[U-Boot-Users] [PATCH] PPC: Use r2 instead of r29 as global data pointer
R29 was an unlucky choice as with recent toolchains (gcc-4.2.x) gcc will refuse to use load/store multiple insns; instead, it issues a list of simple load/store instructions upon function entry and exit, resulting in bigger code size, which in turn makes the build for a few boards fail.
Use r2 instead.
Signed-off-by: Wolfgang Denk wd@denx.de --- README | 4 ++-- cpu/74xx_7xx/config.mk | 2 +- cpu/mpc512x/config.mk | 2 +- cpu/mpc5xx/config.mk | 2 +- cpu/mpc5xxx/config.mk | 2 +- cpu/mpc8220/config.mk | 2 +- cpu/mpc824x/config.mk | 2 +- cpu/mpc8260/config.mk | 2 +- cpu/mpc83xx/config.mk | 2 +- cpu/mpc85xx/config.mk | 3 ++- cpu/mpc86xx/config.mk | 2 +- cpu/mpc86xx/start.S | 2 +- cpu/mpc8xx/config.mk | 2 +- cpu/ppc4xx/config.mk | 2 +- doc/README.standalone | 2 +- examples/stubs.c | 4 ++-- examples/test_burst_lib.S | 2 +- examples/x86-testapp.c | 6 +++--- include/asm-ppc/global_data.h | 2 +- 19 files changed, 24 insertions(+), 23 deletions(-)
diff --git a/README b/README index a5ffbb5..b4966a0 100644 --- a/README +++ b/README @@ -3499,7 +3499,7 @@ GCC's implementation.
For PowerPC, the following registers have specific use: R1: stack pointer - R2: TOC pointer + R2: reserved for system use R3-R4: parameter passing and return values R5-R10: parameter passing R13: small data area pointer @@ -3508,7 +3508,7 @@ For PowerPC, the following registers have specific use:
(U-Boot also uses R14 as internal GOT pointer.)
- ==> U-Boot will use R29 to hold a pointer to the global data + ==> U-Boot will use R2 to hold a pointer to the global data
Note: on PPC, we could use a static initializer (since the address of the global data structure is known at compile time), diff --git a/cpu/74xx_7xx/config.mk b/cpu/74xx_7xx/config.mk index 417d99f..324f62b 100644 --- a/cpu/74xx_7xx/config.mk +++ b/cpu/74xx_7xx/config.mk @@ -23,4 +23,4 @@
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi -fno-strict-aliasing
-PLATFORM_CPPFLAGS += -DCONFIG_74xx_7xx -ffixed-r2 -ffixed-r29 -mstring +PLATFORM_CPPFLAGS += -DCONFIG_74xx_7xx -ffixed-r2 -mstring diff --git a/cpu/mpc512x/config.mk b/cpu/mpc512x/config.mk index 8a07c5a..5b7e1f2 100644 --- a/cpu/mpc512x/config.mk +++ b/cpu/mpc512x/config.mk @@ -22,4 +22,4 @@ PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
PLATFORM_CPPFLAGS += -DCONFIG_MPC512X -DCONFIG_E300 \ - -ffixed-r2 -ffixed-r29 -msoft-float -mcpu=603e + -ffixed-r2 -msoft-float -mcpu=603e diff --git a/cpu/mpc5xx/config.mk b/cpu/mpc5xx/config.mk index 64cd600..6d66c32 100644 --- a/cpu/mpc5xx/config.mk +++ b/cpu/mpc5xx/config.mk @@ -30,7 +30,7 @@
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
