Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Revert x86 sigcontext cleanups
This reverts commits 9a036b93a344 ("x86/signal/64: Remove 'fs' and 'gs'
from sigcontext") and c6f2062935c8 ("x86/signal/64: Fix SS handling for
signals delivered to 64-bit programs").
They were cleanups, but they break dosemu by changing the signal return
behavior (and removing 'fs' and 'gs' from the sigcontext struct - while
not actually changing any behavior - causes build problems).
Reported-and-tested-by: Stas Sergeev <stsp@list.ru>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+17
-36
+3
-3
arch/x86/include/asm/sigcontext.h
+3
-3
arch/x86/include/asm/sigcontext.h
···
57
57
unsigned long ip;
58
58
unsigned long flags;
59
59
unsigned short cs;
60
-
unsigned short __pad2; /* Was called gs, but was always zero. */
61
-
unsigned short __pad1; /* Was called fs, but was always zero. */
62
-
unsigned short ss;
60
+
unsigned short gs;
61
+
unsigned short fs;
62
+
unsigned short __pad0;
63
63
unsigned long err;
64
64
unsigned long trapno;
65
65
unsigned long oldmask;
+3
-18
arch/x86/include/uapi/asm/sigcontext.h
+3
-18
arch/x86/include/uapi/asm/sigcontext.h
···
177
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__u64 rip;
178
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__u64 eflags; /* RFLAGS */
179
179
__u16 cs;
180
-
181
-
/*
182
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* Prior to 2.5.64 ("[PATCH] x86-64 updates for 2.5.64-bk3"),
183
-
* Linux saved and restored fs and gs in these slots. This
184
-
* was counterproductive, as fsbase and gsbase were never
185
-
* saved, so arch_prctl was presumably unreliable.
186
-
*
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-
* If these slots are ever needed for any other purpose, there
188
-
* is some risk that very old 64-bit binaries could get
189
-
* confused. I doubt that many such binaries still work,
190
-
* though, since the same patch in 2.5.64 also removed the
191
-
* 64-bit set_thread_area syscall, so it appears that there is
192
-
* no TLS API that works in both pre- and post-2.5.64 kernels.
193
-
*/
194
-
__u16 __pad2; /* Was gs. */
195
-
__u16 __pad1; /* Was fs. */
196
-
197
-
__u16 ss;
180
+
__u16 gs;
181
+
__u16 fs;
182
+
__u16 __pad0;
198
183
__u64 err;
199
184
__u64 trapno;
200
185
__u64 oldmask;
+11
-15
arch/x86/kernel/signal.c
+11
-15
arch/x86/kernel/signal.c
···
93
93
COPY(r15);
94
94
#endif /* CONFIG_X86_64 */
95
95
96
+
#ifdef CONFIG_X86_32
96
97
COPY_SEG_CPL3(cs);
97
98
COPY_SEG_CPL3(ss);
99
+
#else /* !CONFIG_X86_32 */
100
+
/* Kernel saves and restores only the CS segment register on signals,
101
+
* which is the bare minimum needed to allow mixed 32/64-bit code.
102
+
* App's signal handler can save/restore other segments if needed. */
103
+
COPY_SEG_CPL3(cs);
104
+
#endif /* CONFIG_X86_32 */
98
105
99
106
get_user_ex(tmpflags, &sc->flags);
100
107
regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
···
161
154
#else /* !CONFIG_X86_32 */
162
155
put_user_ex(regs->flags, &sc->flags);
163
156
put_user_ex(regs->cs, &sc->cs);
164
-
put_user_ex(0, &sc->__pad2);
165
-
put_user_ex(0, &sc->__pad1);
166
-
put_user_ex(regs->ss, &sc->ss);
157
+
put_user_ex(0, &sc->gs);
158
+
put_user_ex(0, &sc->fs);
167
159
#endif /* CONFIG_X86_32 */
168
160
169
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put_user_ex(fpstate, &sc->fpstate);
···
457
451
458
452
regs->sp = (unsigned long)frame;
459
453
460
-
/*
461
-
* Set up the CS and SS registers to run signal handlers in
462
-
* 64-bit mode, even if the handler happens to be interrupting
463
-
* 32-bit or 16-bit code.
464
-
*
465
-
* SS is subtle. In 64-bit mode, we don't need any particular
466
-
* SS descriptor, but we do need SS to be valid. It's possible
467
-
* that the old SS is entirely bogus -- this can happen if the
468
-
* signal we're trying to deliver is #GP or #SS caused by a bad
469
-
* SS value.
470
-
*/
454
+
/* Set up the CS register to run signal handlers in 64-bit mode,
455
+
even if the handler happens to be interrupting 32-bit code. */
471
456
regs->cs = __USER_CS;
472
-
regs->ss = __USER_DS;
473
457
474
458
return 0;
475
459
}