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x86/entry/32: Enable pt_regs based syscalls 

Enable pt_regs based syscalls for 32-bit.  This makes the 32-bit native
kernel consistent with the 64-bit kernel, and improves the syscall
interface by not needing to push all 6 potential arguments onto the stack.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Link: https://lkml.kernel.org/r/20200313195144.164260-17-brgerst@gmail.com
This commit is contained in:
Brian Gerst 2020-03-13 15:51:42 -04:00 committed by Thomas Gleixner
parent 121b32a58a
commit 25c619e59b
6 changed files with 64 additions and 114 deletions
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2
arch/x86/Kconfig
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@ -30,7 +30,6 @@ config X86_64
select MODULES_USE_ELF_RELA
select NEED_DMA_MAP_STATE
select SWIOTLB
select ARCH_HAS_SYSCALL_WRAPPER
config FORCE_DYNAMIC_FTRACE
def_bool y
@ -80,6 +79,7 @@ config X86
select ARCH_HAS_STRICT_KERNEL_RWX
select ARCH_HAS_STRICT_MODULE_RWX
select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
select ARCH_HAS_SYSCALL_WRAPPER
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI

15
arch/x86/entry/common.c
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@ -333,20 +333,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
if (likely(nr < IA32_NR_syscalls)) {
nr = array_index_nospec(nr, IA32_NR_syscalls);
#ifdef CONFIG_IA32_EMULATION
regs->ax = ia32_sys_call_table[nr](regs);
#else
/*
* It's possible that a 32-bit syscall implementation
* takes a 64-bit parameter but nonetheless assumes that
* the high bits are zero. Make sure we zero-extend all
* of the args.
*/
regs->ax = ia32_sys_call_table[nr](
(unsigned int)regs->bx, (unsigned int)regs->cx,
(unsigned int)regs->dx, (unsigned int)regs->si,
(unsigned int)regs->di, (unsigned int)regs->bp);
#endif /* CONFIG_IA32_EMULATION */
}
syscall_return_slowpath(regs);
@ -439,9 +426,7 @@ __visible long do_fast_syscall_32(struct pt_regs *regs)
}
#endif
#ifdef CONFIG_X86_64
SYSCALL_DEFINE0(ni_syscall)
{
return -ENOSYS;
}
#endif

15
arch/x86/entry/syscall_32.c
View File

@ -4,33 +4,22 @@
#include <linux/linkage.h>
#include <linux/sys.h>
#include <linux/cache.h>
#include <linux/syscalls.h>
#include <asm/unistd.h>
#include <asm/syscall.h>
#ifdef CONFIG_IA32_EMULATION
/* On X86_64, we use struct pt_regs * to pass parameters to syscalls */
#define __SYSCALL_I386(nr, sym) extern asmlinkage long __ia32_##sym(const struct pt_regs *);
#define __sys_ni_syscall __ia32_sys_ni_syscall
#else /* CONFIG_IA32_EMULATION */
#define __SYSCALL_I386(nr, sym) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
#define __sys_ni_syscall sys_ni_syscall
#endif /* CONFIG_IA32_EMULATION */
#include <asm/syscalls_32.h>
#undef __SYSCALL_I386
#ifdef CONFIG_IA32_EMULATION
#define __SYSCALL_I386(nr, sym) [nr] = __ia32_##sym,
#else /* CONFIG_IA32_EMULATION */
#define __SYSCALL_I386(nr, sym) [nr] = sym,
#endif /* CONFIG_IA32_EMULATION */
__visible const sys_call_ptr_t ia32_sys_call_table[__NR_ia32_syscall_max+1] = {
/*
* Smells like a compiler bug -- it doesn't work
* when the & below is removed.
*/
[0 ... __NR_ia32_syscall_max] = &__sys_ni_syscall,
[0 ... __NR_ia32_syscall_max] = &__ia32_sys_ni_syscall,
#include <asm/syscalls_32.h>
};

