tldr; Just FYI, I'm carrying this on the perf tools tree.

Full explanation:

There used to be no copies, with tools/ code using kernel headers
directly. From time to time tools/perf/ broke due to legitimate kernel
hacking. At some point Linus complained about such direct usage. Then we
adopted the current model.

The way these headers are used in perf are not restricted to just
including them to compile something.

There are sometimes used in scripts that convert defines into string
tables, etc, so some change may break one of these scripts, or new MSRs
may use some different #define pattern, etc.

E.g.:

  $ ls -1 tools/perf/trace/beauty/*.sh | head -5
  tools/perf/trace/beauty/arch_errno_names.sh
  tools/perf/trace/beauty/drm_ioctl.sh
  tools/perf/trace/beauty/fadvise.sh
  tools/perf/trace/beauty/fsconfig.sh
  tools/perf/trace/beauty/fsmount.sh
  $
  $ tools/perf/trace/beauty/fadvise.sh
  static const char *fadvise_advices[] = {
        [0] = "NORMAL",
        [1] = "RANDOM",
        [2] = "SEQUENTIAL",
        [3] = "WILLNEED",
        [4] = "DONTNEED",
        [5] = "NOREUSE",
  };
  $

The tools/perf/check-headers.sh script, part of the tools/ build
process, points out changes in the original files.

So its important not to touch the copies in tools/ when doing changes in
the original kernel headers, that will be done later, when
check-headers.sh inform about the change to the perf tools hackers.

Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20231121225650.390246-12-namhyung@kernel.org

Pull ia64 removal and asm-generic updates from Arnd Bergmann:

 - The ia64 architecture gets its well-earned retirement as planned,
   now that there is one last (mostly) working release that will be
   maintained as an LTS kernel.

 - The architecture specific system call tables are updated for the
   added map_shadow_stack() syscall and to remove references to the
   long-gone sys_lookup_dcookie() syscall.

* tag 'asm-generic-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic:
  hexagon: Remove unusable symbols from the ptrace.h uapi
  asm-generic: Fix spelling of architecture
  arch: Reserve map_shadow_stack() syscall number for all architectures
  syscalls: Cleanup references to sys_lookup_dcookie()
  Documentation: Drop or replace remaining mentions of IA64
  lib/raid6: Drop IA64 support
  Documentation: Drop IA64 from feature descriptions
  kernel: Drop IA64 support from sig_fault handlers
  arch: Remove Itanium (IA-64) architecture

commit 'be65de6b03aa ("fs: Remove dcookies support")' removed the
syscall definition for lookup_dcookie.  However, syscall tables still
point to the old sys_lookup_dcookie() definition. Update syscall tables
of all architectures to directly point to sys_ni_syscall() instead.

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Namhyung Kim <namhyung@kernel.org> # for perf
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

To pick the changes in these csets:

  c35559f94ebc3e3b ("x86/shstk: Introduce map_shadow_stack syscall")
  78252deb023cf087 ("arch: Register fchmodat2, usually as syscall 452")

That add support for this new syscall in tools such as 'perf trace'.

For instance, this is now possible:

  # perf trace -v -e fchmodat*,map_shadow_stack --max-events=4
  Using CPUID AuthenticAMD-25-21-0
  Reusing "openat" BPF sys_enter augmenter for "fchmodat"
  event qualifier tracepoint filter: (common_pid != 3499340 && common_pid != 11259) && (id == 268 || id == 452 || id == 453)
  ^C#

  And it'll work as with other syscalls, for instance openat:

  # perf trace -e openat* --max-events=4
     0.000 ( 0.015 ms): systemd-oomd/1150 openat(dfd: CWD, filename: "/proc/meminfo", flags: RDONLY|CLOEXEC)    = 11
     0.068 ( 0.019 ms): systemd-oomd/1150 openat(dfd: CWD, filename: "/sys/fs/cgroup/user.slice/user-1001.slice/user@1001.service/memory.pressure", flags: RDONLY|CLOEXEC) = 11
     0.119 ( 0.008 ms): systemd-oomd/1150 openat(dfd: CWD, filename: "/sys/fs/cgroup/user.slice/user-1001.slice/user@1001.service/memory.current", flags: RDONLY|CLOEXEC) = 11
     0.138 ( 0.006 ms): systemd-oomd/1150 openat(dfd: CWD, filename: "/sys/fs/cgroup/user.slice/user-1001.slice/user@1001.service/memory.min", flags: RDONLY|CLOEXEC) = 11
  #

That is the filter expression attached to the raw_syscalls:sys_{enter,exit}
tracepoints.

