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[PATCH v3 1/3] syscalls,x86 Expose arch_prctl on x86-32.

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  [PATCH v3 1/3] syscalls,x86 Expose arch_prctl on x86-32. Kyle Huey <me@kylehuey.com> - 2016-09-16 01:40 +0200
    Re: [PATCH v3 1/3] syscalls,x86 Expose arch_prctl on x86-32. Andy Lutomirski <luto@amacapital.net> - 2016-09-16 02:00 +0200
    Re: [PATCH v3 1/3] syscalls,x86 Expose arch_prctl on x86-32. Thomas Gleixner <tglx@linutronix.de> - 2016-09-16 10:00 +0200
      Re: [PATCH v3 1/3] syscalls,x86 Expose arch_prctl on x86-32. Kyle Huey <me@kylehuey.com> - 2016-09-16 18:00 +0200

#1484618 — [PATCH v3 1/3] syscalls,x86 Expose arch_prctl on x86-32.

arch_prctl is currently 64-bit only. Wire it up for 32-bits, as a no-op for
now. Rename the second arg to a more generic name.

Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
 arch/x86/entry/syscalls/syscall_32.tbl |  1 +
 arch/x86/include/asm/proto.h           |  5 ++++-
 arch/x86/kernel/process.c              | 10 ++++++++++
 arch/x86/kernel/process_64.c           | 33 +++++++++++++++++++++------------
 arch/x86/kernel/ptrace.c               |  8 ++++----
 arch/x86/um/Makefile                   |  2 +-
 arch/x86/um/syscalls_32.c              |  7 +++++++
 arch/x86/um/syscalls_64.c              |  4 ++--
 include/linux/compat.h                 |  2 ++
 9 files changed, 52 insertions(+), 20 deletions(-)
 create mode 100644 arch/x86/um/syscalls_32.c

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index f848572..666fa61 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -386,3 +386,4 @@
 377	i386	copy_file_range		sys_copy_file_range
 378	i386	preadv2			sys_preadv2			compat_sys_preadv2
 379	i386	pwritev2		sys_pwritev2			compat_sys_pwritev2
+380	i386	arch_prctl		compat_sys_arch_prctl		compat_sys_arch_prctl
diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
index 9b9b30b..f0e86aa 100644
--- a/arch/x86/include/asm/proto.h
+++ b/arch/x86/include/asm/proto.h
@@ -30,6 +30,9 @@ void x86_report_nx(void);
 
 extern int reboot_force;
 
-long do_arch_prctl(struct task_struct *task, int code, unsigned long addr);
+long do_arch_prctl_common(struct task_struct *task, int code, unsigned long addr);
+#ifdef CONFIG_X86_64
+long do_arch_prctl_64(struct task_struct *task, int code, unsigned long addr);
+#endif
 
 #endif /* _ASM_X86_PROTO_H */
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 62c0b0e..1421451 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -567,3 +567,13 @@ unsigned long get_wchan(struct task_struct *p)
 	} while (count++ < 16 && p->state != TASK_RUNNING);
 	return 0;
 }
+
+long do_arch_prctl_common(struct task_struct *task, int code, unsigned long arg2)
+{
+	return -EINVAL;
+}
+
+asmlinkage long compat_sys_arch_prctl(int code, unsigned long arg2)
+{
+	return do_arch_prctl_common(current, code, arg2);
+}
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 63236d8..0e44608 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -35,6 +35,7 @@
 #include <linux/uaccess.h>
 #include <linux/io.h>
 #include <linux/ftrace.h>
+#include <linux/syscalls.h>
 
 #include <asm/pgtable.h>
 #include <asm/processor.h>
@@ -196,7 +197,7 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 				(struct user_desc __user *)tls, 0);
 		else
 #endif
-			err = do_arch_prctl(p, ARCH_SET_FS, tls);
+			err = do_arch_prctl_64(p, ARCH_SET_FS, tls);
 		if (err)
 			goto out;
 	}
@@ -524,7 +525,7 @@ void set_personality_ia32(bool x32)
 }
 EXPORT_SYMBOL_GPL(set_personality_ia32);
 
