From 51495272972424e3d388c9fcf2a75412ac883664 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 13 Jun 2016 13:34:56 +0100 Subject: linux-user: Implement safe_syscall for 64-bit ARM Implement the host assembly fragment needed for safe_syscall for 64-bit ARM. Signed-off-by: Peter Maydell --- linux-user/host/aarch64/hostdep.h | 23 +++++++++ linux-user/host/aarch64/safe-syscall.inc.S | 78 ++++++++++++++++++++++++++++++ 2 files changed, 101 insertions(+) create mode 100644 linux-user/host/aarch64/safe-syscall.inc.S diff --git a/linux-user/host/aarch64/hostdep.h b/linux-user/host/aarch64/hostdep.h index 7609bf5cd7..e2c28e6ea6 100644 --- a/linux-user/host/aarch64/hostdep.h +++ b/linux-user/host/aarch64/hostdep.h @@ -12,4 +12,27 @@ #ifndef QEMU_HOSTDEP_H #define QEMU_HOSTDEP_H +/* We have a safe-syscall.inc.S */ +#define HAVE_SAFE_SYSCALL + +#ifndef __ASSEMBLER__ + +/* These are defined by the safe-syscall.inc.S file */ +extern char safe_syscall_start[]; +extern char safe_syscall_end[]; + +/* Adjust the signal context to rewind out of safe-syscall if we're in it */ +static inline void rewind_if_in_safe_syscall(void *puc) +{ + struct ucontext *uc = puc; + unsigned long long *pcreg = &uc->uc_mcontext.pc; + + if (*pcreg > (uintptr_t)safe_syscall_start + && *pcreg < (uintptr_t)safe_syscall_end) { + *pcreg = (uintptr_t)safe_syscall_start; + } +} + +#endif /* __ASSEMBLER__ */ + #endif diff --git a/linux-user/host/aarch64/safe-syscall.inc.S b/linux-user/host/aarch64/safe-syscall.inc.S new file mode 100644 index 0000000000..2c21489e66 --- /dev/null +++ b/linux-user/host/aarch64/safe-syscall.inc.S @@ -0,0 +1,78 @@ +/* + * 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 Peter Maydell + * + * Copyright (C) 2016 Linaro Limited + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, %function + .align 4 + + /* 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'). + * We return a long which is the syscall's return value, which + * may be negative-errno on failure. Conversion to the + * -1-and-errno-set convention is done by the calling wrapper. + */ +safe_syscall_base: + .cfi_startproc + + /* The syscall calling convention isn't the same as the + * C one: + * we enter with x0 == *signal_pending + * x1 == syscall number + * x2, x3, x4, x5, x6, x7 == syscall arguments + * and return the result in x0 + * and the syscall instruction needs + * x8 == syscall number + * x0, x1, x2, x3, x4, x5 == syscall arguments + * and returns the result in r0 + * Shuffle everything around appropriately. + */ + mov x9, x0 /* signal-pending pointer */ + mov x8, x1 /* syscall number */ + /* and the syscall arguments */ + mov x0, x2 + mov x1, x3 + mov x2, x4 + mov x3, x5 + mov x4, x6 + mov x5, x7 + + /* 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 */ + ldr w10, [x9] + cmp w10, #0 + b.ne return_ERESTARTSYS + svc 0x0 +safe_syscall_end: + /* code path for having successfully executed the syscall */ + /* NB: we assume we're not trying to do old ARMv4T interworking */ + ret + +return_ERESTARTSYS: + /* code path when we didn't execute the syscall */ + mov x0, #-TARGET_ERESTARTSYS + ret + .cfi_endproc + + .size safe_syscall_base, .-safe_syscall_base -- cgit v1.2.3