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x86, math-emu: fix init_fpu for task != current
Impact: fix math-emu related crash while using GDB/ptrace init_fpu() calls finit to initialize a task's xstate, while finit always works on the current task. If we use PTRACE_GETFPREGS on another process and both processes did not already use floating point, we get a null pointer exception in finit. This patch creates a new function finit_task that takes a task_struct parameter. finit becomes a wrapper that simply calls finit_task with current. On the plus side this avoids many calls to get_current which would each resolve to an inline assembler mov instruction. An empty finit_task has been added to i387.h to avoid linker errors in case the compiler still emits the call in init_fpu when CONFIG_MATH_EMULATION is not defined. The declaration of finit in i387.h has been removed as the remaining code using this function gets its prototype from fpu_proto.h. Signed-off-by: Daniel Glöckner <dg@emlix.com> Cc: Suresh Siddha <suresh.b.siddha@intel.com> Cc: "Pallipadi Venkatesh" <venkatesh.pallipadi@intel.com> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Bill Metzenthen <billm@melbpc.org.au> LKML-Reference: <E1Lew31-0004il-Fg@mailer.emlix.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -172,7 +172,13 @@ static inline void __save_init_fpu(struct task_struct *tsk)
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#else /* CONFIG_X86_32 */
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extern void finit(void);
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#ifdef CONFIG_MATH_EMULATION
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extern void finit_task(struct task_struct *tsk);
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#else
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static inline void finit_task(struct task_struct *tsk)
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{
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}
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#endif
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static inline void tolerant_fwait(void)
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{
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@ -136,7 +136,7 @@ int init_fpu(struct task_struct *tsk)
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#ifdef CONFIG_X86_32
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if (!HAVE_HWFP) {
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memset(tsk->thread.xstate, 0, xstate_size);
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finit();
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finit_task(tsk);
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set_stopped_child_used_math(tsk);
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return 0;
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}
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@ -30,20 +30,29 @@ static void fclex(void)
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}
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/* Needs to be externally visible */
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void finit(void)
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void finit_task(struct task_struct *tsk)
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{
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control_word = 0x037f;
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partial_status = 0;
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top = 0; /* We don't keep top in the status word internally. */
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fpu_tag_word = 0xffff;
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struct i387_soft_struct *soft = &tsk->thread.xstate->soft;
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struct address *oaddr, *iaddr;
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soft->cwd = 0x037f;
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soft->swd = 0;
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soft->ftop = 0; /* We don't keep top in the status word internally. */
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soft->twd = 0xffff;
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/* The behaviour is different from that detailed in
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Section 15.1.6 of the Intel manual */
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operand_address.offset = 0;
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operand_address.selector = 0;
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instruction_address.offset = 0;
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instruction_address.selector = 0;
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instruction_address.opcode = 0;
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no_ip_update = 1;
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oaddr = (struct address *)&soft->foo;
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oaddr->offset = 0;
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oaddr->selector = 0;
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iaddr = (struct address *)&soft->fip;
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iaddr->offset = 0;
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iaddr->selector = 0;
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iaddr->opcode = 0;
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soft->no_update = 1;
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}
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void finit(void)
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{
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finit_task(current);
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}
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/*
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