diff options
| 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/Kconfig | |
| parent | 1bd21c6c21e848996339508d3ffb106d505256a8 (diff) | |
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/Kconfig')
| -rw-r--r-- | arch/x86/Kconfig | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 27fede438959..67348efc2540 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2954,3 +2954,8 @@ source "crypto/Kconfig" source "arch/x86/kvm/Kconfig" source "lib/Kconfig" + +config SYSCALL_PTREGS + def_bool y + depends on X86_64 && !COMPAT + select ARCH_HAS_SYSCALL_WRAPPER |