From: Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>
To: Christophe Lyon <christophe.lyon@st.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Subject: Re: [ARM/FDPIC v5 09/21] [ARM] FDPIC: Add support for taking address of nested function
Date: Tue, 16 Jul 2019 13:31:00 -0000 [thread overview]
Message-ID: <decb4cde-76b2-d02f-182d-9925c9cbcb64@foss.arm.com> (raw)
In-Reply-To: <21a7e3bb-40ab-8b7e-1c66-b991231eb808@foss.arm.com>
On 7/16/19 12:18 PM, Kyrill Tkachov wrote:
> Hi Christophe
>
> On 5/15/19 1:39 PM, Christophe Lyon wrote:
> > In FDPIC mode, the trampoline generated to support pointers to nested
> > functions looks like:
> >
> > Â Â Â Â Â Â Â Â Â Â .word trampoline address
> > Â Â Â Â Â Â Â Â Â Â .word trampoline GOT address
> >           ldr           r12, [pc, #8]
> >           ldr           r9, [pc, #8]
> >           ldr          pc, [pc, #8]
> > Â Â Â Â Â Â Â Â Â Â .word static chain value
> > Â Â Â Â Â Â Â Â Â Â .word GOT address
> > Â Â Â Â Â Â Â Â Â Â .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-XX-XXÂ Christophe Lyon <christophe.lyon@st.com>
> >        Mickaël Guêné <mickael.guene@st.com>
> >
> > Â Â Â Â Â Â Â gcc/
> > Â Â Â Â Â Â Â * config/arm/arm.c (arm_asm_trampoline_template): Add FDPIC
> > Â Â Â Â Â Â Â support.
> > Â Â Â Â Â Â Â (arm_trampoline_init): Likewise.
> > Â Â Â Â Â Â Â (arm_trampoline_init): Likewise.
> > Â Â Â Â Â Â Â * config/arm/arm.h (TRAMPOLINE_SIZE): Likewise.
> >
> > Change-Id: Idc4d5f629ae4f8d79bdf9623517481d524a0c144
> >
> > diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
> > index 40e3f3b..99d13bf 100644
> > --- a/gcc/config/arm/arm.c
> > +++ b/gcc/config/arm/arm.c
> > @@ -3976,13 +3976,50 @@ arm_warn_func_return (tree decl)
> > Â Â Â Â Â Â Â Â Â Â Â .word static chain value
> > Â Â Â Â Â Â Â Â Â Â Â .word function's address
> >    XXX FIXME: When the trampoline returns, r8 will be clobbered. */
> > +/* In FDPIC mode, the trampoline looks like:
> > +Â Â Â Â Â Â Â Â Â .word trampoline address
> > +Â Â Â Â Â Â Â Â Â .word trampoline GOT address
> > +         ldr           r12, [pc, #8] ; #4 for Thumb2
> > +         ldr           r9, [pc, #8] ; #4 for Thumb2
> > +         ldr          pc, [pc, #8] ; #4 for Thumb2
> > +Â Â Â Â Â Â Â Â Â .word static chain value
> > +Â Â Â Â Â Â Â Â Â .word GOT address
> > +Â Â Â Â Â Â Â Â Â .word function's address
> > +*/
>
>
> I think this comment is not right for Thumb2.
>
> These load instructionshave 32-bit encodings, even in Thumb2 (they use
> high registers).
Andre and Wilco pointed out to me offline that the offset should be #4
for Arm mode.
The Arm ARM at E1.2.3 says:
PC, the program counter
* When executing an A32 instruction, PC reads as the address of the
current instruction plus 8.
* When executing a T32 instruction, PC reads as the address of the
current instruction plus 4.
