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gcc7.32254
gcc7-pfe-0001-Backport-Add-entry-for-patchable_...
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File gcc7-pfe-0001-Backport-Add-entry-for-patchable_function_entry.patch of Package gcc7.32254
From 1258c4f8a08681cce523c40352a37584f9ba63bd Mon Sep 17 00:00:00 2001 From: Torsten Duwe <duwe@suse.de> Date: Tue, 25 Jul 2017 14:16:10 +0000 Subject: [PATCH 01/22] Backport "Add entry for "patchable_function_entry". 2021-10-07 Giuliano Belinassi <gbelinassi@suse.de> Backport from mainline 2017-07-07 Torsten Duwe <duwe@suse.de> c-family/ * c-attribs.c (c_common_attribute_table): Add entry for "patchable_function_entry". lto/ * lto-lang.c (lto_attribute_table): Add entry for "patchable_function_entry". * 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: Re-generate. * 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. --- gcc/c-family/c-attribs.c | 12 +++++ gcc/common.opt | 11 +++++ gcc/doc/extend.texi | 21 +++++++++ gcc/doc/invoke.texi | 28 +++++++++++ gcc/doc/tm.texi | 9 ++++ gcc/doc/tm.texi.in | 2 + gcc/lto/lto-lang.c | 12 +++++ gcc/opts.c | 27 +++++++++++ gcc/target.def | 11 +++++ gcc/targhooks.c | 46 +++++++++++++++++++ gcc/targhooks.h | 3 ++ .../patchable_function_entry-decl.c | 16 +++++++ .../patchable_function_entry-default.c | 16 +++++++ .../patchable_function_entry-definition.c | 16 +++++++ gcc/toplev.c | 4 +- gcc/varasm.c | 46 +++++++++++++++++++ 16 files changed, 279 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/c-c++-common/patchable_function_entry-decl.c create mode 100644 gcc/testsuite/c-c++-common/patchable_function_entry-default.c create mode 100644 gcc/testsuite/c-c++-common/patchable_function_entry-definition.c diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c index 90b17bc00d2..b2820dd1586 100644 --- a/gcc/c-family/c-attribs.c +++ b/gcc/c-family/c-attribs.c @@ -139,6 +139,8 @@ 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. @@ -345,6 +347,9 @@ 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 } }; @@ -3178,3 +3183,10 @@ 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 437db8e8615..ca1613b6808 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 @@ -2022,6 +2029,10 @@ 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 1ef46799907..6860a391f62 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -3083,6 +3083,27 @@ 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 8f279e454b0..ad71be54e07 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -11417,6 +11417,34 @@ 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 1bb5a9d9579..b4456f7cd40 100644 --- a/gcc/doc/tm.texi +++ b/gcc/doc/tm.texi @@ -4566,6 +4566,15 @@ 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 d4047142027..b188c94ae5e 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 fdd6ae08a1c..530d9dc31d0 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 b98a0ca73a8..d0430e777ee 100644 --- a/gcc/opts.c +++ b/gcc/opts.c @@ -2201,6 +2201,33 @@ 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 6bebfd5b9d6..bea79404836 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 1cdec068ed8..77ca69105d0 100644 --- a/gcc/targhooks.c +++ b/gcc/targhooks.c @@ -72,6 +72,7 @@ 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" @@ -1609,6 +1610,51 @@ 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 18070df7839..6206fe20823 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 6f0bc9fe736..7d3aa280f15 100644 --- a/gcc/toplev.c +++ b/gcc/toplev.c @@ -1612,8 +1612,10 @@ 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 1b9030029ac..6e9a8c3133e 100644 --- a/gcc/varasm.c +++ b/gcc/varasm.c @@ -1829,6 +1829,46 @@ 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); @@ -1837,6 +1877,12 @@ 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; } -- 2.33.1
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