1b2441318SGreg Kroah-Hartman /* SPDX-License-Identifier: GPL-2.0 */ 2478dc89cSAndy Lutomirski #include <linux/jump_label.h> 38c1f7558SJosh Poimboeuf #include <asm/unwind_hints.h> 48a09317bSDave Hansen #include <asm/cpufeatures.h> 58a09317bSDave Hansen #include <asm/page_types.h> 66fd166aaSPeter Zijlstra #include <asm/percpu.h> 76fd166aaSPeter Zijlstra #include <asm/asm-offsets.h> 86fd166aaSPeter Zijlstra #include <asm/processor-flags.h> 9478dc89cSAndy Lutomirski 10d36f9479SIngo Molnar /* 11d36f9479SIngo Molnar 12d36f9479SIngo Molnar x86 function call convention, 64-bit: 13d36f9479SIngo Molnar ------------------------------------- 14d36f9479SIngo Molnar arguments | callee-saved | extra caller-saved | return 15d36f9479SIngo Molnar [callee-clobbered] | | [callee-clobbered] | 16d36f9479SIngo Molnar --------------------------------------------------------------------------- 17d36f9479SIngo Molnar rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**] 18d36f9479SIngo Molnar 19d36f9479SIngo Molnar ( rsp is obviously invariant across normal function calls. (gcc can 'merge' 20d36f9479SIngo Molnar functions when it sees tail-call optimization possibilities) rflags is 21d36f9479SIngo Molnar clobbered. Leftover arguments are passed over the stack frame.) 22d36f9479SIngo Molnar 23d36f9479SIngo Molnar [*] In the frame-pointers case rbp is fixed to the stack frame. 24d36f9479SIngo Molnar 25d36f9479SIngo Molnar [**] for struct return values wider than 64 bits the return convention is a 26d36f9479SIngo Molnar bit more complex: up to 128 bits width we return small structures 27d36f9479SIngo Molnar straight in rax, rdx. For structures larger than that (3 words or 28d36f9479SIngo Molnar larger) the caller puts a pointer to an on-stack return struct 29d36f9479SIngo Molnar [allocated in the caller's stack frame] into the first argument - i.e. 30d36f9479SIngo Molnar into rdi. All other arguments shift up by one in this case. 31d36f9479SIngo Molnar Fortunately this case is rare in the kernel. 32d36f9479SIngo Molnar 33d36f9479SIngo Molnar For 32-bit we have the following conventions - kernel is built with 34d36f9479SIngo Molnar -mregparm=3 and -freg-struct-return: 35d36f9479SIngo Molnar 36d36f9479SIngo Molnar x86 function calling convention, 32-bit: 37d36f9479SIngo Molnar ---------------------------------------- 38d36f9479SIngo Molnar arguments | callee-saved | extra caller-saved | return 39d36f9479SIngo Molnar [callee-clobbered] | | [callee-clobbered] | 40d36f9479SIngo Molnar ------------------------------------------------------------------------- 41d36f9479SIngo Molnar eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**] 42d36f9479SIngo Molnar 43d36f9479SIngo Molnar ( here too esp is obviously invariant across normal function calls. eflags 44d36f9479SIngo Molnar is clobbered. Leftover arguments are passed over the stack frame. ) 45d36f9479SIngo Molnar 46d36f9479SIngo Molnar [*] In the frame-pointers case ebp is fixed to the stack frame. 