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Date: Mon, 02 Mar 2009 16:19:49 +0100
From: Daniel Glöckner <dg@...ix.com>
To: x86@...nel.org
CC: Bill Metzenthen <billm@...urbia.net>, linux-kernel@...r.kernel.org
Subject: [PATCH] x86, math-emu: fix init_fpu for task != current
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.
Signed-off-by: Daniel Glöckner <dg@...ix.com>
---
arch/x86/include/asm/i387.h | 1 +
arch/x86/kernel/i387.c | 2 +-
arch/x86/math-emu/fpu_aux.c | 31 ++++++++++++++++++++-----------
3 files changed, 22 insertions(+), 12 deletions(-)
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index 48f0004..10f349b 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -172,6 +172,7 @@ static inline void __save_init_fpu(struct task_struct *tsk)
#else /* CONFIG_X86_32 */
+extern void finit_task(struct task_struct *tsk);
extern void finit(void);
static inline void tolerant_fwait(void)
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index b0f61f0..f2f8540 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -136,7 +136,7 @@ int init_fpu(struct task_struct *tsk)
#ifdef CONFIG_X86_32
if (!HAVE_HWFP) {
memset(tsk->thread.xstate, 0, xstate_size);
- finit();
+ finit_task(tsk);
set_stopped_child_used_math(tsk);
return 0;
}
diff --git a/arch/x86/math-emu/fpu_aux.c b/arch/x86/math-emu/fpu_aux.c
index 491e737..aa09870 100644
--- a/arch/x86/math-emu/fpu_aux.c
+++ b/arch/x86/math-emu/fpu_aux.c
@@ -30,20 +30,29 @@ static void fclex(void)
}
/* Needs to be externally visible */
-void finit(void)
+void finit_task(struct task_struct *tsk)
{
- control_word = 0x037f;
- partial_status = 0;
- top = 0; /* We don't keep top in the status word internally. */
- fpu_tag_word = 0xffff;
+ struct i387_soft_struct *soft = &tsk->thread.xstate->soft;
+ struct address *oaddr, *iaddr;
+ soft->cwd = 0x037f;
+ soft->swd = 0;
+ soft->ftop = 0; /* We don't keep top in the status word internally. */
+ soft->twd = 0xffff;
/* The behaviour is different from that detailed in
Section 15.1.6 of the Intel manual */
- operand_address.offset = 0;
- operand_address.selector = 0;
- instruction_address.offset = 0;
- instruction_address.selector = 0;
- instruction_address.opcode = 0;
- no_ip_update = 1;
+ oaddr = (struct address *)&soft->foo;
+ oaddr->offset = 0;
+ oaddr->selector = 0;
+ iaddr = (struct address *)&soft->fip;
+ iaddr->offset = 0;
+ iaddr->selector = 0;
+ iaddr->opcode = 0;
+ soft->no_update = 1;
+}
+
+void finit(void)
+{
+ finit_task(current);
}
/*
--
1.5.6
--
Dipl.-Math. Daniel Glöckner, emlix GmbH, http://www.emlix.com
Fon +49 551 30664-0, Fax -11, Bahnhofsallee 1b, 37081 Göttingen, Germany
Geschäftsführung: Dr. Uwe Kracke, Dr. Cord Seele, Ust-IdNr.: DE 205 198 055
Sitz der Gesellschaft: Göttingen, Amtsgericht Göttingen HR B 3160
emlix - your embedded linux partner
--
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