Signed-off-by: Richard Henderson <richard.hender...@linaro.org> --- common-user/host/mips/hostdep.h | 2 + common-user/host/mips/safe-syscall.inc.S | 135 +++++++++++++++++++++++ 2 files changed, 137 insertions(+) create mode 100644 common-user/host/mips/hostdep.h create mode 100644 common-user/host/mips/safe-syscall.inc.S
diff --git a/common-user/host/mips/hostdep.h b/common-user/host/mips/hostdep.h new file mode 100644 index 0000000000..b18aca1deb --- /dev/null +++ b/common-user/host/mips/hostdep.h @@ -0,0 +1,2 @@ +/* We have a safe-syscall.inc.S */ +#define HAVE_SAFE_SYSCALL diff --git a/common-user/host/mips/safe-syscall.inc.S b/common-user/host/mips/safe-syscall.inc.S new file mode 100644 index 0000000000..1e2f5a079c --- /dev/null +++ b/common-user/host/mips/safe-syscall.inc.S @@ -0,0 +1,135 @@ +/* + * 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 linux-user/safe-syscall.S + * + * Written by Richard Henderson <r...@twiddle.net> + * Copyright (C) 2021 Linaro, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "sys/regdef.h" +#include "sys/asm.h" + + .text + .set nomips16 + .set noreorder + + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_start, @function + .type safe_syscall_end, @function + + /* + * 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'). + */ + +#if _MIPS_SIM == _ABIO32 +/* Do not allocate a stack frame and store into the parameter space. */ +#define FRAME 0 +#define ERRNOP 4 +#else +/* Allocate a stack frame and store into the first allocated slot. */ +#define FRAME 16 +#define ERRNOP 0 +#endif + +NESTED(safe_syscall_base, FRAME, ra) + .cfi_startproc +#if _MIPS_SIM == _ABIO32 + /* + * The syscall calling convention is nearly the same as C: + * we enter with a0 == &signal_pending + * a1 == &errno + * a2 == syscall number + * a3, stack == syscall arguments + * and return the result in a0 + * and the syscall instruction needs + * v0 == syscall number + * a0 ... a3, stack == syscall arguments + * and returns the result in v0 + * Shuffle everything around appropriately. + */ + move t0, a0 /* signal_pending pointer */ + sw a1, ERRNOP(sp) /* errno pointer */ + move v0, a2 /* syscall number */ + move a0, a3 /* syscall arguments */ + lw a1, 16(sp) + lw a2, 20(sp) + lw a3, 24(sp) + lw t4, 28(sp) + lw t5, 32(sp) + lw t6, 40(sp) + lw t7, 44(sp) + sw t4, 16(sp) + sw t5, 20(sp) + sw t6, 24(sp) + sw t7, 28(sp) +#else + PTR_ADDIU sp, sp, -FRAME + .cfi_adjust_cfa_offset FRAME + + /* + * The syscall calling convention is nearly the same as C: + * we enter with a0 == &signal_pending + * a1 == &errno + * a2 == syscall number + * a3 ... a7, stack == syscall arguments + * and return the result in a0 + * and the syscall instruction needs + * v0 == syscall number + * a0 ... a5 == syscall arguments + * and returns the result in v0 + * Shuffle everything around appropriately. + */ + move t0, a0 /* signal_pending pointer */ + PTR_S a1, ERRNOP(sp) /* save errno pointer */ + move v0, a2 /* syscall number */ + move a0, a3 /* syscall arguments */ + move a1, a4 + move a2, a5 + move a3, a6 + move a4, a7 + ld a5, 16(sp) +#endif + + /* + * 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 */ + lw t1, 0(t0) + bnez t1, 0f + nop + syscall +safe_syscall_end: + + /* code path for having successfully executed the syscall */ + bnez a3, 1f + nop + jr ra + PTR_ADDIU sp, sp, FRAME + + /* code path when we didn't execute the syscall */ +0: li v0, TARGET_ERESTARTSYS + + /* code path setting errno */ +1: PTR_L t0, ERRNOP(sp) + sw v0, 0(t0) /* store errno */ + li v0, -1 + jr ra + PTR_ADDIU sp, sp, FRAME + + .cfi_endproc +END(safe_syscall_base) -- 2.25.1