47d36f9479SIngo Molnar 48d36f9479SIngo Molnar [**] We build with -freg-struct-return, which on 32-bit means similar 49d36f9479SIngo Molnar semantics as on 64-bit: edx can be used for a second return value 50d36f9479SIngo Molnar (i.e. covering integer and structure sizes up to 64 bits) - after that 51d36f9479SIngo Molnar it gets more complex and more expensive: 3-word or larger struct returns 52d36f9479SIngo Molnar get done in the caller's frame and the pointer to the return struct goes 53d36f9479SIngo Molnar into regparm0, i.e. eax - the other arguments shift up and the 54d36f9479SIngo Molnar function's register parameters degenerate to regparm=2 in essence. 55d36f9479SIngo Molnar 56d36f9479SIngo Molnar */ 57d36f9479SIngo Molnar 58d36f9479SIngo Molnar #ifdef CONFIG_X86_64 59d36f9479SIngo Molnar 60d36f9479SIngo Molnar /* 61d36f9479SIngo Molnar * 64-bit system call stack frame layout defines and helpers, 62d36f9479SIngo Molnar * for assembly code: 63d36f9479SIngo Molnar */ 64d36f9479SIngo Molnar 65d36f9479SIngo Molnar /* The layout forms the "struct pt_regs" on the stack: */ 66d36f9479SIngo Molnar /* 67d36f9479SIngo Molnar * C ABI says these regs are callee-preserved. They aren't saved on kernel entry 68d36f9479SIngo Molnar * unless syscall needs a complete, fully filled "struct pt_regs". 69d36f9479SIngo Molnar */ 70d36f9479SIngo Molnar #define R15 0*8 71d36f9479SIngo Molnar #define R14 1*8 72d36f9479SIngo Molnar #define R13 2*8 73d36f9479SIngo Molnar #define R12 3*8 74d36f9479SIngo Molnar #define RBP 4*8 75d36f9479SIngo Molnar #define RBX 5*8 76d36f9479SIngo Molnar /* These regs are callee-clobbered. Always saved on kernel entry. */ 77d36f9479SIngo Molnar #define R11 6*8 78d36f9479SIngo Molnar #define R10 7*8 79d36f9479SIngo Molnar #define R9 8*8 80d36f9479SIngo Molnar #define R8 9*8 81d36f9479SIngo Molnar #define RAX 10*8 82d36f9479SIngo Molnar #define RCX 11*8 83d36f9479SIngo Molnar #define RDX 12*8 84d36f9479SIngo Molnar #define RSI 13*8 85d36f9479SIngo Molnar #define RDI 14*8 86d36f9479SIngo Molnar /* 87d36f9479SIngo Molnar * On syscall entry, this is syscall#. On CPU exception, this is error code. 88d36f9479SIngo Molnar * On hw interrupt, it's IRQ number: 89d36f9479SIngo Molnar */ 90d36f9479SIngo Molnar #define ORIG_RAX 15*8 91d36f9479SIngo Molnar /* Return frame for iretq */ 92d36f9479SIngo Molnar #define RIP 16*8 93d36f9479SIngo Molnar #define CS 17*8 94d36f9479SIngo Molnar #define EFLAGS 18*8 95d36f9479SIngo Molnar #define RSP 19*8 96d36f9479SIngo Molnar #define SS 20*8 97d36f9479SIngo Molnar 98d36f9479SIngo Molnar #define SIZEOF_PTREGS 21*8 99d36f9479SIngo Molnar 10059df2268SAlexander Kuleshov .macro ALLOC_PT_GPREGS_ON_STACK 10159df2268SAlexander Kuleshov addq $-(15*8), %rsp 102d36f9479SIngo Molnar .endm 103d36f9479SIngo Molnar 1042e3f0098SDominik Brodowski .macro SAVE_REGS offset=0 105d36f9479SIngo Molnar movq %rdi, 14*8+\offset(%rsp) 1062e3f0098SDominik Brodowski movq %rsi, 13*8+\offset(%rsp) 1072e3f0098SDominik Brodowski movq %rdx, 12*8+\offset(%rsp) 1082e3f0098SDominik