From 8b4b9f27e57584f3d90e0bb84cf800ad81cfe3a1 Mon Sep 17 00:00:00 2001 From: Paul Moore Date: Fri, 15 Feb 2013 12:21:43 -0500 Subject: [PATCH] x86: remove the x32 syscall bitmask from syscall_get_nr() Commit fca460f95e928bae373daa8295877b6905bc62b8 simplified the x32 implementation by creating a syscall bitmask, equal to 0x40000000, that could be applied to x32 syscalls such that the masked syscall number would be the same as a x86_64 syscall. While that patch was a nice way to simplify the code, it went a bit too far by adding the mask to syscall_get_nr(); returning the masked syscall numbers can cause confusion with callers that expect syscall numbers matching the x32 ABI, e.g. unmasked syscall numbers. This patch fixes this by simply removing the mask from syscall_get_nr() while preserving the other changes from the original commit. While there are several syscall_get_nr() callers in the kernel, most simply check that the syscall number is greater than zero, in this case this patch will have no effect. Of those remaining callers, they appear to be few, seccomp and ftrace, and from my testing of seccomp without this patch the original commit definitely breaks things; the seccomp filter does not correctly filter the syscalls due to the difference in syscall numbers in the BPF filter and the value from syscall_get_nr(). Applying this patch restores the seccomp BPF filter functionality on x32. I've tested this patch with the seccomp BPF filters as well as ftrace and everything looks reasonable to me; needless to say general usage seemed fine as well. Signed-off-by: Paul Moore Link: http://lkml.kernel.org/r/20130215172143.12549.10292.stgit@localhost Cc: Cc: Will Drewry Cc: H. Peter Anvin Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/syscall.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h index 1ace47b62592..2e188d68397c 100644 --- a/arch/x86/include/asm/syscall.h +++ b/arch/x86/include/asm/syscall.h @@ -29,13 +29,13 @@ 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 & __SYSCALL_MASK; + return regs->orig_ax; } static inline void syscall_rollback(struct task_struct *task, struct pt_regs *regs) { - regs->ax = regs->orig_ax & __SYSCALL_MASK; + regs->ax = regs->orig_ax; } static inline long syscall_get_error(struct task_struct *task, -- 2.30.2