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Subject[PATCH 03/11] x86: fix math_emu register frame access
Date
do_device_not_available() is the handler for #NM and it declares that
it takes a unsigned long and calls math_emu(), which takes a long
argument and surprisingly expects the stack frame starting at the zero
argument would match struct math_emu_info, which isn't true regardless
of configuration in the current code.

This patch makes do_device_not_available() take struct pt_regs like
other exception handlers and initialize struct math_emu_info with
pointer to it and pass pointer to the math_emu_info to math_emulate()
like normal C functions do. This way, unless gcc makes a copy of
struct pt_regs in do_device_not_available(), the register frame is
correctly accessed regardless of kernel configuration or compiler
used.

This doesn't fix all math_emu problems but it at least gets it
somewhat working.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
arch/x86/include/asm/math_emu.h | 4 +-
arch/x86/include/asm/traps.h | 4 +-
arch/x86/kernel/traps.c | 15 +++++---
arch/x86/math-emu/fpu_entry.c | 4 +-
arch/x86/math-emu/fpu_proto.h | 2 +-
arch/x86/math-emu/fpu_system.h | 16 +++------
arch/x86/math-emu/get_address.c | 66 +++++++++++++++++++-------------------
7 files changed, 55 insertions(+), 56 deletions(-)
diff --git a/arch/x86/include/asm/math_emu.h b/arch/x86/include/asm/math_emu.h
index 302492c..031f626 100644
--- a/arch/x86/include/asm/math_emu.h
+++ b/arch/x86/include/asm/math_emu.h
@@ -11,8 +11,8 @@
struct math_emu_info {
long ___orig_eip;
union {
- struct pt_regs regs;
- struct kernel_vm86_regs vm86;
+ struct pt_regs *regs;
+ struct kernel_vm86_regs *vm86;
};
};
#endif /* _ASM_X86_MATH_EMU_H */
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 2ee0a3b..36ad79f 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -41,7 +41,7 @@ dotraplinkage void do_int3(struct pt_regs *, long);
dotraplinkage void do_overflow(struct pt_regs *, long);
dotraplinkage void do_bounds(struct pt_regs *, long);
dotraplinkage void do_invalid_op(struct pt_regs *, long);
-dotraplinkage void do_device_not_available(struct pt_regs *, long);
+dotraplinkage void do_device_not_available(struct pt_regs);
dotraplinkage void do_coprocessor_segment_overrun(struct pt_regs *, long);
dotraplinkage void do_invalid_TSS(struct pt_regs *, long);
dotraplinkage void do_segment_not_present(struct pt_regs *, long);
@@ -77,7 +77,7 @@ extern int panic_on_unrecovered_nmi;
extern int kstack_depth_to_print;

void math_error(void __user *);
-asmlinkage void math_emulate(long);
+asmlinkage void math_emulate(struct math_emu_info *);
#ifdef CONFIG_X86_32
unsigned long patch_espfix_desc(unsigned long, unsigned long);
#else
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index afb46c0..84bdf8f 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -900,7 +900,7 @@ asmlinkage void math_state_restore(void)
EXPORT_SYMBOL_GPL(math_state_restore);

#ifndef CONFIG_MATH_EMULATION
-asmlinkage void math_emulate(long arg)
+void math_emulate(struct math_emu_info *info)
{
printk(KERN_EMERG
"math-emulation not enabled and no coprocessor found.\n");
@@ -910,16 +910,19 @@ asmlinkage void math_emulate(long arg)
}
#endif /* CONFIG_MATH_EMULATION */

-dotraplinkage void __kprobes
-do_device_not_available(struct pt_regs *regs, long error)
+dotraplinkage void __kprobes do_device_not_available(struct pt_regs regs)
{
#ifdef CONFIG_X86_32
if (read_cr0() & X86_CR0_EM) {
- conditional_sti(regs);
- math_emulate(0);
+ struct math_emu_info info = { };
+
+ conditional_sti(&regs);
+
+ info.regs = &regs;
+ math_emulate(&info);
} else {
math_state_restore(); /* interrupts still off */
- conditional_sti(regs);
+ conditional_sti(&regs);
}
#else
math_state_restore();
diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
index c268abe..5d87f58 100644
--- a/arch/x86/math-emu/fpu_entry.c
+++ b/arch/x86/math-emu/fpu_entry.c
@@ -131,7 +131,7 @@ u_char emulating = 0;
static int valid_prefix(u_char *Byte, u_char __user ** fpu_eip,
overrides * override);

