Blackfin arch: defines and provides entry points for certain user space functions...

This patch defines (and provides) entry points for certain user space functions
at fixed addresses.  The Blackfin has no usable atomic instructions, but we can
ensure that these code sequences appear atomic from a user space point of view
by detecting when we're in the process of executing them during the interrupt
handler return path.  This allows much more efficient pthread lock
implementations than the bfin_spinlock syscall we're currently using.

Also provided is a small sys_rt_sigreturn stub which can be used by the signal
handler setup code.  The signal.c part will be committed separately.

Signed-off-by: Bernd Schmidt <bernd.schmidt@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

diff --git a/arch/blackfin/kernel/Makefile b/arch/blackfin/kernel/Makefile
index 93d21406cade974b268cb0e8695becd4059251b9..b7b6de824011a6783c481e2b2ed7b46f18a23e1f 100644 (file)
--- a/arch/blackfin/kernel/Makefile
+++ b/arch/blackfin/kernel/Makefile
@@ -6,7 +6,8 @@ extra-y := init_task.o vmlinux.lds
 
 obj-y := \
        entry.o process.o bfin_ksyms.o ptrace.o setup.o signal.o \
-       sys_bfin.o time.o traps.o irqchip.o dma-mapping.o flat.o
+       sys_bfin.o time.o traps.o irqchip.o dma-mapping.o flat.o \
+       fixed_code.o
 
 obj-$(CONFIG_BF53x)                 += bfin_gpio.o
 obj-$(CONFIG_BF561)                 += bfin_gpio.o

diff --git a/arch/blackfin/kernel/fixed_code.S b/arch/blackfin/kernel/fixed_code.S
new file mode 100644 (file)
index 0000000..99ea296
--- /dev/null
+++ b/arch/blackfin/kernel/fixed_code.S
@@ -0,0 +1,132 @@
+/*
+ * This file contains sequences of code that will be copied to a
+ * fixed location, defined in <asm/atomic_seq.h>.  The interrupt
+ * handlers ensure that these sequences appear to be atomic when
+ * executed from userspace.
+ * These are aligned to 16 bytes, so that we have some space to replace
+ * these sequences with something else (e.g. kernel traps if we ever do
+ * BF561 SMP).
+ */
+#include <linux/linkage.h>
+#include <asm/entry.h>
+#include <asm/unistd.h>
+
+.text
+ENTRY(_fixed_code_start)
+
+.align 16
+ENTRY(_sigreturn_stub)
+       P0 = __NR_rt_sigreturn;
+       EXCPT 0;
+       /* Speculative execution paranoia.  */
+0:     JUMP.S 0b;
+ENDPROC (_sigreturn_stub)
+
+.align 16
+       /*
+        * Atomic swap, 8 bit.
+        * Inputs:      P0: memory address to use
+        *              R1: value to store
+        * Output:      R0: old contents of the memory address, zero extended.
+        */
+ENTRY(_atomic_xchg32)
+       R0 = [P0];
+       [P0] = R1;
+       rts;
+ENDPROC (_atomic_xchg32)
+
+.align 16
+       /*
+        * Compare and swap, 32 bit.
+        * Inputs:      P0: memory address to use
+        *              R1: compare value
+        *              R2: new value to store
+        * The new value is stored if the contents of the memory
+        * address is equal to the compare value.
+        * Output:      R0: old contents of the memory address.
+        */
+ENTRY(_atomic_cas32)
+       R0 = [P0];
+       CC = R0 == R1;
+       IF !CC JUMP 1f;
+       [P0] = R2;
+1:
+       rts;
+ENDPROC (_atomic_cas32)
+
+.align 16
+       /*
+        * Atomic add, 32 bit.
+        * Inputs:      P0: memory address to use
+        *              R0: value to add
+        * Outputs:     R0: new contents of the memory address.
+        *              R1: previous contents of the memory address.
+        */
+ENTRY(_atomic_add32)
+       R1 = [P0];
+       R0 = R1 + R0;
+       [P0] = R0;
+       rts;
+ENDPROC (_atomic_add32)
+
+.align 16
+       /*
+        * Atomic sub, 32 bit.
+        * Inputs:      P0: memory address to use
+        *              R0: value to subtract
+        * Outputs:     R0: new contents of the memory address.
+        *              R1: previous contents of the memory address.
+        */
+ENTRY(_atomic_sub32)
+       R1 = [P0];
+       R0 = R1 - R0;
+       [P0] = R0;
+       rts;
+ENDPROC (_atomic_sub32)
+
+.align 16
+       /*
+        * Atomic ior, 32 bit.
+        * Inputs:      P0: memory address to use
+        *              R0: value to ior
+        * Outputs:     R0: new contents of the memory address.
+        *              R1: previous contents of the memory address.
+        */
+ENTRY(_atomic_ior32)
+       R1 = [P0];
+       R0 = R1 | R0;
+       [P0] = R0;
+       rts;
+ENDPROC (_atomic_ior32)
+
+.align 16
+       /*
+        * Atomic ior, 32 bit.
+        * Inputs:      P0: memory address to use
+        *              R0: value to ior
+        * Outputs:     R0: new contents of the memory address.
+        *              R1: previous contents of the memory address.
+        */
+ENTRY(_atomic_and32)
+       R1 = [P0];
+       R0 = R1 & R0;
+       [P0] = R0;
+       rts;
+ENDPROC (_atomic_ior32)
+
+.align 16
+       /*
+        * Atomic ior, 32 bit.
+        * Inputs:      P0: memory address to use
+        *              R0: value to ior
+        * Outputs:     R0: new contents of the memory address.
+        *              R1: previous contents of the memory address.
+        */
+ENTRY(_atomic_xor32)
+       R1 = [P0];
+       R0 = R1 ^ R0;
+       [P0] = R0;
+       rts;
+ENDPROC (_atomic_ior32)
+
+ENTRY(_fixed_code_end)