-long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
+long do_arch_prctl_64(struct task_struct *task, int code, unsigned long arg2)
 {
 	int ret = 0;
 	int doit = task == current;
@@ -532,48 +533,50 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
 
 	switch (code) {
 	case ARCH_SET_GS:
-		if (addr >= TASK_SIZE_MAX)
+		if (arg2 >= TASK_SIZE_MAX)
 			return -EPERM;
 		cpu = get_cpu();
 		task->thread.gsindex = 0;
-		task->thread.gsbase = addr;
+		task->thread.gsbase = arg2;
 		if (doit) {
 			load_gs_index(0);
-			ret = wrmsrl_safe(MSR_KERNEL_GS_BASE, addr);
+			ret = wrmsrl_safe(MSR_KERNEL_GS_BASE, arg2);
 		}
 		put_cpu();
 		break;
 	case ARCH_SET_FS:
 		/* Not strictly needed for fs, but do it for symmetry
 		   with gs */
-		if (addr >= TASK_SIZE_MAX)
+		if (arg2 >= TASK_SIZE_MAX)
 			return -EPERM;
 		cpu = get_cpu();
 		task->thread.fsindex = 0;
-		task->thread.fsbase = addr;
+		task->thread.fsbase = arg2;
 		if (doit) {
 			/* set the selector to 0 to not confuse __switch_to */
 			loadsegment(fs, 0);
-			ret = wrmsrl_safe(MSR_FS_BASE, addr);
+			ret = wrmsrl_safe(MSR_FS_BASE, arg2);
 		}
 		put_cpu();
 		break;
 	case ARCH_GET_FS: {
 		unsigned long base;
+
 		if (doit)
 			rdmsrl(MSR_FS_BASE, base);
 		else
 			base = task->thread.fsbase;
-		ret = put_user(base, (unsigned long __user *)addr);
+		ret = put_user(base, (unsigned long __user *)arg2);
 		break;
 	}
 	case ARCH_GET_GS: {
 		unsigned long base;
+
 		if (doit)
 			rdmsrl(MSR_KERNEL_GS_BASE, base);
 		else
 			base = task->thread.gsbase;
-		ret = put_user(base, (unsigned long __user *)addr);
+		ret = put_user(base, (unsigned long __user *)arg2);
 		break;
 	}
 
@@ -585,9 +588,15 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
 	return ret;
 }
 
-long sys_arch_prctl(int code, unsigned long addr)
+SYSCALL_DEFINE2(arch_prctl, int, code, unsigned long, arg2)
 {
-	return do_arch_prctl(current, code, addr);
+	long ret;
+
+	ret = do_arch_prctl_64(current, code, arg2);
+	if (ret == -EINVAL)
+		ret = do_arch_prctl_common(current, code, arg2);
+
+	return ret;
 }
 
 unsigned long KSTK_ESP(struct task_struct *task)
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index f79576a..030cbc5 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -395,12 +395,12 @@ static int putreg(struct task_struct *child,
 		if (value >= TASK_SIZE_MAX)
 			return -EIO;
 		/*
-		 * When changing the segment base, use do_arch_prctl
+		 * When changing the segment base, use do_arch_prctl_64
 		 * to set either thread.fs or thread.fsindex and the
 		 * corresponding GDT slot.
 		 */
 		if (child->thread.fsbase != value)
-			return do_arch_prctl(child, ARCH_SET_FS, value);
+			return do_arch_prctl_64(child, ARCH_SET_FS, value);
 		return 0;
 	case offsetof(struct user_regs_struct,gs_base):
 		/*
@@ -409,7 +409,7 @@ static int putreg(struct task_struct *child,
 		if (value >= TASK_SIZE_MAX)
 			return -EIO;
 		if (child->thread.gsbase != value)
-			return do_arch_prctl(child, ARCH_SET_GS, value);
+			return do_arch_prctl_64(child, ARCH_SET_GS, value);
 		return 0;
 #endif
 	}
@@ -868,7 +868,7 @@ long arch_ptrace(struct task_struct *child, long request,
 		   Works just like arch_prctl, except that the arguments
 		   are reversed. */
 	case PTRACE_ARCH_PRCTL:
-		ret = do_arch_prctl(child, data, addr);
+		ret = do_arch_prctl_64(child, data, addr);
 		break;
 #endif
 
diff --git a/arch/x86/um/Makefile b/arch/x86/um/Makefile
index 3ee2bb6..5e039d6 100644
--- a/arch/x86/um/Makefile
+++ b/arch/x86/um/Makefile
@@ -16,7 +16,7 @@ obj-y = bug.o bugs_$(BITS).o delay.o fault.o ksyms.o ldt.o \
 
 ifeq ($(CONFIG_X86_32),y)
 