-PLATFORM_CPPFLAGS += -DCONFIG_5xx -ffixed-r2 -ffixed-r29 -mpowerpc -msoft-float +PLATFORM_CPPFLAGS += -DCONFIG_5xx -ffixed-r2 -mpowerpc -msoft-float
# Use default linker script. Board port can override in board/*/config.mk LDSCRIPT := $(SRCTREE)/cpu/mpc5xx/u-boot.lds diff --git a/cpu/mpc5xxx/config.mk b/cpu/mpc5xxx/config.mk index 0df51ba..b0ce2ee 100644 --- a/cpu/mpc5xxx/config.mk +++ b/cpu/mpc5xxx/config.mk @@ -23,7 +23,7 @@
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
-PLATFORM_CPPFLAGS += -DCONFIG_MPC5xxx -ffixed-r2 -ffixed-r29 \ +PLATFORM_CPPFLAGS += -DCONFIG_MPC5xxx -ffixed-r2 \ -mstring -mcpu=603e -mmultiple
# Use default linker script. Board port can override in board/*/config.mk diff --git a/cpu/mpc8220/config.mk b/cpu/mpc8220/config.mk index 8e3ba54..5819048 100644 --- a/cpu/mpc8220/config.mk +++ b/cpu/mpc8220/config.mk @@ -23,7 +23,7 @@
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
-PLATFORM_CPPFLAGS += -DCONFIG_MPC8220 -ffixed-r2 -ffixed-r29 \ +PLATFORM_CPPFLAGS += -DCONFIG_MPC8220 -ffixed-r2 \ -mstring -mcpu=603e -mmultiple
# Use default linker script. Board port can override in board/*/config.mk diff --git a/cpu/mpc824x/config.mk b/cpu/mpc824x/config.mk index 66207f4..1bb0487 100644 --- a/cpu/mpc824x/config.mk +++ b/cpu/mpc824x/config.mk @@ -23,7 +23,7 @@
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi -fno-strict-aliasing
-PLATFORM_CPPFLAGS += -DCONFIG_MPC824X -ffixed-r2 -ffixed-r29 -mstring -mcpu=603e -msoft-float +PLATFORM_CPPFLAGS += -DCONFIG_MPC824X -ffixed-r2 -mstring -mcpu=603e -msoft-float
# Use default linker script. Board port can override in board/*/config.mk LDSCRIPT := $(SRCTREE)/cpu/mpc824x/u-boot.lds diff --git a/cpu/mpc8260/config.mk b/cpu/mpc8260/config.mk index 683b6fb..2cb0270 100644 --- a/cpu/mpc8260/config.mk +++ b/cpu/mpc8260/config.mk @@ -23,7 +23,7 @@
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
-PLATFORM_CPPFLAGS += -DCONFIG_8260 -DCONFIG_CPM2 -ffixed-r2 -ffixed-r29 \ +PLATFORM_CPPFLAGS += -DCONFIG_8260 -DCONFIG_CPM2 -ffixed-r2 \ -mstring -mcpu=603e -mmultiple
# Use default linker script. Board port can override in board/*/config.mk diff --git a/cpu/mpc83xx/config.mk b/cpu/mpc83xx/config.mk index ecf8a60..2f0f1ce 100644 --- a/cpu/mpc83xx/config.mk +++ b/cpu/mpc83xx/config.mk @@ -23,7 +23,7 @@ PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
PLATFORM_CPPFLAGS += -DCONFIG_MPC83XX -DCONFIG_E300 \ - -ffixed-r2 -ffixed-r29 -msoft-float + -ffixed-r2 -msoft-float
# Use default linker script. Board port can override in board/*/config.mk LDSCRIPT := $(SRCTREE)/cpu/mpc83xx/u-boot.lds diff --git a/cpu/mpc85xx/config.mk b/cpu/mpc85xx/config.mk index 6121074..f6df702 100644 --- a/cpu/mpc85xx/config.mk +++ b/cpu/mpc85xx/config.mk @@ -23,4 +23,5 @@
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
