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[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.


Co-Authored-By: Mickaël Guêné <mickael.guene@st.com>

From-SVN: r275571
This commit is contained in:
Christophe Lyon 2019-09-10 09:52:02 +02:00 committed by Christophe Lyon
parent 96ef8d00f7
commit bc87cffb13
3 changed files with 87 additions and 9 deletions
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10
gcc/ChangeLog
View File

@ -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>

84
gcc/config/arm/arm.c
View File

@ -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);
mem = adjust_address (m_tramp, SImode, TARGET_32BIT ? 12 : 16);
fnaddr = XEXP (DECL_RTL (fndecl), 0);
emit_move_insn (mem, fnaddr);
/* 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);
}
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;

2
gcc/config/arm/arm.h
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@ -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