Brodowski movq %rcx, 11*8+\offset(%rsp) 1092e3f0098SDominik Brodowski movq %rax, 10*8+\offset(%rsp) 1102e3f0098SDominik Brodowski movq %r8, 9*8+\offset(%rsp) 1112e3f0098SDominik Brodowski movq %r9, 8*8+\offset(%rsp) 1122e3f0098SDominik Brodowski movq %r10, 7*8+\offset(%rsp) 1132e3f0098SDominik Brodowski movq %r11, 6*8+\offset(%rsp) 114d36f9479SIngo Molnar movq %rbx, 5*8+\offset(%rsp) 1152e3f0098SDominik Brodowski movq %rbp, 4*8+\offset(%rsp) 1162e3f0098SDominik Brodowski movq %r12, 3*8+\offset(%rsp) 1172e3f0098SDominik Brodowski movq %r13, 2*8+\offset(%rsp) 1182e3f0098SDominik Brodowski movq %r14, 1*8+\offset(%rsp) 1192e3f0098SDominik Brodowski movq %r15, 0*8+\offset(%rsp) 1208c1f7558SJosh Poimboeuf UNWIND_HINT_REGS offset=\offset 121d36f9479SIngo Molnar .endm 122d36f9479SIngo Molnar 1233ac6d8c7SDan Williams /* 1243ac6d8c7SDan Williams * Sanitize registers of values that a speculation attack 1253ac6d8c7SDan Williams * might otherwise want to exploit. The lower registers are 1263ac6d8c7SDan Williams * likely clobbered well before they could be put to use in 1273ac6d8c7SDan Williams * a speculative execution gadget: 1283ac6d8c7SDan Williams */ 1293ac6d8c7SDan Williams .macro CLEAR_REGS_NOSPEC 1303ac6d8c7SDan Williams xorl %ebp, %ebp 1313ac6d8c7SDan Williams xorl %ebx, %ebx 1323ac6d8c7SDan Williams xorq %r8, %r8 1333ac6d8c7SDan Williams xorq %r9, %r9 1343ac6d8c7SDan Williams xorq %r10, %r10 1353ac6d8c7SDan Williams xorq %r11, %r11 1363ac6d8c7SDan Williams xorq %r12, %r12 1373ac6d8c7SDan Williams xorq %r13, %r13 1383ac6d8c7SDan Williams xorq %r14, %r14 1393ac6d8c7SDan Williams xorq %r15, %r15 1403ac6d8c7SDan Williams .endm 1413ac6d8c7SDan Williams 142502af0d7SDominik Brodowski .macro POP_REGS pop_rdi=1 skip_r11rcx=0 143e872045bSAndy Lutomirski popq %r15 144e872045bSAndy Lutomirski popq %r14 145e872045bSAndy Lutomirski popq %r13 146e872045bSAndy Lutomirski popq %r12 147e872045bSAndy Lutomirski popq %rbp 148e872045bSAndy Lutomirski popq %rbx 149502af0d7SDominik Brodowski .if \skip_r11rcx 150502af0d7SDominik Brodowski popq %rsi 151502af0d7SDominik Brodowski .else 152e872045bSAndy Lutomirski popq %r11 153502af0d7SDominik Brodowski .endif 154e872045bSAndy Lutomirski popq %r10 155e872045bSAndy Lutomirski popq %r9 156e872045bSAndy Lutomirski popq %r8 157e872045bSAndy Lutomirski popq %rax 158502af0d7SDominik Brodowski .if \skip_r11rcx 159502af0d7SDominik Brodowski popq %rsi 160502af0d7SDominik Brodowski .else 161e872045bSAndy Lutomirski popq %rcx 162502af0d7SDominik Brodowski .endif 163e872045bSAndy Lutomirski popq %rdx 164e872045bSAndy Lutomirski popq %rsi 165502af0d7SDominik Brodowski .if \pop_rdi 166e872045bSAndy Lutomirski popq %rdi 167502af0d7SDominik Brodowski .endif 168d36f9479SIngo Molnar .endm 169d36f9479SIngo Molnar 170d36f9479SIngo Molnar .macro icebp 171d36f9479SIngo Molnar .byte 0xf1 172d36f9479SIngo Molnar .endm 173d36f9479SIngo Molnar 174946c1911SJosh Poimboeuf /* 175946c1911SJosh Poimboeuf * This is a sneaky trick to help the unwinder find pt_regs on the stack. The 176946c1911SJosh Poimboeuf * frame pointer is replaced with an encoded pointer to pt_regs. The encoding 177946c1911SJosh Poimboeuf * is just setting the LSB, which makes it an invalid stack address and is also 178946c1911SJosh Poimboeuf * a signal to the unwinder that it's a pt_regs pointer in disguise. 