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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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131484c8da
So the dwarf2 annotations in low level assembly code have become an increasing hindrance: unreadable, messy macros mixed into some of the most security sensitive code paths of the Linux kernel. These debug info annotations don't even buy the upstream kernel anything: dwarf driven stack unwinding has caused problems in the past so it's out of tree, and the upstream kernel only uses the much more robust framepointers based stack unwinding method. In addition to that there's a steady, slow bitrot going on with these annotations, requiring frequent fixups. There's no tooling and no functionality upstream that keeps it correct. So burn down the sick forest, allowing new, healthier growth: 27 files changed, 350 insertions(+), 1101 deletions(-) Someone who has the willingness and time to do this properly can attempt to reintroduce dwarf debuginfo in x86 assembly code plus dwarf unwinding from first principles, with the following conditions: - it should be maximally readable, and maximally low-key to 'ordinary' code reading and maintenance. - find a build time method to insert dwarf annotations automatically in the most common cases, for pop/push instructions that manipulate the stack pointer. This could be done for example via a preprocessing step that just looks for common patterns - plus special annotations for the few cases where we want to depart from the default. We have hundreds of CFI annotations, so automating most of that makes sense. - it should come with build tooling checks that ensure that CFI annotations are sensible. We've seen such efforts from the framepointer side, and there's no reason it couldn't be done on the dwarf side. Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frédéric Weisbecker <fweisbec@gmail.com Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jan Beulich <JBeulich@suse.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
225 lines
3.7 KiB
ArmAsm
225 lines
3.7 KiB
ArmAsm
/*
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* Copyright 2002, 2003 Andi Kleen, SuSE Labs.
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file COPYING in the main directory of this archive
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* for more details. No warranty for anything given at all.
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*/
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#include <linux/linkage.h>
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#include <asm/errno.h>
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#include <asm/asm.h>
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/*
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* Checksum copy with exception handling.
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* On exceptions src_err_ptr or dst_err_ptr is set to -EFAULT and the
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* destination is zeroed.
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*
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* Input
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* rdi source
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* rsi destination
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* edx len (32bit)
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* ecx sum (32bit)
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* r8 src_err_ptr (int)
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* r9 dst_err_ptr (int)
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*
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* Output
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* eax 64bit sum. undefined in case of exception.
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*
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* Wrappers need to take care of valid exception sum and zeroing.
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* They also should align source or destination to 8 bytes.
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*/
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.macro source
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10:
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_ASM_EXTABLE(10b, .Lbad_source)
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.endm
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.macro dest
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20:
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_ASM_EXTABLE(20b, .Lbad_dest)
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.endm
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.macro ignore L=.Lignore
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30:
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_ASM_EXTABLE(30b, \L)
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.endm
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ENTRY(csum_partial_copy_generic)
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cmpl $3*64, %edx
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jle .Lignore
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.Lignore:
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subq $7*8, %rsp
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movq %rbx, 2*8(%rsp)
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movq %r12, 3*8(%rsp)
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movq %r14, 4*8(%rsp)
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movq %r13, 5*8(%rsp)
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movq %rbp, 6*8(%rsp)
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movq %r8, (%rsp)
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movq %r9, 1*8(%rsp)
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movl %ecx, %eax
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movl %edx, %ecx
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xorl %r9d, %r9d
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movq %rcx, %r12
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shrq $6, %r12
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jz .Lhandle_tail /* < 64 */
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clc
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/* main loop. clear in 64 byte blocks */
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/* r9: zero, r8: temp2, rbx: temp1, rax: sum, rcx: saved length */
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/* r11: temp3, rdx: temp4, r12 loopcnt */
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/* r10: temp5, rbp: temp6, r14 temp7, r13 temp8 */
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.p2align 4
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.Lloop:
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source
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movq (%rdi), %rbx
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source
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movq 8(%rdi), %r8
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source
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movq 16(%rdi), %r11
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source
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movq 24(%rdi), %rdx
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source
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movq 32(%rdi), %r10
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source
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movq 40(%rdi), %rbp
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source
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movq 48(%rdi), %r14
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source
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movq 56(%rdi), %r13
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ignore 2f
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prefetcht0 5*64(%rdi)
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2:
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adcq %rbx, %rax
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adcq %r8, %rax
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adcq %r11, %rax
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adcq %rdx, %rax
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adcq %r10, %rax
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adcq %rbp, %rax
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adcq %r14, %rax
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adcq %r13, %rax
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decl %r12d
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dest
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movq %rbx, (%rsi)
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dest
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movq %r8, 8(%rsi)
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dest
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movq %r11, 16(%rsi)
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dest
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movq %rdx, 24(%rsi)
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dest
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movq %r10, 32(%rsi)
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dest
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movq %rbp, 40(%rsi)
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dest
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movq %r14, 48(%rsi)
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dest
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movq %r13, 56(%rsi)
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3:
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leaq 64(%rdi), %rdi
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leaq 64(%rsi), %rsi
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jnz .Lloop
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adcq %r9, %rax
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/* do last up to 56 bytes */
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.Lhandle_tail:
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/* ecx: count */
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movl %ecx, %r10d
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andl $63, %ecx
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shrl $3, %ecx
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jz .Lfold
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clc
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.p2align 4
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.Lloop_8:
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source
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movq (%rdi), %rbx
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adcq %rbx, %rax
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decl %ecx
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dest
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movq %rbx, (%rsi)
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leaq 8(%rsi), %rsi /* preserve carry */
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leaq 8(%rdi), %rdi
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jnz .Lloop_8
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adcq %r9, %rax /* add in carry */
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.Lfold:
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/* reduce checksum to 32bits */
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movl %eax, %ebx
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shrq $32, %rax
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addl %ebx, %eax
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adcl %r9d, %eax
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/* do last up to 6 bytes */
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.Lhandle_7:
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movl %r10d, %ecx
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andl $7, %ecx
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shrl $1, %ecx
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jz .Lhandle_1
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movl $2, %edx
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xorl %ebx, %ebx
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clc
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.p2align 4
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.Lloop_1:
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source
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movw (%rdi), %bx
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adcl %ebx, %eax
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decl %ecx
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dest
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movw %bx, (%rsi)
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leaq 2(%rdi), %rdi
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leaq 2(%rsi), %rsi
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jnz .Lloop_1
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adcl %r9d, %eax /* add in carry */
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/* handle last odd byte */
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.Lhandle_1:
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testb $1, %r10b
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jz .Lende
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xorl %ebx, %ebx
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source
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movb (%rdi), %bl
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dest
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movb %bl, (%rsi)
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addl %ebx, %eax
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adcl %r9d, %eax /* carry */
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.Lende:
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movq 2*8(%rsp), %rbx
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movq 3*8(%rsp), %r12
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movq 4*8(%rsp), %r14
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movq 5*8(%rsp), %r13
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movq 6*8(%rsp), %rbp
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addq $7*8, %rsp
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ret
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/* Exception handlers. Very simple, zeroing is done in the wrappers */
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.Lbad_source:
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movq (%rsp), %rax
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testq %rax, %rax
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jz .Lende
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movl $-EFAULT, (%rax)
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jmp .Lende
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.Lbad_dest:
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movq 8(%rsp), %rax
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testq %rax, %rax
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jz .Lende
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movl $-EFAULT, (%rax)
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jmp .Lende
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ENDPROC(csum_partial_copy_generic)
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