[prev in list] [next in list] [prev in thread] [next in thread]
List: qemu-ppc
Subject: Re: [PATCH 1/2] common-user/host/ppc: Implement safe-syscall.inc.S
From: Daniel Henrique Barboza <danielhb413 () gmail ! com>
Date: 2022-07-30 10:35:25
Message-ID: 9c95bf54-d246-42dc-1e8f-6d15327bd702 () gmail ! com
[Download RAW message or body]
On 7/29/22 14:21, Richard Henderson wrote:
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> common-user/host/ppc/safe-syscall.inc.S | 107 ++++++++++++++++++++++++
> 1 file changed, 107 insertions(+)
> create mode 100644 common-user/host/ppc/safe-syscall.inc.S
>
> 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 0000000000..0851f6c0b8
> --- /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
[prev in list] [next in list] [prev in thread] [next in thread]
Configure |
About |
News |
Add a list |
Sponsored by KoreLogic