x86/syscalls: Document the fact that syscalls 512-547 are a legacy mistake (c3b484c4) · Commits · 戴 / test

Since this commit: ("x86/syscalls: Split the x32 syscalls into their own table") there is no need for special x32-specific syscall numbers. I forgot to update the comments in syscall_64.tbl. Add comments to make it clear to future contributors that this range is a legacy wart. Reported-by:

Jessica Clarke <jrtc27@jrtc27.com> Signed-off-by:

Andy Lutomirski <luto@kernel.org> Signed-off-by:

Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/6c56fb4ddd18fc60a238eb4d867e4b3d97c6351e.1602471055.git.luto@kernel.org

arch/x86/entry/syscalls/syscall_64.tbl

+6 −4

Original line number	Diff line number	Diff line
		@@ -363,10 +363,10 @@
		439 common faccessat2 sys_faccessat2

		#
		# x32-specific system call numbers start at 512 to avoid cache impact
		# for native 64-bit operation. The __x32_compat_sys stubs are created
		# on-the-fly for compat_sys_*() compatibility system calls if X86_X32
		# is defined.
		# Due to a historical design error, certain syscalls are numbered differently
		# in x32 as compared to native x86_64. These syscalls have numbers 512-547.
		# Do not add new syscalls to this range. Numbers 548 and above are available
		# for non-x32 use.
		#
		512 x32 rt_sigaction compat_sys_rt_sigaction
		513 x32 rt_sigreturn compat_sys_x32_rt_sigreturn
		@@ -404,3 +404,5 @@
		545 x32 execveat compat_sys_execveat
		546 x32 preadv2 compat_sys_preadv64v2
		547 x32 pwritev2 compat_sys_pwritev64v2
		# This is the end of the legacy x32 range. Numbers 548 and above are
		# not special and are not to be used for x32-specific syscalls.

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