What is the next step now? Is anybody going to commit that patch?
Torsten
On Fri, Jul 07, 2017 at 02:57:55PM +0100, Richard Earnshaw (lists) wrote:
> On 06/07/17 15:03, Torsten Duwe wrote:
> +#if TARGET_HAVE_NAMED_SECTIONS
No, this is a hook. You need to test targetm_common.have_named_sections.
OK with that change.
R.
On Fri, Jul 07, 2017 at 09:30:28PM +0200, Torsten Duwe wrote:
> Change since v11:
>
> < +#if TARGET_HAVE_NAMED_SECTIONS
>
> > + if (record_p && targetm_common.have_named_sections)
>
> (plus > +#include "common/common-target.h" )
>
> Torsten
>
>
> gcc/c-family/ChangeLog
> 2017-07-07 Torsten Duwe <d...@suse.de>
>
> * c-attribs.c (c_common_attribute_table): Add entry for
> "patchable_function_entry".
>
> gcc/lto/ChangeLog
> 2017-07-07 Torsten Duwe <d...@suse.de>
>
> * lto-lang.c (lto_attribute_table): Add entry for
> "patchable_function_entry".
>
> gcc/ChangeLog
> 2017-07-07 Torsten Duwe <d...@suse.de>
>
> * common.opt: Introduce -fpatchable-function-entry
> command line option, and its variables function_entry_patch_area_size
> and function_entry_patch_area_start.
> * opts.c (common_handle_option): Add -fpatchable_function_entry_ case,
> including a two-value parser.
> * target.def (print_patchable_function_entry): New target hook.
> * targhooks.h (default_print_patchable_function_entry): New function.
> * targhooks.c (default_print_patchable_function_entry): Likewise.
> * toplev.c (process_options): Switch off IPA-RA if
> patchable function entries are being generated.
> * varasm.c (assemble_start_function): Look at the
> patchable-function-entry command line switch and current
> function attributes and maybe generate NOP instructions by
> calling the print_patchable_function_entry hook.
> * doc/extend.texi: Document patchable_function_entry attribute.
> * doc/invoke.texi: Document -fpatchable_function_entry
> command line option.
> * doc/tm.texi.in (TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY):
> New target hook.
> * doc/tm.texi: Likewise.
>
> gcc/testsuite/ChangeLog
> 2017-07-07 Torsten Duwe <d...@suse.de>
>
> * c-c++-common/patchable_function_entry-default.c: New test.
> * c-c++-common/patchable_function_entry-decl.c: Likewise.
> * c-c++-common/patchable_function_entry-definition.c: Likewise.
>
> diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
> index 626ffa1cde7..ecb00c1d5b9 100644
> --- a/gcc/c-family/c-attribs.c
> +++ b/gcc/c-family/c-attribs.c
> @@ -142,6 +142,8 @@ static tree handle_bnd_variable_size_attribute (tree *,
> tree, tree, int, bool *)
> static tree handle_bnd_legacy (tree *, tree, tree, int, bool *);
> static tree handle_bnd_instrument (tree *, tree, tree, int, bool *);
> static tree handle_fallthrough_attribute (tree *, tree, tree, int, bool *);
> +static tree handle_patchable_function_entry_attribute (tree *, tree, tree,
> + int, bool *);
>
> /* Table of machine-independent attributes common to all C-like languages.
>
> @@ -351,6 +353,9 @@ const struct attribute_spec c_common_attribute_table[] =
> handle_bnd_instrument, false },
> { "fallthrough", 0, 0, false, false, false,
> handle_fallthrough_attribute, false },
> + { "patchable_function_entry", 1, 2, true, false, false,
> + handle_patchable_function_entry_attribute,
> + false },
> { NULL, 0, 0, false, false, false, NULL, false }
> };
>
> @@ -3260,3 +3265,10 @@ handle_fallthrough_attribute (tree *, tree name, tree,
> int,
> *no_add_attrs = true;
> return NULL_TREE;
> }
> +
> +static tree
> +handle_patchable_function_entry_attribute (tree *, tree, tree, int, bool *)
> +{
> + /* Nothing to be done here. */
> + return NULL_TREE;
> +}
> diff --git a/gcc/common.opt b/gcc/common.opt
> index e81165c488b..78cfa568a95 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -163,6 +163,13 @@ bool flag_stack_usage_info = false
> Variable
> int flag_debug_asm
>
> +; How many NOP insns to place at each function entry by default
> +Variable
> +HOST_WIDE_INT function_entry_patch_area_size
> +
> +; And how far the real asm entry point is into this area
> +Variable
> +HOST_WIDE_INT function_entry_patch_area_start
>
> ; Balance between GNAT encodings and standard DWARF to emit.
