exchange.  */
 typedef int (__kernel_cmpxchg_t) (int oldval, int newval, int *ptr);
+#if __FDPIC__
+#define __kernel_cmpxchg __fdpic_cmpxchg
+#else
 #define __kernel_cmpxchg (*(__kernel_cmpxchg_t *) 0xffff0fc0)
+#endif

 /* Kernel helper for memory barrier.  */
 typedef void (__kernel_dmb_t) (void);
+#if __FDPIC__
+#define __kernel_dmb __fdpic_dmb
+#else
 #define __kernel_dmb (*(__kernel_dmb_t *) 0xffff0fa0)
+#endif
+
+#if __FDPIC__
+static int __fdpic_cmpxchg (int oldval, int newval, int *ptr)
+{
+#if __ARM_ARCH__ < 6
+  #error architecture support not yet implemented
+  /* Use swap instruction (but is it always safe ? (interrupt?))  */
+#else
+  int result;
+
+  asm volatile ("1: ldrex r3, [%[ptr]]\n\t"
+               "subs  r3, r3, %[oldval]\n\t"
+               "itt eq\n\t"
+               "strexeq r3, %[newval], [%[ptr]]\n\t"
+               "teqeq r3, #1\n\t"
+               "it eq\n\t"
+               "beq 1b\n\t"
+               "rsbs  %[result], r3, #0\n\t"
+               : [result] "=r" (result)
+               : [oldval] "r" (oldval) , [newval] "r" (newval), [ptr] "r" (ptr)
+               : "r3");
+    return result;
+#endif
+}
+
+static void __fdpic_dmb ()
+{
+#if __ARM_ARCH__ < 6
+  /* No op? Perhaps flush write buffer ?  */
+  return ;
+#else
+ #if __ARM_ARCH__ >= 7
+  asm volatile ("dmb\n\t");
+ #elif __ARM_ARCH__ == 6
+  asm volatile ("mcr p15, 0, r0, c7, c10, 5\n\t");
+ #endif
+#endif
+}
+
+#endif

 /* Note: we implement byte, short and int versions of atomic operations using
    the above kernel helpers; see linux-atomic-64bit.c for "long long" (64-bit)
diff --git a/libgcc/config/arm/unwind-arm.h b/libgcc/config/arm/unwind-arm.h
index 9f7d3f2..a9598eb 100644
--- a/libgcc/config/arm/unwind-arm.h
+++ b/libgcc/config/arm/unwind-arm.h
@@ -36,6 +36,25 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
+_Unwind_Ptr __attribute__((weak)) __gnu_Unwind_Find_got (_Unwind_Ptr);
+
+static inline _Unwind_Ptr gnu_Unwind_Find_got (_Unwind_Ptr ptr)
+{
+    _Unwind_Ptr res;
+
+    if (__gnu_Unwind_Find_got)
+       res =  __gnu_Unwind_Find_got (ptr);
+    else
+      {
+       asm volatile ("mov %[result], r9"
+                     : [result]"=r" (res)
+                     :
+                     :);
+    }
+
+    return res;
+}
+
   /* Decode an R_ARM_TARGET2 relocation.  */
   static inline _Unwind_Word
   _Unwind_decode_typeinfo_ptr (_Unwind_Word base __attribute__ ((unused)),
@@ -48,7 +67,12 @@ extern "C" {
       if (!tmp)
         return 0;

-#if (defined(linux) && !defined(__uClinux__)) || defined(__NetBSD__) \
+#if __FDPIC__
+      /* For FDPIC, we store the offset of the GOT entry. */
+      /* So, first get GOT from dynamic linker and then use indirect access.  */
+      tmp += gnu_Unwind_Find_got (ptr);
+      tmp = *(_Unwind_Word *) tmp;
+#elif (defined(linux) && !defined(__uClinux__)) || defined(__NetBSD__) \
     || defined(__FreeBSD__) || defined(__fuchsia__)
       /* Pc-relative indirect.  */
 #define _GLIBCXX_OVERRIDE_TTYPE_ENCODING (DW_EH_PE_pcrel | DW_EH_PE_indirect)
diff --git a/libgcc/unwind-arm-common.inc b/libgcc/unwind-arm-common.inc
index 76f8fc3..f5415c1 100644
--- a/libgcc/unwind-arm-common.inc
+++ b/libgcc/unwind-arm-common.inc
@@ -62,6 +62,7 @@ __gnu_Unwind_Find_exidx (_Unwind_Ptr, int *);
 #define UCB_PR_ADDR(ucbp) ((ucbp)->unwinder_cache.reserved2)
 #define UCB_SAVED_CALLSITE_ADDR(ucbp) ((ucbp)->unwinder_cache.reserved3)
 #define UCB_FORCED_STOP_ARG(ucbp) ((ucbp)->unwinder_cache.reserved4)
+#define UCB_PR_GOT(ucbp) ((ucbp)->unwinder_cache.reserved5)