-asmlinkage void math_emulate(long arg)
+void math_emulate(struct math_emu_info *info)
{
u_char FPU_modrm, byte1;
unsigned short code;
@@ -161,7 +161,7 @@ asmlinkage void math_emulate(long arg)
RE_ENTRANT_CHECK_ON;
#endif /* RE_ENTRANT_CHECKING */

- SETUP_DATA_AREA(arg);
+ FPU_info = info;

FPU_ORIG_EIP = FPU_EIP;

diff --git a/arch/x86/math-emu/fpu_proto.h b/arch/x86/math-emu/fpu_proto.h
index 51bfbb6..9779df4 100644
--- a/arch/x86/math-emu/fpu_proto.h
+++ b/arch/x86/math-emu/fpu_proto.h
@@ -51,7 +51,7 @@ extern void ffreep(void);
extern void fst_i_(void);
extern void fstp_i(void);
/* fpu_entry.c */
-asmlinkage extern void math_emulate(long arg);
+extern void math_emulate(struct math_emu_info *info);
extern void math_abort(struct math_emu_info *info, unsigned int signal);
/* fpu_etc.c */
extern void FPU_etc(void);
diff --git a/arch/x86/math-emu/fpu_system.h b/arch/x86/math-emu/fpu_system.h
index 6729c6a..50fa0ec 100644
--- a/arch/x86/math-emu/fpu_system.h
+++ b/arch/x86/math-emu/fpu_system.h
@@ -16,10 +16,6 @@
#include <linux/kernel.h>
#include <linux/mm.h>

-/* This sets the pointer FPU_info to point to the argument part
- of the stack frame of math_emulate() */
-#define SETUP_DATA_AREA(arg) FPU_info = (struct math_emu_info *) &arg
-
/* s is always from a cpu register, and the cpu does bounds checking
* during register load --> no further bounds checks needed */
#define LDT_DESCRIPTOR(s) (((struct desc_struct *)current->mm->context.ldt)[(s) >> 3])
@@ -38,12 +34,12 @@
#define I387 (current->thread.xstate)
#define FPU_info (I387->soft.info)

-#define FPU_CS (*(unsigned short *) &(FPU_info->regs.cs))
-#define FPU_SS (*(unsigned short *) &(FPU_info->regs.ss))
-#define FPU_DS (*(unsigned short *) &(FPU_info->regs.ds))
-#define FPU_EAX (FPU_info->regs.ax)
-#define FPU_EFLAGS (FPU_info->regs.flags)
-#define FPU_EIP (FPU_info->regs.ip)
+#define FPU_CS (*(unsigned short *) &(FPU_info->regs->cs))
+#define FPU_SS (*(unsigned short *) &(FPU_info->regs->ss))
+#define FPU_DS (*(unsigned short *) &(FPU_info->regs->ds))
+#define FPU_EAX (FPU_info->regs->ax)
+#define FPU_EFLAGS (FPU_info->regs->flags)
+#define FPU_EIP (FPU_info->regs->ip)
#define FPU_ORIG_EIP (FPU_info->___orig_eip)

#define FPU_lookahead (I387->soft.lookahead)
diff --git a/arch/x86/math-emu/get_address.c b/arch/x86/math-emu/get_address.c
index 62daa7f..420b3b6 100644
--- a/arch/x86/math-emu/get_address.c
+++ b/arch/x86/math-emu/get_address.c
@@ -29,43 +29,43 @@
#define FPU_WRITE_BIT 0x10

static int reg_offset[] = {
- offsetof(struct math_emu_info, regs.ax),
- offsetof(struct math_emu_info, regs.cx),
- offsetof(struct math_emu_info, regs.dx),
- offsetof(struct math_emu_info, regs.bx),
- offsetof(struct math_emu_info, regs.sp),
- offsetof(struct math_emu_info, regs.bp),
- offsetof(struct math_emu_info, regs.si),
- offsetof(struct math_emu_info, regs.di)
+ offsetof(struct pt_regs, ax),
+ offsetof(struct pt_regs, cx),
+ offsetof(struct pt_regs, dx),
+ offsetof(struct pt_regs, bx),
+ offsetof(struct pt_regs, sp),
+ offsetof(struct pt_regs, bp),
+ offsetof(struct pt_regs, si),
+ offsetof(struct pt_regs, di)
};