> Variable
> @@ -2030,6 +2037,10 @@ fprofile-reorder-functions
> Common Report Var(flag_profile_reorder_functions)
> Enable function reordering that improves code placement.
>
> +fpatchable-function-entry=
> +Common Joined Optimization
> +Insert NOP instructions at each function entry.
> +
> frandom-seed
> Common Var(common_deferred_options) Defer
>
> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
> index 5cb512fe575..9c171abc121 100644
> --- a/gcc/doc/extend.texi
> +++ b/gcc/doc/extend.texi
> @@ -3105,6 +3105,27 @@ that affect more than one function.
> This attribute should be used for debugging purposes only. It is not
> suitable in production code.
>
> +@item patchable_function_entry
> +@cindex @code{patchable_function_entry} function attribute
> +@cindex extra NOP instructions at the function entry point
> +In case the target's text segment can be made writable at run time by
> +any means, padding the function entry with a number of NOPs can be
> +used to provide a universal tool for instrumentation.
> +
> +The @code{patchable_function_entry} function attribute can be used to
> +change the number of NOPs to any desired value. The two-value syntax
> +is the same as for the command-line switch
> +@option{-fpatchable-function-entry=N,M}, generating @var{N} NOPs, with
> +the function entry point before the @var{M}th NOP instruction.
> +@var{M} defaults to 0 if omitted e.g. function entry point is before
> +the first NOP.
> +
> +If patchable function entries are enabled globally using the command-line
> +option @option{-fpatchable-function-entry=N,M}, then you must disable
> +instrumentation on all functions that are part of the instrumentation
> +framework with the attribute @code{patchable_function_entry (0)}
> +to prevent recursion.
> +
> @item pure
> @cindex @code{pure} function attribute
> @cindex functions that have no side effects
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index d0b90503ced..dc93f0ccd50 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -11520,6 +11520,34 @@ of the function name, it is considered to be a
> match. For C99 and C++
> extended identifiers, the function name must be given in UTF-8, not
> using universal character names.
>
> +@item -fpatchable-function-entry=@var{N}[,@var{M}]
> +@opindex fpatchable-function-entry
> +Generate @var{N} NOPs right at the beginning
> +of each function, with the function entry point before the @var{M}th NOP.
> +If @var{M} is omitted, it defaults to @code{0} so the
> +function entry points to the address just at the first NOP.
> +The NOP instructions reserve extra space which can be used to patch in
> +any desired instrumentation at run time, provided that the code segment
> +is writable. The amount of space is controllable indirectly via
> +the number of NOPs; the NOP instruction used corresponds to the instruction
> +emitted by the internal GCC back-end interface @code{gen_nop}. This behavior
> +is target-specific and may also depend on the architecture variant and/or
> +other compilation options.
> +
> +For run-time identification, the starting addresses of these areas,
> +which correspond to their respective function entries minus @var{M},
> +are additionally collected in the @code{__patchable_function_entries}
> +section of the resulting binary.
> +
> +Note that the value of @code{__attribute__ ((patchable_function_entry
> +(N,M)))} takes precedence over command-line option
> +@option{-fpatchable-function-entry=N,M}. This can be used to increase
> +the area size or to remove it completely on a single function.
> +If @code{N=0}, no pad location is recorded.
> +
> +The NOP instructions are inserted at---and maybe before, depending on
> +@var{M}---the function entry address, even before the prologue.
> +
> @end table
>
>
> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> index 795e49246af..23e85c7afea 100644
> --- a/gcc/doc/tm.texi
> +++ b/gcc/doc/tm.texi
> @@ -4573,6 +4573,15 @@ will select the smallest suitable mode.
> This section describes the macros that output function entry
> (@dfn{prologue}) and exit (@dfn{epilogue}) code.
>
> +@deftypefn {Target Hook} void TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY
> (FILE *@var{file}, unsigned HOST_WIDE_INT @var{patch_area_size}, bool
> @var{record_p})
> +Generate a patchable area at the function start, consisting of
> +@var{patch_area_size} NOP instructions. If the target supports named
> +sections and if @var{record_p} is true, insert a pointer to the current
> +location in the table of patchable functions. The default implementation
> +of the hook places the table of pointers in the special section named
> +@code{__patchable_function_entries}.
> +@end deftypefn
> +
> @deftypefn {Target Hook} void TARGET_ASM_FUNCTION_PROLOGUE (FILE
> *@var{file}, HOST_WIDE_INT @var{size})
> If defined, a function that outputs the assembler code for entry to a
> function. The prologue is responsible for setting up the stack frame,
> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
> index 98f2e6bce5f..6df08a2c477 100644
> --- a/gcc/doc/tm.texi.in
> +++ b/gcc/doc/tm.texi.in
> @@ -3650,6 +3650,8 @@ will select the smallest suitable mode.
