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syscalls/core: Prepare CONFIG_ARCH_HAS_SYSCALL_WRAPPER=y for compat syscalls

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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: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Linus 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dominik Brodowski 2018-04-05 11:53:03 +02:00 committed by Ingo Molnar
parent fa697140f9
commit 7303e30ec1
4 changed files with 48 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
include/linux/compat.h
View File

@ -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

9
init/Kconfig
View File

@ -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

10
kernel/sys_ni.c
View File

@ -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.

10
kernel/time/posix-stubs.c
View File

@ -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);