[PATCH v3 1/2] Add -f[no-]direct-extern-access
Richard Biener
richard.guenther@gmail.com
Mon Jul 12 06:13:45 GMT 2021
On Fri, Jul 9, 2021 at 4:50 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> -fdirect-extern-access is the default. With -fno-direct-extern-access:
>
> 1. Always use GOT to access undefined data and function symbols,
> including in PIE and non-PIE. These will avoid copy relocations
> in executables. This is compatible with existing executables and
> shared libraries.
> 2. In executable and shared library, bind symbols with the STV_PROTECTED
> visibility locally:
> a. The address of data symbol is the address of data body.
> b. For systems without function descriptor, the function pointer is
> the address of function body.
> c. The resulting shared libraries may not be incompatible with
> executables which have copy relocations on protected symbols or
> use executable PLT entries as function addresses for protected
> functions in shared libraries.
> 3. Update asm_preferred_eh_data_format to select PC relative EH encoding
> format with -fno-direct-extern-access to avoid copy relocation.
> 4. Add ix86_reloc_rw_mask for TARGET_ASM_RELOC_RW_MASK to avoid copy
> relocation with -fno-direct-extern-access.
Did you check how relocations in .debug_info behave? I don't remember whether
we're doing anything special there or if we just copy how we emit
relocs in .text
Richard.
> gcc/
>
> PR target/35513
> PR target/100593
> * common.opt: Add -fdirect-extern-access.
> * config/i386/i386-protos.h (ix86_force_load_from_GOT_p): Add a
> bool argument.
> * config/i386/i386.c (ix86_force_load_from_GOT_p): Add a bool
> argument to indicate call operand. Force non-call load
> from GOT for -fno-direct-extern-access.
> (legitimate_pic_address_disp_p): Avoid copy relocation in PIE
> for -fno-direct-extern-access.
> (ix86_print_operand): Pass true to ix86_force_load_from_GOT_p
> for call operand.
> (asm_preferred_eh_data_format): Use PC-relative format for
> -fno-direct-extern-access to avoid copy relocation. Check
> ptr_mode instead of TARGET_64BIT when selecting DW_EH_PE_sdata4.
> (ix86_binds_local_p): Don't treat protected data as extern and
> avoid copy relocation on common symbol with
> -fno-direct-extern-access.
> (ix86_reloc_rw_mask): New to avoid copy relocation for
> -fno-direct-extern-access.
> (TARGET_ASM_RELOC_RW_MASK): New.
> * doc/invoke.texi: Document -f[no-]direct-extern-access.
>
> gcc/testsuite/
>
> PR target/35513
> PR target/100593
> * g++.dg/pr35513-1.C: New file.
> * g++.dg/pr35513-2.C: Likewise.
> * gcc.target/i386/pr35513-1.c: Likewise.
> * gcc.target/i386/pr35513-2.c: Likewise.
> * gcc.target/i386/pr35513-3.c: Likewise.
> * gcc.target/i386/pr35513-4.c: Likewise.
> * gcc.target/i386/pr35513-5.c: Likewise.
> * gcc.target/i386/pr35513-6.c: Likewise.
> * gcc.target/i386/pr35513-7.c: Likewise.
> * gcc.target/i386/pr35513-8.c: Likewise.