179946c1911SJosh Poimboeuf * 1802e3f0098SDominik Brodowski * NOTE: This macro must be used *after* SAVE_REGS because it corrupts 181946c1911SJosh Poimboeuf * the original rbp. 182946c1911SJosh Poimboeuf */ 183946c1911SJosh Poimboeuf .macro ENCODE_FRAME_POINTER ptregs_offset=0 184946c1911SJosh Poimboeuf #ifdef CONFIG_FRAME_POINTER 185946c1911SJosh Poimboeuf .if \ptregs_offset 186946c1911SJosh Poimboeuf leaq \ptregs_offset(%rsp), %rbp 187946c1911SJosh Poimboeuf .else 188946c1911SJosh Poimboeuf mov %rsp, %rbp 189946c1911SJosh Poimboeuf .endif 190946c1911SJosh Poimboeuf orq $0x1, %rbp 191946c1911SJosh Poimboeuf #endif 192946c1911SJosh Poimboeuf .endm 193946c1911SJosh Poimboeuf 1948a09317bSDave Hansen #ifdef CONFIG_PAGE_TABLE_ISOLATION 1958a09317bSDave Hansen 1966fd166aaSPeter Zijlstra /* 1976fd166aaSPeter Zijlstra * PAGE_TABLE_ISOLATION PGDs are 8k. Flip bit 12 to switch between the two 1986fd166aaSPeter Zijlstra * halves: 1996fd166aaSPeter Zijlstra */ 200f10ee3dcSThomas Gleixner #define PTI_USER_PGTABLE_BIT PAGE_SHIFT 201f10ee3dcSThomas Gleixner #define PTI_USER_PGTABLE_MASK (1 << PTI_USER_PGTABLE_BIT) 202f10ee3dcSThomas Gleixner #define PTI_USER_PCID_BIT X86_CR3_PTI_PCID_USER_BIT 203f10ee3dcSThomas Gleixner #define PTI_USER_PCID_MASK (1 << PTI_USER_PCID_BIT) 204f10ee3dcSThomas Gleixner #define PTI_USER_PGTABLE_AND_PCID_MASK (PTI_USER_PCID_MASK | PTI_USER_PGTABLE_MASK) 2058a09317bSDave Hansen 2066fd166aaSPeter Zijlstra .macro SET_NOFLUSH_BIT reg:req 2076fd166aaSPeter Zijlstra bts $X86_CR3_PCID_NOFLUSH_BIT, \reg 2088a09317bSDave Hansen .endm 2098a09317bSDave Hansen 2106fd166aaSPeter Zijlstra .macro ADJUST_KERNEL_CR3 reg:req 2116fd166aaSPeter Zijlstra ALTERNATIVE "", "SET_NOFLUSH_BIT \reg", X86_FEATURE_PCID 2126fd166aaSPeter Zijlstra /* Clear PCID and "PAGE_TABLE_ISOLATION bit", point CR3 at kernel pagetables: */ 213f10ee3dcSThomas Gleixner andq $(~PTI_USER_PGTABLE_AND_PCID_MASK), \reg 2148a09317bSDave Hansen .endm 2158a09317bSDave Hansen 2168a09317bSDave Hansen .macro SWITCH_TO_KERNEL_CR3 scratch_reg:req 217aa8c6248SThomas Gleixner ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI 2188a09317bSDave Hansen mov %cr3, \scratch_reg 2198a09317bSDave Hansen ADJUST_KERNEL_CR3 \scratch_reg 2208a09317bSDave Hansen mov \scratch_reg, %cr3 221aa8c6248SThomas Gleixner .Lend_\@: 2228a09317bSDave Hansen .endm 2238a09317bSDave Hansen 2246fd166aaSPeter Zijlstra #define THIS_CPU_user_pcid_flush_mask \ 2256fd166aaSPeter Zijlstra PER_CPU_VAR(cpu_tlbstate) + TLB_STATE_user_pcid_flush_mask 2266fd166aaSPeter Zijlstra 2276fd166aaSPeter Zijlstra .macro SWITCH_TO_USER_CR3_NOSTACK scratch_reg:req scratch_reg2:req 228aa8c6248SThomas Gleixner ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI 2298a09317bSDave Hansen mov %cr3, \scratch_reg 2306fd166aaSPeter Zijlstra 2316fd166aaSPeter Zijlstra ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID 2326fd166aaSPeter Zijlstra 2336fd166aaSPeter Zijlstra /* 2346fd166aaSPeter Zijlstra * Test if the ASID needs a flush. 