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syscalls/x86: Use 'struct pt_regs' based syscall calling for IA32_EMULATION and x32

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Extend ARCH_HAS_SYSCALL_WRAPPER for i386 emulation and for x32 on 64-bit
x86.

For x32, all we need to do is to create an additional stub for each
compat syscall which decodes the parameters in x86-64 ordering, e.g.:

	asmlinkage long __compat_sys_x32_xyzzy(struct pt_regs *regs)
	{
		return c_SyS_xyzzy(regs->di, regs->si, regs->dx);
	}

For i386 emulation, we need to teach compat_sys_*() to take struct
pt_regs as its only argument, e.g.:

	asmlinkage long __compat_sys_ia32_xyzzy(struct pt_regs *regs)
	{
		return c_SyS_xyzzy(regs->bx, regs->cx, regs->dx);
	}

In addition, we need to create additional stubs for common syscalls
(that is, for syscalls which have the same parameters on 32-bit and
64-bit), e.g.:

	asmlinkage long __sys_ia32_xyzzy(struct pt_regs *regs)
	{
		return c_sys_xyzzy(regs->bx, regs->cx, regs->dx);
	}

This approach avoids leaking random user-provided register content down
the call chain.

This patch is based on an original proof-of-concept

 | From: Linus Torvalds <torvalds@linux-foundation.org>
 | Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

and was split up and heavily modified by me, in particular to base it on
ARCH_HAS_SYSCALL_WRAPPER.

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/20180405095307.3730-6-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dominik Brodowski
2018-04-05 11:53:04 +02:00
committed by Ingo Molnar
parent 7303e30ec1
commit ebeb8c82ff
6 changed files with 509 additions and 380 deletions
Download Patch File Download Diff File Expand all files Collapse all files

117
arch/x86/include/asm/syscall_wrapper.h
View File

@@ -6,6 +6,111 @@
#ifndef _ASM_X86_SYSCALL_WRAPPER_H
#define _ASM_X86_SYSCALL_WRAPPER_H
/* Mapping of registers to parameters for syscalls on x86-64 and x32 */
#define SC_X86_64_REGS_TO_ARGS(x, ...) \
__MAP(x,__SC_ARGS \
,,regs->di,,regs->si,,regs->dx \
,,regs->r10,,regs->r8,,regs->r9) \
/* Mapping of registers to parameters for syscalls on i386 */
#define SC_IA32_REGS_TO_ARGS(x, ...) \
__MAP(x,__SC_ARGS \
,,(unsigned int)regs->bx,,(unsigned int)regs->cx \
,,(unsigned int)regs->dx,,(unsigned int)regs->si \
,,(unsigned int)regs->di,,(unsigned int)regs->bp)
#ifdef CONFIG_IA32_EMULATION
/*
* For IA32 emulation, we need to handle "compat" syscalls *and* create
* additional wrappers (aptly named __sys_ia32_sys_xyzzy) which decode the
* ia32 regs in the proper order for shared or "common" syscalls. As some
* syscalls may not be implemented, we need to expand COND_SYSCALL in
* kernel/sys_ni.c and SYS_NI in kernel/time/posix-stubs.c to cover this
* case as well.
*/
#define COMPAT_SC_IA32_STUBx(x, name, ...) \
asmlinkage long __compat_sys_ia32##name(const struct pt_regs *regs);\
ALLOW_ERROR_INJECTION(__compat_sys_ia32##name, ERRNO); \
asmlinkage long __compat_sys_ia32##name(const struct pt_regs *regs)\
{ \
return c_SyS##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__));\
} \
#define SC_IA32_WRAPPERx(x, name, ...) \
asmlinkage long __sys_ia32##name(const struct pt_regs *regs); \
ALLOW_ERROR_INJECTION(__sys_ia32##name, ERRNO); \
asmlinkage long __sys_ia32##name(const struct pt_regs *regs) \
{ \
return SyS##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__)); \
}
#define COND_SYSCALL(name) \
cond_syscall(sys_##name); \
cond_syscall(__sys_ia32_##name)
#define SYS_NI(name) \
SYSCALL_ALIAS(sys_##name, sys_ni_posix_timers); \
SYSCALL_ALIAS(__sys_ia32_##name, sys_ni_posix_timers)
#else /* CONFIG_IA32_EMULATION */
#define COMPAT_SC_IA32_STUBx(x, name, ...)
#define SC_IA32_WRAPPERx(x, fullname, name, ...)
#endif /* CONFIG_IA32_EMULATION */
#ifdef CONFIG_X86_X32
/*
* For the x32 ABI, we need to create a stub for compat_sys_*() which is aware
* of the x86-64-style parameter ordering of x32 syscalls. The syscalls common
* with x86_64 obviously do not need such care.
*/
#define COMPAT_SC_X32_STUBx(x, name, ...) \
asmlinkage long __compat_sys_x32##name(const struct pt_regs *regs);\
ALLOW_ERROR_INJECTION(__compat_sys_x32##name, ERRNO); \
asmlinkage long __compat_sys_x32##name(const struct pt_regs *regs)\
{ \
return c_SyS##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\
} \
#else /* CONFIG_X86_X32 */
#define COMPAT_SC_X32_STUBx(x, name, ...)
#endif /* CONFIG_X86_X32 */
#ifdef CONFIG_COMPAT
/*
* Compat means IA32_EMULATION and/or X86_X32. As they use a different
* mapping of registers to parameters, we need to generate stubs for each
* of them. There is no need to implement COMPAT_SYSCALL_DEFINE0, as it is
* unused on x86.
*/
#define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
static long c_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
COMPAT_SC_IA32_STUBx(x, name, __VA_ARGS__) \
COMPAT_SC_X32_STUBx(x, name, __VA_ARGS__) \
static long c_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
{ \
return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__)); \
} \
static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
/*
* As some compat syscalls may not be implemented, we need to expand
* COND_SYSCALL_COMPAT in kernel/sys_ni.c and COMPAT_SYS_NI in
* kernel/time/posix-stubs.c to cover this case as well.
*/
#define COND_SYSCALL_COMPAT(name) \
cond_syscall(__compat_sys_ia32_##name); \
cond_syscall(__compat_sys_x32_##name)
#define COMPAT_SYS_NI(name) \
SYSCALL_ALIAS(__compat_sys_ia32_##name, sys_ni_posix_timers); \
SYSCALL_ALIAS(__compat_sys_x32_##name, sys_ni_posix_timers)
#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
@@ -34,9 +139,14 @@
* 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 __sys_ia32_*() which decodes the struct pt_regs *regs according
* to the i386 calling convention (bx, cx, dx, si, di, bp).
*
* As the generic SYSCALL_DEFINE0() macro does not decode any parameters for
* obvious reasons, and passing struct pt_regs *regs to it in %rdi does not
* hurt, there is no need to override it.
* hurt, there is no need to override it, or to define it differently for
* IA32_EMULATION.
*/
#define __SYSCALL_DEFINEx(x, name, ...) \
asmlinkage long sys##name(const struct pt_regs *regs); \
@@ -45,10 +155,9 @@
static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
asmlinkage long sys##name(const struct pt_regs *regs) \
{ \
return SyS##name(__MAP(x,__SC_ARGS \
,,regs->di,,regs->si,,regs->dx \
,,regs->r10,,regs->r8,,regs->r9)); \
return SyS##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\
} \
SC_IA32_WRAPPERx(x, name, __VA_ARGS__) \
static long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
{ \
long ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \