This add relocation of .got entries produced by -fpic. -fpic produces 2-3% smaller code and is faster. Unfortunately gcc promotes -fpic to -fPIC when -mrelocatable is used so one need a very small patch to gcc too(sent upstream).
-fpic puts its GOT entries in .got section(s) and linker defines the symbol _GLOBAL_OFFSET_TABLE_ to point to the middle of this table. The entry at _GLOBAL_OFFSET_TABLE_-4 contains a blrl insn which is used to find the table's real address by branching to _GLOBAL_OFFSET_TABLE_-4.
Here are some size examples for my board: size with -fPIC text data bss dec hex filename 224687 14400 24228 263315 40493 u-boot
size with -mbss-plt -fPIC text data bss dec hex filename 222687 14400 24228 261315 3fcc3 u-boot
size with -mbss-plt -fpic text data bss dec hex filename 225179 6580 24228 255987 3e7f3 u-boot
size with -mbss-plt -fpic -msingle-pic-base text data bss dec hex filename 222091 6580 24228 252899 3dbe3 u-boot
Note: -msingle-pic-base is not supported upstarem yet.
Signed-off-by: Joakim Tjernlund Joakim.Tjernlund@transmode.se --- v2: Better commit msg Fix linker script for two NAND boards. Only compile the new -fpic code if compiled with -fpic to reduce size.
arch/powerpc/cpu/mpc83xx/start.S | 31 +++++++++++++++++++++- arch/powerpc/cpu/mpc83xx/u-boot.lds | 1 + nand_spl/board/freescale/mpc8313erdb/u-boot.lds | 2 + nand_spl/board/freescale/mpc8315erdb/u-boot.lds | 2 + 4 files changed, 34 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/cpu/mpc83xx/start.S b/arch/powerpc/cpu/mpc83xx/start.S index c7d85a8..8b540bc 100644 --- a/arch/powerpc/cpu/mpc83xx/start.S +++ b/arch/powerpc/cpu/mpc83xx/start.S @@ -69,6 +69,10 @@ */ START_GOT GOT_ENTRY(_GOT2_TABLE_) +#if defined(__pic__) && __pic__ == 1 + GOT_ENTRY(_GOT_TABLE_) + GOT_ENTRY(_GLOBAL_OFFSET_TABLE_) +#endif GOT_ENTRY(__bss_start) GOT_ENTRY(_end)
@@ -296,7 +300,11 @@ in_flash: /*------------------------------------------------------*/
GET_GOT /* initialize GOT access */ - +#if defined(__pic__) && __pic__ == 1 + /* Needed for upcoming -msingle-pic-base */ + bl _GLOBAL_OFFSET_TABLE_@local-4 + mflr r30 +#endif /* r3: IMMR */ lis r3, CONFIG_SYS_IMMR@h /* run low-level CPU init code (in Flash)*/ @@ -950,7 +958,26 @@ in_ram: add r0,r0,r11 stw r0,0(r3) 2: bdnz 1b - +#if defined(__pic__) && __pic__ == 1 + /* + * Relocation of *.got(-fpic) + */ + lwz r4,GOT(_GLOBAL_OFFSET_TABLE_) + addi r4,r4,-4 /* don't write over blrl in GOT */ + lwz r3,GOT(_GOT_TABLE_) + subf. r4,r3,r4 /* r4 - r3 */ + ble 3f + srwi r4,r4,2 /* r4/4 */ + mtctr r4 + addi r3,r3,-4 +1: lwzu r0,4(r3) + cmpwi r0,0 + beq- 2f + add r0,r0,r11 + stw r0,0(r3) +2: bdnz 1b +3: +#endif #ifndef CONFIG_NAND_SPL /* * Now adjust the fixups and the pointers to the fixups diff --git a/arch/powerpc/cpu/mpc83xx/u-boot.lds b/arch/powerpc/cpu/mpc83xx/u-boot.lds index 0b74a13..a498a37 100644 --- a/arch/powerpc/cpu/mpc83xx/u-boot.lds +++ b/arch/powerpc/cpu/mpc83xx/u-boot.lds @@ -67,6 +67,7 @@ SECTIONS PROVIDE (erotext = .); .reloc : { + _GOT_TABLE_ = .; *(.got) _GOT2_TABLE_ = .; *(.got2) diff --git a/nand_spl/board/freescale/mpc8313erdb/u-boot.lds b/nand_spl/board/freescale/mpc8313erdb/u-boot.lds index ad82589..1a3e44f 100644 --- a/nand_spl/board/freescale/mpc8313erdb/u-boot.lds +++ b/nand_spl/board/freescale/mpc8313erdb/u-boot.lds @@ -38,6 +38,8 @@ SECTIONS .data : { *(.data*) *(.sdata*) + _GOT_TABLE_ = .; + *(.got) _GOT2_TABLE_ = .; *(.got2) __got2_entries = (. - _GOT2_TABLE_) >> 2; diff --git a/nand_spl/board/freescale/mpc8315erdb/u-boot.lds b/nand_spl/board/freescale/mpc8315erdb/u-boot.lds index ad82589..1a3e44f 100644 --- a/nand_spl/board/freescale/mpc8315erdb/u-boot.lds +++ b/nand_spl/board/freescale/mpc8315erdb/u-boot.lds @@ -38,6 +38,8 @@ SECTIONS .data : { *(.data*) *(.sdata*) + _GOT_TABLE_ = .; + *(.got) _GOT2_TABLE_ = .; *(.got2) __got2_entries = (. - _GOT2_TABLE_) >> 2;