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b35f549df1
At Linux Plumbers, Andy Lutomirski approached me and pointed out that the function call syscall_get_arguments() implemented in x86 was horribly written and not optimized for the standard case of passing in 0 and 6 for the starting index and the number of system calls to get. When looking at all the users of this function, I discovered that all instances pass in only 0 and 6 for these arguments. Instead of having this function handle different cases that are never used, simply rewrite it to return the first 6 arguments of a system call. This should help out the performance of tracing system calls by ptrace, ftrace and perf. Link: http://lkml.kernel.org/r/20161107213233.754809394@goodmis.org Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Dave Martin <dave.martin@arm.com> Cc: "Dmitry V. Levin" <ldv@altlinux.org> Cc: x86@kernel.org Cc: linux-snps-arc@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-c6x-dev@linux-c6x.org Cc: uclinux-h8-devel@lists.sourceforge.jp Cc: linux-hexagon@vger.kernel.org Cc: linux-ia64@vger.kernel.org Cc: linux-mips@vger.kernel.org Cc: nios2-dev@lists.rocketboards.org Cc: openrisc@lists.librecores.org Cc: linux-parisc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-riscv@lists.infradead.org Cc: linux-s390@vger.kernel.org Cc: linux-sh@vger.kernel.org Cc: sparclinux@vger.kernel.org Cc: linux-um@lists.infradead.org Cc: linux-xtensa@linux-xtensa.org Cc: linux-arch@vger.kernel.org Acked-by: Paul Burton <paul.burton@mips.com> # MIPS parts Acked-by: Max Filippov <jcmvbkbc@gmail.com> # For xtensa changes Acked-by: Will Deacon <will.deacon@arm.com> # For the arm64 bits Reviewed-by: Thomas Gleixner <tglx@linutronix.de> # for x86 Reviewed-by: Dmitry V. Levin <ldv@altlinux.org> Reported-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
168 lines
5.6 KiB
C
168 lines
5.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved.
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// Copyright (C) 2005-2017 Andes Technology Corporation
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#ifndef _ASM_NDS32_SYSCALL_H
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#define _ASM_NDS32_SYSCALL_H 1
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#include <linux/err.h>
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struct task_struct;
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struct pt_regs;
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/**
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* syscall_get_nr - find what system call a task is executing
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* @task: task of interest, must be blocked
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* @regs: task_pt_regs() of @task
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*
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* If @task is executing a system call or is at system call
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* tracing about to attempt one, returns the system call number.
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* If @task is not executing a system call, i.e. it's blocked
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* inside the kernel for a fault or signal, returns -1.
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*
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* Note this returns int even on 64-bit machines. Only 32 bits of
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* system call number can be meaningful. If the actual arch value
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* is 64 bits, this truncates to 32 bits so 0xffffffff means -1.
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*
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* It's only valid to call this when @task is known to be blocked.
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*/
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int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
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{
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return regs->syscallno;
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}
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/**
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* syscall_rollback - roll back registers after an aborted system call
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* @task: task of interest, must be in system call exit tracing
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* @regs: task_pt_regs() of @task
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*
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* It's only valid to call this when @task is stopped for system
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* call exit tracing (due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),
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* after tracehook_report_syscall_entry() returned nonzero to prevent
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* the system call from taking place.
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*
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* This rolls back the register state in @regs so it's as if the
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* system call instruction was a no-op. The registers containing
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* the system call number and arguments are as they were before the
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* system call instruction. This may not be the same as what the
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* register state looked like at system call entry tracing.
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*/
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void syscall_rollback(struct task_struct *task, struct pt_regs *regs)
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{
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regs->uregs[0] = regs->orig_r0;
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}
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/**
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* syscall_get_error - check result of traced system call
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* @task: task of interest, must be blocked
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* @regs: task_pt_regs() of @task
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*
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* Returns 0 if the system call succeeded, or -ERRORCODE if it failed.
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*
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* It's only valid to call this when @task is stopped for tracing on exit
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* from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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*/
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long syscall_get_error(struct task_struct *task, struct pt_regs *regs)
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{
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unsigned long error = regs->uregs[0];
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return IS_ERR_VALUE(error) ? error : 0;
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}
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/**
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* syscall_get_return_value - get the return value of a traced system call
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* @task: task of interest, must be blocked
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* @regs: task_pt_regs() of @task
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*
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* Returns the return value of the successful system call.
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* This value is meaningless if syscall_get_error() returned nonzero.
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*
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* It's only valid to call this when @task is stopped for tracing on exit
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* from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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*/
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long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs)
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{
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return regs->uregs[0];
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}
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/**
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* syscall_set_return_value - change the return value of a traced system call
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* @task: task of interest, must be blocked
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* @regs: task_pt_regs() of @task
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* @error: negative error code, or zero to indicate success
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* @val: user return value if @error is zero
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*
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* This changes the results of the system call that user mode will see.
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* If @error is zero, the user sees a successful system call with a
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* return value of @val. If @error is nonzero, it's a negated errno
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* code; the user sees a failed system call with this errno code.
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*
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* It's only valid to call this when @task is stopped for tracing on exit
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* from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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*/
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void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
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int error, long val)
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{
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regs->uregs[0] = (long)error ? error : val;
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}
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/**
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* syscall_get_arguments - extract system call parameter values
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* @task: task of interest, must be blocked
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* @regs: task_pt_regs() of @task
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* @args: array filled with argument values
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*
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* Fetches 6 arguments to the system call (from 0 through 5). The first
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* argument is stored in @args[0], and so on.
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*
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* It's only valid to call this when @task is stopped for tracing on
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* entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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*/
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#define SYSCALL_MAX_ARGS 6
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void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
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unsigned long *args)
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{
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args[0] = regs->orig_r0;
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args++;
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memcpy(args, ®s->uregs[0] + 1, 5 * sizeof(args[0]));
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}
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/**
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* syscall_set_arguments - change system call parameter value
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* @task: task of interest, must be in system call entry tracing
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* @regs: task_pt_regs() of @task
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* @i: argument index [0,5]
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* @n: number of arguments; n+i must be [1,6].
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* @args: array of argument values to store
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*
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* Changes @n arguments to the system call starting with the @i'th argument.
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* Argument @i gets value @args[0], and so on.
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* An arch inline version is probably optimal when @i and @n are constants.
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*
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* It's only valid to call this when @task is stopped for tracing on
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* entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
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* It's invalid to call this with @i + @n > 6; we only support system calls
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* taking up to 6 arguments.
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*/
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void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
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unsigned int i, unsigned int n,
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const unsigned long *args)
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{
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if (n == 0)
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return;
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if (i + n > SYSCALL_MAX_ARGS) {
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pr_warn("%s called with max args %d, handling only %d\n",
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__func__, i + n, SYSCALL_MAX_ARGS);
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n = SYSCALL_MAX_ARGS - i;
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}
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if (i == 0) {
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regs->orig_r0 = args[0];
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args++;
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i++;
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n--;
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}
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memcpy(®s->uregs[0] + i, args, n * sizeof(args[0]));
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}
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#endif /* _ASM_NDS32_SYSCALL_H */
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