[sanitizer] Handle TLS sizes for glibc < 2.13

[Kostya Serebryany]

On Mon, Feb 3, 2014 at 2:24 PM, Jakub Jelinek <jakub at redhat.com> wrote:
> As discussed in http://gcc.gnu.org/PR60038, the hardcoded sizeof(struct thread)
> values are incorrect for glibc older than 2.13.  The following patch
> provides values for older glibcs (for newer glibcs hopefully some new API
> will be provided by glibc).
>
> --- lib/sanitizer_common/sanitizer_linux_libcdep.cc.jj  2014-02-03 11:19:51.425383965 +0100
> +++ lib/sanitizer_common/sanitizer_linux_libcdep.cc     2014-02-03 11:20:03.846319794 +0100
> @@ -21,6 +21,7 @@
>  #include "sanitizer_placement_new.h"
>  #include "sanitizer_procmaps.h"
>  #include "sanitizer_stacktrace.h"
> +#include "sanitizer_atomic.h"
>
>  #include <dlfcn.h>
>  #include <pthread.h>
> @@ -32,6 +33,7 @@
>  #if !SANITIZER_ANDROID
>  #include <elf.h>
>  #include <link.h>
> +#include <unistd.h>
>  #endif
>
>  #ifndef SANITIZER_GO
> @@ -227,16 +229,41 @@ uptr GetTlsSize() {
>
>  #if defined(__x86_64__) || defined(__i386__)
>  // sizeof(struct thread) from glibc.
> -// There has been a report of this being different on glibc 2.11 and 2.13. We
> -// don't know when this change happened, so 2.14 is a conservative estimate.
> -#if __GLIBC_PREREQ(2, 14)
> -const uptr kThreadDescriptorSize = FIRST_32_SECOND_64(1216, 2304);
> -#else
> -const uptr kThreadDescriptorSize = FIRST_32_SECOND_64(1168, 2304);
> -#endif
> +static atomic_uintptr_t kThreadDescriptorSize;
>
>  uptr ThreadDescriptorSize() {
> -  return kThreadDescriptorSize;
> +  char buf[64];
> +  uptr val = atomic_load(&kThreadDescriptorSize, memory_order_acquire);

memory_order_relaxed should be enough here and below.
otherwise the patch looks great, thank you!
I'll commit it first thing tomorrow.

--kcc


> +  if (val)
> +    return val;
> +#ifdef _CS_GNU_LIBC_VERSION
> +  uptr len = confstr(_CS_GNU_LIBC_VERSION, buf, sizeof(buf));
> +  if (len < sizeof(buf) && internal_strncmp(buf, "glibc 2.", 8) == 0) {
> +    char *end;
> +    int minor = internal_simple_strtoll(buf + 8, &end, 10);
> +    if (end != buf + 8 && (*end == '\0' || *end == '.')) {
> +      /* sizeof(struct thread) values from various glibc versions.  */
> +      if (minor <= 3)
> +        val = FIRST_32_SECOND_64(1104, 1696);
> +      else if (minor == 4)
> +        val = FIRST_32_SECOND_64(1120, 1728);
> +      else if (minor == 5)
> +        val = FIRST_32_SECOND_64(1136, 1728);
> +      else if (minor <= 9)
> +        val = FIRST_32_SECOND_64(1136, 1712);
> +      else if (minor == 10)
> +        val = FIRST_32_SECOND_64(1168, 1776);
> +      else if (minor <= 12)
> +        val = FIRST_32_SECOND_64(1168, 2288);
> +      else
> +        val = FIRST_32_SECOND_64(1216, 2304);
> +    }
> +    if (val)
> +      atomic_store(&kThreadDescriptorSize, val, memory_order_release);
> +    return val;
> +  }
> +#endif
> +  return 0;
>  }
>
>  // The offset at which pointer to self is located in the thread descriptor.
> @@ -264,7 +291,7 @@ void GetThreadStackAndTls(bool main, upt
>    *tls_addr = ThreadSelf();
>    *tls_size = GetTlsSize();
>    *tls_addr -= *tls_size;
> -  *tls_addr += kThreadDescriptorSize;
> +  *tls_addr += ThreadDescriptorSize();
>  #else
>    *tls_addr = 0;
>    *tls_size = 0;
>
>         Jakub
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