#include <asm/glue.h>
#include <asm/vfpmacros.h>
-#include <asm/hardware.h> @ should be moved into entry-macro.S
-#include <asm/arch/irqs.h> @ should be moved into entry-macro.S
+#include <asm/hardware.h> /* should be moved into entry-macro.S */
+#include <asm/arch/irqs.h> /* should be moved into entry-macro.S */
#include <asm/arch/entry-macro.S>
#include "entry-header.S"
add r5, sp, #S_PC
ldmia r7, {r2 - r4} @ Get USR pc, cpsr
+#if __LINUX_ARM_ARCH__ < 6 && !defined(CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG)
+ @ make sure our user space atomic helper is aborted
+ cmp r2, #VIRT_OFFSET
+ bichs r3, r3, #PSR_Z_BIT
+#endif
+
@
@ We are now ready to fill in the remaining blanks on the stack:
@
mra r4, r5, acc0
stmia ip, {r4, r5}
#endif
+#if defined(CONFIG_HAS_TLS_REG)
+ mcr p15, 0, r3, c13, c0, 3 @ set TLS register
+#elif !defined(CONFIG_TLS_REG_EMUL)
mov r4, #0xffff0fff
- str r3, [r4, #-3] @ Set TLS ptr
+ str r3, [r4, #-15] @ TLS val at 0xffff0ff0
+#endif
mcr p15, 0, r6, c3, c0, 0 @ Set domain register
#ifdef CONFIG_VFP
@ Always disable VFP so we can lazily save/restore the old
ldmib r2, {r4 - sl, fp, sp, pc} @ Load all regs saved previously
__INIT
+
+/*
+ * User helpers.
+ *
+ * These are segment of kernel provided user code reachable from user space
+ * at a fixed address in kernel memory. This is used to provide user space
+ * with some operations which require kernel help because of unimplemented
+ * native feature and/or instructions in many ARM CPUs. The idea is for
+ * this code to be executed directly in user mode for best efficiency but
+ * which is too intimate with the kernel counter part to be left to user
+ * libraries. In fact this code might even differ from one CPU to another
+ * depending on the available instruction set and restrictions like on
+ * SMP systems. In other words, the kernel reserves the right to change
+ * this code as needed without warning. Only the entry points and their
+ * results are guaranteed to be stable.
+ *
+ * Each segment is 32-byte aligned and will be moved to the top of the high
+ * vector page. New segments (if ever needed) must be added in front of
+ * existing ones. This mechanism should be used only for things that are
+ * really small and justified, and not be abused freely.
+ *
+ * User space is expected to implement those things inline when optimizing
+ * for a processor that has the necessary native support, but only if such
+ * resulting binaries are already to be incompatible with earlier ARM
+ * processors due to the use of unsupported instructions other than what
+ * is provided here. In other words don't make binaries unable to run on
+ * earlier processors just for the sake of not using these kernel helpers
+ * if your compiled code is not going to use the new instructions for other
+ * purpose.
+ */
+
+ .align 5
+ .globl __kuser_helper_start
+__kuser_helper_start:
+
+/*
+ * Reference prototype:
+ *
+ * int __kernel_cmpxchg(int oldval, int newval, int *ptr)
+ *
+ * Input:
+ *
+ * r0 = oldval
+ * r1 = newval
+ * r2 = ptr
+ * lr = return address
+ *
+ * Output:
+ *
+ * r0 = returned value (zero or non-zero)
+ * C flag = set if r0 == 0, clear if r0 != 0
+ *
+ * Clobbered:
+ *
+ * r3, ip, flags
+ *
+ * Definition and user space usage example:
+ *
+ * typedef int (__kernel_cmpxchg_t)(int oldval, int newval, int *ptr);
+ * #define __kernel_cmpxchg (*(__kernel_cmpxchg_t *)0xffff0fc0)
+ *
+ * Atomically store newval in *ptr if *ptr is equal to oldval for user space.
+ * Return zero if *ptr was changed or non-zero if no exchange happened.
+ * The C flag is also set if *ptr was changed to allow for assembly
+ * optimization in the calling code.