> ---
> gcc/common.opt | 4 ++
> gcc/config/i386/i386-protos.h | 2 +-
> gcc/config/i386/i386.c | 50 +++++++++++++++------
> gcc/doc/invoke.texi | 13 ++++++
> gcc/testsuite/g++.dg/pr35513-1.C | 25 +++++++++++
> gcc/testsuite/g++.dg/pr35513-2.C | 53 +++++++++++++++++++++++
> gcc/testsuite/gcc.target/i386/pr35513-1.c | 16 +++++++
> gcc/testsuite/gcc.target/i386/pr35513-2.c | 15 +++++++
> gcc/testsuite/gcc.target/i386/pr35513-3.c | 15 +++++++
> gcc/testsuite/gcc.target/i386/pr35513-4.c | 15 +++++++
> gcc/testsuite/gcc.target/i386/pr35513-5.c | 15 +++++++
> gcc/testsuite/gcc.target/i386/pr35513-6.c | 14 ++++++
> gcc/testsuite/gcc.target/i386/pr35513-7.c | 15 +++++++
> gcc/testsuite/gcc.target/i386/pr35513-8.c | 41 ++++++++++++++++++
> 14 files changed, 278 insertions(+), 15 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/pr35513-1.C
> create mode 100644 gcc/testsuite/g++.dg/pr35513-2.C
> create mode 100644 gcc/testsuite/gcc.target/i386/pr35513-1.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr35513-2.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr35513-3.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr35513-4.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr35513-5.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr35513-6.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr35513-7.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr35513-8.c
>
> diff --git a/gcc/common.opt b/gcc/common.opt
> index d9da1131eda..67ad811d54d 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -1432,6 +1432,10 @@ fdiagnostics-minimum-margin-width=
> Common Joined UInteger Var(diagnostics_minimum_margin_width) Init(6)
> Set minimum width of left margin of source code when showing source.
>
> +fdirect-extern-access
> +Common Var(flag_direct_extern_access) Init(1) Optimization
> +Do not use GOT to access external symbols.
> +
> fdisable-
> Common Joined RejectNegative Var(common_deferred_options) Defer
> -fdisable-[tree|rtl|ipa]-<pass>=range1+range2 Disable an optimization pass.
> diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h
> index 51376fcc454..693cc3e5c78 100644
> --- a/gcc/config/i386/i386-protos.h
> +++ b/gcc/config/i386/i386-protos.h
> @@ -79,7 +79,7 @@ extern bool ix86_expand_cmpstrn_or_cmpmem (rtx, rtx, rtx, rtx, rtx, bool);
> extern bool constant_address_p (rtx);
> extern bool legitimate_pic_operand_p (rtx);
> extern bool legitimate_pic_address_disp_p (rtx);
> -extern bool ix86_force_load_from_GOT_p (rtx);
> +extern bool ix86_force_load_from_GOT_p (rtx, bool = false);
> extern void print_reg (rtx, int, FILE*);
> extern void ix86_print_operand (FILE *, rtx, int);
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index cff26909292..7dee311051d 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -10312,13 +10312,17 @@ darwin_local_data_pic (rtx disp)
> }
>
> /* True if the function symbol operand X should be loaded from GOT.
> + If CALL_P is true, X is a call operand.
> +
> + NB: -fno-direct-extern-access doesn't force load from GOT for
> + call.
>
> NB: In 32-bit mode, only non-PIC is allowed in inline assembly
> statements, since a PIC register could not be available at the
> call site. */
>
> bool
> -ix86_force_load_from_GOT_p (rtx x)
> +ix86_force_load_from_GOT_p (rtx x, bool call_p)
> {
> return ((TARGET_64BIT || (!flag_pic && HAVE_AS_IX86_GOT32X))
> && !TARGET_PECOFF && !TARGET_MACHO
> @@ -10326,11 +10330,12 @@ ix86_force_load_from_GOT_p (rtx x)
> && ix86_cmodel != CM_LARGE
> && ix86_cmodel != CM_LARGE_PIC
> && GET_CODE (x) == SYMBOL_REF
> - && SYMBOL_REF_FUNCTION_P (x)
> - && (!flag_plt
> - || (SYMBOL_REF_DECL (x)
