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| -rw-r--r-- | common-user/host/ppc/safe-syscall.inc.S | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/common-user/host/ppc/safe-syscall.inc.S b/common-user/host/ppc/safe-syscall.inc.S new file mode 100644 index 0000000..0851f6c --- /dev/null +++ b/common-user/host/ppc/safe-syscall.inc.S @@ -0,0 +1,107 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Copyright (C) 2022 Linaro, Ltd. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +/* + * Standardize on the _CALL_FOO symbols used by GCC: + * Apple XCode does not define _CALL_DARWIN. + * Clang defines _CALL_ELF (64-bit) but not _CALL_SYSV (32-bit). + */ +#if !defined(_CALL_SYSV) && \ + !defined(_CALL_DARWIN) && \ + !defined(_CALL_AIX) && \ + !defined(_CALL_ELF) +# if defined(__APPLE__) +# define _CALL_DARWIN +# elif defined(__ELF__) && TCG_TARGET_REG_BITS == 32 +# define _CALL_SYSV +# else +# error "Unknown ABI" +# endif +#endif + +#ifndef _CALL_SYSV +# error "Unsupported ABI" +#endif + + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, @function + + .text + + /* + * This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ +safe_syscall_base: + .cfi_startproc + stwu 1, -8(1) + .cfi_def_cfa_offset 8 + stw 30, 4(1) + .cfi_offset 30, -4 + + /* + * We enter with r3 == &signal_pending + * r4 == syscall number + * r5 ... r10 == syscall arguments + * and return the result in r3 + * and the syscall instruction needs + * r0 == syscall number + * r3 ... r8 == syscall arguments + * and returns the result in r3 + * Shuffle everything around appropriately. + */ + mr 30, 3 /* signal_pending */ + mr 0, 4 /* syscall number */ + mr 3, 5 /* syscall arguments */ + mr 4, 6 + mr 5, 7 + mr 6, 8 + mr 7, 9 + mr 8, 10 + + /* + * This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* if signal_pending is non-zero, don't do the call */ + lwz 12, 0(30) + cmpwi 0, 12, 0 + bne- 2f + sc +safe_syscall_end: + /* code path when we did execute the syscall */ + lwz 30, 4(1) /* restore r30 */ + addi 1, 1, 8 /* restore stack */ + .cfi_restore 30 + .cfi_def_cfa_offset 0 + bnslr+ /* return on success */ + b safe_syscall_set_errno_tail + + /* code path when we didn't execute the syscall */ +2: lwz 30, 4(1) + addi 1, 1, 8 + addi 3, 0, QEMU_ERESTARTSYS + b safe_syscall_set_errno_tail + + .cfi_endproc + + .size safe_syscall_base, .-safe_syscall_base |