  $ find tools/perf/arch/ -name "syscall*tbl" | xargs grep -E fchmodat\|sys_map_shadow_stack
  tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl:258	n64	fchmodat			sys_fchmodat
  tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl:452	n64	fchmodat2			sys_fchmodat2
  tools/perf/arch/powerpc/entry/syscalls/syscall.tbl:297	common	fchmodat			sys_fchmodat
  tools/perf/arch/powerpc/entry/syscalls/syscall.tbl:452	common	fchmodat2			sys_fchmodat2
  tools/perf/arch/s390/entry/syscalls/syscall.tbl:299  common	fchmodat		sys_fchmodat			sys_fchmodat
  tools/perf/arch/s390/entry/syscalls/syscall.tbl:452  common	fchmodat2		sys_fchmodat2			sys_fchmodat2
  tools/perf/arch/x86/entry/syscalls/syscall_64.tbl:268	common	fchmodat		sys_fchmodat
  tools/perf/arch/x86/entry/syscalls/syscall_64.tbl:452	common	fchmodat2		sys_fchmodat2
  tools/perf/arch/x86/entry/syscalls/syscall_64.tbl:453	64	map_shadow_stack	sys_map_shadow_stack
  $

  $ grep -Ew map_shadow_stack\|fchmodat2 /tmp/build/perf-tools/arch/x86/include/generated/asm/syscalls_64.c
	[452] = "fchmodat2",
	[453] = "map_shadow_stack",
  $

This addresses these perf build warnings:

  Warning: Kernel ABI header differences:
    diff -u tools/include/uapi/asm-generic/unistd.h include/uapi/asm-generic/unistd.h
    diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl
    diff -u tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl
    diff -u tools/perf/arch/s390/entry/syscalls/syscall.tbl arch/s390/kernel/syscalls/syscall.tbl
    diff -u tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl arch/mips/kernel/syscalls/syscall_n64.tbl

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Link: https://lore.kernel.org/lkml/ZP8bE7aXDBu%2Fdrak@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

To pick the changes in these csets:

  cf264e1329fb0307 ("cachestat: implement cachestat syscall")

That add support for this new syscall in tools such as 'perf trace'.

For instance, this is now possible:

  # perf trace -e cachestat
  ^C[root@five ~]#
  # perf trace -v -e cachestat
  Using CPUID AuthenticAMD-25-21-0
  event qualifier tracepoint filter: (common_pid != 3163687 && common_pid != 3147) && (id == 451)
  mmap size 528384B
  ^C[root@five ~]

  # perf trace -v -e *stat* --max-events=10
  Using CPUID AuthenticAMD-25-21-0
  event qualifier tracepoint filter: (common_pid != 3163713 && common_pid != 3147) && (id == 4 || id == 5 || id == 6 || id == 136 || id == 137 || id == 138 || id == 262 || id == 332 || id == 451)
  mmap size 528384B
       0.000 ( 0.009 ms): Cache2 I/O/4544 statfs(pathname: 0x45635288, buf: 0x7f8745725b60)                     = 0
       0.012 ( 0.003 ms): Cache2 I/O/4544 newfstatat(dfd: CWD, filename: 0x45635288, statbuf: 0x7f874569d250)   = 0
       0.036 ( 0.002 ms): Cache2 I/O/4544 newfstatat(dfd: 138, filename: 0x541b7093, statbuf: 0x7f87457256f0, flag: 4096) = 0
       0.372 ( 0.006 ms): Cache2 I/O/4544 statfs(pathname: 0x45635288, buf: 0x7f8745725b10)                     = 0
       0.379 ( 0.003 ms): Cache2 I/O/4544 newfstatat(dfd: CWD, filename: 0x45635288, statbuf: 0x7f874569d250)   = 0
       0.390 ( 0.002 ms): Cache2 I/O/4544 newfstatat(dfd: 138, filename: 0x541b7093, statbuf: 0x7f87457256a0, flag: 4096) = 0
       0.609 ( 0.005 ms): Cache2 I/O/4544 statfs(pathname: 0x45635288, buf: 0x7f8745725b60)                     = 0
       0.615 ( 0.003 ms): Cache2 I/O/4544 newfstatat(dfd: CWD, filename: 0x45635288, statbuf: 0x7f874569d250)   = 0
       0.625 ( 0.002 ms): Cache2 I/O/4544 newfstatat(dfd: 138, filename: 0x541b7093, statbuf: 0x7f87457256f0, flag: 4096) = 0
       0.826 ( 0.005 ms): Cache2 I/O/4544 statfs(pathname: 0x45635288, buf: 0x7f8745725b10)                     = 0
  #

That is the filter expression attached to the raw_syscalls:sys_{enter,exit}
tracepoints.

