Commit fca460f9 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x32: Handle the x32 system call flag 



x32 shares most system calls with x86-64, but unfortunately some
subsystem (the input subsystem is the chief offender) which require
is_compat() when operating with a 32-bit userspace.  The input system
actually has text files in sysfs whose meaning is dependent on
sizeof(long) in userspace!

We could solve this by having two completely disjoint system call
tables; requiring that each system call be duplicated.  This patch
takes a different approach: we add a flag to the system call number;
this flag doesn't affect the system call dispatch but requests compat
treatment from affected subsystems for the duration of the system call.

The change of cmpq to cmpl is safe since it immediately follows the
and.

Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 9d389763

arch/x86/include/asm/compat.h

+11 −2
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#include <linux/types.h>

#include <linux/sched.h>

#include <asm/user32.h>

#include <asm/unistd.h>



#define COMPAT_USER_HZ		100

#define COMPAT_UTS_MACHINE	"i686\0\0"
@@ -212,9 +213,17 @@ static inline void __user *arch_compat_alloc_user_space(long len) 
	return (void __user *)regs->sp - len;

}



static inline int is_compat_task(void)

static inline bool is_compat_task(void)

{

	return current_thread_info()->status & TS_COMPAT;

#ifdef CONFIG_IA32_EMULATION

	if (current_thread_info()->status & TS_COMPAT)

		return true;

#endif

#ifdef CONFIG_X86_X32_ABI

	if (task_pt_regs(current)->orig_ax & __X32_SYSCALL_BIT)

		return true;

#endif

	return false;

}



#endif /* _ASM_X86_COMPAT_H */

arch/x86/include/asm/syscall.h

+3 −2
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/sched.h>

#include <linux/err.h>

#include <asm/asm-offsets.h>	/* For NR_syscalls */

#include <asm/unistd.h>



extern const unsigned long sys_call_table[];
@@ -26,13 +27,13 @@ extern const unsigned long sys_call_table[]; 
 */

static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)

{

	return regs->orig_ax;

	return regs->orig_ax & __SYSCALL_MASK;

}



static inline void syscall_rollback(struct task_struct *task,

				    struct pt_regs *regs)

{

	regs->ax = regs->orig_ax;

	regs->ax = regs->orig_ax & __SYSCALL_MASK;

}



static inline long syscall_get_error(struct task_struct *task,

arch/x86/include/asm/unistd.h

+7 −0
Original line number Diff line number Diff line
@@ -5,6 +5,13 @@ 
#define __X32_SYSCALL_BIT	0x40000000



#ifdef __KERNEL__



# ifdef CONFIG_X86_X32_ABI

#  define __SYSCALL_MASK (~(__X32_SYSCALL_BIT))

# else

#  define __SYSCALL_MASK (~0)

# endif



# ifdef CONFIG_X86_32



#  include <asm/unistd_32.h>

arch/x86/kernel/entry_64.S

+10 −0
Original line number Diff line number Diff line
@@ -482,7 +482,12 @@ GLOBAL(system_call_after_swapgs) 
	testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)

	jnz tracesys

system_call_fastpath:

#if __SYSCALL_MASK == ~0

	cmpq $__NR_syscall_max,%rax

#else

	andl $__SYSCALL_MASK,%eax

	cmpl $__NR_syscall_max,%eax

#endif

	ja badsys

	movq %r10,%rcx

	call *sys_call_table(,%rax,8)  # XXX:	 rip relative
@@ -596,7 +601,12 @@ tracesys: 
	 */

	LOAD_ARGS ARGOFFSET, 1

	RESTORE_REST

#if __SYSCALL_MASK == ~0

	cmpq $__NR_syscall_max,%rax

#else

	andl $__SYSCALL_MASK,%eax

	cmpl $__NR_syscall_max,%eax

#endif

	ja   int_ret_from_sys_call	/* RAX(%rsp) set to -ENOSYS above */

	movq %r10,%rcx	/* fixup for C */

	call *sys_call_table(,%rax,8)

CRA Git | Maintained and supported by SUSTech CRA and CCSE