linux-kernel - Re: [tip:x86/asm] x86/syscalls: Remove __SYSCALL_COMMON and __SYSCALL

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Message-ID: <CALCETrWJarxEuH4_hjPzrQ4Uf+bFqy1jf=96VoezRznAy9OAAQ@mail.gmail.com>
Date:	Fri, 29 Jan 2016 14:23:49 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Brian Gerst <brgerst@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>,
	tip-bot for Andy Lutomirski <tipbot@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [tip:x86/asm] x86/syscalls: Remove __SYSCALL_COMMON and __SYSCALL_X32

On Fri, Jan 29, 2016 at 2:19 PM, Brian Gerst <brgerst@...il.com> wrote:
> On Fri, Jan 29, 2016 at 4:23 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> On January 29, 2016 3:34:44 AM PST, tip-bot for Andy Lutomirski <tipbot@...or.com> wrote:
>>>Commit-ID:  32324ce15ea8cb4c8acc28acb2fd36fabf73e9db
>>>Gitweb:
>>>http://git.kernel.org/tip/32324ce15ea8cb4c8acc28acb2fd36fabf73e9db
>>>Author:     Andy Lutomirski <luto@...nel.org>
>>>AuthorDate: Thu, 28 Jan 2016 15:11:22 -0800
>>>Committer:  Ingo Molnar <mingo@...nel.org>
>>>CommitDate: Fri, 29 Jan 2016 09:46:37 +0100
>>>
>>>x86/syscalls: Remove __SYSCALL_COMMON and __SYSCALL_X32
>>>
>>>The common/64/x32 distinction has no effect other than
>>>determining which kernels actually support the syscall.  Move
>>>the logic into syscalltbl.sh.
>>>
>>>Signed-off-by: Andy Lutomirski <luto@...nel.org>
>>>Cc: Andy Lutomirski <luto@...capital.net>
>>>Cc: Borislav Petkov <bp@...en8.de>
>>>Cc: Brian Gerst <brgerst@...il.com>
>>>Cc: Denys Vlasenko <dvlasenk@...hat.com>
>>>Cc: Frederic Weisbecker <fweisbec@...il.com>
>>>Cc: H. Peter Anvin <hpa@...or.com>
>>>Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>>>Cc: Peter Zijlstra <peterz@...radead.org>
>>>Cc: Thomas Gleixner <tglx@...utronix.de>
>>>Link:
>>>http://lkml.kernel.org/r/58d4a95f40e43b894f93288b4a3633963d0ee22e.1454022279.git.luto@kernel.org
>>>Signed-off-by: Ingo Molnar <mingo@...nel.org>
>>>---
>>> arch/x86/entry/syscall_64.c           |  8 --------
>>> arch/x86/entry/syscalls/syscalltbl.sh | 17 ++++++++++++++++-
>>> arch/x86/kernel/asm-offsets_64.c      |  6 ------
>>> arch/x86/um/sys_call_table_64.c       |  3 ---
>>> arch/x86/um/user-offsets.c            |  2 --
>>> 5 files changed, 16 insertions(+), 20 deletions(-)
>>>
>>>diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c
>>>index 41283d2..974fd89 100644
>>>--- a/arch/x86/entry/syscall_64.c
>>>+++ b/arch/x86/entry/syscall_64.c
>>>@@ -6,14 +6,6 @@
>>> #include <asm/asm-offsets.h>
>>> #include <asm/syscall.h>
>>>
>>>-#define __SYSCALL_COMMON(nr, sym, compat) __SYSCALL_64(nr, sym,
>>>compat)
>>>-
>>>-#ifdef CONFIG_X86_X32_ABI
>>>-# define __SYSCALL_X32(nr, sym, compat) __SYSCALL_64(nr, sym, compat)
>>>-#else
>>>-# define __SYSCALL_X32(nr, sym, compat) /* nothing */
>>>-#endif
>>>-
>>>#define __SYSCALL_64(nr, sym, compat) extern asmlinkage long
>>>sym(unsigned long, unsigned long, unsigned long, unsigned long,
>>>unsigned long, unsigned long) ;
>>> #include <asm/syscalls_64.h>
>>> #undef __SYSCALL_64
>>>diff --git a/arch/x86/entry/syscalls/syscalltbl.sh
>>>b/arch/x86/entry/syscalls/syscalltbl.sh
>>>index 167965e..5ebeaf1 100644