> This section describes the macros that output function entry
> (@dfn{prologue}) and exit (@dfn{epilogue}) code.
>
> +@hook TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY
> +
> @hook TARGET_ASM_FUNCTION_PROLOGUE
>
> @hook TARGET_ASM_FUNCTION_END_PROLOGUE
> diff --git a/gcc/lto/lto-lang.c b/gcc/lto/lto-lang.c
> index 58935172b2c..6e9a138fa3b 100644
> --- a/gcc/lto/lto-lang.c
> +++ b/gcc/lto/lto-lang.c
> @@ -48,6 +48,8 @@ static tree handle_sentinel_attribute (tree *, tree, tree,
> int, bool *);
> static tree handle_type_generic_attribute (tree *, tree, tree, int, bool *);
> static tree handle_transaction_pure_attribute (tree *, tree, tree, int, bool
> *);
> static tree handle_returns_twice_attribute (tree *, tree, tree, int, bool *);
> +static tree handle_patchable_function_entry_attribute (tree *, tree, tree,
> + int, bool *);
> static tree ignore_attribute (tree *, tree, tree, int, bool *);
>
> static tree handle_format_attribute (tree *, tree, tree, int, bool *);
> @@ -76,6 +78,9 @@ const struct attribute_spec lto_attribute_table[] =
> handle_nonnull_attribute, false },
> { "nothrow", 0, 0, true, false, false,
> handle_nothrow_attribute, false },
> + { "patchable_function_entry", 1, 2, true, false, false,
> + handle_patchable_function_entry_attribute,
> + false },
> { "returns_twice", 0, 0, true, false, false,
> handle_returns_twice_attribute, false },
> { "sentinel", 0, 1, false, true, true,
> @@ -473,6 +478,13 @@ handle_returns_twice_attribute (tree *node, tree
> ARG_UNUSED (name),
> return NULL_TREE;
> }
>
> +static tree
> +handle_patchable_function_entry_attribute (tree *, tree, tree, int, bool *)
> +{
> + /* Nothing to be done here. */
> + return NULL_TREE;
> +}
> +
> /* Ignore the given attribute. Used when this attribute may be usefully
> overridden by the target, but is not used generically. */
>
> diff --git a/gcc/opts.c b/gcc/opts.c
> index 7555ed55434..fecf97978fc 100644
> --- a/gcc/opts.c
> +++ b/gcc/opts.c
> @@ -2199,6 +2199,33 @@ common_handle_option (struct gcc_options *opts,
> opts->x_flag_ipa_reference = false;
> break;
>
> + case OPT_fpatchable_function_entry_:
> + {
> + char *patch_area_arg = xstrdup (arg);
> + char *comma = strchr (patch_area_arg, ',');
> + if (comma)
> + {
> + *comma = '\0';
> + function_entry_patch_area_size =
> + integral_argument (patch_area_arg);
> + function_entry_patch_area_start =
> + integral_argument (comma + 1);
> + }
> + else
> + {
> + function_entry_patch_area_size =
> + integral_argument (patch_area_arg);
> + function_entry_patch_area_start = 0;
> + }
> + if (function_entry_patch_area_size < 0
> + || function_entry_patch_area_start < 0
> + || function_entry_patch_area_size
> + < function_entry_patch_area_start)
> + error ("invalid arguments for %<-fpatchable_function_entry%>");
> + free (patch_area_arg);
> + }
> + break;
> +
> case OPT_ftree_vectorize:
> if (!opts_set->x_flag_tree_loop_vectorize)
> opts->x_flag_tree_loop_vectorize = value;
> diff --git a/gcc/target.def b/gcc/target.def
> index bbd9c015189..6d67b1fe8ba 100644
> --- a/gcc/target.def
> +++ b/gcc/target.def
> @@ -288,6 +288,17 @@ hidden, protected or internal visibility as specified by
> @var{visibility}.",
> void, (tree decl, int visibility),
> default_assemble_visibility)
>
> +DEFHOOK
> +(print_patchable_function_entry,
> + "Generate a patchable area at the function start, consisting of\n\
> +@var{patch_area_size} NOP instructions. If the target supports named\n\
> +sections and if @var{record_p} is true, insert a pointer to the current\n\
> +location in the table of patchable functions. The default implementation\n\
> +of the hook places the table of pointers in the special section named\n\
> +@code{__patchable_function_entries}.",
> + void, (FILE *file, unsigned HOST_WIDE_INT patch_area_size, bool record_p),
> + default_print_patchable_function_entry)
> +
