From: AKASHI Takahiro <takahiro.akashi@linaro.org>
Date: Fri, 28 Nov 2014 05:26:35 +0000 (+0000)
Subject: arm64: ptrace: allow tracer to skip a system call
X-Git-Tag: omap-for-v3.19/fixes-for-merge-window~18^2~12
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1014c81d9a5546b64352c04cdb93494aceb317fc;p=pandora-kernel.git

arm64: ptrace: allow tracer to skip a system call

If tracer modifies a syscall number to -1, this traced system call should
be skipped with a return value specified in x0.
This patch implements this semantics.

Please note:
* syscall entry tracing and syscall exit tracing (ftrace tracepoint and
  audit) are always executed, if enabled, even when skipping a system call
  (that is, -1).
  In this way, we can avoid a potential bug where audit_syscall_entry()
  might be called without audit_syscall_exit() at the previous system call
  being called, that would cause OOPs in audit_syscall_entry().

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
[will: fixed up conflict with blr rework]
Signed-off-by: Will Deacon <will.deacon@arm.com>
---

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