On Wed, Nov 17, 2021 at 9:04 AM Richard Henderson < richard.hender...@linaro.org> wrote:
> 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 > Reviewed-by: Warner Losh <i...@bsdimp.com> > 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 > >