-PLATFORM_CPPFLAGS += -DCONFIG_MPC85xx -DCONFIG_E500 -ffixed-r2 -ffixed-r29 -Wa,-me500 -msoft-float -mno-string +PLATFORM_CPPFLAGS += -DCONFIG_MPC85xx -DCONFIG_E500 -ffixed-r2 \ + -Wa,-me500 -msoft-float -mno-string diff --git a/cpu/mpc86xx/config.mk b/cpu/mpc86xx/config.mk index 3c54f4a..d767269 100644 --- a/cpu/mpc86xx/config.mk +++ b/cpu/mpc86xx/config.mk @@ -23,4 +23,4 @@
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
-PLATFORM_CPPFLAGS += -DCONFIG_MPC86xx -ffixed-r2 -ffixed-r29 -mstring +PLATFORM_CPPFLAGS += -DCONFIG_MPC86xx -ffixed-r2 -mstring diff --git a/cpu/mpc86xx/start.S b/cpu/mpc86xx/start.S index fa9736b..09f4cee 100644 --- a/cpu/mpc86xx/start.S +++ b/cpu/mpc86xx/start.S @@ -723,7 +723,7 @@ relocate_code:
mr r1, r3 /* Set new stack pointer */ mr r9, r4 /* Save copy of Global Data pointer */ - mr r29, r9 /* Save for DECLARE_GLOBAL_DATA_PTR */ + mr r2, r9 /* Save for DECLARE_GLOBAL_DATA_PTR */ mr r10, r5 /* Save copy of Destination Address */
mr r3, r5 /* Destination Address */ diff --git a/cpu/mpc8xx/config.mk b/cpu/mpc8xx/config.mk index bfa6625..6031e7f 100644 --- a/cpu/mpc8xx/config.mk +++ b/cpu/mpc8xx/config.mk @@ -23,4 +23,4 @@
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi -fno-strict-aliasing
-PLATFORM_CPPFLAGS += -DCONFIG_8xx -ffixed-r2 -ffixed-r29 -mstring -mcpu=860 -msoft-float +PLATFORM_CPPFLAGS += -DCONFIG_8xx -ffixed-r2 -mstring -mcpu=860 -msoft-float diff --git a/cpu/ppc4xx/config.mk b/cpu/ppc4xx/config.mk index 4fd5108..311c97b 100644 --- a/cpu/ppc4xx/config.mk +++ b/cpu/ppc4xx/config.mk @@ -22,7 +22,7 @@ #
PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi -fno-strict-aliasing -PLATFORM_CPPFLAGS += -DCONFIG_4xx -ffixed-r2 -ffixed-r29 -mstring -msoft-float +PLATFORM_CPPFLAGS += -DCONFIG_4xx -ffixed-r2 -mstring -msoft-float
cfg=$(shell grep configs $(OBJTREE)/include/config.h | sed 's/.*<(configs.*)>/\1/') is440=$(shell grep CONFIG_440 $(TOPDIR)/include/$(cfg)) diff --git a/doc/README.standalone b/doc/README.standalone index 3998831..f9237a6 100644 --- a/doc/README.standalone +++ b/doc/README.standalone @@ -21,7 +21,7 @@ Design Notes on Exporting U-Boot Functions to Standalone Applications: 2. The pointer to the jump table is passed to the application in a machine-dependent way. PowerPC, ARM and MIPS architectures use a dedicated register to hold the pointer to the 'global_data' - structure: r29 on PowerPC, r8 on ARM and k0 on MIPS. The x86 + structure: r2 on PowerPC, r8 on ARM and k0 on MIPS. The x86 architecture does not use such a register; instead, the pointer to the 'global_data' structure is passed as 'argv[-1]' pointer.
