Re: [PATCH v6 1/9] ppc64 (le): prepare for -mprofile-kernel
From: Jiri Kosina <jikos@kernel.org>
Date: 2016-02-04 21:48:01
Also in:
lkml
On Thu, 4 Feb 2016, AKASHI Takahiro wrote:
On arm/arm64, link register must be saved before any function call. So anyhow we will have to add something, 3 instructions at the minimum, like: save lr branch _mcount restore lr <prologue> ... <body> ...
This means that we have at least two architectures that need one instruction before the mcount/mfentry call, and the rest of the prologue to follow afterwards. On x86, we don't need any "pre-prologue". Persumably the corresponding opcodes have different sizes. This nicely demonstrates my point -- if this one-gcc-option-to-rule-them-all would exist, it needs to be generic enough to describe these kinds of constraints (who knows what other restrictions will pop up when exploring other, more exotic, architectures later). Thanks, -- Jiri Kosina SUSE Labs