Thanks,
Kyrill
>
> Also, please merge this comment with the one above (no separate /**/)
>
> >
> > Â static void
> > Â arm_asm_trampoline_template (FILE *f)
> > Â {
> > Â Â fprintf (f, "\t.syntax unified\n");
> >
> > -Â if (TARGET_ARM)
> > +Â if (TARGET_FDPIC)
> > +Â Â Â {
> > +Â Â Â Â Â /* The first two words are a function descriptor pointing to the
> > +       trampoline code just below. */
> > +Â Â Â Â Â if (TARGET_ARM)
> > +Â Â Â Â Â Â fprintf (f, "\t.arm\n");
> > +Â Â Â Â Â else if (TARGET_THUMB2)
> > +Â Â Â Â Â Â fprintf (f, "\t.thumb\n");
> > +Â Â Â Â Â else
> > +      /* Only ARM and Thumb-2 are supported. */
> > +Â Â Â Â Â Â gcc_unreachable ();
> > +
> > +Â Â Â Â Â assemble_aligned_integer (UNITS_PER_WORD, const0_rtx);
> > +Â Â Â Â Â assemble_aligned_integer (UNITS_PER_WORD, const0_rtx);
> > +Â Â Â Â Â /* Trampoline code which sets the static chain register but also
> > +Â Â Â Â Â Â Â PIC register before jumping into real code. */
> > +Â Â Â Â Â asm_fprintf (f, "\tldr\t%r, [%r, #%d]\n",
> > +Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â STATIC_CHAIN_REGNUM, PC_REGNUM,
> > +Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â TARGET_THUMB2 ? 8 : 4);
> > +Â Â Â Â Â asm_fprintf (f, "\tldr\t%r, [%r, #%d]\n",
> > +Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â PIC_OFFSET_TABLE_REGNUM, PC_REGNUM,
> > +Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â TARGET_THUMB2 ? 8 : 4);
> > +Â Â Â Â Â asm_fprintf (f, "\tldr\t%r, [%r, #%d]\n",
> > +Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â PC_REGNUM, PC_REGNUM,
> > +Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â TARGET_THUMB2 ? 8 : 4);
>
>
> As above, I think the offset should be 8 for both Arm and Thumb2.
>
> Thanks,
>
> Kyrill
>
>
> > +Â Â Â Â Â assemble_aligned_integer (UNITS_PER_WORD, const0_rtx);
> > +Â Â Â }
> > +Â else if (TARGET_ARM)
> > Â Â Â Â {
> > Â Â Â Â Â Â fprintf (f, "\t.arm\n");
> > Â Â Â Â Â Â asm_fprintf (f, "\tldr\t%r, [%r, #0]\n", STATIC_CHAIN_REGNUM,
> > PC_REGNUM);
> > @@ -4023,12 +4060,40 @@ arm_trampoline_init (rtx m_tramp, tree fndecl,
> > rtx chain_value)
> > Â Â emit_block_move (m_tramp, assemble_trampoline_template (),
> > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â GEN_INT (TRAMPOLINE_SIZE), BLOCK_OP_NORMAL);
> >
> > -Â mem = adjust_address (m_tramp, SImode, TARGET_32BIT ? 8 : 12);
> > -Â emit_move_insn (mem, chain_value);
> > +Â if (TARGET_FDPIC)
> > +Â Â Â {
> > +Â Â Â Â Â rtx funcdesc = XEXP (DECL_RTL (fndecl), 0);
> > +Â Â Â Â Â rtx fnaddr = gen_rtx_MEM (Pmode, funcdesc);
> > +Â Â Â Â Â rtx gotaddr = gen_rtx_MEM (Pmode, plus_constant (Pmode,
> > funcdesc, 4));
> > +Â Â Â Â Â /* The function start address is at offset 8, but in Thumb mode
> > +Â Â Â Â Â Â Â we want bit 0 set to 1 to indicate Thumb-ness, hence 9