6
arch/x86/include/asm/syscall.h
View File

@ -16,13 +16,7 @@
#include <asm/thread_info.h> /* for TS_COMPAT */
#include <asm/unistd.h>
#ifdef CONFIG_X86_64
typedef asmlinkage long (*sys_call_ptr_t)(const struct pt_regs *);
#else
typedef asmlinkage long (*sys_call_ptr_t)(unsigned long, unsigned long,
unsigned long, unsigned long,
unsigned long, unsigned long);
#endif /* CONFIG_X86_64 */
extern const sys_call_ptr_t sys_call_table[];
#if defined(CONFIG_X86_32)

111
arch/x86/include/asm/syscall_wrapper.h
View File

@ -11,6 +11,47 @@ struct pt_regs;
extern asmlinkage long __x64_sys_ni_syscall(const struct pt_regs *regs);
extern asmlinkage long __ia32_sys_ni_syscall(const struct pt_regs *regs);
/*
* Instead of the generic __SYSCALL_DEFINEx() definition, the x86 version takes
* struct pt_regs *regs as the only argument of the syscall stub(s) named as:
* __x64_sys_*() - 64-bit native syscall
* __ia32_sys_*() - 32-bit native syscall or common compat syscall
* __ia32_compat_sys_*() - 32-bit compat syscall
* __x32_compat_sys_*() - 64-bit X32 compat syscall
*
* The registers are decoded according to the ABI:
* 64-bit: RDI, RSI, RDX, R10, R8, R9
* 32-bit: EBX, ECX, EDX, ESI, EDI, EBP
*
* The stub then passes the decoded arguments to the __se_sys_*() wrapper to
* perform sign-extension (omitted for zero-argument syscalls). Finally the
* arguments are passed to the __do_sys_*() function which is the actual
* syscall. These wrappers are marked as inline so the compiler can optimize
* the functions where appropriate.
*
* Example assembly (slightly re-ordered for better readability):
*
* <__x64_sys_recv>: <-- syscall with 4 parameters
* callq <__fentry__>
*
* mov 0x70(%rdi),%rdi <-- decode regs->di
* mov 0x68(%rdi),%rsi <-- decode regs->si
* mov 0x60(%rdi),%rdx <-- decode regs->dx
* mov 0x38(%rdi),%rcx <-- decode regs->r10
*
* xor %r9d,%r9d <-- clear %r9
* xor %r8d,%r8d <-- clear %r8
*
* callq __sys_recvfrom <-- do the actual work in __sys_recvfrom()
* which takes 6 arguments
*
* cltq <-- extend return value to 64-bit
* retq <-- return
*
* This approach avoids leaking random user-provided register content down
* the call chain.
*/
/* Mapping of registers to parameters for syscalls on x86-64 and x32 */
#define SC_X86_64_REGS_TO_ARGS(x, ...) \
__MAP(x,__SC_ARGS \
@ -68,6 +109,26 @@ extern asmlinkage long __ia32_sys_ni_syscall(const struct pt_regs *regs);
#define __X64_SYS_NI(name)
#endif /* CONFIG_X86_64 */
#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
#define __IA32_SYS_STUB0(name) \
__SYS_STUB0(ia32, sys_##name)
#define __IA32_SYS_STUBx(x, name, ...) \
__SYS_STUBx(ia32, sys##name, \
SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
#define __IA32_COND_SYSCALL(name) \
__COND_SYSCALL(ia32, sys_##name)
#define __IA32_SYS_NI(name) \
__SYS_NI(ia32, sys_##name)
#else /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
#define __IA32_SYS_STUB0(name)
#define __IA32_SYS_STUBx(x, name, ...)
#define __IA32_COND_SYSCALL(name)
#define __IA32_SYS_NI(name)
#endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
#ifdef CONFIG_IA32_EMULATION
/*
* For IA32 emulation, we need to handle "compat" syscalls *and* create
@ -90,27 +151,11 @@ extern asmlinkage long __ia32_sys_ni_syscall(const struct pt_regs *regs);
