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author | Jake Zimmerman <zimmerman.jake@gmail.com> | 2020-07-10 12:05:34 -0700 |
---|---|---|
committer | Nobuyoshi Nakada <nobu@ruby-lang.org> | 2020-07-22 20:46:36 +0900 |
commit | 8b0dc77a621ded75f72486c33f55404ce73f00d7 (patch) | |
tree | dd0eaa4393b3128fb65efeaeb897926a525bdfa4 /configure.ac | |
parent | 7befc0cdfcf972023842eca5836fe4709ec2ad46 (diff) |
configure.ac: Bump the size of sigaltstack
The RubyVM uses C macro defines to feature detect whether
`backtrace(2)` support is available, and if so it includes C level backtraces
when the RubyVM itself crashes.
But on my machine, C level backtraces from `vm_dump.c` didn't work when
using a version of Ruby buillt on the machine, but worked fine when using a
version of Ruby built on another machine and copied to my machine.
The default autoconf test for backtraces uses a sigaltstack size that is
too small, so the SIGSEGV signal handler itself causes a SIGSEGV).
I noticed that signal.c uses a larger sigaltstack size:
https://github.com/ruby/ruby/blob/v2_6_5/signal.c#L568
The specific variables it looks at:
- `HAVE_BACKTRACE`
this is a macro defined by autoconf because there is a line in the
configure script like `AC_CHECK_FUNCS(backtrace)` (see the autoconf
docs for more).
- `BROKEN_BACKTRACE`
this comes from a custom program that Ruby's configure script runs to
attempt to figure out whether actually using backtrace(2) in a real
program works. You can see the autoconf program here.
<https://github.com/ruby/ruby/blob/v2_6_5/configure.ac#L2817-L2863>
It uses sigaltstack and SA_ONSTACK to create a seperate stack for
handling signals.
The problem was: SIGSTKSZ (which comes from a system header!) was not
suggesting a large enough stack size. When checking on an Ubuntu 16.04
box, we found that SIGSTKSZ was 8192 and MINSIGSTKSZ was 2048.
Notes
Notes:
Merged: https://github.com/ruby/ruby/pull/3307
Diffstat (limited to 'configure.ac')
-rw-r--r-- | configure.ac | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/configure.ac b/configure.ac index dc4ab53caa..ae908f7516 100644 --- a/configure.ac +++ b/configure.ac @@ -2948,12 +2948,12 @@ main(void) stack_t ss; struct sigaction sa; - ss.ss_sp = malloc(SIGSTKSZ); + ss.ss_sp = malloc(16*1024); if (ss.ss_sp == NULL) { fprintf(stderr, "cannot allocate memory for sigaltstack\n"); return EXIT_FAILURE; } - ss.ss_size = SIGSTKSZ; + ss.ss_size = 16*1024; ss.ss_flags = 0; if (sigaltstack(&ss, NULL) == -1) { fprintf(stderr, "sigaltstack failed\n"); |