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

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Date:	Fri, 29 Jan 2016 17:19:29 -0500
From:	Brian Gerst <brgerst@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-tip-commits@...r.kernel.org,
	tip-bot for Andy Lutomirski <tipbot@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	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 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.

--
Brian Gerst