diff options
Diffstat (limited to 'arch/sh/kernel/entry-common.S')
| -rw-r--r-- | arch/sh/kernel/entry-common.S | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/arch/sh/kernel/entry-common.S b/arch/sh/kernel/entry-common.S index 13047a4facd2..c001f782c5f1 100644 --- a/arch/sh/kernel/entry-common.S +++ b/arch/sh/kernel/entry-common.S @@ -268,20 +268,29 @@ debug_trap: * Syscall #: R3 * Arguments #0 to #3: R4--R7 * Arguments #4 to #6: R0, R1, R2 - * TRA: (number of arguments + ABI revision) x 4 + * TRA: See following table. * - * This code also handles delegating other traps to the BIOS/gdb stub - * according to: - * - * Trap number * (TRA>>2) Purpose * -------- ------- * 0x00-0x0f original SH-3/4 syscall ABI (not in general use). * 0x10-0x1f general SH-3/4 syscall ABI. - * 0x20-0x2f syscall ABI for SH-2 parts. + * 0x1f unified SH-2/3/4 syscall ABI (preferred). + * 0x20-0x2f original SH-2 syscall ABI. * 0x30-0x3f debug traps used by the kernel. * 0x40-0xff Not supported by all parts, so left unhandled. * + * For making system calls, any trap number in the range for the + * given cpu model may be used, but the unified trap number 0x1f is + * preferred for compatibility with all models. + * + * The low bits of the trap number were once documented as matching + * the number of arguments, but they were never actually used as such + * by the kernel. SH-2 originally used its own separate trap range + * because several hardware exceptions fell in the range used for the + * SH-3/4 syscall ABI. + * + * This code also handles delegating other traps to the BIOS/gdb stub. + * * Note: When we're first called, the TRA value must be shifted * right 2 bits in order to get the value that was used as the "trapa" * argument. |