> > +       below. */
> > +Â Â Â Â Â rtx trampoline_code_start
> > +Â Â Â Â Â Â = plus_constant (Pmode, XEXP (m_tramp, 0), TARGET_THUMB2 ? 9
> : 8);
> > +
> > +     /* Write initial funcdesc which points to the trampoline. */
> > +Â Â Â Â Â mem = adjust_address (m_tramp, SImode, 0);
> > +Â Â Â Â Â emit_move_insn (mem, trampoline_code_start);
> > +Â Â Â Â Â mem = adjust_address (m_tramp, SImode, 4);
> > +Â Â Â Â Â emit_move_insn (mem, gen_rtx_REG (Pmode,
> PIC_OFFSET_TABLE_REGNUM));
> > +     /* Setup static chain. */
> > +Â Â Â Â Â mem = adjust_address (m_tramp, SImode, 20);
> > +Â Â Â Â Â emit_move_insn (mem, chain_value);
> > +     /* GOT + real function entry point. */
> > +Â Â Â Â Â mem = adjust_address (m_tramp, SImode, 24);
> > +Â Â Â Â Â emit_move_insn (mem, gotaddr);
> > +Â Â Â Â Â mem = adjust_address (m_tramp, SImode, 28);
> > +Â Â Â Â Â emit_move_insn (mem, fnaddr);
> > +Â Â Â }
> > +Â else
> > +Â Â Â {
> > +Â Â Â Â Â mem = adjust_address (m_tramp, SImode, TARGET_32BIT ? 8 : 12);
> > +Â Â Â Â Â emit_move_insn (mem, chain_value);
> >
> > -Â mem = adjust_address (m_tramp, SImode, TARGET_32BIT ? 12 : 16);
> > -Â fnaddr = XEXP (DECL_RTL (fndecl), 0);
> > -Â emit_move_insn (mem, fnaddr);
> > +Â Â Â Â Â mem = adjust_address (m_tramp, SImode, TARGET_32BIT ? 12 : 16);
> > +Â Â Â Â Â fnaddr = XEXP (DECL_RTL (fndecl), 0);
> > +Â Â Â Â Â emit_move_insn (mem, fnaddr);
> > +Â Â Â }
> >
> > Â Â a_tramp = XEXP (m_tramp, 0);
> > Â Â emit_library_call (gen_rtx_SYMBOL_REF (Pmode, "__clear_cache"),
> > @@ -4042,7 +4107,9 @@ arm_trampoline_init (rtx m_tramp, tree fndecl,
> > rtx chain_value)
> > Â static rtx
> > Â arm_trampoline_adjust_address (rtx addr)
> > Â {
> > -Â if (TARGET_THUMB)
> > +Â /* For FDPIC don't fix trampoline address since it's a function
> > +    descriptor and not a function address. */
> > +Â if (TARGET_THUMB && !TARGET_FDPIC)
> > Â Â Â Â addr = expand_simple_binop (Pmode, IOR, addr, const1_rtx,
> > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â NULL, 0, OPTAB_LIB_WIDEN);
> > Â Â return addr;
> > diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
> > index 45c0e2b..f80df63 100644
> > --- a/gcc/config/arm/arm.h
> > +++ b/gcc/config/arm/arm.h
> > @@ -1602,7 +1602,7 @@ typedef struct
> > Â #define INIT_EXPANDERSÂ arm_init_expanders ()
> >
> > Â /* Length in units of the trampoline for entering a nested
> function. */
> > -#define TRAMPOLINE_SIZEÂ (TARGET_32BIT ? 16 : 20)
> > +#define TRAMPOLINE_SIZEÂ (TARGET_FDPIC ? 32 : (TARGET_32BIT ? 16 : 20))
> >
> >  /* Alignment required for a trampoline in bits. */
> > Â #define TRAMPOLINE_ALIGNMENTÂ 32
> > --
> > 2.6.3
> >
next prev parent reply other threads:[~2019-07-16 12:42 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-15 12:40 [ARM/FDPIC v5 00/21] FDPIC ABI for ARM Christophe Lyon