>>>--- a/arch/x86/entry/syscalls/syscalltbl.sh
>>>+++ b/arch/x86/entry/syscalls/syscalltbl.sh
>>>@@ -18,6 +18,21 @@ emit() {
>>> grep '^[0-9]' "$in" | sort -n | (
>>>     while read nr abi name entry compat; do
>>>       abi=`echo "$abi" | tr '[a-z]' '[A-Z]'`
>>>-      emit "$abi" "$nr" "$entry" "$compat"
>>>+      if [ "$abi" == "COMMON" -o "$abi" == "64" ]; then
>>>+          # COMMON is the same as 64, except that we don't expect X32
>>>+          # programs to use it.  Our expectation has nothing to do with
>>>+          # any generated code, so treat them the same.
>>>+          emit 64 "$nr" "$entry" "$compat"
>>>+      elif [ "$abi" == "X32" ]; then
>>>+          # X32 is equivalent to 64 on an X32-compatible kernel.
>>>+          echo "#ifdef CONFIG_X86_X32_ABI"
>>>+          emit 64 "$nr" "$entry" "$compat"
>>>+          echo "#endif"
>>>+      elif [ "$abi" == "I386" ]; then
>>>+          emit "$abi" "$nr" "$entry" "$compat"
>>>+      else
>>>+          echo "Unknown abi $abi" >&2
>>>+          exit 1
>>>+      fi
>>>     done
>>> ) > "$out"
>>>diff --git a/arch/x86/kernel/asm-offsets_64.c
>>>b/arch/x86/kernel/asm-offsets_64.c
>>>index f2edafb..29db3b3 100644
>>>--- a/arch/x86/kernel/asm-offsets_64.c
>>>+++ b/arch/x86/kernel/asm-offsets_64.c
>>>@@ -5,12 +5,6 @@
>>> #include <asm/ia32.h>
>>>
>>> #define __SYSCALL_64(nr, sym, compat) [nr] = 1,
>>>-#define __SYSCALL_COMMON(nr, sym, compat) [nr] = 1,
>>>-#ifdef CONFIG_X86_X32_ABI
>>>-# define __SYSCALL_X32(nr, sym, compat) [nr] = 1,
>>>-#else
>>>-# define __SYSCALL_X32(nr, sym, compat) /* nothing */
>>>-#endif
>>> static char syscalls_64[] = {
>>> #include <asm/syscalls_64.h>
>>> };
>>>diff --git a/arch/x86/um/sys_call_table_64.c
>>>b/arch/x86/um/sys_call_table_64.c
>>>index b74ea6c..71a497c 100644
>>>--- a/arch/x86/um/sys_call_table_64.c
>>>+++ b/arch/x86/um/sys_call_table_64.c
>>>@@ -35,9 +35,6 @@
>>> #define stub_execveat sys_execveat
>>> #define stub_rt_sigreturn sys_rt_sigreturn
>>>
>>>-#define __SYSCALL_COMMON(nr, sym, compat) __SYSCALL_64(nr, sym,
>>>compat)
>>>-#define __SYSCALL_X32(nr, sym, compat) /* Not supported */
>>>-
>>>#define __SYSCALL_64(nr, sym, compat) extern asmlinkage long
>>>sym(unsigned long, unsigned long, unsigned long, unsigned long,
>>>unsigned long, unsigned long) ;
>>> #include <asm/syscalls_64.h>
>>>
>>>diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
>>>index ce7e360..5edf4f4 100644
>>>--- a/arch/x86/um/user-offsets.c
>>>+++ b/arch/x86/um/user-offsets.c
>>>@@ -15,8 +15,6 @@ static char syscalls[] = {
>>> };
>>> #else
>>> #define __SYSCALL_64(nr, sym, compat) [nr] = 1,
>>>-#define __SYSCALL_COMMON(nr, sym, compat) [nr] = 1,
>>>-#define __SYSCALL_X32(nr, sym, compat) /* Not supported */
>>> static char syscalls[] = {
>>> #include <asm/syscalls_64.h>
>>> };
>>
>> I am really unhappy about this change.  syscalltbl.sh is written so that other architectures can use it, and so I would really prefer for it to stay arch-neutral and encourage other arches to use it, too.
>
> We could use a qualifier (ie. /x32 or /x32ptregs) instead.

No combinatorial explosion, please.  We could use __SYSCALL(nr, sym,
abi, qual), though.

--Andy