Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org> Signed-off-by: Richard Henderson <richard.hender...@linaro.org> --- linux-user/host/sparc64/hostdep.h | 3 + linux-user/host/sparc64/safe-syscall.inc.S | 89 ++++++++++++++++++++++ 2 files changed, 92 insertions(+) create mode 100644 linux-user/host/sparc64/safe-syscall.inc.S
diff --git a/linux-user/host/sparc64/hostdep.h b/linux-user/host/sparc64/hostdep.h index ce3968fca0..d832868cb1 100644 --- a/linux-user/host/sparc64/hostdep.h +++ b/linux-user/host/sparc64/hostdep.h @@ -12,4 +12,7 @@ #ifndef SPARC64_HOSTDEP_H #define SPARC64_HOSTDEP_H +/* We have a safe-syscall.inc.S */ +#define HAVE_SAFE_SYSCALL + #endif diff --git a/linux-user/host/sparc64/safe-syscall.inc.S b/linux-user/host/sparc64/safe-syscall.inc.S new file mode 100644 index 0000000000..901db15959 --- /dev/null +++ b/linux-user/host/sparc64/safe-syscall.inc.S @@ -0,0 +1,89 @@ +/* + * 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 <richard.hender...@linaro.org> + * 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. + */ + + .text + .balign 4 + + .register %g2, #scratch + .register %g3, #scratch + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, @function + .type safe_syscall_start, @function + .type safe_syscall_end, @function + +#define STACK_BIAS 2047 +#define PARAM(N) STACK_BIAS + N*8 + + /* + * 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 + /* + * The syscall calling convention isn't the same as the C one: + * we enter with o0 == &signal_pending + * o1 == syscall number + * o2 ... o5, (stack) == syscall arguments + * and return the result in x0 + * and the syscall instruction needs + * g1 == syscall number + * o0 ... o5 == syscall arguments + * and returns the result in o0 + * Shuffle everything around appropriately. + */ + mov %o0, %g2 /* signal_pending pointer */ + mov %o1, %g1 /* syscall number */ + mov %o2, %o0 /* syscall arguments */ + mov %o3, %o1 + mov %o4, %o2 + mov %o5, %o3 + ldx [%sp + PARAM(6)], %o4 + ldx [%sp + PARAM(7)], %o5 + + /* + * 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 */ + lduw [%g2], %g3 + brnz,pn %g3, 2f + nop + ta 0x6d +safe_syscall_end: + /* code path for having successfully executed the syscall */ + bcs,pn %xcc, 1f + nop + ret + nop + + /* code path when we didn't execute the syscall */ +2: set TARGET_ERESTARTSYS, %o0 + + /* code path setting errno */ +1: mov %o7, %g1 + call safe_syscall_set_errno_tail + mov %g1, %o7 + + .cfi_endproc + .size safe_syscall_base, .-safe_syscall_base -- 2.25.1
