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diff --git a/Documentation/powerpc/syscall64-abi.rst b/Documentation/powerpc/syscall64-abi.rst deleted file mode 100644 index e49f69f941b9..000000000000 --- a/Documentation/powerpc/syscall64-abi.rst +++ /dev/null @@ -1,110 +0,0 @@ -=============================================== -Power Architecture 64-bit Linux system call ABI -=============================================== - -syscall -======= - -syscall calling sequence\ [1]_ matches the Power Architecture 64-bit ELF ABI -specification C function calling sequence, including register preservation -rules, with the following differences. - -.. [1] Some syscalls (typically low-level management functions) may have - different calling sequences (e.g., rt_sigreturn). - -Parameters and return value ---------------------------- -The system call number is specified in r0. - -There is a maximum of 6 integer parameters to a syscall, passed in r3-r8. - -Both a return value and a return error code are returned. cr0.SO is the return -error code, and r3 is the return value or error code. When cr0.SO is clear, -the syscall succeeded and r3 is the return value. When cr0.SO is set, the -syscall failed and r3 is the error code that generally corresponds to errno. - -Stack ------ -System calls do not modify the caller's stack frame. For example, the caller's -stack frame LR and CR save fields are not used. - -Register preservation rules ---------------------------- -Register preservation rules match the ELF ABI calling sequence with the -following differences: - -=========== ============= ======================================== -r0 Volatile (System call number.) -r3 Volatile (Parameter 1, and return value.) -r4-r8 Volatile (Parameters 2-6.) -cr0 Volatile (cr0.SO is the return error condition) -cr1, cr5-7 Nonvolatile -lr Nonvolatile -=========== ============= ======================================== - -All floating point and vector data registers as well as control and status -registers are nonvolatile. - -Invocation ----------- -The syscall is performed with the sc instruction, and returns with execution -continuing at the instruction following the sc instruction. - -Transactional Memory --------------------- -Syscall behavior can change if the processor is in transactional or suspended -transaction state, and the syscall can affect the behavior of the transaction. - -If the processor is in suspended state when a syscall is made, the syscall -will be performed as normal, and will return as normal. The syscall will be -performed in suspended state, so its side effects will be persistent according -to the usual transactional memory semantics. A syscall may or may not result -in the transaction being doomed by hardware. - -If the processor is in transactional state when a syscall is made, then the -behavior depends on the presence of PPC_FEATURE2_HTM_NOSC in the AT_HWCAP2 ELF -auxiliary vector. - -- If present, which is the case for newer kernels, then the syscall will not - be performed and the transaction will be doomed by the kernel with the - failure code TM_CAUSE_SYSCALL | TM_CAUSE_PERSISTENT in the TEXASR SPR. - -- If not present (older kernels), then the kernel will suspend the - transactional state and the syscall will proceed as in the case of a - suspended state syscall, and will resume the transactional state before - returning to the caller. This case is not well defined or supported, so this - behavior should not be relied upon. - - -vsyscall -======== - -vsyscall calling sequence matches the syscall calling sequence, with the -following differences. Some vsyscalls may have different calling sequences. - -Parameters and return value ---------------------------- -r0 is not used as an input. The vsyscall is selected by its address. - -Stack ------ -The vsyscall may or may not use the caller's stack frame save areas. - -Register preservation rules ---------------------------- - -=========== ======== -r0 Volatile -cr1, cr5-7 Volatile -lr Volatile -=========== ======== - -Invocation ----------- -The vsyscall is performed with a branch-with-link instruction to the vsyscall -function address. - -Transactional Memory --------------------- -vsyscalls will run in the same transactional state as the caller. A vsyscall -may or may not result in the transaction being doomed by hardware. |