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Date: Fri, 27 Aug 2010 13:54:58 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Matteo Croce <matteo@...nwrt.org>
CC: linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
Natale Vinto <ebballon@...il.com>
Subject: Re: AMD Geode NOPL emulation for kernel 2.6.36-rc2
You actually have to check the get_user return, or use exception brackets....
"Matteo Croce" <matteo@...nwrt.org> wrote:
>On Fri, Aug 27, 2010 at 8:48 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> You're doing user-space references without get_user().
>>
>> -hpa
>>
>> --
>> H. Peter Anvin, Intel Open Source Technology Center
>> I work for Intel. I don't speak on their behalf.
>>
>>
>
>Here with get_user.
>I CC Natale which is my beta tester, he have some Alix boards running 24/24
>with my patch
>
>--- a/arch/x86/kernel/Makefile 2010-08-27 19:42:01.795858001 +0200
>+++ b/arch/x86/kernel/Makefile 2010-08-27 19:42:12.525858001 +0200
>@@ -88,6 +88,8 @@
> obj-$(CONFIG_APB_TIMER) += apb_timer.o
>
> obj-$(CONFIG_K8_NB) += k8.o
>+obj-$(CONFIG_GEODE_NOPL) += nopl_emu.o
>+obj-$(CONFIG_GEODE_NOPL) += nopl_emu.o
> obj-$(CONFIG_DEBUG_RODATA_TEST) += test_rodata.o
> obj-$(CONFIG_DEBUG_NX_TEST) += test_nx.o
>
>--- a/arch/x86/kernel/cpu/amd.c 2010-08-27 19:42:01.855858001 +0200
>+++ b/arch/x86/kernel/cpu/amd.c 2010-08-27 19:42:12.535858001 +0200
>@@ -137,11 +137,15 @@
> return;
> }
>
>+#ifdef CONFIG_GEODE_NOPL
> if (c->x86_model == 10) {
>- /* AMD Geode LX is model 10 */
>- /* placeholder for any needed mods */
>+ /* Geode only lacks the NOPL instruction to be i686,
>+ but we can promote it to a i686 class cpu
>+ and emulate NOPLs in the exception handler*/
>+ boot_cpu_data.x86 = 6;
> return;
> }
>+#endif
> }
>
> static void __cpuinit amd_k7_smp_check(struct cpuinfo_x86 *c)
>--- a/arch/x86/kernel/entry_32.S 2010-08-27 19:42:01.735858001 +0200
>+++ b/arch/x86/kernel/entry_32.S 2010-08-27 19:42:12.535858001 +0200
>@@ -978,7 +978,11 @@
> RING0_INT_FRAME
> pushl $0
> CFI_ADJUST_CFA_OFFSET 4
>+#ifdef CONFIG_GEODE_NOPL
>+ pushl $do_nopl_emu
>+#else
> pushl $do_invalid_op
>+#endif
> CFI_ADJUST_CFA_OFFSET 4
> jmp error_code
> CFI_ENDPROC
>--- /dev/null 1970-01-01 00:00:00.000000000 +0000
>+++ b/arch/x86/kernel/nopl_emu.c 2010-08-27 22:09:58.005858001 +0200
>@@ -0,0 +1,124 @@
>+/*
>+ * linux/arch/x86/kernel/nopl_emu.c
>+ *
>+ * Copyright (C) 2002 Willy Tarreau
>+ * Copyright (C) 2010 Matteo Croce
>+ */
>+
>+#include <asm/processor.h>
>+#include <asm/traps.h>
>+#include <asm/uaccess.h>
>+
>+/* This code can be used to allow the AMD Geode to hopefully correctly execute
>+ * some code which was originally compiled for an i686, by emulating NOPL,
>+ * the only missing i686 instruction in the CPU
>+ *
>+ * Willy Tarreau <willy@...a-x.org>
>+ * Matteo Croce <technoboy85@...il.com>
>+ */
>+
>+static inline int do_1f(u8 *ip)
>+{
>+ u8 val1, val2;
>+ int length = 3;
>+ get_user(val1, ip);
>+ switch (val1) {
>+ case 0x84:
>+ get_user(val1, ip + 5);
>+ if (!val1)
>+ length++;
>+ else
>+ return 0;
>+ case 0x80:
>+ get_user(val1, ip + 4);
>+ get_user(val2, ip + 3);
>+ if (!val1 && !val2)
>+ length += 2;
>+ else
>+ return 0;
>+ case 0x44:
>+ get_user(val1, ip + 2);
>+ if (!val1)
>+ length++;
>+ else
>+ return 0;
>+ case 0x40:
>+ get_user(val1, ip + 1);
>+ if (!val1)
>+ length++;
>+ else
>+ return 0;
>+ case 0x00:
>+ return length;
>+ }
>+ return 0;
>+}
>+
>+static inline int do_0f(u8 *ip)
>+{
>+ u8 val;
>+ get_user(val, ip);
>+ if (val == 0x1f)
>+ return do_1f(ip + 1);
>+ return 0;
>+}
>+
>+static inline int do_66(u8 *ip)
>+{
>+ u8 val;
>+ get_user(val, ip);
>+ if (val == 0x90)
>+ return 2;
>+ if (val == 0x0f) {
>+ int res = do_0f(ip + 1);
>+ if (res)
>+ return res + 1;
>+ else
>+ return 0;
>+ }
>+ return 0;
>+}
>+
>+static inline int do_start(u8 *ip)
>+{
>+ u8 val;
>+ get_user(val, ip);
>+ if (val == 0x0f)
>+ return do_0f(ip + 1);
>+ if (val == 0x66)
>+ return do_66(ip + 1);
>+ return 0;
>+}
>+
>+/* [do_nopl_emu] is called by exception 6 after an invalid opcode has been
>+ * encountered. It will try to emulate it by doing nothing,
>+ * and will send a SIGILL or SIGSEGV to the process if not possible.
>+ * the NOPL can have variable length opcodes:
>+
>+bytes number opcode
>+ 2 66 90
>+ 3 0f 1f 00
>+ 4 0f 1f 40 00
>+ 5 0f 1f 44 00 00
>+ 6 66 0f 1f 44 00 00
>+ 7 0f 1f 80 00 00 00 00
>+ 8 0f 1f 84 00 00 00 00 00
>+ 9 66 0f 1f 84 00 00 00 00 00
>+*/
>+void do_nopl_emu(struct pt_regs *regs, long error_code)
>+{
>+ u8 *ip = (u8 *)instruction_pointer(regs);
>+ int res = do_start(ip);
>+
>+ if (res) {
>+ int i = 0;
>+ do {
>+ ip += res;
>+ i++;
>+ res = do_start(ip);
>+ } while(res);
>+ printk(KERN_DEBUG "geode_nopl: emulated %d instructions\n", i);
>+ regs->ip = (typeof(regs->ip))ip;
>+ } else
>+ do_invalid_op(regs, error_code);
>+}
>
>
>--
>Matteo Croce
>OpenWrt developer
> _______ ________ __
> | |.-----.-----.-----.| | | |.----.| |_
> | - || _ | -__| || | | || _|| _|
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