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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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8474ba7419
Make sure the compiler does not modify arguments of syscall functions. This can happen if the compiler generates a tailcall to another function. For example, without asmlinkage_protect sys_openat is compiled into this function: sys_openat: clr.l %d0 move.w 18(%sp),%d0 move.l %d0,16(%sp) jbra do_sys_open Note how the fourth argument is modified in place, modifying the register %d4 that gets restored from this stack slot when the function returns to user-space. The caller may expect the register to be unmodified across system calls. Signed-off-by: Andreas Schwab <schwab@linux-m68k.org> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Cc: stable@vger.kernel.org
38 lines
1.5 KiB
C
38 lines
1.5 KiB
C
#ifndef __ASM_LINKAGE_H
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#define __ASM_LINKAGE_H
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#define __ALIGN .align 4
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#define __ALIGN_STR ".align 4"
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/*
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* Make sure the compiler doesn't do anything stupid with the
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* arguments on the stack - they are owned by the *caller*, not
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* the callee. This just fools gcc into not spilling into them,
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* and keeps it from doing tailcall recursion and/or using the
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* stack slots for temporaries, since they are live and "used"
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* all the way to the end of the function.
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*/
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#define asmlinkage_protect(n, ret, args...) \
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__asmlinkage_protect##n(ret, ##args)
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#define __asmlinkage_protect_n(ret, args...) \
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__asm__ __volatile__ ("" : "=r" (ret) : "0" (ret), ##args)
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#define __asmlinkage_protect0(ret) \
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__asmlinkage_protect_n(ret)
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#define __asmlinkage_protect1(ret, arg1) \
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__asmlinkage_protect_n(ret, "m" (arg1))
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#define __asmlinkage_protect2(ret, arg1, arg2) \
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__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2))
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#define __asmlinkage_protect3(ret, arg1, arg2, arg3) \
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__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3))
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#define __asmlinkage_protect4(ret, arg1, arg2, arg3, arg4) \
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__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \
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"m" (arg4))
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#define __asmlinkage_protect5(ret, arg1, arg2, arg3, arg4, arg5) \
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__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \
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"m" (arg4), "m" (arg5))
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#define __asmlinkage_protect6(ret, arg1, arg2, arg3, arg4, arg5, arg6) \
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__asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \
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"m" (arg4), "m" (arg5), "m" (arg6))
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#endif
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