[v3] manual, NEWS: Document malloc side effect of dynamic TLS changes
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Commit Message
The increased malloc subsystem usage is a side effect of
commit d2123d68275acc0f061e73d5f86ca504e0d5a344 ("elf: Fix slow tls
access after dlopen [BZ #19924]").
---
v3: Wording changes suggested by Szabolcs.
NEWS | 6 ++++++
manual/memory.texi | 8 ++++++++
2 files changed, 14 insertions(+)
base-commit: 49b668324d12fde8ed42ceecee28f11b4e49b9b0
Comments
The 01/22/2024 16:30, Florian Weimer wrote:
> The increased malloc subsystem usage is a side effect of
> commit d2123d68275acc0f061e73d5f86ca504e0d5a344 ("elf: Fix slow tls
> access after dlopen [BZ #19924]").
looks good.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
>
> ---
> v3: Wording changes suggested by Szabolcs.
>
> NEWS | 6 ++++++
> manual/memory.texi | 8 ++++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/NEWS b/NEWS
> index 1da3a6e6ee..6fff3fe6fa 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -80,6 +80,12 @@ Deprecated and removed features, and other changes affecting compatibility:
> of GNU libc are advised to check whether their build processes can be
> simplified.
>
> +* The dynamic linker calls the malloc and free functions in more cases
> + during TLS access if a shared object with dynamic TLS is loaded and
> + unloaded. This can result in an infinite recursion if a malloc
> + replacement library or its dependencies use dynamic TLS instead of
> + initial-exec TLS.
> +
> * The ia64*-*-linux-gnu configurations are no longer supported.
>
> Changes to build and runtime requirements:
> diff --git a/manual/memory.texi b/manual/memory.texi
> index 258fdbd3a0..fb875f4c3c 100644
> --- a/manual/memory.texi
> +++ b/manual/memory.texi
> @@ -1815,6 +1815,14 @@ using shared object dependencies or @code{LD_PRELOAD}. For static
> linking, the @code{malloc} replacement library must be linked in before
> linking against @code{libc.a} (explicitly or implicitly).
>
> +Care must be taken not to use functionality from @theglibc{} that uses
> +@code{malloc} internally. For example, the @code{fopen},
> +@code{opendir}, @code{dlopen}, and @code{pthread_setspecific} functions
> +currently use the @code{malloc} subsystem internally. If the
> +replacement @code{malloc} or its dependencies use thread-local storage
> +(TLS), it must use the initial-exec TLS model, and not one of the
> +dynamic TLS variants.
> +
> @strong{Note:} Failure to provide a complete set of replacement
> functions (that is, all the functions used by the application,
> @theglibc{}, and other linked-in libraries) can lead to static linking
>
> base-commit: 49b668324d12fde8ed42ceecee28f11b4e49b9b0
>
@@ -80,6 +80,12 @@ Deprecated and removed features, and other changes affecting compatibility:
of GNU libc are advised to check whether their build processes can be
simplified.
+* The dynamic linker calls the malloc and free functions in more cases
+ during TLS access if a shared object with dynamic TLS is loaded and
+ unloaded. This can result in an infinite recursion if a malloc
+ replacement library or its dependencies use dynamic TLS instead of
+ initial-exec TLS.
+
* The ia64*-*-linux-gnu configurations are no longer supported.
Changes to build and runtime requirements:
@@ -1815,6 +1815,14 @@ using shared object dependencies or @code{LD_PRELOAD}. For static
linking, the @code{malloc} replacement library must be linked in before
linking against @code{libc.a} (explicitly or implicitly).
+Care must be taken not to use functionality from @theglibc{} that uses
+@code{malloc} internally. For example, the @code{fopen},
+@code{opendir}, @code{dlopen}, and @code{pthread_setspecific} functions
+currently use the @code{malloc} subsystem internally. If the
+replacement @code{malloc} or its dependencies use thread-local storage
+(TLS), it must use the initial-exec TLS model, and not one of the
+dynamic TLS variants.
+
@strong{Note:} Failure to provide a complete set of replacement
functions (that is, all the functions used by the application,
@theglibc{}, and other linked-in libraries) can lead to static linking