-obj-y += checksum_32.o
+obj-y += checksum_32.o syscalls_32.o
 obj-$(CONFIG_ELF_CORE) += elfcore.o
 
 subarch-y = ../lib/string_32.o ../lib/atomic64_32.o ../lib/atomic64_cx8_32.o
diff --git a/arch/x86/um/syscalls_32.c b/arch/x86/um/syscalls_32.c
new file mode 100644
index 0000000..c6812c1
--- /dev/null
+++ b/arch/x86/um/syscalls_32.c
@@ -0,0 +1,7 @@
+#include <linux/syscalls.h>
+#include <os.h>
+
+long compat_sys_arch_prctl(int code, unsigned long arg2)
+{
+	return -EINVAL;
+}
diff --git a/arch/x86/um/syscalls_64.c b/arch/x86/um/syscalls_64.c
index e655227..d0a7160 100644
--- a/arch/x86/um/syscalls_64.c
+++ b/arch/x86/um/syscalls_64.c
@@ -72,9 +72,9 @@ long arch_prctl(struct task_struct *task, int code, unsigned long __user *addr)
 	return ret;
 }
 
-long sys_arch_prctl(int code, unsigned long addr)
+long sys_arch_prctl(int code, unsigned long arg2)
 {
-	return arch_prctl(current, code, (unsigned long __user *) addr);
+	return arch_prctl(current, code, (unsigned long __user *) arg2);
 }
 
 void arch_switch_to(struct task_struct *to)
diff --git a/include/linux/compat.h b/include/linux/compat.h
index f964ef7..0039d53 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -722,6 +722,8 @@ asmlinkage long compat_sys_sched_rr_get_interval(compat_pid_t pid,
 asmlinkage long compat_sys_fanotify_mark(int, unsigned int, __u32, __u32,
 					    int, const char __user *);
 
+asmlinkage long compat_sys_arch_prctl(int, unsigned long);
+
 /*
  * For most but not all architectures, "am I in a compat syscall?" and
  * "am I a compat task?" are the same question.  For architectures on which
-- 
2.9.3

base-commit: 4cea8776571b18db7485930cb422faa739580c8c

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#1484627

On Thu, Sep 15, 2016 at 4:33 PM, Kyle Huey <me@kylehuey.com> wrote:
> arch_prctl is currently 64-bit only. Wire it up for 32-bits, as a no-op for
> now. Rename the second arg to a more generic name.
>
> Signed-off-by: Kyle Huey <khuey@kylehuey.com>
> ---
>  arch/x86/entry/syscalls/syscall_32.tbl |  1 +
>  arch/x86/include/asm/proto.h           |  5 ++++-
>  arch/x86/kernel/process.c              | 10 ++++++++++
>  arch/x86/kernel/process_64.c           | 33 +++++++++++++++++++++------------
>  arch/x86/kernel/ptrace.c               |  8 ++++----
>  arch/x86/um/Makefile                   |  2 +-
>  arch/x86/um/syscalls_32.c              |  7 +++++++
>  arch/x86/um/syscalls_64.c              |  4 ++--
>  include/linux/compat.h                 |  2 ++
>  9 files changed, 52 insertions(+), 20 deletions(-)
>  create mode 100644 arch/x86/um/syscalls_32.c
>
> diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
> index f848572..666fa61 100644
> --- a/arch/x86/entry/syscalls/syscall_32.tbl
> +++ b/arch/x86/entry/syscalls/syscall_32.tbl
> @@ -386,3 +386,4 @@
>  377    i386    copy_file_range         sys_copy_file_range
>  378    i386    preadv2                 sys_preadv2                     compat_sys_preadv2
>  379    i386    pwritev2                sys_pwritev2                    compat_sys_pwritev2
> +380    i386    arch_prctl              compat_sys_arch_prctl           compat_sys_arch_prctl

Let's call this sys_arch_prctl_32, even if it's unconventional.  See below.

> diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
> index 9b9b30b..f0e86aa 100644
> --- a/arch/x86/include/asm/proto.h
> +++ b/arch/x86/include/asm/proto.h
> @@ -30,6 +30,9 @@ void x86_report_nx(void);
>
>  extern int reboot_force;
>
> -long do_arch_prctl(struct task_struct *task, int code, unsigned long addr);
> +long do_arch_prctl_common(struct task_struct *task, int code, unsigned long addr);
> +#ifdef CONFIG_X86_64
> +long do_arch_prctl_64(struct task_struct *task, int code, unsigned long addr);
> +#endif
>
>  #endif /* _ASM_X86_PROTO_H */
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index 62c0b0e..1421451 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -567,3 +567,13 @@ unsigned long get_wchan(struct task_struct *p)
>         } while (count++ < 16 && p->state != TASK_RUNNING);
>         return 0;
>  }
> +
> +long do_arch_prctl_common(struct task_struct *task, int code, unsigned long arg2)
> +{
> +       return -EINVAL;
> +}
> +
> +asmlinkage long compat_sys_arch_prctl(int code, unsigned long arg2)

I believe you mean COMPAT_SYSCALL_DEFINE2 here.