diff --git a/examples/stubs.c b/examples/stubs.c index 571c4d5..9b3cadd 100644 --- a/examples/stubs.c +++ b/examples/stubs.c @@ -25,14 +25,14 @@ gd_t *global_data; : : "i"(XF_ ## x * sizeof(void *)) : "eax", "ecx"); #elif defined(CONFIG_PPC) /* - * r29 holds the pointer to the global_data, r11 is a call-clobbered + * r2 holds the pointer to the global_data, r11 is a call-clobbered * register */ #define EXPORT_FUNC(x) \ asm volatile ( \ " .globl " #x "\n" \ #x ":\n" \ -" lwz %%r11, %0(%%r29)\n" \ +" lwz %%r11, %0(%%r2)\n" \ " lwz %%r11, %1(%%r11)\n" \ " mtctr %%r11\n" \ " bctr\n" \ diff --git a/examples/test_burst_lib.S b/examples/test_burst_lib.S index 5bb4981..aef4e32 100644 --- a/examples/test_burst_lib.S +++ b/examples/test_burst_lib.S @@ -70,7 +70,7 @@ mmu_init: * we can load the instruction and data TLB registers with the * same values. */ - lwz r9,20(r29) /* gd->ram_size */ + lwz r9,20(r2) /* gd->ram_size */ addis r9,r9,-0x80
mr r8, r9 /* Higher 8 Meg in SDRAM */ diff --git a/examples/x86-testapp.c b/examples/x86-testapp.c index a1ab319..e8603d9 100644 --- a/examples/x86-testapp.c +++ b/examples/x86-testapp.c @@ -30,11 +30,11 @@ asm volatile ( \ asm volatile ( \ " .globl mon_" #x "\n" \ "mon_" #x ":\n" \ -" lwz %%r11, %0(%%r29)\n" \ +" lwz %%r11, %0(%%r2)\n" \ " lwz %%r11, %1(%%r11)\n" \ " mtctr %%r11\n" \ " bctr\n" \ - : : "i"(offsetof(xxx_t, pfunc)), "i"(XF_ ## x * sizeof(void *)) : "r11", "r29"); + : : "i"(offsetof(xxx_t, pfunc)), "i"(XF_ ## x * sizeof(void *)) : "r11", "r2"); #elif defined(__arm__) #define EXPORT_FUNC(x) \ asm volatile ( \ @@ -67,7 +67,7 @@ int main(void) #if defined(__i386__) xxx_t *pq; #elif defined(__powerpc__) - register volatile xxx_t *pq asm("r29"); + register volatile xxx_t *pq asm("r2"); #elif defined(__arm__) register volatile xxx_t *pq asm("r8"); #elif defined(__mips__) diff --git a/include/asm-ppc/global_data.h b/include/asm-ppc/global_data.h index aa6384c..bacd02d 100644 --- a/include/asm-ppc/global_data.h +++ b/include/asm-ppc/global_data.h @@ -163,7 +163,7 @@ typedef struct global_data { #define GD_FLG_SILENT 0x00004 /* Silent mode */
#if 1 -#define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r29") +#define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r2") #else /* We could use plain global data, but the resulting code is bigger */ #define XTRN_DECLARE_GLOBAL_DATA_PTR extern #define DECLARE_GLOBAL_DATA_PTR XTRN_DECLARE_GLOBAL_DATA_PTR \
Hello Wolfgang, you wrote:
R29 was an unlucky choice as with recent toolchains (gcc-4.2.x) gcc will refuse to use load/store multiple insns; instead, it issues a list of simple load/store instructions upon function entry and exit, resulting in bigger code size, which in turn makes the build for a few boards fail.
Use r2 instead.
How about switching r14 (GOT ptr) to r13 in a similar way? Quite like the r2, r13 is a dedicated register (small data area purposes) and it would let us avoid using the -ffixed completely.
This would also resolve a general problem with standalone applications that is lurking in the dark: the global data and GOT pointers are not saved/restored upon exception/interrupt, so for example, upon a decrementer hit U-Boot code starts using the dedicated regs blindly, but they could be scratched by the app's code that was interrupted. This doesn't surface with the U-Boot in-tree example applications, as they are built using system config.mk and contain proper -ffixed tweaks and happen to be in sync, but this a general problem, which should be addressed, as is biting applications built outside of U-Boot tree..
If we used another dedicated register for GOT purposes, which applications code would never use by definition, those issues dissapear. Otherwise we need to provide explicit save/restore in the exception prologue/epilogue.
I can provide patches, but let me know your thoughts first.
kind regards, Rafal
Dear Rafal,
in message 47B85ECF.5080207@semihalf.com you wrote:
How about switching r14 (GOT ptr) to r13 in a similar way? Quite like the r2, r13 is a dedicated register (small data area purposes) and it would let us avoid using the -ffixed completely.
I have to admit that I don;t understand enough of these things to judge if R13 (listed as "small data area pointer") is really free for use for our purposes.
I can provide patches, but let me know your thoughts first.
I guess you already ran some tests? If you are sure about this, and if it really works, then please submit your patches!
Best regards,
Wolfgang Denk
participants (2)
-
Rafal Jaworowski -
Wolfgang Denk