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Re: glibc 2.19 - asyn-signal safe TLS and ASan.
- From: Siddhesh Poyarekar <siddhesh at redhat dot com>
- To: Andrew Hunter <ahh at google dot com>
- Cc: Kostya Serebryany <kcc at google dot com>, "Carlos O'Donell" <carlos at redhat dot com>, GNU C Library <libc-alpha at sourceware dot org>, Roland McGrath <roland at hack dot frob dot com>, Paul Pluzhnikov <ppluzhnikov at google dot com>, address-sanitizer at googlegroups dot com
- Date: Fri, 24 Jan 2014 13:29:13 +0530
- Subject: Re: glibc 2.19 - asyn-signal safe TLS and ASan.
- Authentication-results: sourceware.org; auth=none
- References: <52D0BCED dot 3000109 at redhat dot com> <52DDBF0E dot 8010501 at redhat dot com> <CAN=P9piS3Xczq2AKrzh4rsK9JxiHtJXawcQs9_+xsYXxrbLQWQ at mail dot gmail dot com> <CADroS=6vODmWCdBsynOf7oM9uVDymwdxrSDFbmD6kT5P9gbBRw at mail dot gmail dot com> <20140124061622 dot GY5544 at spoyarek dot pnq dot redhat dot com>
On Fri, Jan 24, 2014 at 11:46:22AM +0530, Siddhesh Poyarekar wrote:
> On Thu, Jan 23, 2014 at 01:59:08PM -0800, Andrew Hunter wrote:
> > FYI -- you could easily do the same thing with calls to
> > signal_safe_memalign from libc as a stopgap. (Well, we'd need to
> > export the symbols from libc, like I wanted to in the first place.)
>
> Or we could just add a thread-local flag that malloc looks at and if
> set, short-circuits its way to mmap and have signal_safe_malloc use
> it:
Jakub pointed out to me offline that this won't work when applications
override malloc. The alternate malloc may not necessarily be
async-signal safe and we'll have the same problem all over again.
Siddhesh