Re: [RFC PATCH] grep: allow for run time disabling of JIT in PCRE
- From
Johannes Schindelin <johannes.schindelin@gmx.de>
- Date
- Jul 31, 2019, 12:24 UTC
- Message-ID
- <nycvar.QRO.7.76.6.1907311421140.21907@tvgsbejvaqbjf.bet>
- In-Reply-To
- <20190728235427.41425-1-carenas@gmail.com>
Hi,
On Sun, 28 Jul 2019, Carlo Marcelo Arenas Belón wrote:
Show 7 quoted lines
> PCRE1 allowed for a compile time flag to disable JIT, but PCRE2 never > had one, forcing the use of JIT if -P was requested. > > After ed0479ce3d (Merge branch 'ab/no-kwset' into next, 2019-07-15) > the PCRE2 engine will be used more broadly and therefore adding this > knob will give users a fallback for situations like the one observed > in OpenBSD with a JIT enabled PCRE2, because of W^X restrictions:
Just so that nobody else needs to feel like an idiot for not knowing what on the burning planet "W^X" is supposed to mean: https://en.wikipedia.org/wiki/W%5EX says it is essentially an OS-level mechanism to prevent executing code that was written into memory by the same process, i.e. JIT.
Makes me wonder whether node.js works on OpenBSD, or any decently fast web browser like Firefox or Chromium...
But I digress. I just wanted to chime in with the results of my web hunt for that "W^X" term.
Ciao, Dscho
Show 102 quoted lines
>
> $ git grep 'foo bar'
> fatal: Couldn't JIT the PCRE2 pattern 'foo bar', got '-48'
> $ git grep -G 'foo bar'
> fatal: Couldn't JIT the PCRE2 pattern 'foo bar', got '-48'
> $ git grep -E 'foo bar'
> fatal: Couldn't JIT the PCRE2 pattern 'foo bar', got '-48'
> $ git grep -F 'foo bar'
> fatal: Couldn't JIT the PCRE2 pattern 'foo bar', got '-48'
>
> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
> ---
> Documentation/git-grep.txt | 4 ++++
> grep.c | 15 +++++++++++++--
> grep.h | 1 +
> 3 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
> index c89fb569e3..ff544bdeec 100644
> --- a/Documentation/git-grep.txt
> +++ b/Documentation/git-grep.txt
> @@ -69,6 +69,10 @@ grep.fallbackToNoIndex::
> If set to true, fall back to git grep --no-index if git grep
> is executed outside of a git repository. Defaults to false.
>
> +pcre.jit::
> + If set to false, disable JIT when using PCRE. Defaults to
> + true.
> +
>
> OPTIONS
> -------
> diff --git a/grep.c b/grep.c
> index c7c06ae08d..3524d353dd 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -56,6 +56,7 @@ void init_grep_defaults(struct repository *repo)
> opt->repo = repo;
> opt->relative = 1;
> opt->pathname = 1;
> + opt->pcre_jit = 1;
> opt->max_depth = -1;
> opt->pattern_type_option = GREP_PATTERN_TYPE_UNSPECIFIED;
> color_set(opt->colors[GREP_COLOR_CONTEXT], "");
> @@ -125,6 +126,12 @@ int grep_config(const char *var, const char *value, void *cb)
> return 0;
> }
>
> + if (!strcmp(var, "pcre.jit")) {
> + int is_bool;
> + opt->pcre_jit = git_config_bool_or_int(var, value, &is_bool);
> + return 0;
> + }
> +
> if (!strcmp(var, "color.grep"))
> opt->color = git_config_colorbool(var, value);
> if (!strcmp(var, "color.grep.match")) {
> @@ -163,6 +170,7 @@ void grep_init(struct grep_opt *opt, struct repository *repo, const char *prefix
> opt->pattern_tail = &opt->pattern_list;
> opt->header_tail = &opt->header_list;
>
> + opt->pcre_jit = def->pcre_jit;
> opt->only_matching = def->only_matching;
> opt->color = def->color;
> opt->extended_regexp_option = def->extended_regexp_option;
> @@ -393,7 +401,8 @@ static void compile_pcre1_regexp(struct grep_pat *p, const struct grep_opt *opt)
> die("%s", error);
>
> #ifdef GIT_PCRE1_USE_JIT
> - pcre_config(PCRE_CONFIG_JIT, &p->pcre1_jit_on);
> + if (opt->pcre_jit)
> + pcre_config(PCRE_CONFIG_JIT, &p->pcre1_jit_on);
> #endif
> }
>
> @@ -489,7 +498,9 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
> compile_regexp_failed(p, (const char *)&errbuf);
> }
>
> - pcre2_config(PCRE2_CONFIG_JIT, &p->pcre2_jit_on);
> + if (opt->pcre_jit)
> + pcre2_config(PCRE2_CONFIG_JIT, &p->pcre2_jit_on);
> +
> if (p->pcre2_jit_on) {
> jitret = pcre2_jit_compile(p->pcre2_pattern, PCRE2_JIT_COMPLETE);
> if (jitret)
> diff --git a/grep.h b/grep.h
> index c0c71eb4a9..fff152e606 100644
> --- a/grep.h
> +++ b/grep.h
> @@ -151,6 +151,7 @@ struct grep_opt {
> int allow_textconv;
> int extended;
> int use_reflog_filter;
> + int pcre_jit;
> int pcre1;
> int pcre2;
> int relative;
> --
> 2.22.0
>
>