> - && lookup_attribute ("noplt",
> - DECL_ATTRIBUTES (SYMBOL_REF_DECL (x)))))
> + && ((!call_p && !flag_direct_extern_access)
> + || (SYMBOL_REF_FUNCTION_P (x)
> + && (!flag_plt
> + || (SYMBOL_REF_DECL (x)
> + && lookup_attribute ("noplt",
> + DECL_ATTRIBUTES (SYMBOL_REF_DECL (x)))))))
> && !SYMBOL_REF_LOCAL_P (x));
> }
>
> @@ -10596,7 +10601,8 @@ legitimate_pic_address_disp_p (rtx disp)
> }
> else if (!SYMBOL_REF_FAR_ADDR_P (op0)
> && (SYMBOL_REF_LOCAL_P (op0)
> - || (HAVE_LD_PIE_COPYRELOC
> + || (flag_direct_extern_access
> + && HAVE_LD_PIE_COPYRELOC
> && flag_pie
> && !SYMBOL_REF_WEAK (op0)
> && !SYMBOL_REF_FUNCTION_P (op0)))
> @@ -13498,7 +13504,7 @@ ix86_print_operand (FILE *file, rtx x, int code)
>
> if (code == 'P')
> {
> - if (ix86_force_load_from_GOT_p (x))
> + if (ix86_force_load_from_GOT_p (x, true))
> {
> /* For inline assembly statement, load function address
> from GOT with 'P' operand modifier to avoid PLT. */
> @@ -21935,10 +21941,10 @@ int
> asm_preferred_eh_data_format (int code, int global)
> {
> /* PE-COFF is effectively always -fPIC because of the .reloc section. */
> - if (flag_pic || TARGET_PECOFF)
> + if (flag_pic || TARGET_PECOFF || !flag_direct_extern_access)
> {
> int type = DW_EH_PE_sdata8;
> - if (!TARGET_64BIT
> + if (ptr_mode == SImode
> || ix86_cmodel == CM_SMALL_PIC
> || (ix86_cmodel == CM_MEDIUM_PIC && (global || code)))
> type = DW_EH_PE_sdata4;
> @@ -23028,10 +23034,21 @@ ix86_atomic_assign_expand_fenv (tree *hold, tree *clear, tree *update)
> static bool
> ix86_binds_local_p (const_tree exp)
> {
> - return default_binds_local_p_3 (exp, flag_shlib != 0, true, true,
> - (!flag_pic
> - || (TARGET_64BIT
> - && HAVE_LD_PIE_COPYRELOC != 0)));
> + return default_binds_local_p_3 (exp, flag_shlib != 0, true,
> + flag_direct_extern_access,
> + (flag_direct_extern_access
> + && (!flag_pic
> + || (TARGET_64BIT
> + && HAVE_LD_PIE_COPYRELOC != 0))));
> +}
> +
> +/* If flag_pic or flag_direct_extern_access is false, then neither
> + local nor global relocs should be placed in readonly memory. */
> +
> +static int
> +ix86_reloc_rw_mask (void)
> +{
> + return (flag_pic || !flag_direct_extern_access) ? 3 : 0;
> }
> #endif
>
> @@ -24071,6 +24088,11 @@ ix86_run_selftests (void)
> #define TARGET_GET_MULTILIB_ABI_NAME \
> ix86_get_multilib_abi_name
>
> +#if !TARGET_MACHO && !TARGET_DLLIMPORT_DECL_ATTRIBUTES
> +# undef TARGET_ASM_RELOC_RW_MASK
> +# define TARGET_ASM_RELOC_RW_MASK ix86_reloc_rw_mask
> +#endif
> +
> static bool ix86_libc_has_fast_function (int fcode ATTRIBUTE_UNUSED)
> {
> #ifdef OPTION_GLIBC
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index e67d47af676..2959c84cc3d 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -658,6 +658,7 @@ Objective-C and Objective-C++ Dialects}.
> -fnon-call-exceptions -fdelete-dead-exceptions -funwind-tables @gol
> -fasynchronous-unwind-tables @gol
> -fno-gnu-unique @gol
> +-fno-direct-extern-access @gol
> -finhibit-size-directive -fcommon -fno-ident @gol
> -fpcc-struct-return -fpic -fPIC -fpie -fPIE -fno-plt @gol
> -fno-jump-tables -fno-bit-tests @gol
> @@ -16633,6 +16634,18 @@ through the PLT for specific external functions.
> In position-dependent code, a few targets also convert calls to
> functions that are marked to not use the PLT to use the GOT instead.
>
> +@item -fno-direct-extern-access
> +@opindex fno-direct-extern-access
> +@opindex fdirect-extern-access
> +Without @option{-fpic} nor @option{-fPIC}, always use the GOT pointer
> +to access external symbols. With @option{-fpic} or @option{-fPIC},
> +treat access to protected symbols as local symbols.
