mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-15 01:36:46 +07:00
4332195c56
Up until now we have always paid attention to make sure the length of the new instruction replacing the old one is at least less or equal to the length of the old instruction. If the new instruction is longer, at the time it replaces the old instruction it will overwrite the beginning of the next instruction in the kernel image and cause your pants to catch fire. So instead of having to pay attention, teach the alternatives framework to pad shorter old instructions with NOPs at buildtime - but only in the case when len(old instruction(s)) < len(new instruction(s)) and add nothing in the >= case. (In that case we do add_nops() when patching). This way the alternatives user shouldn't have to care about instruction sizes and simply use the macros. Add asm ALTERNATIVE* flavor macros too, while at it. Also, we need to save the pad length in a separate struct alt_instr member for NOP optimization and the way to do that reliably is to carry the pad length instead of trying to detect whether we're looking at single-byte NOPs or at pathological instruction offsets like e9 90 90 90 90, for example, which is a valid instruction. Thanks to Michael Matz for the great help with toolchain questions. Signed-off-by: Borislav Petkov <bp@suse.de>
209 lines
4.2 KiB
ArmAsm
209 lines
4.2 KiB
ArmAsm
/* Copyright 2002 Andi Kleen */
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#include <linux/linkage.h>
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#include <asm/cpufeature.h>
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#include <asm/dwarf2.h>
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#include <asm/alternative-asm.h>
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/*
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* memcpy - Copy a memory block.
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*
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* Input:
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* rdi destination
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* rsi source
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* rdx count
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*
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* Output:
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* rax original destination
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*/
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/*
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* memcpy_c() - fast string ops (REP MOVSQ) based variant.
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*
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* This gets patched over the unrolled variant (below) via the
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* alternative instructions framework:
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*/
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.section .altinstr_replacement, "ax", @progbits
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.Lmemcpy_c:
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movq %rdi, %rax
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movq %rdx, %rcx
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shrq $3, %rcx
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andl $7, %edx
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rep movsq
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movl %edx, %ecx
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rep movsb
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ret
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.Lmemcpy_e:
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.previous
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/*
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* memcpy_c_e() - enhanced fast string memcpy. This is faster and simpler than
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* memcpy_c. Use memcpy_c_e when possible.
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*
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* This gets patched over the unrolled variant (below) via the
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* alternative instructions framework:
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*/
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.section .altinstr_replacement, "ax", @progbits
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.Lmemcpy_c_e:
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movq %rdi, %rax
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movq %rdx, %rcx
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rep movsb
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ret
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.Lmemcpy_e_e:
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.previous
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.weak memcpy
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ENTRY(__memcpy)
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ENTRY(memcpy)
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CFI_STARTPROC
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movq %rdi, %rax
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cmpq $0x20, %rdx
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jb .Lhandle_tail
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/*
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* We check whether memory false dependence could occur,
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* then jump to corresponding copy mode.
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*/
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cmp %dil, %sil
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jl .Lcopy_backward
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subq $0x20, %rdx
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.Lcopy_forward_loop:
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subq $0x20, %rdx
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/*
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* Move in blocks of 4x8 bytes:
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*/
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movq 0*8(%rsi), %r8
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movq 1*8(%rsi), %r9
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movq 2*8(%rsi), %r10
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movq 3*8(%rsi), %r11
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leaq 4*8(%rsi), %rsi
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movq %r8, 0*8(%rdi)
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movq %r9, 1*8(%rdi)
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movq %r10, 2*8(%rdi)
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movq %r11, 3*8(%rdi)
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leaq 4*8(%rdi), %rdi
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jae .Lcopy_forward_loop
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addl $0x20, %edx
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jmp .Lhandle_tail
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.Lcopy_backward:
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/*
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* Calculate copy position to tail.
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*/
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addq %rdx, %rsi
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addq %rdx, %rdi
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subq $0x20, %rdx
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/*
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* At most 3 ALU operations in one cycle,
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* so append NOPS in the same 16 bytes trunk.
