[PATCH] powerpc: Implement support for setting little-endian mode via prctl

This adds the PowerPC part of the code to allow processes to change
their endian mode via prctl.

This also extends the alignment exception handler to be able to fix up
alignment exceptions that occur in little-endian mode, both for
"PowerPC" little-endian and true little-endian.

We always enter signal handlers in big-endian mode -- the support for
little-endian mode does not amount to the creation of a little-endian
user/kernel ABI.  If the signal handler returns, the endian mode is
restored to what it was when the signal was delivered.

We have two new kernel CPU feature bits, one for PPC little-endian and
one for true little-endian.  Most of the classic 32-bit processors
support PPC little-endian, and this is reflected in the CPU feature
table.  There are two corresponding feature bits reported to userland
in the AT_HWCAP aux vector entry.

This is based on an earlier patch by Anton Blanchard.

Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 36 insertions, 22 deletions

diff --git a/include/asm-powerpc/cputable.h b/include/asm-powerpc/cputable.h
index defc166379d2..69f2c242797f 100644
--- a/include/asm-powerpc/cputable.h
+++ b/include/asm-powerpc/cputable.h
@@ -24,6 +24,9 @@
 #define PPC_FEATURE_ICACHE_SNOOP        0x00002000
 #define PPC_FEATURE_ARCH_2_05           0x00001000
 
+#define PPC_FEATURE_TRUE_LE             0x00000002
+#define PPC_FEATURE_PPC_LE              0x00000001
+
 #ifdef __KERNEL__
 #ifndef __ASSEMBLY__
 
@@ -111,6 +114,8 @@ extern void do_cpu_ftr_fixups(unsigned long offset);
 #define CPU_FTR_NO_BTIC                 ASM_CONST(0x0000000000040000)
 #define CPU_FTR_BIG_PHYS                ASM_CONST(0x0000000000080000)
 #define CPU_FTR_NODSISRALIGN            ASM_CONST(0x0000000000100000)
+#define CPU_FTR_PPC_LE                  ASM_CONST(0x0000000000200000)
+#define CPU_FTR_REAL_LE                 ASM_CONST(0x0000000000400000)
 