But I see what you're doing here.  Could you instead do:

#if defined(CONFIG_IA32_EMULATION) || defined(CONFIG_X86_32)
#ifdef CONFIG_X86_32
COMPAT_SYSCALL_DEFINE2(...)
#else
SYSCALL_DEFINE2(...)
#endif

... body here ...
#endif

and name the thing do_arch_prctl_32?

It's too bad we don't have a SYSCALL_DEFINE_32 macro.  But you could add one...


> diff --git a/arch/x86/um/syscalls_32.c b/arch/x86/um/syscalls_32.c
> new file mode 100644
> index 0000000..c6812c1
> --- /dev/null
> +++ b/arch/x86/um/syscalls_32.c
> @@ -0,0 +1,7 @@
> +#include <linux/syscalls.h>
> +#include <os.h>
> +
> +long compat_sys_arch_prctl(int code, unsigned long arg2)

COMPAT_SYSCALL_DEFINE2

Also, does this really need a new file?

> -long sys_arch_prctl(int code, unsigned long addr)
> +long sys_arch_prctl(int code, unsigned long arg2)

SYSCALL_DEFINE2

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#1484757

On Thu, 15 Sep 2016, Kyle Huey wrote:

First of all, please add a cover letter [PATCH 0/N] to your patch series
and send it with something which provides proper mail threading. 
See: git-send-email, quilt 

> arch_prctl is currently 64-bit only. Wire it up for 32-bits, as a no-op for
> now. Rename the second arg to a more generic name.

This changelog is useless.

- it does not provide any rationale for this change, i.e. why this is
  required. Just because its 64bit only is not a reason.

- "Rename the second arg to a more generic name" does not give
  any useful information.

Misleading information is worse than no information.

Further your patch does 5 things at once. It wants to be split into parts:

1) Rename do_arch_prctl() and change the argument name,

> -long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
> +long do_arch_prctl_64(struct task_struct *task, int code, unsigned long arg2)

2) Provide do_arch_prctl_common() and hook it up to the arch_prctl syscall

> -long sys_arch_prctl(int code, unsigned long addr)
> +SYSCALL_DEFINE2(arch_prctl, int, code, unsigned long, arg2)
>  {
> -	return do_arch_prctl(current, code, addr);
> +	long ret;
> +
> +	ret = do_arch_prctl_64(current, code, arg2);
> +	if (ret == -EINVAL)
> +		ret = do_arch_prctl_common(current, code, arg2);
> +
> +	return ret;
>  }

3) Implement the compat version
  
Thanks,

	tflx

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#1485147

On Fri, Sep 16, 2016 at 12:50 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Thu, 15 Sep 2016, Kyle Huey wrote:
>
> First of all, please add a cover letter [PATCH 0/N] to your patch series
> and send it with something which provides proper mail threading.
> See: git-send-email, quilt

I did ... seems like using git-send-email with
--cc-cmd=scripts/get_maintainer.pl is not a good idea since people get
CCd to some parts of the thread and not others.

https://lkml.org/lkml/2016/9/15/811

>> arch_prctl is currently 64-bit only. Wire it up for 32-bits, as a no-op for
>> now. Rename the second arg to a more generic name.
>
> This changelog is useless.
>
> - it does not provide any rationale for this change, i.e. why this is
>   required. Just because its 64bit only is not a reason.
>
> - "Rename the second arg to a more generic name" does not give
>   any useful information.
>
> Misleading information is worse than no information.
>
> Further your patch does 5 things at once. It wants to be split into parts:
>
> 1) Rename do_arch_prctl() and change the argument name,
>
>> -long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
>> +long do_arch_prctl_64(struct task_struct *task, int code, unsigned long arg2)
>
> 2) Provide do_arch_prctl_common() and hook it up to the arch_prctl syscall
>
>> -long sys_arch_prctl(int code, unsigned long addr)
>> +SYSCALL_DEFINE2(arch_prctl, int, code, unsigned long, arg2)
>>  {
>> -     return do_arch_prctl(current, code, addr);
>> +     long ret;
>> +
>> +     ret = do_arch_prctl_64(current, code, arg2);
>> +     if (ret == -EINVAL)
>> +             ret = do_arch_prctl_common(current, code, arg2);
>> +
>> +     return ret;
>>  }
>
> 3) Implement the compat version

Ok.

- Kyle

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