2019-05-15 12:40 ` [ARM/FDPIC v5 01/21] [ARM] FDPIC: Add -mfdpic option support Christophe Lyon
2019-07-16 10:18 ` Richard Sandiford
2019-08-29 15:08 ` Christophe Lyon
2019-08-30 10:06 ` Richard Sandiford
2019-05-15 12:41 ` [ARM/FDPIC v5 05/21] [ARM] FDPIC: Fix __do_global_dtors_aux and frame_dummy generation Christophe Lyon
2019-07-12 6:49 ` Richard Sandiford
2019-07-12 14:25 ` Christophe Lyon
2019-08-29 15:39 ` Christophe Lyon
2019-08-30 8:41 ` Richard Sandiford
2019-05-15 12:41 ` [ARM/FDPIC v5 02/21] [ARM] FDPIC: Handle arm*-*-uclinuxfdpiceabi in configure scripts Christophe Lyon
2019-07-12 7:44 ` Richard Sandiford
2019-07-12 13:25 ` Christophe Lyon
2019-07-12 13:28 ` Richard Sandiford
2019-08-29 15:14 ` Christophe Lyon
2019-08-30 9:30 ` Richard Sandiford
2019-08-30 14:48 ` Christophe Lyon
2019-08-30 15:15 ` Richard Sandiford
2019-09-02 7:51 ` Christophe Lyon
2019-09-02 8:31 ` Richard Sandiford
2019-08-30 14:40 ` Jonathan Wakely
2019-05-15 12:41 ` [ARM/FDPIC v5 03/21] [ARM] FDPIC: Force FDPIC related options unless -mno-fdpic is provided Christophe Lyon
2019-05-15 13:55 ` Szabolcs Nagy
2019-05-15 14:37 ` Rich Felker
2019-05-15 15:12 ` Christophe Lyon
2019-05-15 15:37 ` Rich Felker
2019-05-15 15:59 ` Szabolcs Nagy
2019-05-15 16:07 ` Rich Felker
2019-05-21 15:29 ` Christophe Lyon
2019-05-21 15:48 ` Rich Felker
2019-05-22 8:39 ` Szabolcs Nagy
2019-05-22 8:45 ` Christophe Lyon
2019-05-23 12:45 ` Christophe Lyon
2019-07-16 10:38 ` Richard Sandiford
2019-07-16 20:00 ` Rich Felker
2019-08-01 10:13 ` Christophe Lyon
2019-08-06 14:28 ` Richard Sandiford
2019-08-29 15:14 ` Christophe Lyon
2019-08-30 9:40 ` Richard Sandiford
2019-05-15 12:41 ` [ARM/FDPIC v5 04/21] [ARM] FDPIC: Add support for FDPIC for arm architecture Christophe Lyon
2019-07-16 12:33 ` Richard Sandiford
2019-08-20 17:13 ` Christophe Lyon
2019-08-29 15:39 ` Christophe Lyon
2019-09-02 16:12 ` Richard Sandiford
2019-09-02 20:04 ` Christophe Lyon
2019-09-03 8:40 ` Richard Sandiford
2019-09-04 19:59 ` Christophe Lyon
2019-09-05 8:03 ` Richard Sandiford
2019-05-15 12:42 ` [ARM/FDPIC v5 07/21] [ARM] FDPIC: Avoid saving/restoring r9 on stack since it is read-only Christophe Lyon
2019-07-16 10:42 ` Kyrill Tkachov
2019-05-15 12:42 ` [ARM/FDPIC v5 06/21] [ARM] FDPIC: Add support for c++ exceptions Christophe Lyon
2019-08-30 9:31 ` Kyrill Tkachov
2019-08-30 14:44 ` Jonathan Wakely
2019-05-15 12:43 ` [ARM/FDPIC v5 09/21] [ARM] FDPIC: Add support for taking address of nested function Christophe Lyon
2019-07-16 11:53 ` Kyrill Tkachov
2019-07-16 13:31 ` Kyrill Tkachov [this message]
2019-07-31 14:48 ` Christophe Lyon
2019-08-29 15:40 ` Christophe Lyon
2019-08-30 8:54 ` Kyrill Tkachov