-#define REG_(x) (*(long *)(reg_offset[(x)]+(u_char *) FPU_info))
+#define REG_(x) (*(long *)(reg_offset[(x)] + (u_char *)FPU_info->regs))

static int reg_offset_vm86[] = {
- offsetof(struct math_emu_info, regs.cs),
- offsetof(struct math_emu_info, vm86.ds),
- offsetof(struct math_emu_info, vm86.es),
- offsetof(struct math_emu_info, vm86.fs),
- offsetof(struct math_emu_info, vm86.gs),
- offsetof(struct math_emu_info, regs.ss),
- offsetof(struct math_emu_info, vm86.ds)
+ offsetof(struct pt_regs, cs),
+ offsetof(struct kernel_vm86_regs, ds),
+ offsetof(struct kernel_vm86_regs, es),
+ offsetof(struct kernel_vm86_regs, fs),
+ offsetof(struct kernel_vm86_regs, gs),
+ offsetof(struct pt_regs, ss),
+ offsetof(struct kernel_vm86_regs, ds)
};

#define VM86_REG_(x) (*(unsigned short *) \
- (reg_offset_vm86[((unsigned)x)]+(u_char *) FPU_info))
+ (reg_offset_vm86[((unsigned)x)] + (u_char *)FPU_info->regs))

static int reg_offset_pm[] = {
- offsetof(struct math_emu_info, regs.cs),
- offsetof(struct math_emu_info, regs.ds),
- offsetof(struct math_emu_info, regs.es),
- offsetof(struct math_emu_info, regs.fs),
- offsetof(struct math_emu_info, regs.ds), /* dummy, not saved on stack */
- offsetof(struct math_emu_info, regs.ss),
- offsetof(struct math_emu_info, regs.ds)
+ offsetof(struct pt_regs, cs),
+ offsetof(struct pt_regs, ds),
+ offsetof(struct pt_regs, es),
+ offsetof(struct pt_regs, fs),
+ offsetof(struct pt_regs, ds), /* dummy, not saved on stack */
+ offsetof(struct pt_regs, ss),
+ offsetof(struct pt_regs, ds)
};

#define PM_REG_(x) (*(unsigned short *) \
- (reg_offset_pm[((unsigned)x)]+(u_char *) FPU_info))
+ (reg_offset_pm[((unsigned)x)] + (u_char *)FPU_info->regs))

/* Decode the SIB byte. This function assumes mod != 0 */
static int sib(int mod, unsigned long *fpu_eip)
@@ -346,34 +346,34 @@ void __user *FPU_get_address_16(u_char FPU_modrm, unsigned long *fpu_eip,
}
switch (rm) {
case 0:
- address += FPU_info->regs.bx + FPU_info->regs.si;
+ address += FPU_info->regs->bx + FPU_info->regs->si;
break;
case 1:
- address += FPU_info->regs.bx + FPU_info->regs.di;
+ address += FPU_info->regs->bx + FPU_info->regs->di;
break;
case 2:
- address += FPU_info->regs.bp + FPU_info->regs.si;
+ address += FPU_info->regs->bp + FPU_info->regs->si;
if (addr_modes.override.segment == PREFIX_DEFAULT)
addr_modes.override.segment = PREFIX_SS_;
break;
case 3:
- address += FPU_info->regs.bp + FPU_info->regs.di;
+ address += FPU_info->regs->bp + FPU_info->regs->di;
if (addr_modes.override.segment == PREFIX_DEFAULT)
addr_modes.override.segment = PREFIX_SS_;
break;
case 4:
- address += FPU_info->regs.si;
+ address += FPU_info->regs->si;
break;
case 5:
- address += FPU_info->regs.di;
+ address += FPU_info->regs->di;
break;
case 6:
- address += FPU_info->regs.bp;
+ address += FPU_info->regs->bp;
if (addr_modes.override.segment == PREFIX_DEFAULT)
addr_modes.override.segment = PREFIX_SS_;
break;
case 7:
- address += FPU_info->regs.bx;
+ address += FPU_info->regs->bx;
break;
}

--
1.6.0.2


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