> +
> +@strong{Warning:} shared libraries compiled with
> +@option{-fno-direct-extern-access} and executable compiled with
> +@option{-fdirect-extern-access} may not be binary compatible if
> +protected symbols are used in shared libraries and executable.
> +
> @item -fno-jump-tables
> @opindex fno-jump-tables
> @opindex fjump-tables
> diff --git a/gcc/testsuite/g++.dg/pr35513-1.C b/gcc/testsuite/g++.dg/pr35513-1.C
> new file mode 100644
> index 00000000000..8423e826da8
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/pr35513-1.C
> @@ -0,0 +1,25 @@
> +// { dg-do run }
> +// { dg-options "-O2 -fno-direct-extern-access" }
> +
> +#include <iostream>
> +
> +class Bug
> +{
> +};
> +
> +int throw_bug()
> +{
> + throw Bug();
> +
> + return 0;
> +}
> +
> +int main()
> +{
> + try {
> + std::cout << throw_bug();
> + } catch (Bug bug) {
> + };
> +
> + return 0;
> +}
> diff --git a/gcc/testsuite/g++.dg/pr35513-2.C b/gcc/testsuite/g++.dg/pr35513-2.C
> new file mode 100644
> index 00000000000..56ed19ae1eb
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/pr35513-2.C
> @@ -0,0 +1,53 @@
> +// { dg-do run }
> +// { dg-options "-O2 -fno-direct-extern-access" }
> +
> +class Foo
> +{
> +public:
> + Foo(int n) : n_(n) { }
> + int f() { return n_; }
> +
> + int badTest();
> + int goodTest();
> +
> +private:
> +
> + int n_;
> +};
> +
> +int Foo::badTest()
> +{
> + try {
> + throw int(99);
> + }
> +
> + catch (int &i) {
> + n_ = 16;
> + }
> +
> + return n_;
> +}
> +
> +
> +int Foo::goodTest()
> +{
> + int n;
> +
> + try {
> + throw int(99);
> + }
> +
> + catch (int &i) {
> + n = 16;
> + }
> +
> + return n_;
> +}
> +
> +int main()
> +{
> + Foo foo(5);
> + foo.goodTest();
> + foo.badTest();
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.target/i386/pr35513-1.c b/gcc/testsuite/gcc.target/i386/pr35513-1.c
> new file mode 100644
> index 00000000000..c5dbabc3704
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr35513-1.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fno-pic -fno-direct-extern-access" } */
> +
> +extern void bar (void);
> +extern void *p;
> +
> +void
> +foo (void)
> +{
> + p = &bar;
> +}
> +
> +/* { dg-final { scan-assembler "mov\(l|q\)\[ \t\]*bar@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]*bar@GOT," { target { ia32 && got32x_reloc } } } } */
> +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*\\\$bar," { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*\\\$bar," { target { ia32 && got32x_reloc } } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr35513-2.c b/gcc/testsuite/gcc.target/i386/pr35513-2.c
> new file mode 100644
> index 00000000000..8bb7cb4c13d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr35513-2.c
> @@ -0,0 +1,15 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fno-pic -fno-direct-extern-access" } */
> +
> +extern int bar;
> +
> +int
> +foo (void)
> +{
> + return bar;
> +}
> +
> +/* { dg-final { scan-assembler "mov\(l|q\)\[ \t\]*bar@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]*bar@GOT," { target { ia32 && got32x_reloc } } } } */
> +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*\\\$bar," { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*\\\$bar," { target { ia32 && got32x_reloc } } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr35513-3.c b/gcc/testsuite/gcc.target/i386/pr35513-3.c
> new file mode 100644
> index 00000000000..98dc54e3bf4
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr35513-3.c
> @@ -0,0 +1,15 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fpie -fno-direct-extern-access" } */
> +
> +extern int bar;
> +
> +int
> +foo (void)
> +{
> + return bar;
> +}
> +
> +/* { dg-final { scan-assembler "mov\(l|q\)\[ \t\]*bar@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "movl\[ \t\]*bar@GOT" { target { ia32 && got32x_reloc } } } } */
> +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*\\\$bar," { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*\\\$bar," { target { ia32 && got32x_reloc } } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr35513-4.c b/gcc/testsuite/gcc.target/i386/pr35513-4.c
