[ARM/FDPIC v6 09/24] [ARM] FDPIC: Add support for taking address of nested function

In FDPIC mode, the trampoline generated to support pointers to nested
functions looks like:

	   .word	trampoline address
	   .word	trampoline GOT address
	   ldr 		r12, [pc, #8]
	   ldr 		r9, [pc, #8]
	   ldr		pc, [pc, #8]
	   .word	static chain value
	   .word	GOT address
	   .word	function's address

because in FDPIC function pointers are actually pointers to function
descriptors, we have to actually generate a function descriptor for
the trampoline.

2019--09-10  Christophe Lyon  <christophe.lyon@st.com>
	Mickaël Guêné <mickael.guene@st.com>

	gcc/
	* config/arm/arm.c (arm_asm_trampoline_template): Add FDPIC
	support.
	(arm_trampoline_init): Likewise.
	(arm_trampoline_adjust_address): Likewise.
	* config/arm/arm.h (TRAMPOLINE_SIZE): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@275571 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 36a20df5fa001459500aae5989fcfcbb9e68c11b..1bfa16d88111f5e841d69ea7cdf41513814e52f0 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2019-09-10  Christophe Lyon  <christophe.lyon@st.com>
+       Mickaël Guêné <mickael.guene@st.com>
+
+       gcc/
+       * config/arm/arm.c (arm_asm_trampoline_template): Add FDPIC
+       support.
+       (arm_trampoline_init): Likewise.
+       (arm_trampoline_adjust_address): Likewise.
+       * config/arm/arm.h (TRAMPOLINE_SIZE): Likewise.
+
 2019-09-10  Christophe Lyon  <christophe.lyon@st.com>
        Mickaël Guêné <mickael.guene@st.com>
 

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 6b0c95f5752bbe61d6ccb13592a08d4ec0772c92..d01fae312311565979e39995151c50af6199d9ee 100644 (file)
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -3939,14 +3939,52 @@ arm_warn_func_return (tree decl)
           ldr          pc, [pc]
           .word        static chain value
           .word        function's address
-   XXX FIXME: When the trampoline returns, r8 will be clobbered.  */
+   XXX FIXME: When the trampoline returns, r8 will be clobbered.
+
+   In FDPIC mode, the trampoline looks like:
+          .word        trampoline address
+          .word        trampoline GOT address
+          ldr          r12, [pc, #8] ; #4 for Arm mode
+          ldr          r9,  [pc, #8] ; #4 for Arm mode
+          ldr          pc,  [pc, #8] ; #4 for Arm mode
+          .word        static chain value
+          .word        GOT address
+          .word        function's address
+*/
 
 static void
 arm_asm_trampoline_template (FILE *f)
 {
   fprintf (f, "\t.syntax unified\n");
 
-  if (TARGET_ARM)
+  if (TARGET_FDPIC)
+    {
+      /* The first two words are a function descriptor pointing to the
+        trampoline code just below.  */
+      if (TARGET_ARM)
+       fprintf (f, "\t.arm\n");
+      else if (TARGET_THUMB2)
+       fprintf (f, "\t.thumb\n");
+      else
+       /* Only ARM and Thumb-2 are supported.  */
+       gcc_unreachable ();
+
+      assemble_aligned_integer (UNITS_PER_WORD, const0_rtx);
+      assemble_aligned_integer (UNITS_PER_WORD, const0_rtx);
+      /* Trampoline code which sets the static chain register but also
+        PIC register before jumping into real code.  */
+      asm_fprintf (f, "\tldr\t%r, [%r, #%d]\n",
+                  STATIC_CHAIN_REGNUM, PC_REGNUM,
+                  TARGET_THUMB2 ? 8 : 4);
+      asm_fprintf (f, "\tldr\t%r, [%r, #%d]\n",
+                  PIC_OFFSET_TABLE_REGNUM, PC_REGNUM,
+                  TARGET_THUMB2 ? 8 : 4);
+      asm_fprintf (f, "\tldr\t%r, [%r, #%d]\n",
+                  PC_REGNUM, PC_REGNUM,
+                  TARGET_THUMB2 ? 8 : 4);
+      assemble_aligned_integer (UNITS_PER_WORD, const0_rtx);
+    }
+  else if (TARGET_ARM)
     {
       fprintf (f, "\t.arm\n");
       asm_fprintf (f, "\tldr\t%r, [%r, #0]\n", STATIC_CHAIN_REGNUM, PC_REGNUM);
@@ -3987,12 +4025,40 @@ arm_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
   emit_block_move (m_tramp, assemble_trampoline_template (),
                   GEN_INT (TRAMPOLINE_SIZE), BLOCK_OP_NORMAL);
 
