[RFC] Symbol versioning in libutee.so, the easy part #5833
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To add link flags for a shared library, a makefile variable is used that is called lib-ldflags$(libuuid). That's incorrect because the UUID is not enough to uniquely identify a shared library in the build. For example when both 32-bit and 64-bit user space is generated there are two versions of the shared library with the same UUID. It is not a problem at the moment because lib-ldflags$(libuuid) is used only for one target: ta_arm64, but fix this anyways so that the variable may be used for more complex cases. Signed-off-by: Jerome Forissier <[email protected]>
If a user-space library such as lib/libutee is compiled as a shared library (CFG_ULIBS_SHARED=y) and a file called lib/libutee/libutee.ver exists, then use this file as a version script for the linker. Signed-off-by: Jerome Forissier <[email protected]>
Add the SYMVER_GP131() and SYMVER_COMPAT_GP11() macros to help define
versioned symbols for functions when building shared libraries.
- SYMVER_GP131(foo) associates version GP_1.3.1 to symbol foo and
makes it the default version, that is, the version that is recorded
by the linker when a TA links against the shared library and references
foo. Such a symbol is shown as foo@@GP_1.3.1 by the command:
readelf -W --dyn-syms libname.so
The undefined symbol created in the application by linking against
this entry is displayed as foo@GP_1.3.1.
Symbol foo (unversioned) is removed from the linker output.
- SYMVER_COMPAT_GP11(foo) defines symbol foo with version GP_1.1
and makes it the same as the unversioned symbol __GP11_foo.
Signed-off-by: Jerome Forissier <[email protected]>
Add the required macros and version script to associate version numbers
with TEE API functions when libutee is built as a shared library
(CFG_ULIBS_SHARED=y).
The version script lib/libutee/libutee.ver declares two versions: GP_1.1
and GP_1.3.1. All symbols matching the glob pattern "TEE_[A-Z]*" are
tagged with default version GP_1.1 (TEE_foo@@GP_1.1), unless version
GP_1.3.1 is explicitly assigned in the source code via SYMVER_GP131().
In this case the default version symbol is GP_1.3.1 (TEE_foo@@GP_1.3.1).
All GP1.3.1 function have a compatibility inplementation called __GP11_*()
which is globally visible as an unversioned symbol (otherwise TAs that
use the __OPTEE_CORE_API_COMPAT_1_1 mechanism would not work) and also as
a versioned TEE_foo symbol with non-default version GP_1.1
(TEE_foo@GP_1.1).
The UUID of libutee is reverted to the one it had before the GP 1.3.1
update since the library is now compatible with the old one.
FIXME: THIS CAN NOT WORK until ldelf can resolve versioned symbols.
Test case: xtest 4002. There is an infinite loop as follows:
__utee_entry()
entry_open_session()
init_instance()
get_memtag_implementation
TEE_GetPropertyAsU32()
TEE_CheckMemoryAccessRights()
/*
* That should call 1.3.1 but due to ldelf not knowing
* about versions, __GP11_TEE_CheckMemoryAccessRights()
* is called instead, which is supposed to call
* TEE_CheckMemoryAccessRights() 1.3.1 => infinite loop
*/
Signed-off-by: Jerome Forissier <[email protected]>
| @@ -62,13 +63,17 @@ ifeq ($(CFG_ULIBS_SHARED),y) | |||
| ifeq ($(sm)-$(CFG_TA_BTI),ta_arm64-y) | |||
| lib-ldflags$(lib-shlibfile) += $$(call ld-option,-z force-bti) --fatal-warnings | |||
| endif | |||
| $(lib-shlibfile): $(objs) $(lib-needed-so-files) | |||
| ifneq (,$(wildcard $(lib-verscript))) | |||
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I'm not so sure about the wildcard, that could hide an invalid value in lib-verscript.
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Its purpose is to make the version script optional. $(lib-verscript) is well defined above and only depends on the name of the library, not on any user input. It is for example lib/libutee/libutee.ver or lib/libutils/libutils.ver etc. so it seems pretty natural to use wildcard to obtain the name of the file if it exist or empty otherwise, no?
|
"build: mk/lib.mk: use full path to shared library in flags variable" would make sense upstream by itself. |
Indeed. #5834. |
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This RFC/Draft pull request applies versions
GP_1.1andGP_1.3.1to GP API symbols whenlibuteeis built as a shared object (dynamic library). It cannot work as is, because the dynamic loader (ldelf) lacks support for versioned symbols, see commit description for "[WIP] libutee: add symbol versioning for shared library". Such support has to be introduced first.If anyone feels like working on the dynamic loader part, please feel free to do it and re-use these commits.
More details in https://docs.google.com/document/d/1qvN4WIIcmk3MGWdpdB3-hpg3oOErI7tgYbfGx9VR6FA.