| Message ID | 1287004319-21282-1-git-send-email-Joakim.Tjernlund@transmode.se |
|---|---|
| State | RFC |
| Headers | show |
> From: Joakim Tjernlund <Joakim.Tjernlund@transmode.se> > To: u-boot@lists.denx.de, Scott Wood <scottwood@freescale.com>, Kim Phillips > <kim.phillips@freescale.com> > Cc: Joakim Tjernlund <Joakim.Tjernlund@transmode.se> > Date: 2010/10/13 23:12 > Subject: [U-Boot] [PATCHv3] mpc83xx: Add -fpic relocation support > Sent by: u-boot-bounces@lists.denx.de > > This adds 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. Ping? Jocke
> From: Joakim Tjernlund <joakim.tjernlund@transmode.se> > > > From: Joakim Tjernlund <Joakim.Tjernlund@transmode.se> > > To: u-boot@lists.denx.de, Scott Wood <scottwood@freescale.com>, Kim > Phillips > > <kim.phillips@freescale.com> > > Cc: Joakim Tjernlund <Joakim.Tjernlund@transmode.se> > > Date: 2010/10/13 23:12 > > Subject: [U-Boot] [PATCHv3] mpc83xx: Add -fpic relocation support > > Sent by: u-boot-bounces@lists.denx.de > > > > This adds 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. > > Ping? Ping ping :) I should mention that this work tougher with -msingle-pic-base paves the way for true PIC with minimal changes to C source code.
diff --git a/arch/powerpc/cpu/mpc83xx/start.S b/arch/powerpc/cpu/mpc83xx/start.S index c7d85a8..c9bb0ea 100644 --- a/arch/powerpc/cpu/mpc83xx/start.S +++ b/arch/powerpc/cpu/mpc83xx/start.S @@ -296,7 +296,11 @@ 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 +954,25 @@ in_ram: add r0,r0,r11 stw r0,0(r3) 2: bdnz 1b - +#if defined(__pic__) && __pic__ == 1 + /* + * Relocation of *.got(-fpic) + * + * Adjust got pointers, no need to check for 0, this code + * already puts one entry in the table. + */ + li r0,__got_entries@sectoff@l + lwz r3,_GOT_TABLE_@got(r30) + add r3,r3,r11 + mtctr r0 + 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 +#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..8b189d9 100644 --- a/arch/powerpc/cpu/mpc83xx/u-boot.lds +++ b/arch/powerpc/cpu/mpc83xx/u-boot.lds @@ -67,12 +67,15 @@ SECTIONS PROVIDE (erotext = .); .reloc : { + _GOT_TABLE_ = .; + PROVIDE(_GLOBAL_OFFSET_TABLE_ = . + 4); *(.got) _GOT2_TABLE_ = .; *(.got2) _FIXUP_TABLE_ = .; *(.fixup) } + __got_entries = ((_GLOBAL_OFFSET_TABLE_ - _GOT_TABLE_) >> 2)-1; __got2_entries = (_FIXUP_TABLE_ - _GOT2_TABLE_) >> 2; __fixup_entries = (. - _FIXUP_TABLE_) >> 2; diff --git a/nand_spl/board/freescale/mpc8313erdb/u-boot.lds b/nand_spl/board/freescale/mpc8313erdb/u-boot.lds index ad82589..a3cacf6 100644 --- a/nand_spl/board/freescale/mpc8313erdb/u-boot.lds +++ b/nand_spl/board/freescale/mpc8313erdb/u-boot.lds @@ -38,11 +38,14 @@ SECTIONS .data : { *(.data*) *(.sdata*) + _GOT_TABLE_ = .; + PROVIDE(_GLOBAL_OFFSET_TABLE_ = . + 4); + *(.got) _GOT2_TABLE_ = .; *(.got2) - __got2_entries = (. - _GOT2_TABLE_) >> 2; } - + __got_entries = ((_GLOBAL_OFFSET_TABLE_ - _GOT_TABLE_) >> 2)-1; + __got2_entries = (. - _GOT2_TABLE_) >> 2; . = ALIGN(8); __bss_start = .; .bss (NOLOAD) : { *(.*bss) } diff --git a/nand_spl/board/freescale/mpc8315erdb/u-boot.lds b/nand_spl/board/freescale/mpc8315erdb/u-boot.lds index ad82589..a3cacf6 100644 --- a/nand_spl/board/freescale/mpc8315erdb/u-boot.lds +++ b/nand_spl/board/freescale/mpc8315erdb/u-boot.lds @@ -38,11 +38,14 @@ SECTIONS .data : { *(.data*) *(.sdata*) + _GOT_TABLE_ = .; + PROVIDE(_GLOBAL_OFFSET_TABLE_ = . + 4); + *(.got) _GOT2_TABLE_ = .; *(.got2) - __got2_entries = (. - _GOT2_TABLE_) >> 2; } - + __got_entries = ((_GLOBAL_OFFSET_TABLE_ - _GOT_TABLE_) >> 2)-1; + __got2_entries = (. - _GOT2_TABLE_) >> 2; . = ALIGN(8); __bss_start = .; .bss (NOLOAD) : { *(.*bss) }
This adds 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 upstream yet. Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se> --- v3: - Make the new -fpic code to have zero impact when not compled with -fpic - linker __got*_entries sysm needs to be defined outside the referenced scope. Add linker sym __got_entries for -fpic relocs. Very likely more *lds scripts needs fixing but that is somebody elses problem :) - NAND SPL still don't fit for MPC8315ERDB and SIMPC8313 but these didn't fit before either. Note that my tree isn't current so it migth be fixed in master. arch/powerpc/cpu/mpc83xx/start.S | 26 +++++++++++++++++++++- arch/powerpc/cpu/mpc83xx/u-boot.lds | 3 ++ nand_spl/board/freescale/mpc8313erdb/u-boot.lds | 7 ++++- nand_spl/board/freescale/mpc8315erdb/u-boot.lds | 7 ++++- 4 files changed, 37 insertions(+), 6 deletions(-)