diff --git a/arch/blackfin/kernel/process.c b/arch/blackfin/kernel/process.c
index 3eff7439d8d3f0e3a5bd542a307491f85a96a287..6b7a94ab96c20469d2ada9fb9a96529dbead1b2f 100644 (file)
--- a/arch/blackfin/kernel/process.c
+++ b/arch/blackfin/kernel/process.c
@@ -35,6 +35,7 @@
 
 #include <asm/blackfin.h>
 #include <asm/uaccess.h>
+#include <asm/fixed_code.h>
 
 #define        LED_ON  0
 #define        LED_OFF 1
@@ -350,6 +351,70 @@ unsigned long get_wchan(struct task_struct *p)
        return 0;
 }
 
+void finish_atomic_sections (struct pt_regs *regs)
+{
+       if (regs->pc < ATOMIC_SEQS_START || regs->pc >= ATOMIC_SEQS_END)
+               return;
+
+       switch (regs->pc) {
+       case ATOMIC_XCHG32 + 2:
+               put_user(regs->r1, (int *)regs->p0);
+               regs->pc += 2;
+               break;
+
+       case ATOMIC_CAS32 + 2:
+       case ATOMIC_CAS32 + 4:
+               if (regs->r0 == regs->r1)
+                       put_user(regs->r2, (int *)regs->p0);
+               regs->pc = ATOMIC_CAS32 + 8;
+               break;
+       case ATOMIC_CAS32 + 6:
+               put_user(regs->r2, (int *)regs->p0);
+               regs->pc += 2;
+               break;
+
+       case ATOMIC_ADD32 + 2:
+               regs->r0 = regs->r1 + regs->r0;
+               /* fall through */
+       case ATOMIC_ADD32 + 4:
+               put_user(regs->r0, (int *)regs->p0);
+               regs->pc = ATOMIC_ADD32 + 6;
+               break;
+
+       case ATOMIC_SUB32 + 2:
+               regs->r0 = regs->r1 - regs->r0;
+               /* fall through */
+       case ATOMIC_SUB32 + 4:
+               put_user(regs->r0, (int *)regs->p0);
+               regs->pc = ATOMIC_SUB32 + 6;
+               break;
+
+       case ATOMIC_IOR32 + 2:
+               regs->r0 = regs->r1 | regs->r0;
+               /* fall through */
+       case ATOMIC_IOR32 + 4:
+               put_user(regs->r0, (int *)regs->p0);
+               regs->pc = ATOMIC_IOR32 + 6;
+               break;
+
+       case ATOMIC_AND32 + 2:
+               regs->r0 = regs->r1 & regs->r0;
+               /* fall through */
+       case ATOMIC_AND32 + 4:
+               put_user(regs->r0, (int *)regs->p0);
+               regs->pc = ATOMIC_AND32 + 6;
+               break;
+
+       case ATOMIC_XOR32 + 2:
+               regs->r0 = regs->r1 ^ regs->r0;
+               /* fall through */
+       case ATOMIC_XOR32 + 4:
+               put_user(regs->r0, (int *)regs->p0);
+               regs->pc = ATOMIC_XOR32 + 6;
+               break;
+       }
+}
+
 #if defined(CONFIG_ACCESS_CHECK)
 int _access_ok(unsigned long addr, unsigned long size)
 {

