[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <20231105213731.1878100-1-ubizjak@gmail.com>
Date: Sun, 5 Nov 2023 22:34:34 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH -tip v2 0/3] x86/callthunks: Fix and unify call thunk assembly snippets
Currently INCREMENT_CALL_DEPTH and thunk debug macros explicitly
define %gs: segment register prefix for their percpu variables.
This is not compatible with !CONFIG_SMP, which requires non-prefixed
percpu variables.
Contrary to alternatives, relocations are currently not supported in
call thunk templates. Due to unsupported relocations, two variants of
INCREMENT_CALL_DEPTH macro are needed, ASM_ prefixed that allows
relocations and non-prefixed version that allows only absolute
addresses.
The following patch series fixes above issues by
a) Making PER_CPU_VAR macro from percpu.h also available without
__ASSEMBLY__, so it can be used in 'asm' statements to conditionally
use %gs: segment register prefix, depending on CONFIG_SMP.
b) Re-using existing infrastructure from alternative.c to allow
%rip-relative relocations when copying call thunk template from its
storage location.
c) Fixing call thunks debug macros to use PER_CPU_VAR macro from
percpu.h to conditionally use %gs: segment register prefix, depending
on CONFIG_SMP.
d) Unifying ASM_ prefixed assembly macros with their non-prefixed
variants. With support of %rip-relative relocations in place, call
thunk templates allow %rip-relative addressing, so unified assembly
snippet can be used everywhere.
v2:
- Make PER_CPU_VAR macro available in 'asm' statements instead of
moving 'asm' statements to *.S assembly files.
- Re-use existing relocation infrastructure from alternative.c
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Uros Bizjak (3):
x86/percpu: Define PER_CPU_VAR macro also for !__ASSEMBLY__
x86/callthunks: Handle %rip-relative relocations in call thunk
template
x86/callthunks: Fix and unify call thunks assembly snippets
arch/x86/include/asm/nospec-branch.h | 23 ++++++--------------
arch/x86/include/asm/percpu.h | 5 +++++
arch/x86/include/asm/text-patching.h | 2 ++
arch/x86/kernel/alternative.c | 3 +--
arch/x86/kernel/callthunks.c | 32 ++++++++++++++++++++++------
5 files changed, 40 insertions(+), 25 deletions(-)
--
2.41.0
Powered by blists - more mailing lists