Commit-ID: e82f114d61effc06385f61bce9047a8f13d28337 Gitweb: http://git.kernel.org/tip/e82f114d61effc06385f61bce9047a8f13d28337 Author: Andy Lutomirski <[email protected]> AuthorDate: Thu, 12 Mar 2015 13:57:52 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 16 Mar 2015 09:14:51 +0100
x86/signal/64: Remove 'fs' and 'gs' from sigcontext As far as I can tell, these fields have been set to zero on save and ignored on restore since Linux was imported into git. Rename them '__pad1' and '__pad2' to avoid confusion. This may also allow us to recycle them some day. This also adds a comment clarifying the history of those fields. I'm intentionally avoiding calling either of them '__pad0': the field formerly known as '__pad0' is now 'ss'. Signed-off-by: Andy Lutomirski <[email protected]> Reviewed-by: Oleg Nesterov <[email protected]> Cc: Al Viro <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/844f8490e938780c03355be4c9b69eb4c494bf4e.1426193719.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/include/asm/sigcontext.h | 4 ++-- arch/x86/include/uapi/asm/sigcontext.h | 19 +++++++++++++++++-- arch/x86/kernel/signal.c | 4 ++-- 3 files changed, 21 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/sigcontext.h b/arch/x86/include/asm/sigcontext.h index f910cdc..6fe6b18 100644 --- a/arch/x86/include/asm/sigcontext.h +++ b/arch/x86/include/asm/sigcontext.h @@ -57,8 +57,8 @@ struct sigcontext { unsigned long ip; unsigned long flags; unsigned short cs; - unsigned short gs; - unsigned short fs; + unsigned short __pad2; /* Was called gs, but was always zero. */ + unsigned short __pad1; /* Was called fs, but was always zero. */ unsigned short ss; unsigned long err; unsigned long trapno; diff --git a/arch/x86/include/uapi/asm/sigcontext.h b/arch/x86/include/uapi/asm/sigcontext.h index 076b11f..16dc4e8 100644 --- a/arch/x86/include/uapi/asm/sigcontext.h +++ b/arch/x86/include/uapi/asm/sigcontext.h @@ -177,8 +177,23 @@ struct sigcontext { __u64 rip; __u64 eflags; /* RFLAGS */ __u16 cs; - __u16 gs; - __u16 fs; + + /* + * Prior to 2.5.64 ("[PATCH] x86-64 updates for 2.5.64-bk3"), + * Linux saved and restored fs and gs in these slots. This + * was counterproductive, as fsbase and gsbase were never + * saved, so arch_prctl was presumably unreliable. + * + * If these slots are ever needed for any other purpose, there + * is some risk that very old 64-bit binaries could get + * confused. I doubt that many such binaries still work, + * though, since the same patch in 2.5.64 also removed the + * 64-bit set_thread_area syscall, so it appears that there is + * no TLS API that works in both pre- and post-2.5.64 kernels. + */ + __u16 __pad2; /* Was gs. */ + __u16 __pad1; /* Was fs. */ + __u16 ss; __u64 err; __u64 trapno; diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index e2f6061..edcb862 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -155,8 +155,8 @@ int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate, #else /* !CONFIG_X86_32 */ put_user_ex(regs->flags, &sc->flags); put_user_ex(regs->cs, &sc->cs); - put_user_ex(0, &sc->gs); - put_user_ex(0, &sc->fs); + put_user_ex(0, &sc->__pad2); + put_user_ex(0, &sc->__pad1); put_user_ex(regs->ss, &sc->ss); #endif /* CONFIG_X86_32 */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