diff --git a/arch/blackfin/kernel/setup.c b/arch/blackfin/kernel/setup.c
index 76bf2cea61d7f14d4ab209a8f8f759c6d97e43cb..534227f4da309800d08a816df0ef3e5a6667cfb2 100644 (file)
--- a/arch/blackfin/kernel/setup.c
+++ b/arch/blackfin/kernel/setup.c
@@ -42,6 +42,7 @@
 #include <asm/cacheflush.h>
 #include <asm/blackfin.h>
 #include <asm/cplbinit.h>
+#include <asm/fixed_code.h>
 
 u16 _bfin_swrst;
 
@@ -404,6 +405,27 @@ void __init setup_arch(char **cmdline_p)
 
        printk(KERN_INFO "Hardware Trace Enabled\n");
        bfin_write_TBUFCTL(0x03);
+
+       /* Copy atomic sequences to their fixed location, and sanity check that
+          these locations are the ones that we advertise to userspace.  */
+       memcpy((void *)FIXED_CODE_START, &fixed_code_start,
+              FIXED_CODE_END - FIXED_CODE_START);
+       BUG_ON((char *)&sigreturn_stub - (char *)&fixed_code_start
+              != SIGRETURN_STUB - FIXED_CODE_START);
+       BUG_ON((char *)&atomic_xchg32 - (char *)&fixed_code_start
+              != ATOMIC_XCHG32 - FIXED_CODE_START);
+       BUG_ON((char *)&atomic_cas32 - (char *)&fixed_code_start
+              != ATOMIC_CAS32 - FIXED_CODE_START);
+       BUG_ON((char *)&atomic_add32 - (char *)&fixed_code_start
+              != ATOMIC_ADD32 - FIXED_CODE_START);
+       BUG_ON((char *)&atomic_sub32 - (char *)&fixed_code_start
+              != ATOMIC_SUB32 - FIXED_CODE_START);
+       BUG_ON((char *)&atomic_ior32 - (char *)&fixed_code_start
+              != ATOMIC_IOR32 - FIXED_CODE_START);
+       BUG_ON((char *)&atomic_and32 - (char *)&fixed_code_start
+              != ATOMIC_AND32 - FIXED_CODE_START);
+       BUG_ON((char *)&atomic_xor32 - (char *)&fixed_code_start
+              != ATOMIC_XOR32 - FIXED_CODE_START);
 }
 
 static int __init topology_init(void)

diff --git a/arch/blackfin/mach-common/entry.S b/arch/blackfin/mach-common/entry.S
index 40045b1386ad888d608fd80d02de1dbb5341ecd8..c4a32ea06c4b39c8cbe7b48794f57411b83bb853 100644 (file)
--- a/arch/blackfin/mach-common/entry.S
+++ b/arch/blackfin/mach-common/entry.S
@@ -741,6 +741,10 @@ _schedule_and_signal_from_int:
        r0 = [p0];
        sti r0;
 
