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author | Torsten Duwe <duwe@suse.de> | 2017-07-25 14:16:10 +0000 |
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committer | Richard Biener <rguenth@gcc.gnu.org> | 2017-07-25 14:16:10 +0000 |
commit | 417ca0117a1a9a8aaf5bc5ca530adfd68cb00399 (patch) | |
tree | c8993d80cd0cc0675b2677e7902c261e0625dd63 /gcc/doc/invoke.texi | |
parent | 774cccdc1a36493ae6925148c08dfbdcb2789e0c (diff) | |
download | gcc-417ca0117a1a9a8aaf5bc5ca530adfd68cb00399.zip gcc-417ca0117a1a9a8aaf5bc5ca530adfd68cb00399.tar.gz gcc-417ca0117a1a9a8aaf5bc5ca530adfd68cb00399.tar.bz2 |
c-attribs.c (c_common_attribute_table): Add entry for "patchable_function_entry".
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.
From-SVN: r250521
Diffstat (limited to 'gcc/doc/invoke.texi')
-rw-r--r-- | gcc/doc/invoke.texi | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 4926c90..a6da37c 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -11519,6 +11519,34 @@ 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 |