 #ifdef __powerpc64__
 /* Add the 64b processor unique features in the top half of the word */
@@ -197,92 +202,95 @@ extern void do_cpu_ftr_fixups(unsigned long offset);
 #define CPU_FTRS_PPC601 (CPU_FTR_COMMON | CPU_FTR_601 | CPU_FTR_HPTE_TABLE)
 #define CPU_FTRS_603    (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | \
-            CPU_FTR_MAYBE_CAN_NAP)
+            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_PPC_LE)
 #define CPU_FTRS_604    (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
-            CPU_FTR_USE_TB | CPU_FTR_604_PERF_MON | CPU_FTR_HPTE_TABLE)
+            CPU_FTR_USE_TB | CPU_FTR_604_PERF_MON | CPU_FTR_HPTE_TABLE | \
+            CPU_FTR_PPC_LE)
 #define CPU_FTRS_740_NOTAU      (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | CPU_FTR_L2CR | \
-            CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP)
+            CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_PPC_LE)
 #define CPU_FTRS_740    (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | CPU_FTR_L2CR | \
-            CPU_FTR_TAU | CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP)
+            CPU_FTR_TAU | CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP | \
+            CPU_FTR_PPC_LE)
 #define CPU_FTRS_750    (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | CPU_FTR_L2CR | \
-            CPU_FTR_TAU | CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP)
+            CPU_FTR_TAU | CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP | \
+            CPU_FTR_PPC_LE)
 #define CPU_FTRS_750FX1 (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | CPU_FTR_L2CR | \
             CPU_FTR_TAU | CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP | \
-            CPU_FTR_DUAL_PLL_750FX | CPU_FTR_NO_DPM)
+            CPU_FTR_DUAL_PLL_750FX | CPU_FTR_NO_DPM | CPU_FTR_PPC_LE)
 #define CPU_FTRS_750FX2 (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | CPU_FTR_L2CR | \
             CPU_FTR_TAU | CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP | \
-            CPU_FTR_NO_DPM)
+            CPU_FTR_NO_DPM | CPU_FTR_PPC_LE)
 #define CPU_FTRS_750FX  (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | CPU_FTR_L2CR | \
             CPU_FTR_TAU | CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP | \
-            CPU_FTR_DUAL_PLL_750FX | CPU_FTR_HAS_HIGH_BATS)
+            CPU_FTR_DUAL_PLL_750FX | CPU_FTR_HAS_HIGH_BATS | CPU_FTR_PPC_LE)
 #define CPU_FTRS_750GX  (CPU_FTR_SPLIT_ID_CACHE | CPU_FTR_MAYBE_CAN_DOZE | \
             CPU_FTR_USE_TB | CPU_FTR_L2CR | CPU_FTR_TAU | \
             CPU_FTR_HPTE_TABLE | CPU_FTR_MAYBE_CAN_NAP | \
-            CPU_FTR_DUAL_PLL_750FX | CPU_FTR_HAS_HIGH_BATS)
+            CPU_FTR_DUAL_PLL_750FX | CPU_FTR_HAS_HIGH_BATS | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7400_NOTAU     (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | CPU_FTR_L2CR | \
             CPU_FTR_ALTIVEC_COMP | CPU_FTR_HPTE_TABLE | \
-            CPU_FTR_MAYBE_CAN_NAP)
+            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7400   (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB | CPU_FTR_L2CR | \
             CPU_FTR_TAU | CPU_FTR_ALTIVEC_COMP | CPU_FTR_HPTE_TABLE | \
-            CPU_FTR_MAYBE_CAN_NAP)
+            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7450_20        (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_USE_TB | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
             CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
-            CPU_FTR_NEED_COHERENT)
+            CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7450_21        (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_USE_TB | \
             CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
             CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
             CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_L3_DISABLE_NAP | \
-            CPU_FTR_NEED_COHERENT)
+            CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7450_23        (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_USE_TB | \
             CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
             CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
-            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_NEED_COHERENT)
+            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7455_1 (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_USE_TB | \
             CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | CPU_FTR_L3CR | \
             CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | CPU_FTR_HAS_HIGH_BATS | \
-            CPU_FTR_NEED_COHERENT)
+            CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7455_20        (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_USE_TB | \
             CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
             CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
             CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_L3_DISABLE_NAP | \
-            CPU_FTR_NEED_COHERENT | CPU_FTR_HAS_HIGH_BATS)
+            CPU_FTR_NEED_COHERENT | CPU_FTR_HAS_HIGH_BATS | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7455   (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_USE_TB | \
             CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
             CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
             CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_HAS_HIGH_BATS | \
-            CPU_FTR_NEED_COHERENT)
+            CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7447_10        (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_USE_TB | \
             CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
             CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
             CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_HAS_HIGH_BATS | \
-            CPU_FTR_NEED_COHERENT | CPU_FTR_NO_BTIC)
+            CPU_FTR_NEED_COHERENT | CPU_FTR_NO_BTIC | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7447   (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_USE_TB | \
             CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
             CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
             CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_HAS_HIGH_BATS | \
-            CPU_FTR_NEED_COHERENT)
+            CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7447A  (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_USE_TB | \
             CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
             CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
             CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_HAS_HIGH_BATS | \
-            CPU_FTR_NEED_COHERENT)
+            CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
 #define CPU_FTRS_82XX   (CPU_FTR_COMMON | CPU_FTR_SPLIT_ID_CACHE | \
             CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB)
 #define CPU_FTRS_G2_LE  (CPU_FTR_SPLIT_ID_CACHE | CPU_FTR_MAYBE_CAN_DOZE | \
@@ -312,7 +320,7 @@ extern void do_cpu_ftr_fixups(unsigned long offset);
 #define CPU_FTRS_GENERIC_32     (CPU_FTR_COMMON | CPU_FTR_NODSISRALIGN)
 #ifdef __powerpc64__
 #define CPU_FTRS_POWER3 (CPU_FTR_SPLIT_ID_CACHE | CPU_FTR_USE_TB | \
-            CPU_FTR_HPTE_TABLE | CPU_FTR_IABR)
+            CPU_FTR_HPTE_TABLE | CPU_FTR_IABR | CPU_FTR_PPC_LE)
 #define CPU_FTRS_RS64   (CPU_FTR_SPLIT_ID_CACHE | CPU_FTR_USE_TB | \
             CPU_FTR_HPTE_TABLE | CPU_FTR_IABR | \
             CPU_FTR_MMCRA | CPU_FTR_CTRL)
@@ -330,7 +338,7 @@ extern void do_cpu_ftr_fixups(unsigned long offset);
             CPU_FTR_HPTE_TABLE | CPU_FTR_PPCAS_ARCH_V2 | \
             CPU_FTR_MMCRA | CPU_FTR_SMT | \
             CPU_FTR_COHERENT_ICACHE | CPU_FTR_LOCKLESS_TLBIE | \
-            CPU_FTR_PURR | CPU_FTR_CI_LARGE_PAGE)
+            CPU_FTR_PURR | CPU_FTR_CI_LARGE_PAGE | CPU_FTR_REAL_LE)
 #define CPU_FTRS_CELL   (CPU_FTR_SPLIT_ID_CACHE | CPU_FTR_USE_TB | \
             CPU_FTR_HPTE_TABLE | CPU_FTR_PPCAS_ARCH_V2 | \
             CPU_FTR_ALTIVEC_COMP | CPU_FTR_MMCRA | CPU_FTR_SMT | \
diff --git a/include/asm-powerpc/processor.h b/include/asm-powerpc/processor.h
index d5c7ef1cca26..fa6163268153 100644
--- a/include/asm-powerpc/processor.h
+++ b/include/asm-powerpc/processor.h
@@ -211,6 +211,12 @@ unsigned long get_wchan(struct task_struct *p);
 extern int get_fpexc_mode(struct task_struct *tsk, unsigned long adr);
 extern int set_fpexc_mode(struct task_struct *tsk, unsigned int val);
 
+#define GET_ENDIAN(tsk, adr) get_endian((tsk), (adr))
+#define SET_ENDIAN(tsk, val) set_endian((tsk), (val))
+
+extern int get_endian(struct task_struct *tsk, unsigned long adr);
+extern int set_endian(struct task_struct *tsk, unsigned int val);
+
 static inline unsigned int __unpack_fe01(unsigned long msr_bits)
 {
         return ((msr_bits & MSR_FE0) >> 10) | ((msr_bits & MSR_FE1) >> 8);