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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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5045ea3737
__kernel_get_syscall_map() and __kernel_clock_getres() use cmpli to
check if the passed in pointer is non zero. cmpli maps to a 32 bit
compare on binutils, so we ignore the top 32 bits.
A simple test case can be created by passing in a bogus pointer with
the bottom 32 bits clear. Using a clk_id that is handled by the VDSO,
then one that is handled by the kernel shows the problem:
printf("%d\n", clock_getres(CLOCK_REALTIME, (void *)0x100000000));
printf("%d\n", clock_getres(CLOCK_BOOTTIME, (void *)0x100000000));
And we get:
0
-1
The bigger issue is if we pass a valid pointer with the bottom 32 bits
clear, in this case we will return success but won't write any data
to the pointer.
I stumbled across this issue because the LLVM integrated assembler
doesn't accept cmpli with 3 arguments. Fix this by converting them to
cmpldi.
Fixes: a7f290dad3 ("[PATCH] powerpc: Merge vdso's and add vdso support to 32 bits kernel")
Cc: stable@vger.kernel.org # v2.6.15+
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
88 lines
2.0 KiB
ArmAsm
88 lines
2.0 KiB
ArmAsm
/*
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* Access to the shared data page by the vDSO & syscall map
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*
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* Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org), IBM Corp.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <asm/processor.h>
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#include <asm/ppc_asm.h>
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#include <asm/asm-offsets.h>
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#include <asm/unistd.h>
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#include <asm/vdso.h>
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.text
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.global __kernel_datapage_offset;
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__kernel_datapage_offset:
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.long 0
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V_FUNCTION_BEGIN(__get_datapage)
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.cfi_startproc
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/* We don't want that exposed or overridable as we want other objects
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* to be able to bl directly to here
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*/
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.protected __get_datapage
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.hidden __get_datapage
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mflr r0
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.cfi_register lr,r0
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bcl 20,31,data_page_branch
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data_page_branch:
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mflr r3
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mtlr r0
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addi r3, r3, __kernel_datapage_offset-data_page_branch
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lwz r0,0(r3)
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add r3,r0,r3
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blr
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.cfi_endproc
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V_FUNCTION_END(__get_datapage)
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/*
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* void *__kernel_get_syscall_map(unsigned int *syscall_count) ;
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*
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* returns a pointer to the syscall map. the map is agnostic to the
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* size of "long", unlike kernel bitops, it stores bits from top to
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* bottom so that memory actually contains a linear bitmap
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* check for syscall N by testing bit (0x80000000 >> (N & 0x1f)) of
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* 32 bits int at N >> 5.
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*/
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V_FUNCTION_BEGIN(__kernel_get_syscall_map)
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.cfi_startproc
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mflr r12
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.cfi_register lr,r12
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mr r4,r3
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bl V_LOCAL_FUNC(__get_datapage)
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mtlr r12
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addi r3,r3,CFG_SYSCALL_MAP64
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cmpldi cr0,r4,0
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crclr cr0*4+so
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beqlr
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li r0,NR_syscalls
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stw r0,0(r4)
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blr
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.cfi_endproc
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V_FUNCTION_END(__kernel_get_syscall_map)
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/*
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* void unsigned long __kernel_get_tbfreq(void);
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*
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* returns the timebase frequency in HZ
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*/
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V_FUNCTION_BEGIN(__kernel_get_tbfreq)
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.cfi_startproc
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mflr r12
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.cfi_register lr,r12
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bl V_LOCAL_FUNC(__get_datapage)
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ld r3,CFG_TB_TICKS_PER_SEC(r3)
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mtlr r12
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crclr cr0*4+so
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blr
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.cfi_endproc
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V_FUNCTION_END(__kernel_get_tbfreq)
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