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Issue #12118 has been updated by Yui NARUSE.
Backport changed from 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN to 2.1: REQUIRED, 2.2: REQUIRED, 2.3: REQUIRED
As far as I understand, the fix should be following:
```diff
diff --git a/thread_pthread.c b/thread_pthread.c
index ef43b36..1fdf3f5 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -693,17 +693,31 @@ reserve_stack(volatile char *limit, size_t size)
const volatile char *end = buf + sizeof(buf);
limit += size;
if (limit > end) {
- size = limit - end;
- limit = alloca(size);
- limit[stack_check_margin+size-1] = 0;
+ /* |<-bottom (=limit(a)) top->|
+ * | .. |<-buf 256B |<-end | stack check |
+ * | 256B | =size= | margin (4KB)|
+ * | =size= limit(b)->| 256B | |
+ * | | alloca(sz) | | |
+ * | .. |<-buf |<-limit(c) [sz-1]->0> | |
+ */
+ size_t sz = limit - end;
+ limit = alloca(sz);
+ limit[sz-1] = 0;
}
}
else {
limit -= size;
if (buf > limit) {
- limit = alloca(buf - limit);
- limit[0] = 0; /* ensure alloca is called */
- limit -= stack_check_margin;
+ /* |<-top (=limit(a)) bottom->|
+ * | .. | 256B buf->| | stack check |
+ * | 256B | =size= | margin (4KB)|
+ * | =size= limit(b)->| 256B | |
+ * | | alloca(sz) | | |
+ * | .. | buf->| limit(c)-><0> | |
+ */
+ size_t sz = buf - limit;
+ limit = alloca(sz);
+ limit[0] = 0;
}
}
}
```
----------------------------------------
Bug #12118: ruby2.3: Segfaults on m68k due to improper stack allocation
https://bugs.ruby-lang.org/issues/12118#change-57662
* Author: John Paul Adrian Glaubitz
* Status: Open
* Priority: Normal
* Assignee:
* ruby -v:
* Backport: 2.1: REQUIRED, 2.2: REQUIRED, 2.3: REQUIRED
----------------------------------------
Hello!
On Motorola 680x0, ruby2.2 and ruby2.3 segfault when running the Ruby interpretor:
./miniruby -I./lib -I. -I.ext/common ./tool/runruby.rb --extout=.ext -- --disable-gems -r./m68k-linux-gnu-fake ./tool/rbinstall.rb --make="/usr/bin/make" --dest-dir="/<<PKGBUILDDIR>>/debian/tmp" --extout=".ext" --mflags="-w" --make-flags="w -- DESTDIR=/<<PKGBUILDDIR>>/debian/tmp" --data-mode=0644 --prog-mode=0755 --installed-list .installed.list --mantype="doc"
installing binary commands: /usr/bin
/<<PKGBUILDDIR>>/lib/fileutils.rb:250: [BUG] Segmentation fault at 0x5f583332
ruby 2.3.0p0 (2015-12-25) [m68k-linux-gnu]
This happens while building ruby2.3 on Debian, for example [1].
Andreas Schwab has already investigated into this issue and he came up with the following patch for ruby2.2 [2]:
```diff
Index: ruby-2.2.3/thread_pthread.c
===================================================================
--- ruby-2.2.3.orig/thread_pthread.c
+++ ruby-2.2.3/thread_pthread.c
@@ -678,15 +678,14 @@ reserve_stack(volatile char *limit, size
limit += size;
if (limit > end) {
size = limit - end;
- limit = alloca(size);
+ limit = alloca(stack_check_margin+size);
limit[stack_check_margin+size-1] = 0;
}
}
else {
limit -= size;
if (buf > limit) {
- limit = alloca(buf - limit);
- limit -= stack_check_margin;
+ limit = alloca(buf - limit + stack_check_margin);
limit[0] = 0;
}
}
```
The same patch works fine on ruby2.3, I although I had to modify it so it still applies the same way in ruby2.3.
The bug can be reproduced in a qemu-m68k chroot environment which can be set up quite easily [3].
It would be very important for Debian's Motorola 680x0 port to get this issue fixed.
Thanks,
Adrian
> [1] https://buildd.debian.org/status/fetch.php?pkg=ruby2.3&arch=m68k&ver=2.3.0-2&stamp=1455092994
> [2] https://lists.debian.org/debian-68k/2015/11/msg00057.html
> [3] https://wiki.debian.org/M68k/sbuildQEMU
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