> /* Output the assembler code for entry to a function. */
> DEFHOOK
> (function_prologue,
> diff --git a/gcc/targhooks.c b/gcc/targhooks.c
> index 940deec67f9..6a8fae656d0 100644
> --- a/gcc/targhooks.c
> +++ b/gcc/targhooks.c
> @@ -73,6 +73,7 @@ along with GCC; see the file COPYING3. If not see
> #include "calls.h"
> #include "expr.h"
> #include "output.h"
> +#include "common/common-target.h"
> #include "reload.h"
> #include "intl.h"
> #include "opts.h"
> @@ -1610,6 +1611,51 @@ default_compare_by_pieces_branch_ratio (machine_mode)
> return 1;
> }
>
> +/* Write PATCH_AREA_SIZE NOPs into the asm outfile FILE around a function
> + entry. If RECORD_P is true and the target supports named sections,
> + the location of the NOPs will be recorded in a special object section
> + called "__patchable_function_entries". This routine may be called
> + twice per function to put NOPs before and after the function
> + entry. */
> +
> +void
> +default_print_patchable_function_entry (FILE *file,
> + unsigned HOST_WIDE_INT patch_area_size,
> + bool record_p)
> +{
> + const char *nop_templ = 0;
> + int code_num;
> + rtx_insn *my_nop = make_insn_raw (gen_nop ());
> +
> + /* We use the template alone, relying on the (currently sane) assumption
> + that the NOP template does not have variable operands. */
> + code_num = recog_memoized (my_nop);
> + nop_templ = get_insn_template (code_num, my_nop);
> +
> + if (record_p && targetm_common.have_named_sections)
> + {
> + char buf[256];
> + static int patch_area_number;
> + section *previous_section = in_section;
> +
> + patch_area_number++;
> + ASM_GENERATE_INTERNAL_LABEL (buf, "LPFE", patch_area_number);
> +
> + switch_to_section (get_section ("__patchable_function_entries",
> + 0, NULL));
> + fputs (integer_asm_op (POINTER_SIZE_UNITS, false), file);
> + assemble_name_raw (file, buf);
> + fputc ('\n', file);
> +
> + switch_to_section (previous_section);
> + ASM_OUTPUT_LABEL (file, buf);
> + }
> +
> + unsigned i;
> + for (i = 0; i < patch_area_size; ++i)
> + fprintf (file, "\t%s\n", nop_templ);
> +}
> +
> bool
> default_profile_before_prologue (void)
> {
> diff --git a/gcc/targhooks.h b/gcc/targhooks.h
> index 1ddb8891fe4..c73ea0bda20 100644
> --- a/gcc/targhooks.h
> +++ b/gcc/targhooks.h
> @@ -203,6 +203,9 @@ extern bool default_use_by_pieces_infrastructure_p
> (unsigned HOST_WIDE_INT,
> bool);
> extern int default_compare_by_pieces_branch_ratio (machine_mode);
>
> +extern void default_print_patchable_function_entry (FILE *,
> + unsigned HOST_WIDE_INT,
> + bool);
> extern bool default_profile_before_prologue (void);
> extern reg_class_t default_preferred_reload_class (rtx, reg_class_t);
> extern reg_class_t default_preferred_output_reload_class (rtx, reg_class_t);
> diff --git a/gcc/testsuite/c-c++-common/patchable_function_entry-decl.c
> b/gcc/testsuite/c-c++-common/patchable_function_entry-decl.c
> new file mode 100644
> index 00000000000..8514b10e820
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/patchable_function_entry-decl.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fpatchable-function-entry=3,1" } */
> +/* { dg-final { scan-assembler-times "nop" 2 } } */
> +
> +extern int a;
> +
> +/* Respect overriding attributes in the declaration. */
> +int f3 (void) __attribute__((patchable_function_entry(2)));
> +
> +/* F3 should now get 2 NOPs. */
> +int
> +__attribute__((noinline))
> +f3 (void)
> +{
> + return 5*a;
> +}
> diff --git a/gcc/testsuite/c-c++-common/patchable_function_entry-default.c
> b/gcc/testsuite/c-c++-common/patchable_function_entry-default.c
> new file mode 100644
> index 00000000000..0dcf1181dde
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/patchable_function_entry-default.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fpatchable-function-entry=3,1" } */
> +/* { dg-final { scan-assembler-times "nop" 3 } } */
> +
> +extern int a;
> +
