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Date: Thu, 23 Jul 2020 01:20:00 +0200
From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>,
linux-sh@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>,
Rich Felker <dalias@...c.org>
Subject: Re: [PATCH 2/4] sh: Rearrange blocks in entry-common.S
On 7/23/20 1:13 AM, Michael Karcher wrote:
> This avoids out-of-range jumps that get auto-replaced by the assembler
> and prepares for the changes needed to implement SECCOMP_FILTER cleanly.
>
> Signed-off-by: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>
> ---
> arch/sh/kernel/entry-common.S | 57 ++++++++++++++++++-----------------
> 1 file changed, 29 insertions(+), 28 deletions(-)
>
> diff --git a/arch/sh/kernel/entry-common.S b/arch/sh/kernel/entry-common.S
> index 9bac5bbb67f3..c4d88d61890d 100644
> --- a/arch/sh/kernel/entry-common.S
> +++ b/arch/sh/kernel/entry-common.S
> @@ -178,34 +178,6 @@ syscall_exit_work:
> bra resume_userspace
> nop
>
> - .align 2
> -syscall_trace_entry:
> - ! Yes it is traced.
> - mov r15, r4
> - mov.l 7f, r11 ! Call do_syscall_trace_enter which notifies
> - jsr @r11 ! superior (will chomp R[0-7])
> - nop
> - mov.l r0, @(OFF_R0,r15) ! Save return value
> - ! Reload R0-R4 from kernel stack, where the
> - ! parent may have modified them using
> - ! ptrace(POKEUSR). (Note that R0-R2 are
> - ! reloaded from the kernel stack by syscall_call
> - ! below, so don't need to be reloaded here.)
> - ! This allows the parent to rewrite system calls
> - ! and args on the fly.
> - mov.l @(OFF_R4,r15), r4 ! arg0
> - mov.l @(OFF_R5,r15), r5
> - mov.l @(OFF_R6,r15), r6
> - mov.l @(OFF_R7,r15), r7 ! arg3
> - mov.l @(OFF_R3,r15), r3 ! syscall_nr
> - !
> - mov.l 6f, r10 ! Number of syscalls
> - cmp/hs r10, r3
> - bf syscall_call
> - mov #-ENOSYS, r0
> - bra syscall_exit
> - mov.l r0, @(OFF_R0,r15) ! Return value
> -
> __restore_all:
> mov #OFF_SR, r0
> mov.l @(r0,r15), r0 ! get status register
> @@ -388,6 +360,35 @@ syscall_exit:
> bf syscall_exit_work
> bra __restore_all
> nop
> +
> + .align 2
> +syscall_trace_entry:
> + ! Yes it is traced.
> + mov r15, r4
> + mov.l 7f, r11 ! Call do_syscall_trace_enter which notifies
> + jsr @r11 ! superior (will chomp R[0-7])
> + nop
> + mov.l r0, @(OFF_R0,r15) ! Save return value
> + ! Reload R0-R4 from kernel stack, where the
> + ! parent may have modified them using
> + ! ptrace(POKEUSR). (Note that R0-R2 are
> + ! reloaded from the kernel stack by syscall_call
> + ! below, so don't need to be reloaded here.)
> + ! This allows the parent to rewrite system calls
> + ! and args on the fly.
> + mov.l @(OFF_R4,r15), r4 ! arg0
> + mov.l @(OFF_R5,r15), r5
> + mov.l @(OFF_R6,r15), r6
> + mov.l @(OFF_R7,r15), r7 ! arg3
> + mov.l @(OFF_R3,r15), r3 ! syscall_nr
> + !
> + mov.l 6f, r10 ! Number of syscalls
> + cmp/hs r10, r3
> + bf syscall_call
> + mov #-ENOSYS, r0
> + bra syscall_exit
> + mov.l r0, @(OFF_R0,r15) ! Return value
> +
> .align 2
> #if !defined(CONFIG_CPU_SH2)
> 1: .long TRA
>
Tested-by: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
--
.''`. John Paul Adrian Glaubitz
: :' : Debian Developer - glaubitz@...ian.org
`. `' Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
`- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
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