  $ find tools/perf/arch/ -name "syscall*tbl" | xargs grep -w sys_cachestat
  tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl:451	n64	cachestat			sys_cachestat
  tools/perf/arch/powerpc/entry/syscalls/syscall.tbl:451	common	cachestat			sys_cachestat
  tools/perf/arch/s390/entry/syscalls/syscall.tbl:451  common	cachestat		sys_cachestat			sys_cachestat
  tools/perf/arch/x86/entry/syscalls/syscall_64.tbl:451	common	cachestat		sys_cachestat
  $

  $ grep -w cachestat /tmp/build/perf-tools/arch/x86/include/generated/asm/syscalls_64.c
  	[451] = "cachestat",
  $

This addresses these perf build warnings:

Warning: Kernel ABI header differences:
  diff -u tools/include/uapi/asm-generic/unistd.h include/uapi/asm-generic/unistd.h
  diff -u tools/include/uapi/linux/mman.h include/uapi/linux/mman.h
  diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl
  diff -u tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl
  diff -u tools/perf/arch/s390/entry/syscalls/syscall.tbl arch/s390/kernel/syscalls/syscall.tbl
  diff -u tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl arch/mips/kernel/syscalls/syscall_n64.tbl

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Link: https://lore.kernel.org/lkml/ZK1pVBJpbjujJNJW@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

syscalltbl_*[] should never be changing, let us declare it as const.

Suggested-by: Ian Rogers <irogers@google.com>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: loongarch@lists.linux.dev
Link: https://lore.kernel.org/r/1685441401-8709-2-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

To pick the changes in these csets:

  ce883a2ba310cd7c ("powerpc/32: fix syscall wrappers with 64-bit arguments")

That doesn't cause any changes in the perf tools.

This table is used in tools perf to allow features as described in the
last update to this file.

This addresses this perf build warning:

  Warning: Kernel ABI header at 'tools/perf/arch/powerpc/entry/syscalls/syscall.tbl' differs from latest version at 'arch/powerpc/kernel/syscalls/syscall.tbl'
  diff -u tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/Y6H0C5plZ4V4aiPm@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

To pick the changes in these csets:

  e237506238352f3b ("powerpc/32: fix syscall wrappers with 64-bit arguments of unaligned register-pairs")

That doesn't cause any changes in the perf tools.

As a reminder, this table is used in tools perf to allow features such as:

  [root@five ~]# perf trace -e set_mempolicy_home_node
  ^C[root@five ~]#
  [root@five ~]# perf trace -v -e set_mempolicy_home_node
  Using CPUID AuthenticAMD-25-21-0
  event qualifier tracepoint filter: (common_pid != 253729 && common_pid != 3585) && (id == 450)
  mmap size 528384B
  ^C[root@five ~]
  [root@five ~]# perf trace -v -e set*  --max-events 5
  Using CPUID AuthenticAMD-25-21-0
  event qualifier tracepoint filter: (common_pid != 253734 && common_pid != 3585) && (id == 38 || id == 54 || id == 105 || id == 106 || id == 109 || id == 112 || id == 113 || id == 114 || id == 116 || id == 117 || id == 119 || id == 122 || id == 123 || id == 141 || id == 160 || id == 164 || id == 170 || id == 171 || id == 188 || id == 205 || id == 218 || id == 238 || id == 273 || id == 308 || id == 450)
  mmap size 528384B
       0.000 ( 0.008 ms): bash/253735 setpgid(pid: 253735 (bash), pgid: 253735 (bash))      = 0
    6849.011 ( 0.008 ms): bash/16046 setpgid(pid: 253736 (bash), pgid: 253736 (bash))       = 0
    6849.080 ( 0.005 ms): bash/253736 setpgid(pid: 253736 (bash), pgid: 253736 (bash))      = 0
    7437.718 ( 0.009 ms): gnome-shell/253737 set_robust_list(head: 0x7f34b527e920, len: 24) = 0
   13445.986 ( 0.010 ms): bash/16046 setpgid(pid: 253738 (bash), pgid: 253738 (bash))       = 0
  [root@five ~]#

That is the filter expression attached to the raw_syscalls:sys_{enter,exit}
tracepoints.