2019-05-15 12:43 ` [ARM/FDPIC v5 10/21] [ARM] FDPIC: Implement TLS support Christophe Lyon
2019-09-04 14:16 ` Kyrill Tkachov
2019-09-04 20:03 ` Christophe Lyon
2019-09-09 8:54 ` Christophe Lyon
2019-05-15 12:43 ` [ARM/FDPIC v5 08/21] [ARM] FDPIC: Enforce local/global binding for function descriptors Christophe Lyon
2019-07-16 10:51 ` Kyrill Tkachov
2019-05-15 12:44 ` [ARM/FDPIC v5 13/21] [ARM] FDPIC: Force LSB bit for PC in Cortex-M architecture Christophe Lyon
2019-08-29 15:37 ` Kyrill Tkachov
2019-09-05 8:30 ` Christophe Lyon
2019-09-05 8:32 ` Christophe Lyon
2019-09-05 20:56 ` Ian Lance Taylor
2019-09-05 9:03 ` Kyrill Tkachov
2019-09-09 8:58 ` Christophe Lyon
2019-05-15 12:44 ` [ARM/FDPIC v5 11/21] [ARM] FDPIC: Add support to unwind FDPIC signal frame Christophe Lyon
2019-09-04 14:19 ` Kyrill Tkachov
2019-05-15 12:44 ` [ARM/FDPIC v5 12/21] [ARM] FDPIC: Restore r9 after we call __aeabi_read_tp Christophe Lyon
2019-08-29 15:40 ` Christophe Lyon
2019-08-29 15:44 ` Kyrill Tkachov
2019-05-15 12:45 ` [ARM/FDPIC v5 15/21] [ARM][testsuite] FDPIC: Adjust scan-assembler patterns Christophe Lyon
2019-07-19 8:54 ` Kyrill Tkachov
2019-05-15 12:45 ` [ARM/FDPIC v5 16/21] [ARM][testsuite] FDPIC: Skip tests that don't work in PIC mode Christophe Lyon
2019-07-19 8:56 ` Kyrill Tkachov
2019-05-15 12:45 ` [ARM/FDPIC v5 14/21] [ARM][testsuite] FDPIC: Skip unsupported tests Christophe Lyon
2019-07-19 8:52 ` Kyrill Tkachov
2019-05-15 12:46 ` [ARM/FDPIC v5 19/21] [ARM][testsuite] FDPIC: Adjust pr43698.c to avoid clash with uclibc Christophe Lyon
2019-07-19 9:00 ` Kyrill Tkachov
2019-05-15 12:46 ` [ARM/FDPIC v5 18/21] [ARM][testsuite] FDPIC: Enable tests on pie_enabled targets Christophe Lyon
2019-07-19 8:59 ` Kyrill Tkachov
2019-07-22 19:50 ` Mike Stump
2019-05-15 12:46 ` [ARM/FDPIC v5 17/21] [ARM][testsuite] FDPIC: Handle *-*-uclinux* Christophe Lyon
2019-07-19 8:57 ` Kyrill Tkachov
2019-07-22 19:37 ` Mike Stump
2019-05-15 12:47 ` [ARM/FDPIC v5 21/21] [ARM] FDPIC: Handle stack-protector combined patterns Christophe Lyon
2019-07-19 9:40 ` Kyrill Tkachov
2019-05-15 12:47 ` [ARM/FDPIC v5 20/21] [ARM][testsuite] FDPIC: Skip tests using architectures unsupported by FDPIC Christophe Lyon
2019-07-19 9:03 ` Kyrill Tkachov
2019-09-06 8:01 ` Christophe Lyon
2019-09-06 8:28 ` Kyrill Tkachov
2019-09-06 9:10 ` Christophe Lyon
2019-09-06 17:44 ` Christophe Lyon
2019-09-09 8:38 ` Christophe Lyon
2019-05-23 12:46 ` [ARM/FDPIC v5 00/21] FDPIC ABI for ARM Christophe Lyon
2019-06-04 12:57 ` Christophe Lyon
2019-06-06 12:36 ` Christophe Lyon
2019-06-17 11:42 ` Christophe Lyon
2019-07-01 12:16 ` Christophe Lyon
2019-07-08 14:28 ` Christophe Lyon
2019-07-16 9:13 ` Christophe Lyon
2019-08-29 14:54 ` Christophe Lyon
2019-08-29 16:29 ` Christophe Lyon
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