> new file mode 100644
> index 00000000000..467081dad65
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr35513-4.c
> @@ -0,0 +1,15 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fplt -fno-pic -fno-direct-extern-access" } */
> +
> +extern void foo (void);
> +
> +int
> +bar (void)
> +{
> + foo ();
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler "call\[ \t\]*foo" } } */
> +/* { dg-final { scan-assembler-not "foo@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "foo@GOT" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr35513-5.c b/gcc/testsuite/gcc.target/i386/pr35513-5.c
> new file mode 100644
> index 00000000000..b0e61b08ba9
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr35513-5.c
> @@ -0,0 +1,15 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fplt -fpic -fno-direct-extern-access" } */
> +
> +extern void foo (void);
> +
> +int
> +bar (void)
> +{
> + foo ();
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler "call\[ \t\]*foo@PLT" } } */
> +/* { dg-final { scan-assembler-not "foo@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "foo@GOT" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr35513-6.c b/gcc/testsuite/gcc.target/i386/pr35513-6.c
> new file mode 100644
> index 00000000000..270504b8d0e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr35513-6.c
> @@ -0,0 +1,14 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fplt -fno-pic -fno-direct-extern-access" } */
> +
> +extern void foo (void);
> +
> +void
> +bar (void)
> +{
> + foo ();
> +}
> +
> +/* { dg-final { scan-assembler "jmp\[ \t\]*foo" } } */
> +/* { dg-final { scan-assembler-not "foo@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "foo@GOT" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr35513-7.c b/gcc/testsuite/gcc.target/i386/pr35513-7.c
> new file mode 100644
> index 00000000000..2c5a83ddef8
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr35513-7.c
> @@ -0,0 +1,15 @@
> +/* { dg-do compile { target *-*-linux* } } */
> +/* { dg-options "-O2 -fplt -fpic -fno-direct-extern-access" } */
> +
> +extern void foo (void);
> +
> +void
> +bar (void)
> +{
> + foo ();
> +}
> +
> +/* { dg-final { scan-assembler "jmp\[ \t\]*foo@PLT" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler "call\[ \t\]*foo@PLT" { target ia32 } } } */
> +/* { dg-final { scan-assembler-not "foo@GOTPCREL" { target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-not "foo@GOT" { target ia32 } } } */
> diff --git a/gcc/testsuite/gcc.target/i386/pr35513-8.c b/gcc/testsuite/gcc.target/i386/pr35513-8.c
> new file mode 100644
> index 00000000000..545979e99c2
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr35513-8.c
> @@ -0,0 +1,41 @@
> +/* { dg-do assemble { target { *-*-linux* && { ! ia32 } } } } */
> +/* { dg-require-effective-target maybe_x32 } */
> +/* { dg-options "-mx32 -O2 -fno-pic -fexceptions -fasynchronous-unwind-tables -fno-direct-extern-access" } */
> +
> +extern int foo (int);
> +extern void exit (int __status) __attribute__ ((__nothrow__ )) __attribute__ ((__noreturn__));
> +struct __pthread_cleanup_frame
> +{
> + void (*__cancel_routine) (void *);
> + void *__cancel_arg;
> + int __do_it;
> + int __cancel_type;
> +};
> +extern __inline void
> +__pthread_cleanup_routine (struct __pthread_cleanup_frame *__frame)
> +{
> + if (__frame->__do_it)
> + __frame->__cancel_routine (__frame->__cancel_arg);
> +}
> +static int cl_called;
> +
> +static void
> +cl (void *arg)
> +{
> + ++cl_called;
> +}
> +
> +
> +void *
> +tf_usleep (void *arg)
> +{
> +
> + do { struct __pthread_cleanup_frame __clframe __attribute__ ((__cleanup__ (__pthread_cleanup_routine))) = { .__cancel_routine = (cl), .__cancel_arg = (
> + ((void *)0)), .__do_it = 1 };;
> +
> + foo (arg == ((void *)0) ? (0x7fffffffL * 2UL + 1UL) : 0);
> +
> + __clframe.__do_it = (0); } while (0);
> +
> + exit (1);
> +}
> --
> 2.31.1
>
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