  $ find tools/perf/arch/ -name "syscall*tbl" | xargs grep -w set_mempolicy_home_node
  tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl:450	common	set_mempolicy_home_node		sys_set_mempolicy_home_node
  tools/perf/arch/powerpc/entry/syscalls/syscall.tbl:450 	nospu	set_mempolicy_home_node		sys_set_mempolicy_home_node
  tools/perf/arch/s390/entry/syscalls/syscall.tbl:450  common	set_mempolicy_home_node	sys_set_mempolicy_home_node	sys_set_mempolicy_home_node
  tools/perf/arch/x86/entry/syscalls/syscall_64.tbl:450	common	set_mempolicy_home_node	sys_set_mempolicy_home_node
  $

  $ grep -w set_mempolicy_home_node /tmp/build/perf/arch/x86/include/generated/asm/syscalls_64.c
	[450] = "set_mempolicy_home_node",
  $

This addresses these perf build warnings:

  Warning: Kernel ABI header at 'tools/include/uapi/asm-generic/unistd.h' differs from latest version at 'include/uapi/asm-generic/unistd.h'
  diff -u tools/include/uapi/asm-generic/unistd.h include/uapi/asm-generic/unistd.h
  Warning: Kernel ABI header at 'tools/perf/arch/x86/entry/syscalls/syscall_64.tbl' differs from latest version at 'arch/x86/entry/syscalls/syscall_64.tbl'
  diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl
  Warning: Kernel ABI header at 'tools/perf/arch/powerpc/entry/syscalls/syscall.tbl' differs from latest version at 'arch/powerpc/kernel/syscalls/syscall.tbl'
  diff -u tools/perf/arch/powerpc/entry/syscalls/syscall.tbl arch/powerpc/kernel/syscalls/syscall.tbl
  Warning: Kernel ABI header at 'tools/perf/arch/s390/entry/syscalls/syscall.tbl' differs from latest version at 'arch/s390/kernel/syscalls/syscall.tbl'
  diff -u tools/perf/arch/s390/entry/syscalls/syscall.tbl arch/s390/kernel/syscalls/syscall.tbl
  Warning: Kernel ABI header at 'tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl' differs from latest version at 'arch/mips/kernel/syscalls/syscall_n64.tbl'
  diff -u tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl arch/mips/kernel/syscalls/syscall_n64.tbl

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Link: https://lore.kernel.org/lkml/Y01HN2DGkWz8tC%2FJ@kernel.org/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Arch-specific implementations of syscall handlers are currently used
over generic implementations for the following reasons:

1. Semantics unique to powerpc
2. Compatibility syscalls require 'argument padding' to comply with
   64-bit argument convention in ELF32 abi.
3. Parameter types or order is different in other architectures.

These syscall handlers have been defined prior to this patch series
without invoking the SYSCALL_DEFINE or COMPAT_SYSCALL_DEFINE macros with
custom input and output types. We remove every such direct definition in
favour of the aforementioned macros.

Also update syscalls.tbl in order to refer to the symbol names generated
by each of these macros. Since ppc64_personality can be called by both
64 bit and 32 bit binaries through compatibility, we must generate both
both compat_sys_ and sys_ symbols for this handler.

As an aside:
A number of architectures including arm and powerpc agree on an
alternative argument order and numbering for most of these arch-specific
handlers. A future patch series may allow for asm/unistd.h to signal
through its defines that a generic implementation of these syscall
handlers with the correct calling convention be emitted, through the
__ARCH_WANT_COMPAT_SYS_... convention.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220921065605.1051927-16-rmclure@linux.ibm.com

Syscall #82 has been implemented for 32-bit platforms in a unique way on
powerpc systems. This hack will in effect guess whether the caller is
expecting new select semantics or old select semantics. It does so via a
guess, based off the first parameter. In new select, this parameter
represents the length of a user-memory array of file descriptors, and in
old select this is a pointer to an arguments structure.

The heuristic simply interprets sufficiently large values of its first
parameter as being a call to old select. The following is a discussion
on how this syscall should be handled.


As discussed in this thread, the existence of such a hack suggests that for
whatever powerpc binaries may predate glibc, it is most likely that they
would have taken use of the old select semantics. x86 and arm64 both
implement this syscall with oldselect semantics.

Remove the powerpc implementation, and update syscall.tbl to refer to emit
a reference to sys_old_select and compat_sys_old_select
for 32-bit binaries, in keeping with how other architectures support
syscall #82.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/lkml/13737de5-0eb7-e881-9af0-163b0d29a1a0@csgroup.eu/
Link: https://lore.kernel.org/r/20220921065605.1051927-12-rmclure@linux.ibm.com