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author | Dominik Brodowski <linux@dominikbrodowski.net> | 2018-04-05 11:53:02 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2018-04-05 16:59:26 +0200 |
commit | fa697140f9a20119a9ec8fd7460cc4314fbdaff3 (patch) | |
tree | f7dbd8c7fe4b9a4db2fb4f14f5faf9f51956ef43 /arch/x86/include/asm | |
parent | 1bd21c6c21e848996339508d3ffb106d505256a8 (diff) | |
download | op-kernel-dev-fa697140f9a20119a9ec8fd7460cc4314fbdaff3.zip op-kernel-dev-fa697140f9a20119a9ec8fd7460cc4314fbdaff3.tar.gz |
syscalls/x86: Use 'struct pt_regs' based syscall calling convention for 64-bit syscalls
Let's make use of ARCH_HAS_SYSCALL_WRAPPER=y on pure 64-bit x86-64 systems:
Each syscall defines a stub which takes struct pt_regs as its only
argument. It decodes just those parameters it needs, e.g:
asmlinkage long sys_xyzzy(const struct pt_regs *regs)
{
return SyS_xyzzy(regs->di, regs->si, regs->dx);
}
This approach avoids leaking random user-provided register content down
the call chain.
For example, for sys_recv() which is a 4-parameter syscall, the assembly
now is (in slightly reordered fashion):
<sys_recv>:
callq <__fentry__>
/* decode regs->di, ->si, ->dx and ->r10 */
mov 0x70(%rdi),%rdi
mov 0x68(%rdi),%rsi
mov 0x60(%rdi),%rdx
mov 0x38(%rdi),%rcx
[ SyS_recv() is automatically inlined by the compiler,
as it is not [yet] used anywhere else ]
/* clear %r9 and %r8, the 5th and 6th args */
xor %r9d,%r9d
xor %r8d,%r8d
/* do the actual work */
callq __sys_recvfrom
/* cleanup and return */
cltq
retq
The only valid place in an x86-64 kernel which rightfully calls
a syscall function on its own -- vsyscall -- needs to be modified
to pass struct pt_regs onwards as well.
To keep the syscall table generation working independent of
SYSCALL_PTREGS being enabled, the stubs are named the same as the
"original" syscall stubs, i.e. sys_*().
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, to limit it to 64-bit-only for the time being,
and to update the vsyscall to the new calling convention.
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/20180405095307.3730-4-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm')
-rw-r--r-- | arch/x86/include/asm/syscall.h | 4 | ||||
-rw-r--r-- | arch/x86/include/asm/syscall_wrapper.h | 70 | ||||
-rw-r--r-- | arch/x86/include/asm/syscalls.h | 7 |
3 files changed, 81 insertions, 0 deletions
diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h index 03eedc2..17c6237 100644 --- a/arch/x86/include/asm/syscall.h +++ b/arch/x86/include/asm/syscall.h @@ -20,9 +20,13 @@ #include <asm/thread_info.h> /* for TS_COMPAT */ #include <asm/unistd.h> +#ifdef CONFIG_SYSCALL_PTREGS +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_SYSCALL_PTREGS */ extern const sys_call_ptr_t sys_call_table[]; #if defined(CONFIG_X86_32) diff --git a/arch/x86/include/asm/syscall_wrapper.h b/arch/x86/include/asm/syscall_wrapper.h new file mode 100644 index 0000000..702bdee --- /dev/null +++ b/arch/x86/include/asm/syscall_wrapper.h @@ -0,0 +1,70 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * syscall_wrapper.h - x86 specific wrappers to syscall definitions + */ + +#ifndef _ASM_X86_SYSCALL_WRAPPER_H +#define _ASM_X86_SYSCALL_WRAPPER_H + +/* + * Instead of the generic __SYSCALL_DEFINEx() definition, this macro takes + * struct pt_regs *regs as the only argument of the syscall stub named + * sys_*(). It decodes just the registers it needs and passes them on to + * the SyS_*() wrapper and then to the SYSC_*() function doing the actual job. + * These wrappers and functions are inlined, meaning that the assembly looks + * as follows (slightly re-ordered): + * + * <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. + * + * 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. + */ +#define __SYSCALL_DEFINEx(x, name, ...) \ + asmlinkage long sys##name(const struct pt_regs *regs); \ + ALLOW_ERROR_INJECTION(sys##name, ERRNO); \ + static long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \ + 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)); \ + } \ + static long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \ + { \ + long ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \ + __MAP(x,__SC_TEST,__VA_ARGS__); \ + __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \ + return ret; \ + } \ + static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)) + +/* + * For VSYSCALLS, we need to declare these three syscalls with the new + * pt_regs-based calling convention for in-kernel use. + */ +struct pt_regs; +asmlinkage long sys_getcpu(const struct pt_regs *regs); /* di,si,dx */ +asmlinkage long sys_gettimeofday(const struct pt_regs *regs); /* di,si */ +asmlinkage long sys_time(const struct pt_regs *regs); /* di */ + +#endif /* _ASM_X86_SYSCALL_WRAPPER_H */ diff --git a/arch/x86/include/asm/syscalls.h b/arch/x86/include/asm/syscalls.h index ae6e05f..e4ad93c 100644 --- a/arch/x86/include/asm/syscalls.h +++ b/arch/x86/include/asm/syscalls.h @@ -18,6 +18,12 @@ /* Common in X86_32 and X86_64 */ /* kernel/ioport.c */ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on); + +#ifndef CONFIG_SYSCALL_PTREGS +/* + * If CONFIG_SYSCALL_PTREGS is enabled, a different syscall calling convention + * is used. Do not include these -- invalid -- prototypes then + */ asmlinkage long sys_ioperm(unsigned long, unsigned long, int); asmlinkage long sys_iopl(unsigned int); @@ -53,4 +59,5 @@ asmlinkage long sys_mmap(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long); #endif /* CONFIG_X86_32 */ +#endif /* CONFIG_SYSCALL_PTREGS */ #endif /* _ASM_X86_SYSCALLS_H */ |