 /* Unwind descriptors.  */

@@ -85,6 +86,12 @@ typedef struct __EIT_entry
   _uw content;
 } __EIT_entry;

+/* Only used in FDPIC case.  */
+struct funcdesc_t {
+    unsigned int ptr;
+    unsigned int got;
+};
+
 /* Assembly helper functions.  */

 /* Restore core register state.  Never returns.  */
@@ -259,7 +266,23 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
     {
       /* One of the predefined standard routines.  */
       _uw idx = (*(_uw *) ucbp->pr_cache.ehtp >> 24) & 0xf;
+#if __FDPIC__
+      {
+       struct funcdesc_t *funcdesc
+         = (struct funcdesc_t *) __gnu_unwind_get_pr_addr (idx);
+       if (funcdesc)
+         {
+           UCB_PR_ADDR (ucbp) = funcdesc->ptr;
+           UCB_PR_GOT (ucbp) = funcdesc->got;
+         }
+       else
+         {
+           UCB_PR_ADDR (ucbp) = 0;
+         }
+      }
+#else
       UCB_PR_ADDR (ucbp) = __gnu_unwind_get_pr_addr (idx);
+#endif
       if (UCB_PR_ADDR (ucbp) == 0)
         {
           /* Failed */
@@ -269,7 +292,13 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
   else
     {
       /* Execute region offset to PR */
+#if __FDPIC__
       UCB_PR_ADDR (ucbp) = selfrel_offset31 (ucbp->pr_cache.ehtp);
+      UCB_PR_GOT (ucbp)
+       = (unsigned int) gnu_Unwind_Find_got ((_Unwind_Ptr) UCB_PR_ADDR (ucbp));
+#else
+      UCB_PR_ADDR (ucbp) = selfrel_offset31 (ucbp->pr_cache.ehtp);
+#endif
     }
   return _URC_OK;
 }
@@ -291,14 +320,29 @@ unwind_phase2 (_Unwind_Control_Block * ucbp, phase2_vrs * vrs)
       UCB_SAVED_CALLSITE_ADDR (ucbp) = VRS_PC(vrs);

       /* Call the pr to decide what to do.  */
+#if __FDPIC__
+      {
+       volatile struct funcdesc_t funcdesc;
+       funcdesc.ptr = UCB_PR_ADDR (ucbp);
+       funcdesc.got = UCB_PR_GOT (ucbp);
+       pr_result = ((personality_routine) &funcdesc)
+         (_US_UNWIND_FRAME_STARTING, ucbp, (_Unwind_Context *) vrs);
+      }
+#else
       pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
         (_US_UNWIND_FRAME_STARTING, ucbp, (_Unwind_Context *) vrs);
+#endif
     }
   while (pr_result == _URC_CONTINUE_UNWIND);

   if (pr_result != _URC_INSTALL_CONTEXT)
     abort();

+#if __FDPIC__
+      /* r9 could have been lost due to PLT jump.  Restore correct value.  */
+      vrs->core.r[9] = gnu_Unwind_Find_got (VRS_PC (vrs));
+#endif
+
   uw_restore_core_regs (vrs, &vrs->core);
 }

@@ -346,8 +390,18 @@ unwind_phase2_forced (_Unwind_Control_Block *ucbp, phase2_vrs *entry_vrs,
           next_vrs = saved_vrs;

           /* Call the pr to decide what to do.  */
+#if __FDPIC__
+         {
+           volatile struct funcdesc_t funcdesc;
+           funcdesc.ptr = UCB_PR_ADDR (ucbp);
+           funcdesc.got = UCB_PR_GOT (ucbp);
+           pr_result = ((personality_routine) &funcdesc)
+             (action, ucbp, (void *) &next_vrs);
+         }
+#else
           pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
             (action, ucbp, (void *) &next_vrs);
+#endif

           saved_vrs.prev_sp = VRS_SP (&next_vrs);
         }
@@ -384,6 +438,11 @@ unwind_phase2_forced (_Unwind_Control_Block *ucbp, phase2_vrs *entry_vrs,
       return _URC_FAILURE;
     }

+#if __FDPIC__
+  /* r9 could have been lost due to PLT jump.  Restore correct value.  */
+  saved_vrs.core.r[9] = gnu_Unwind_Find_got (VRS_PC (&saved_vrs));
+#endif
+
   uw_restore_core_regs (&saved_vrs, &saved_vrs.core);
 }

@@ -429,8 +488,18 @@ __gnu_Unwind_RaiseException (_Unwind_Control_Block * ucbp,
         return _URC_FAILURE;

       /* Call the pr to decide what to do.  */
+#if __FDPIC__
+      {
+       volatile struct funcdesc_t funcdesc;
+       funcdesc.ptr = UCB_PR_ADDR (ucbp);
+       funcdesc.got = UCB_PR_GOT (ucbp);
+       pr_result = ((personality_routine) &funcdesc)
+         (_US_VIRTUAL_UNWIND_FRAME, ucbp, (void *) &saved_vrs);
+      }
+#else
       pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
         (_US_VIRTUAL_UNWIND_FRAME, ucbp, (void *) &saved_vrs);
+#endif
     }
   while (pr_result == _URC_CONTINUE_UNWIND);

@@ -488,13 +557,27 @@ __gnu_Unwind_Resume (_Unwind_Control_Block * ucbp, phase2_vrs * entry_vrs)
     }

   /* Call the cached PR.  */
+#if __FDPIC__
+  {
+    volatile struct funcdesc_t funcdesc;
+    funcdesc.ptr = UCB_PR_ADDR (ucbp);
+    funcdesc.got = UCB_PR_GOT (ucbp);
+    pr_result = ((personality_routine) &funcdesc)
+      (_US_UNWIND_FRAME_RESUME, ucbp, (_Unwind_Context *) entry_vrs);
+  }
+#else
   pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
         (_US_UNWIND_FRAME_RESUME, ucbp, (_Unwind_Context *) entry_vrs);
+#endif

   switch (pr_result)
     {
     case _URC_INSTALL_CONTEXT:
       /* Upload the registers to enter the landing pad.  */
+#if __FDPIC__
+      /* r9 could have been lost due to PLT jump.  Restore correct value.  */
+      entry_vrs->core.r[9] = gnu_Unwind_Find_got (VRS_PC (entry_vrs));
+#endif
       uw_restore_core_regs (entry_vrs, &entry_vrs->core);

     case _URC_CONTINUE_UNWIND:
@@ -586,9 +669,20 @@ __gnu_Unwind_Backtrace(_Unwind_Trace_Fn trace, void * trace_argument,
         }

       /* Call the pr to decide what to do.  */
+#if __FDPIC__
+      {
+       volatile struct funcdesc_t funcdesc;
+       funcdesc.ptr = UCB_PR_ADDR (ucbp);
+       funcdesc.got = UCB_PR_GOT (ucbp);
+       code = ((personality_routine) &funcdesc)
+         (_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND,
+          ucbp, (void *) &saved_vrs);
+      }
+#else
       code = ((personality_routine) UCB_PR_ADDR (ucbp))
         (_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND,
          ucbp, (void *) &saved_vrs);
+#endif
     }
   while (code != _URC_END_OF_STACK
          && code != _URC_FAILURE);
diff --git a/libgcc/unwind-pe.h b/libgcc/unwind-pe.h
index dd5ae95..c18dffe 100644
--- a/libgcc/unwind-pe.h
+++ b/libgcc/unwind-pe.h
@@ -259,10 +259,25 @@ read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,

       if (result != 0)
         {
+#if __FDPIC__
+    if ((encoding & DW_EH_PE_pcrel) && (encoding & DW_EH_PE_indirect))
+      {
+       result += gnu_Unwind_Find_got ((_Unwind_Ptr) u);
+       result = *(_Unwind_Internal_Ptr *) result;
+      }
+    else
+      {
+       result += ((encoding & 0x70) == DW_EH_PE_pcrel
+                  ? (_Unwind_Internal_Ptr) u : base);
+       if (encoding & DW_EH_PE_indirect)
+         result = *(_Unwind_Internal_Ptr *) result;
+      }
+#else
           result += ((encoding & 0x70) == DW_EH_PE_pcrel
                      ? (_Unwind_Internal_Ptr) u : base);
           if (encoding & DW_EH_PE_indirect)
             result = *(_Unwind_Internal_Ptr *) result;
+#endif
         }
     }

diff --git a/libstdc++-v3/libsupc++/eh_personality.cc b/libstdc++-v3/libsupc++/eh_personality.cc
index 1b336c7..138b606 100644
--- a/libstdc++-v3/libsupc++/eh_personality.cc
+++ b/libstdc++-v3/libsupc++/eh_personality.cc
@@ -93,7 +93,13 @@ get_ttype_entry (lsda_header_info *info, _uleb128_t i)
   _Unwind_Ptr ptr;

   i *= size_of_encoded_value (info->ttype_encoding);
-  read_encoded_value_with_base (info->ttype_encoding, info->ttype_base,
+  read_encoded_value_with_base (
+#if __FDPIC__
+               (DW_EH_PE_pcrel | DW_EH_PE_indirect),
+#else
+               info->ttype_encoding,
+#endif
+               info->ttype_base,
                                 info->TType - i, &ptr);

   return reinterpret_cast<const std::type_info *>(ptr);
--
2.6.3



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