forked from Minki/linux
fbfe9c847e
Some time ago Jeff prepared 42daba3165 ("uml: stop saving process FP
state") for UML to stop saving the process FP state between task
switches. The assumption was that since with SKAS0 every guest process
runs inside a host process context the host OS will take care of keeping
the proper FP state.
Unfortunately this is not true for multi-threaded applications, where
all guest threads share a single host process context yet all may use
the FPU on their own. Although I haven't verified it I suspect things
to be even worse in SKAS3 mode where all guest processes run inside a
single host process.
The patch reintroduces the saving and restoring of the FP context
between task switches.
[richard@nod.at: Ingo posted this patch in 2009, sadly it was never applied
and got lost. Now in 2011 the problem was reported by Gunnar.]
Signed-off-by: Ingo van Lil <inguin@gmx.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
Reported-by: <gunnarlindroth@hotmail.com>
Tested-by: <gunnarlindroth@hotmail.com>
Cc: Stanislav Meduna <stano@meduna.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
59 lines
1.1 KiB
C
59 lines
1.1 KiB
C
/*
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* Copyright (C) 2004 PathScale, Inc
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* Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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* Licensed under the GPL
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*/
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#include <errno.h>
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#include <string.h>
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#include <sys/ptrace.h>
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#include "sysdep/ptrace.h"
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#include "sysdep/ptrace_user.h"
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#include "registers.h"
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int save_registers(int pid, struct uml_pt_regs *regs)
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{
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int err;
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err = ptrace(PTRACE_GETREGS, pid, 0, regs->gp);
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if (err < 0)
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return -errno;
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return 0;
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}
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int restore_registers(int pid, struct uml_pt_regs *regs)
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{
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int err;
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err = ptrace(PTRACE_SETREGS, pid, 0, regs->gp);
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if (err < 0)
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return -errno;
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return 0;
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}
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/* This is set once at boot time and not changed thereafter */
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static unsigned long exec_regs[MAX_REG_NR];
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static unsigned long exec_fp_regs[FP_SIZE];
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int init_registers(int pid)
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{
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int err;
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err = ptrace(PTRACE_GETREGS, pid, 0, exec_regs);
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if (err < 0)
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return -errno;
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arch_init_registers(pid);
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get_fp_registers(pid, exec_fp_regs);
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return 0;
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}
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void get_safe_registers(unsigned long *regs, unsigned long *fp_regs)
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{
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memcpy(regs, exec_regs, sizeof(exec_regs));
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if (fp_regs)
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memcpy(fp_regs, exec_fp_regs, sizeof(exec_fp_regs));
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}
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