Messages in this thread Patch in this message | | | From | Matteo Croce <> | Date | Fri, 27 Aug 2010 20:07:03 +0200 | Subject | AMD Geode NOPL emulation for kernel 2.6.36-rc2 |
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Hi, I have received many mails asking to refresh the patch so I decided to post them on the public mailing list In this version such feature is configurable via a kernel config option
Signed-off-by: Matteo Croce <matteo@openwrt.org>
--- a/arch/x86/kernel/Makefile 2010-08-27 00:27:50.101261000 +0200 +++ b/arch/x86/kernel/Makefile 2010-08-27 00:31:11.391261002 +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 00:27:50.161261000 +0200 +++ b/arch/x86/kernel/cpu/amd.c 2010-08-27 00:34:13.371261000 +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 00:27:50.051261000 +0200 +++ b/arch/x86/kernel/entry_32.S 2010-08-27 00:57:35.531261000 +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 00:27:57.881261002 +0200 @@ -0,0 +1,110 @@ +/* + * 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> + +/* 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@meta-x.org> + * Matteo Croce <technoboy85@gmail.com> + */ + +static inline int do_1f(u8 *ip) +{ + int length = 3; + switch (*ip) { + case 0x84: + if (!ip[5]) + length++; + else + return 0; + case 0x80: + if (!ip[4] && !ip[3]) + length += 2; + else + return 0; + case 0x44: + if (!ip[2]) + length++; + else + return 0; + case 0x40: + if (!ip[1]) + length++; + else + return 0; + case 0x00: + return length; + } + return 0; +} + +static inline int do_0f(u8 *ip) +{ + if (*ip == 0x1f) + return do_1f(ip + 1); + return 0; +} + +static inline int do_66(u8 *ip) +{ + if (*ip == 0x90) + return 2; + if (*ip == 0x0f) { + int res = do_0f(ip + 1); + if (res) + return res + 1; + else + return 0; + } + return 0; +} + +static inline int do_start(u8 *ip) +{ + if (*ip == 0x0f) + return do_0f(ip + 1); + if (*ip == 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); +}
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