diff options
| -rw-r--r-- | Makefile | 1 | ||||
| -rw-r--r-- | docs/firmware-design.rst | 23 | ||||
| -rw-r--r-- | include/lib/libc/cdefs.h | 9 | ||||
| -rw-r--r-- | make_helpers/defaults.mk | 4 |
4 files changed, 37 insertions, 0 deletions
@@ -634,6 +634,7 @@ $(eval $(call add_define,PSCI_EXTENDED_STATE_ID)) $(eval $(call add_define,RAS_EXTENSION)) $(eval $(call add_define,RESET_TO_BL31)) $(eval $(call add_define,SEPARATE_CODE_AND_RODATA)) +$(eval $(call add_define,RECLAIM_INIT_CODE)) $(eval $(call add_define,SMCCC_MAJOR_VERSION)) $(eval $(call add_define,SPD_${SPD})) $(eval $(call add_define,SPIN_ON_BL1_EXIT)) diff --git a/docs/firmware-design.rst b/docs/firmware-design.rst index 79bdec98..7cc74855 100644 --- a/docs/firmware-design.rst +++ b/docs/firmware-design.rst @@ -2336,6 +2336,29 @@ implement: SUBSCRIBE_TO_EVENT(foo, foo_handler); + +Reclaiming the BL31 initialization code +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +A significant amount of the code used for the initialization of BL31 is never +needed again after boot time. In order to reduce the runtime memory +footprint, the memory used for this code can be reclaimed after initialization +has finished and be used for runtime data. + +The build option ``RECLAIM_INIT_CODE`` can be set to mark this boot time code +with a ``.text.init.*`` attribute which can be filtered and placed suitably +within the BL image for later reclaimation by the platform. The platform can +specify the fiter and the memory region for this init section in BL31 via the +plat.ld.S linker script. For example, on the FVP, this section is placed +overlapping the secondary CPU stacks so that after the cold boot is done, this +memory can be reclaimed for the stacks. The init memory section is initially +mapped with ``RO``, ``EXECUTE`` attributes. After BL31 initilization has +completed, the FVP changes the attributes of this section to ``RW``, +``EXECUTE_NEVER`` allowing it to be used for runtime data. The memory attributes +are changed within the ``bl31_plat_runtime_setup`` platform hook. The init +section section can be reclaimed for any data which is accessed after cold +boot initialization and it is upto the platform to make the decision. + Performance Measurement Framework --------------------------------- diff --git a/include/lib/libc/cdefs.h b/include/lib/libc/cdefs.h index b1d10ccc..0d007225 100644 --- a/include/lib/libc/cdefs.h +++ b/include/lib/libc/cdefs.h @@ -14,6 +14,15 @@ #define __unused __attribute__((__unused__)) #define __aligned(x) __attribute__((__aligned__(x))) #define __section(x) __attribute__((__section__(x))) +#if RECLAIM_INIT_CODE +/* + * Add each function to a section that is unique so the functions can still + * be garbage collected + */ +#define __init __section(".text.init." __FILE__ "." __XSTRING(__LINE__)) +#else +#define __init +#endif #define __printflike(fmtarg, firstvararg) \ __attribute__((__format__ (__printf__, fmtarg, firstvararg))) diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk index 7df4cd28..435de20e 100644 --- a/make_helpers/defaults.mk +++ b/make_helpers/defaults.mk @@ -146,6 +146,10 @@ SDEI_SUPPORT := 0 # platform Makefile is free to override this value. SEPARATE_CODE_AND_RODATA := 0 +# If the BL31 image initialisation code is recalimed after use for the secondary +# cores stack +RECLAIM_INIT_CODE := 0 + # Default to SMCCC Version 1.X SMCCC_MAJOR_VERSION := 1 |