#define __IA32_COMPAT_SYS_NI(name) \
__SYS_NI(ia32, compat_sys_##name)
#define __IA32_SYS_STUB0(name) \
__SYS_STUB0(ia32, sys_##name)
#define __IA32_SYS_STUBx(x, name, ...) \
__SYS_STUBx(ia32, sys##name, \
SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
#define __IA32_COND_SYSCALL(name) \
__COND_SYSCALL(ia32, sys_##name)
#define __IA32_SYS_NI(name) \
__SYS_NI(ia32, sys_##name)
#else /* CONFIG_IA32_EMULATION */
#define __IA32_COMPAT_SYS_STUB0(name)
#define __IA32_COMPAT_SYS_STUBx(x, name, ...)
#define __IA32_COMPAT_COND_SYSCALL(name)
#define __IA32_COMPAT_SYS_NI(name)
#define __IA32_SYS_STUB0(name)
#define __IA32_SYS_STUBx(x, name, ...)
#define __IA32_COND_SYSCALL(name)
#define __IA32_SYS_NI(name)
#endif /* CONFIG_IA32_EMULATION */
@ -180,40 +225,6 @@ extern asmlinkage long __ia32_sys_ni_syscall(const struct pt_regs *regs);
#endif /* CONFIG_COMPAT */
/*
* Instead of the generic __SYSCALL_DEFINEx() definition, this macro takes
* struct pt_regs *regs as the only argument of the syscall stub named
* __x64_sys_*(). It decodes just the registers it needs and passes them on to
* the __se_sys_*() wrapper performing sign extension and then to the
* __do_sys_*() function doing the actual job. These wrappers and functions
* are inlined (at least in very most cases), meaning that the assembly looks
* as follows (slightly re-ordered for better readability):
*
* <__x64_sys_recv>: <-- syscall with 4 parameters
* callq <__fentry__>
*
* mov 0x70(%rdi),%rdi <-- decode regs->di
* mov 0x68(%rdi),%rsi <-- decode regs->si
* mov 0x60(%rdi),%rdx <-- decode regs->dx
* mov 0x38(%rdi),%rcx <-- decode regs->r10
*
* xor %r9d,%r9d <-- clear %r9
* xor %r8d,%r8d <-- clear %r8
*
* callq __sys_recvfrom <-- do the actual work in __sys_recvfrom()
* which takes 6 arguments
*
* cltq <-- extend return value to 64-bit
* retq <-- return
*
* This approach avoids leaking random user-provided register content down
* the call chain.
*
* If IA32_EMULATION is enabled, this macro generates an additional wrapper
* named __ia32_sys_*() which decodes the struct pt_regs *regs according
* to the i386 calling convention (bx, cx, dx, si, di, bp).
*/
#define __SYSCALL_DEFINEx(x, name, ...) \
static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\

29
arch/x86/include/asm/syscalls.h
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@ -17,33 +17,4 @@
/* kernel/ioport.c */
long ksys_ioperm(unsigned long from, unsigned long num, int turn_on);
#ifdef CONFIG_X86_32
/*
* These definitions are only valid on pure 32-bit systems; x86-64 uses a
* different syscall calling convention
*/
asmlinkage long sys_ioperm(unsigned long, unsigned long, int);
asmlinkage long sys_iopl(unsigned int);
/* kernel/ldt.c */
asmlinkage long sys_modify_ldt(int, void __user *, unsigned long);
/* kernel/signal.c */
asmlinkage long sys_rt_sigreturn(void);
/* kernel/tls.c */
asmlinkage long sys_set_thread_area(struct user_desc __user *);
asmlinkage long sys_get_thread_area(struct user_desc __user *);
/* X86_32 only */
/* kernel/signal.c */
asmlinkage long sys_sigreturn(void);
/* kernel/vm86_32.c */
struct vm86_struct;
asmlinkage long sys_vm86old(struct vm86_struct __user *);
asmlinkage long sys_vm86(unsigned long, unsigned long);
#endif /* CONFIG_X86_32 */
#endif /* _ASM_X86_SYSCALLS_H */