-  mem = adjust_address (m_tramp, SImode, TARGET_32BIT ? 8 : 12);
-  emit_move_insn (mem, chain_value);
+  if (TARGET_FDPIC)
+    {
+      rtx funcdesc = XEXP (DECL_RTL (fndecl), 0);
+      rtx fnaddr = gen_rtx_MEM (Pmode, funcdesc);
+      rtx gotaddr = gen_rtx_MEM (Pmode, plus_constant (Pmode, funcdesc, 4));
+      /* The function start address is at offset 8, but in Thumb mode
+        we want bit 0 set to 1 to indicate Thumb-ness, hence 9
+        below.  */
+      rtx trampoline_code_start
+       = plus_constant (Pmode, XEXP (m_tramp, 0), TARGET_THUMB2 ? 9 : 8);
+
+      /* Write initial funcdesc which points to the trampoline.  */
+      mem = adjust_address (m_tramp, SImode, 0);
+      emit_move_insn (mem, trampoline_code_start);
+      mem = adjust_address (m_tramp, SImode, 4);
+      emit_move_insn (mem, gen_rtx_REG (Pmode, PIC_OFFSET_TABLE_REGNUM));
+      /* Setup static chain.  */
+      mem = adjust_address (m_tramp, SImode, 20);
+      emit_move_insn (mem, chain_value);
+      /* GOT + real function entry point.  */
+      mem = adjust_address (m_tramp, SImode, 24);
+      emit_move_insn (mem, gotaddr);
+      mem = adjust_address (m_tramp, SImode, 28);
+      emit_move_insn (mem, fnaddr);
+    }
+  else
+    {
+      mem = adjust_address (m_tramp, SImode, TARGET_32BIT ? 8 : 12);
+      emit_move_insn (mem, chain_value);
 
-  mem = adjust_address (m_tramp, SImode, TARGET_32BIT ? 12 : 16);
-  fnaddr = XEXP (DECL_RTL (fndecl), 0);
-  emit_move_insn (mem, fnaddr);
+      mem = adjust_address (m_tramp, SImode, TARGET_32BIT ? 12 : 16);
+      fnaddr = XEXP (DECL_RTL (fndecl), 0);
+      emit_move_insn (mem, fnaddr);
+    }
 
   a_tramp = XEXP (m_tramp, 0);
   emit_library_call (gen_rtx_SYMBOL_REF (Pmode, "__clear_cache"),
@@ -4006,7 +4072,9 @@ arm_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
 static rtx
 arm_trampoline_adjust_address (rtx addr)
 {
-  if (TARGET_THUMB)
+  /* For FDPIC don't fix trampoline address since it's a function
+     descriptor and not a function address.  */
+  if (TARGET_THUMB && !TARGET_FDPIC)
     addr = expand_simple_binop (Pmode, IOR, addr, const1_rtx,
                                NULL, 0, OPTAB_LIB_WIDEN);
   return addr;

diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index 490d22d9d649e8436d42182d7856d02f3ad9bffb..8b67c9c3657b312be223ab60c01969958baa9ed3 100644 (file)
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -1595,7 +1595,7 @@ typedef struct
 #define INIT_EXPANDERS  arm_init_expanders ()
 
 /* Length in units of the trampoline for entering a nested function.  */
-#define TRAMPOLINE_SIZE  (TARGET_32BIT ? 16 : 20)
+#define TRAMPOLINE_SIZE  (TARGET_FDPIC ? 32 : (TARGET_32BIT ? 16 : 20))
 
 /* Alignment required for a trampoline in bits.  */
 #define TRAMPOLINE_ALIGNMENT  32