+       r0 = sp;
+       sp += -12;
+       call _finish_atomic_sections;
+       sp += 12;
        jump.s .Lresume_userspace;
 
 _schedule_and_signal:

diff --git a/include/asm-blackfin/Kbuild b/include/asm-blackfin/Kbuild
index c68e1680da0173d5754d1a1df4944120a5239e58..71f8fe7832581b41a60014ba2895e1d9c5cfff10 100644 (file)
--- a/include/asm-blackfin/Kbuild
+++ b/include/asm-blackfin/Kbuild
@@ -1 +1,3 @@
 include include/asm-generic/Kbuild.asm
+
+header-y += fixed_code.h

diff --git a/include/asm-blackfin/bfin-global.h b/include/asm-blackfin/bfin-global.h
index 57f37ccdcdf1db421f25921c8db7bbdc34274671..c4d6cbbf96d490283df0a12fb6375f63f16a16b1 100644 (file)
--- a/include/asm-blackfin/bfin-global.h
+++ b/include/asm-blackfin/bfin-global.h
@@ -67,6 +67,18 @@ extern void evt14_softirq(void);
 extern asmlinkage void asm_do_IRQ(unsigned int irq, struct pt_regs *regs);
 extern void bfin_gpio_interrupt_setup(int irq, int irq_pfx, int type);
 
+extern asmlinkage void finish_atomic_sections (struct pt_regs *regs);
+extern char fixed_code_start;
+extern char fixed_code_end;
+extern int atomic_xchg32(void);
+extern int atomic_cas32(void);
+extern int atomic_add32(void);
+extern int atomic_sub32(void);
+extern int atomic_ior32(void);
+extern int atomic_and32(void);
+extern int atomic_xor32(void);
+extern void sigreturn_stub(void);
+
 extern void *l1_data_A_sram_alloc(size_t);
 extern void *l1_data_B_sram_alloc(size_t);
 extern void *l1_inst_sram_alloc(size_t);

diff --git a/include/asm-blackfin/cplbinit.h b/include/asm-blackfin/cplbinit.h
index 3bad2d1e6a8cd87da60bf12a0a4ef122d62714ea..e14ea397cdbba880342e0bea9eb7ea1d06508d57 100644 (file)
--- a/include/asm-blackfin/cplbinit.h
+++ b/include/asm-blackfin/cplbinit.h
@@ -101,8 +101,8 @@ struct s_cplb {
 static struct cplb_desc cplb_data[] = {
        {
                .start = 0,
-               .end = SIZE_4K,
-               .psize = SIZE_4K,
+               .end = SIZE_1K,
+               .psize = SIZE_1K,
                .attr = INITIAL_T | SWITCH_T | I_CPLB | D_CPLB,
                .i_conf = SDRAM_OOPS,
                .d_conf = SDRAM_OOPS,

diff --git a/include/asm-blackfin/fixed_code.h b/include/asm-blackfin/fixed_code.h
new file mode 100644 (file)
index 0000000..e6df84e
--- /dev/null
+++ b/include/asm-blackfin/fixed_code.h
@@ -0,0 +1,20 @@
+/* This file defines the fixed addresses where userspace programs can find
+   atomic code sequences.  */
+
+#define FIXED_CODE_START       0x400
+
+#define SIGRETURN_STUB         0x400
+
+#define ATOMIC_SEQS_START      0x410
+
+#define ATOMIC_XCHG32          0x410
+#define ATOMIC_CAS32           0x420
+#define ATOMIC_ADD32           0x430
+#define ATOMIC_SUB32           0x440
+#define ATOMIC_IOR32           0x450
+#define ATOMIC_AND32           0x460
+#define ATOMIC_XOR32           0x470
+
+#define ATOMIC_SEQS_END                0x480
+
+#define FIXED_CODE_END         0x480