> +/* Nothing declared must not mean anything. */
> +int f3 (void);
> +
> +/* F3 should get a default-sized NOP area. */
> +int
> +__attribute__((noinline))
> +f3 (void)
> +{
> + return 5*a;
> +}
> diff --git a/gcc/testsuite/c-c++-common/patchable_function_entry-definition.c
> b/gcc/testsuite/c-c++-common/patchable_function_entry-definition.c
> new file mode 100644
> index 00000000000..a007867dcb0
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/patchable_function_entry-definition.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fpatchable-function-entry=3,1" } */
> +/* { dg-final { scan-assembler-times "nop" 1 } } */
> +
> +extern int a;
> +
> +int f3 (void);
> +
> +/* F3 should now get 1 NOP. */
> +int
> +__attribute__((noinline))
> +__attribute__((patchable_function_entry(1)))
> +f3 (void)
> +{
> + return 5*a;
> +}
> diff --git a/gcc/toplev.c b/gcc/toplev.c
> index e6c69a4ba93..b28f1847c83 100644
> --- a/gcc/toplev.c
> +++ b/gcc/toplev.c
> @@ -1630,8 +1630,10 @@ process_options (void)
> }
>
> /* Do not use IPA optimizations for register allocation if profiler is
> active
> + or patchable function entries are inserted for run-time instrumentation
> or port does not emit prologue and epilogue as RTL. */
> - if (profile_flag || !targetm.have_prologue () || !targetm.have_epilogue ())
> + if (profile_flag || function_entry_patch_area_size
> + || !targetm.have_prologue () || !targetm.have_epilogue ())
> flag_ipa_ra = 0;
>
> /* Enable -Werror=coverage-mismatch when -Werror and -Wno-error
> diff --git a/gcc/varasm.c b/gcc/varasm.c
> index fbaebc1b5c0..ec1640ea378 100644
> --- a/gcc/varasm.c
> +++ b/gcc/varasm.c
> @@ -1825,6 +1825,46 @@ assemble_start_function (tree decl, const char *fnname)
> if (DECL_PRESERVE_P (decl))
> targetm.asm_out.mark_decl_preserved (fnname);
>
> + unsigned HOST_WIDE_INT patch_area_size = function_entry_patch_area_size;
> + unsigned HOST_WIDE_INT patch_area_entry = function_entry_patch_area_start;
> +
> + tree patchable_function_entry_attr
> + = lookup_attribute ("patchable_function_entry", DECL_ATTRIBUTES (decl));
> + if (patchable_function_entry_attr)
> + {
> + tree pp_val = TREE_VALUE (patchable_function_entry_attr);
> + tree patchable_function_entry_value1 = TREE_VALUE (pp_val);
> +
> + if (tree_fits_uhwi_p (patchable_function_entry_value1))
> + patch_area_size = tree_to_uhwi (patchable_function_entry_value1);
> + else
> + gcc_unreachable ();
> +
> + patch_area_entry = 0;
> + if (list_length (pp_val) > 1)
> + {
> + tree patchable_function_entry_value2 =
> + TREE_VALUE (TREE_CHAIN (pp_val));
> +
> + if (tree_fits_uhwi_p (patchable_function_entry_value2))
> + patch_area_entry = tree_to_uhwi (patchable_function_entry_value2);
> + else
> + gcc_unreachable ();
> + }
> + }
> +
> + if (patch_area_entry > patch_area_size)
> + {
> + if (patch_area_size > 0)
> + warning (OPT_Wattributes, "Patchable function entry > size");
> + patch_area_entry = 0;
> + }
> +
> + /* Emit the patching area before the entry label, if any. */
> + if (patch_area_entry > 0)
> + targetm.asm_out.print_patchable_function_entry (asm_out_file,
> + patch_area_entry, true);
> +
> /* Do any machine/system dependent processing of the function name. */
> #ifdef ASM_DECLARE_FUNCTION_NAME
> ASM_DECLARE_FUNCTION_NAME (asm_out_file, fnname, current_function_decl);
> @@ -1833,6 +1873,12 @@ assemble_start_function (tree decl, const char *fnname)
> ASM_OUTPUT_FUNCTION_LABEL (asm_out_file, fnname, current_function_decl);
> #endif /* ASM_DECLARE_FUNCTION_NAME */
>
> + /* And the area after the label. Record it if we haven't done so yet. */
> + if (patch_area_size > patch_area_entry)
> + targetm.asm_out.print_patchable_function_entry (asm_out_file,
> + patch_area_size-patch_area_entry,
> + patch_area_entry == 0);
> +
> if (lookup_attribute ("no_split_stack", DECL_ATTRIBUTES (decl)))
> saw_no_split_stack = true;
> }