2356fd166aaSPeter Zijlstra */ 2366fd166aaSPeter Zijlstra movq \scratch_reg, \scratch_reg2 2376fd166aaSPeter Zijlstra andq $(0x7FF), \scratch_reg /* mask ASID */ 2386fd166aaSPeter Zijlstra bt \scratch_reg, THIS_CPU_user_pcid_flush_mask 2396fd166aaSPeter Zijlstra jnc .Lnoflush_\@ 2406fd166aaSPeter Zijlstra 2416fd166aaSPeter Zijlstra /* Flush needed, clear the bit */ 2426fd166aaSPeter Zijlstra btr \scratch_reg, THIS_CPU_user_pcid_flush_mask 2436fd166aaSPeter Zijlstra movq \scratch_reg2, \scratch_reg 244f10ee3dcSThomas Gleixner jmp .Lwrcr3_pcid_\@ 2456fd166aaSPeter Zijlstra 2466fd166aaSPeter Zijlstra .Lnoflush_\@: 2476fd166aaSPeter Zijlstra movq \scratch_reg2, \scratch_reg 2486fd166aaSPeter Zijlstra SET_NOFLUSH_BIT \scratch_reg 2496fd166aaSPeter Zijlstra 250f10ee3dcSThomas Gleixner .Lwrcr3_pcid_\@: 251f10ee3dcSThomas Gleixner /* Flip the ASID to the user version */ 252f10ee3dcSThomas Gleixner orq $(PTI_USER_PCID_MASK), \scratch_reg 253f10ee3dcSThomas Gleixner 2546fd166aaSPeter Zijlstra .Lwrcr3_\@: 255f10ee3dcSThomas Gleixner /* Flip the PGD to the user version */ 256f10ee3dcSThomas Gleixner orq $(PTI_USER_PGTABLE_MASK), \scratch_reg 2578a09317bSDave Hansen mov \scratch_reg, %cr3 258aa8c6248SThomas Gleixner .Lend_\@: 2598a09317bSDave Hansen .endm 2608a09317bSDave Hansen 2616fd166aaSPeter Zijlstra .macro SWITCH_TO_USER_CR3_STACK scratch_reg:req 2626fd166aaSPeter Zijlstra pushq %rax 2636fd166aaSPeter Zijlstra SWITCH_TO_USER_CR3_NOSTACK scratch_reg=\scratch_reg scratch_reg2=%rax 2646fd166aaSPeter Zijlstra popq %rax 2656fd166aaSPeter Zijlstra .endm 2666fd166aaSPeter Zijlstra 2678a09317bSDave Hansen .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req 268aa8c6248SThomas Gleixner ALTERNATIVE "jmp .Ldone_\@", "", X86_FEATURE_PTI 2698a09317bSDave Hansen movq %cr3, \scratch_reg 2708a09317bSDave Hansen movq \scratch_reg, \save_reg 2718a09317bSDave Hansen /* 272f10ee3dcSThomas Gleixner * Test the user pagetable bit. If set, then the user page tables 273f10ee3dcSThomas Gleixner * are active. If clear CR3 already has the kernel page table 274f10ee3dcSThomas Gleixner * active. 2758a09317bSDave Hansen */ 276f10ee3dcSThomas Gleixner bt $PTI_USER_PGTABLE_BIT, \scratch_reg 277f10ee3dcSThomas Gleixner jnc .Ldone_\@ 2788a09317bSDave Hansen 2798a09317bSDave Hansen ADJUST_KERNEL_CR3 \scratch_reg 2808a09317bSDave Hansen movq \scratch_reg, %cr3 2818a09317bSDave Hansen 2828a09317bSDave Hansen .Ldone_\@: 2838a09317bSDave Hansen .endm 2848a09317bSDave Hansen 28521e94459SPeter Zijlstra .macro RESTORE_CR3 scratch_reg:req save_reg:req 286aa8c6248SThomas Gleixner ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI 28721e94459SPeter Zijlstra 28821e94459SPeter Zijlstra ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID 28921e94459SPeter Zijlstra 29021e94459SPeter Zijlstra /* 29121e94459SPeter Zijlstra * KERNEL pages can always resume with NOFLUSH as we do 29221e94459SPeter Zijlstra * explicit flushes. 