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*/
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.p2align 4
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.Lcopy_backward_loop:
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subq $0x20, %rdx
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movq -1*8(%rsi), %r8
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movq -2*8(%rsi), %r9
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movq -3*8(%rsi), %r10
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movq -4*8(%rsi), %r11
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leaq -4*8(%rsi), %rsi
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movq %r8, -1*8(%rdi)
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movq %r9, -2*8(%rdi)
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movq %r10, -3*8(%rdi)
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movq %r11, -4*8(%rdi)
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leaq -4*8(%rdi), %rdi
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jae .Lcopy_backward_loop
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/*
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* Calculate copy position to head.
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*/
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addl $0x20, %edx
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subq %rdx, %rsi
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subq %rdx, %rdi
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.Lhandle_tail:
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cmpl $16, %edx
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jb .Lless_16bytes
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/*
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* Move data from 16 bytes to 31 bytes.
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*/
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movq 0*8(%rsi), %r8
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movq 1*8(%rsi), %r9
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movq -2*8(%rsi, %rdx), %r10
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movq -1*8(%rsi, %rdx), %r11
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movq %r8, 0*8(%rdi)
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movq %r9, 1*8(%rdi)
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movq %r10, -2*8(%rdi, %rdx)
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movq %r11, -1*8(%rdi, %rdx)
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retq
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.p2align 4
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.Lless_16bytes:
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cmpl $8, %edx
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jb .Lless_8bytes
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/*
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* Move data from 8 bytes to 15 bytes.
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*/
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movq 0*8(%rsi), %r8
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movq -1*8(%rsi, %rdx), %r9
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movq %r8, 0*8(%rdi)
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movq %r9, -1*8(%rdi, %rdx)
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retq
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.p2align 4
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.Lless_8bytes:
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cmpl $4, %edx
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jb .Lless_3bytes
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/*
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* Move data from 4 bytes to 7 bytes.
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*/
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movl (%rsi), %ecx
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movl -4(%rsi, %rdx), %r8d
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movl %ecx, (%rdi)
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movl %r8d, -4(%rdi, %rdx)
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retq
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.p2align 4
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.Lless_3bytes:
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subl $1, %edx
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jb .Lend
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/*
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* Move data from 1 bytes to 3 bytes.
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*/
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movzbl (%rsi), %ecx
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jz .Lstore_1byte
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movzbq 1(%rsi), %r8
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movzbq (%rsi, %rdx), %r9
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movb %r8b, 1(%rdi)
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movb %r9b, (%rdi, %rdx)
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.Lstore_1byte:
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movb %cl, (%rdi)
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.Lend:
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retq
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CFI_ENDPROC
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ENDPROC(memcpy)
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ENDPROC(__memcpy)
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/*
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* Some CPUs are adding enhanced REP MOVSB/STOSB feature
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* If the feature is supported, memcpy_c_e() is the first choice.
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* If enhanced rep movsb copy is not available, use fast string copy
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* memcpy_c() when possible. This is faster and code is simpler than
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* original memcpy().
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* Otherwise, original memcpy() is used.
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* In .altinstructions section, ERMS feature is placed after REG_GOOD
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* feature to implement the right patch order.
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*
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* Replace only beginning, memcpy is used to apply alternatives,
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* so it is silly to overwrite itself with nops - reboot is the
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* only outcome...
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*/
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.section .altinstructions, "a"
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altinstruction_entry __memcpy,.Lmemcpy_c,X86_FEATURE_REP_GOOD,\
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.Lmemcpy_e-.Lmemcpy_c,.Lmemcpy_e-.Lmemcpy_c,0
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altinstruction_entry __memcpy,.Lmemcpy_c_e,X86_FEATURE_ERMS, \
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.Lmemcpy_e_e-.Lmemcpy_c_e,.Lmemcpy_e_e-.Lmemcpy_c_e,0
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.previous
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