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Commit 7303e30e authored by Dominik Brodowski's avatar Dominik Brodowski Committed by Ingo Molnar
Browse files

syscalls/core: Prepare CONFIG_ARCH_HAS_SYSCALL_WRAPPER=y for compat syscalls 



It may be useful for an architecture to override the definitions of the
COMPAT_SYSCALL_DEFINE0() and __COMPAT_SYSCALL_DEFINEx() macros in
<linux/compat.h>, in particular to use a different calling convention
for syscalls. This patch provides a mechanism to do so, based on the
previously introduced CONFIG_ARCH_HAS_SYSCALL_WRAPPER. If it is enabled,
<asm/sycall_wrapper.h> is included in <linux/compat.h> and may be used
to define the macros mentioned above. Moreover, as the syscall calling
convention may be different if CONFIG_ARCH_HAS_SYSCALL_WRAPPER is set,
the compat syscall function prototypes in <linux/compat.h> are #ifndef'd
out in that case.

As some of the syscalls and/or compat syscalls may not be present,
the COND_SYSCALL() and COND_SYSCALL_COMPAT() macros in kernel/sys_ni.c
as well as the SYS_NI() and COMPAT_SYS_NI() macros in
kernel/time/posix-stubs.c can be re-defined in <asm/syscall_wrapper.h> iff
CONFIG_ARCH_HAS_SYSCALL_WRAPPER is enabled.

Signed-off-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180405095307.3730-5-linux@dominikbrodowski.net


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent fa697140

include/linux/compat.h

+22 −0
Original line number Diff line number Diff line
@@ -24,6 +24,17 @@ 
#include <asm/siginfo.h>

#include <asm/signal.h>



#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER

/*

 * It may be useful for an architecture to override the definitions of the

 * COMPAT_SYSCALL_DEFINE0 and COMPAT_SYSCALL_DEFINEx() macros, in particular

 * to use a different calling convention for syscalls. To allow for that,

 + the prototypes for the compat_sys_*() functions below will *not* be included

 * if CONFIG_ARCH_HAS_SYSCALL_WRAPPER is enabled.

 */

#include <asm/syscall_wrapper.h>

#endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */



#ifndef COMPAT_USE_64BIT_TIME

#define COMPAT_USE_64BIT_TIME 0

#endif
@@ -32,10 +43,12 @@ 
#define __SC_DELOUSE(t,v) ((__force t)(unsigned long)(v))

#endif



#ifndef COMPAT_SYSCALL_DEFINE0

#define COMPAT_SYSCALL_DEFINE0(name) \

	asmlinkage long compat_sys_##name(void); \

	ALLOW_ERROR_INJECTION(compat_sys_##name, ERRNO); \

	asmlinkage long compat_sys_##name(void)

#endif /* COMPAT_SYSCALL_DEFINE0 */



#define COMPAT_SYSCALL_DEFINE1(name, ...) \

        COMPAT_SYSCALL_DEFINEx(1, _##name, __VA_ARGS__)
@@ -50,6 +63,7 @@ 
#define COMPAT_SYSCALL_DEFINE6(name, ...) \

	COMPAT_SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)



#ifndef COMPAT_SYSCALL_DEFINEx

#define COMPAT_SYSCALL_DEFINEx(x, name, ...)				\

	asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\

	asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
@@ -62,6 +76,7 @@ 
		return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\

	}								\

	static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))

#endif /* COMPAT_SYSCALL_DEFINEx */



#ifndef compat_user_stack_pointer

#define compat_user_stack_pointer() current_user_stack_pointer()
@@ -517,7 +532,12 @@ int __compat_save_altstack(compat_stack_t __user *, unsigned long); 
 * Please note that these prototypes here are only provided for information

 * purposes, for static analysis, and for linking from the syscall table.

 * These functions should not be called elsewhere from kernel code.

 *

 * As the syscall calling convention may be different from the default

 * for architectures overriding the syscall calling convention, do not

 * include the prototypes if CONFIG_ARCH_HAS_SYSCALL_WRAPPER is enabled.

 */

#ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER

asmlinkage long compat_sys_io_setup(unsigned nr_reqs, u32 __user *ctx32p);

asmlinkage long compat_sys_io_submit(compat_aio_context_t ctx_id, int nr,

				     u32 __user *iocb);
@@ -955,6 +975,8 @@ asmlinkage long compat_sys_stime(compat_time_t __user *tptr); 
/* obsolete: net/socket.c */

asmlinkage long compat_sys_socketcall(int call, u32 __user *args);



#endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */





/*

 * For most but not all architectures, "am I in a compat syscall?" and

init/Kconfig

+6 −3
Original line number Diff line number Diff line
@@ -1925,8 +1925,11 @@ config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE 
	bool



# It may be useful for an architecture to override the definitions of the

# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>,

# in particular to use a different calling convention for syscalls.

# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>

# and the COMPAT_ variants in <linux/compat.h>, in particular to use a

# different calling convention for syscalls. They can also override the

# macros for not-implemented syscalls in kernel/sys_ni.c and

# kernel/time/posix-stubs.c. All these overrides need to be available in

# <asm/syscall_wrapper.h>.

config ARCH_HAS_SYSCALL_WRAPPER

	def_bool n
 
	depends on !COMPAT

kernel/sys_ni.c

+10 −0
Original line number Diff line number Diff line
@@ -5,6 +5,11 @@ 


#include <asm/unistd.h>



#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER

/* Architectures may override COND_SYSCALL and COND_SYSCALL_COMPAT */

#include <asm/syscall_wrapper.h>

#endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */



/*  we can't #include <linux/syscalls.h> here,

    but tell gcc to not warn with -Wmissing-prototypes  */

asmlinkage long sys_ni_syscall(void);
@@ -17,8 +22,13 @@ asmlinkage long sys_ni_syscall(void) 
	return -ENOSYS;

}



#ifndef COND_SYSCALL

#define COND_SYSCALL(name) cond_syscall(sys_##name)

#endif /* COND_SYSCALL */



#ifndef COND_SYSCALL_COMPAT

#define COND_SYSCALL_COMPAT(name) cond_syscall(compat_sys_##name)

#endif /* COND_SYSCALL_COMPAT */



/*

 * This list is kept in the same order as include/uapi/asm-generic/unistd.h.

kernel/time/posix-stubs.c

+10 −0
Original line number Diff line number Diff line
@@ -19,6 +19,11 @@ 
#include <linux/posix-timers.h>

#include <linux/compat.h>



#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER

/* Architectures may override SYS_NI and COMPAT_SYS_NI */

#include <asm/syscall_wrapper.h>

#endif



asmlinkage long sys_ni_posix_timers(void)

{

	pr_err_once("process %d (%s) attempted a POSIX timer syscall "
@@ -27,8 +32,13 @@ asmlinkage long sys_ni_posix_timers(void) 
	return -ENOSYS;

}



#ifndef SYS_NI

#define SYS_NI(name)  SYSCALL_ALIAS(sys_##name, sys_ni_posix_timers)

#endif



#ifndef COMPAT_SYS_NI

#define COMPAT_SYS_NI(name)  SYSCALL_ALIAS(compat_sys_##name, sys_ni_posix_timers)

#endif



SYS_NI(timer_create);

SYS_NI(timer_gettime);