+ *
+ * For example, a user space atomic_add implementation could look like this:
+ *
+ * #define atomic_add(ptr, val) \
+ * ({ register unsigned int *__ptr asm("r2") = (ptr); \
+ * register unsigned int __result asm("r1"); \
+ * asm volatile ( \
+ * "1: @ atomic_add\n\t" \
+ * "ldr r0, [r2]\n\t" \
+ * "mov r3, #0xffff0fff\n\t" \
+ * "add lr, pc, #4\n\t" \
+ * "add r1, r0, %2\n\t" \
+ * "add pc, r3, #(0xffff0fc0 - 0xffff0fff)\n\t" \
+ * "bcc 1b" \
+ * : "=&r" (__result) \
+ * : "r" (__ptr), "rIL" (val) \
+ * : "r0","r3","ip","lr","cc","memory" ); \
+ * __result; })
+ */
+
+__kuser_cmpxchg: @ 0xffff0fc0
+
+#if defined(CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG)
+
+ /*
+ * Poor you. No fast solution possible...
+ * The kernel itself must perform the operation.
+ * A special ghost syscall is used for that (see traps.c).
+ */
+ swi #0x9ffff0
+ mov pc, lr
+
+#elif __LINUX_ARM_ARCH__ < 6
+
+ /*
+ * Theory of operation:
+ *
+ * We set the Z flag before loading oldval. If ever an exception
+ * occurs we can not be sure the loaded value will still be the same
+ * when the exception returns, therefore the user exception handler
+ * will clear the Z flag whenever the interrupted user code was
+ * actually from the kernel address space (see the usr_entry macro).
+ *
+ * The post-increment on the str is used to prevent a race with an
+ * exception happening just after the str instruction which would
+ * clear the Z flag although the exchange was done.
+ */
+ teq ip, ip @ set Z flag
+ ldr ip, [r2] @ load current val
+ add r3, r2, #1 @ prepare store ptr
+ teqeq ip, r0 @ compare with oldval if still allowed
+ streq r1, [r3, #-1]! @ store newval if still allowed
+ subs r0, r2, r3 @ if r2 == r3 the str occured
+ mov pc, lr
+
+#else
+
+ ldrex r3, [r2]
+ subs r3, r3, r0
+ strexeq r3, r1, [r2]
+ rsbs r0, r3, #0
+ mov pc, lr
+
+#endif
+
+ .align 5
+
+/*
+ * Reference prototype:
+ *
+ * int __kernel_get_tls(void)
+ *
+ * Input:
+ *
+ * lr = return address
+ *
+ * Output:
+ *
+ * r0 = TLS value
+ *
+ * Clobbered:
+ *
+ * the Z flag might be lost
+ *
+ * Definition and user space usage example:
+ *
+ * typedef int (__kernel_get_tls_t)(void);
+ * #define __kernel_get_tls (*(__kernel_get_tls_t *)0xffff0fe0)
+ *
+ * Get the TLS value as previously set via the __ARM_NR_set_tls syscall.
+ *
+ * This could be used as follows:
+ *
+ * #define __kernel_get_tls() \
+ * ({ register unsigned int __val asm("r0"); \
+ * asm( "mov r0, #0xffff0fff; mov lr, pc; sub pc, r0, #31" \
+ * : "=r" (__val) : : "lr","cc" ); \
+ * __val; })
+ */
+
+__kuser_get_tls: @ 0xffff0fe0
+
+#if !defined(CONFIG_HAS_TLS_REG) && !defined(CONFIG_TLS_REG_EMUL)
+
+ ldr r0, [pc, #(16 - 8)] @ TLS stored at 0xffff0ff0
+ mov pc, lr
+
+#else
+
+ mrc p15, 0, r0, c13, c0, 3 @ read TLS register
+ mov pc, lr
+
+#endif
+
+ .rep 5
+ .word 0 @ pad up to __kuser_helper_version
+ .endr
+
+/*
+ * Reference declaration:
+ *
+ * extern unsigned int __kernel_helper_version;
+ *
+ * Definition and user space usage example:
+ *
+ * #define __kernel_helper_version (*(unsigned int *)0xffff0ffc)
+ *
+ * User space may read this to determine the curent number of helpers
+ * available.
+ */
+
+__kuser_helper_version: @ 0xffff0ffc
+ .word ((__kuser_helper_end - __kuser_helper_start) >> 5)
+
+ .globl __kuser_helper_end
+__kuser_helper_end:
+
+
/*
* Vector stubs.
*
projects / GitHub / mt8127 / android_kernel_alcatel_ttab.git / blobdiff