29321e94459SPeter Zijlstra */ 294f10ee3dcSThomas Gleixner bt $PTI_USER_PGTABLE_BIT, \save_reg 29521e94459SPeter Zijlstra jnc .Lnoflush_\@ 29621e94459SPeter Zijlstra 29721e94459SPeter Zijlstra /* 29821e94459SPeter Zijlstra * Check if there's a pending flush for the user ASID we're 29921e94459SPeter Zijlstra * about to set. 30021e94459SPeter Zijlstra */ 30121e94459SPeter Zijlstra movq \save_reg, \scratch_reg 30221e94459SPeter Zijlstra andq $(0x7FF), \scratch_reg 30321e94459SPeter Zijlstra bt \scratch_reg, THIS_CPU_user_pcid_flush_mask 30421e94459SPeter Zijlstra jnc .Lnoflush_\@ 30521e94459SPeter Zijlstra 30621e94459SPeter Zijlstra btr \scratch_reg, THIS_CPU_user_pcid_flush_mask 30721e94459SPeter Zijlstra jmp .Lwrcr3_\@ 30821e94459SPeter Zijlstra 30921e94459SPeter Zijlstra .Lnoflush_\@: 31021e94459SPeter Zijlstra SET_NOFLUSH_BIT \save_reg 31121e94459SPeter Zijlstra 31221e94459SPeter Zijlstra .Lwrcr3_\@: 3138a09317bSDave Hansen /* 3148a09317bSDave Hansen * The CR3 write could be avoided when not changing its value, 3158a09317bSDave Hansen * but would require a CR3 read *and* a scratch register. 3168a09317bSDave Hansen */ 3178a09317bSDave Hansen movq \save_reg, %cr3 318aa8c6248SThomas Gleixner .Lend_\@: 3198a09317bSDave Hansen .endm 3208a09317bSDave Hansen 3218a09317bSDave Hansen #else /* CONFIG_PAGE_TABLE_ISOLATION=n: */ 3228a09317bSDave Hansen 3238a09317bSDave Hansen .macro SWITCH_TO_KERNEL_CR3 scratch_reg:req 3248a09317bSDave Hansen .endm 3256fd166aaSPeter Zijlstra .macro SWITCH_TO_USER_CR3_NOSTACK scratch_reg:req scratch_reg2:req 3266fd166aaSPeter Zijlstra .endm 3276fd166aaSPeter Zijlstra .macro SWITCH_TO_USER_CR3_STACK scratch_reg:req 3288a09317bSDave Hansen .endm 3298a09317bSDave Hansen .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req 3308a09317bSDave Hansen .endm 33121e94459SPeter Zijlstra .macro RESTORE_CR3 scratch_reg:req save_reg:req 3328a09317bSDave Hansen .endm 3338a09317bSDave Hansen 3348a09317bSDave Hansen #endif 3358a09317bSDave Hansen 336d36f9479SIngo Molnar #endif /* CONFIG_X86_64 */ 337d36f9479SIngo Molnar 338478dc89cSAndy Lutomirski /* 339478dc89cSAndy Lutomirski * This does 'call enter_from_user_mode' unless we can avoid it based on 340478dc89cSAndy Lutomirski * kernel config or using the static jump infrastructure. 341478dc89cSAndy Lutomirski */ 342478dc89cSAndy Lutomirski .macro CALL_enter_from_user_mode 343478dc89cSAndy Lutomirski #ifdef CONFIG_CONTEXT_TRACKING 344478dc89cSAndy Lutomirski #ifdef HAVE_JUMP_LABEL 345478dc89cSAndy Lutomirski STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0 346478dc89cSAndy Lutomirski #endif 347478dc89cSAndy Lutomirski call enter_from_user_mode 348478dc89cSAndy Lutomirski .Lafter_call_\@: 349478dc89cSAndy Lutomirski #endif 350478dc89cSAndy Lutomirski .endm 351