diff options
| author | Andy Lutomirski <luto@amacapital.net> | 2015-03-12 23:57:52 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-03-17 11:25:26 +0300 |
| commit | 9a036b93a344235b7899401d04e97c34f3a2554c (patch) | |
| tree | 62a66cf3356c6fdd4835868d6fae5816a1c12cb3 /arch/x86 | |
| parent | c6f2062935c8fcb31235799eaee8bcd5b649936b (diff) | |
| download | linux-9a036b93a344235b7899401d04e97c34f3a2554c.tar.xz | |
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 <luto@amacapital.net>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/844f8490e938780c03355be4c9b69eb4c494bf4e.1426193719.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/include/asm/sigcontext.h | 4 | ||||
| -rw-r--r-- | arch/x86/include/uapi/asm/sigcontext.h | 19 | ||||
| -rw-r--r-- | 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 f910cdcb71fd..6fe6b182c998 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 076b11fd6fa1..16dc4e8a2cd3 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 e2f6061a9003..edcb862cdcae 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 */ |