linux.git/arch/x86/net, branch v6.2 Linux kernel source tree Merge tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2022-12-14T23:03:00+00:00 Linus Torvalds torvalds@linux-foundation.org 2022-12-14T23:03:00+00:00 94a855111ed9106971ca2617c5d075269e6aefde Pull x86 core updates from Borislav Petkov: - Add the call depth tracking mitigation for Retbleed which has been long in the making. It is a lighterweight software-only fix for Skylake-based cores where enabling IBRS is a big hammer and causes a significant performance impact. What it basically does is, it aligns all kernel functions to 16 bytes boundary and adds a 16-byte padding before the function, objtool collects all functions' locations and when the mitigation gets applied, it patches a call accounting thunk which is used to track the call depth of the stack at any time. When that call depth reaches a magical, microarchitecture-specific value for the Return Stack Buffer, the code stuffs that RSB and avoids its underflow which could otherwise lead to the Intel variant of Retbleed. This software-only solution brings a lot of the lost performance back, as benchmarks suggest: https://lore.kernel.org/all/20220915111039.092790446@infradead.org/ That page above also contains a lot more detailed explanation of the whole mechanism - Implement a new control flow integrity scheme called FineIBT which is based on the software kCFI implementation and uses hardware IBT support where present to annotate and track indirect branches using a hash to validate them - Other misc fixes and cleanups * tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (80 commits) x86/paravirt: Use common macro for creating simple asm paravirt functions x86/paravirt: Remove clobber bitmask from .parainstructions x86/debug: Include percpu.h in debugreg.h to get DECLARE_PER_CPU() et al x86/cpufeatures: Move X86_FEATURE_CALL_DEPTH from bit 18 to bit 19 of word 11, to leave space for WIP X86_FEATURE_SGX_EDECCSSA bit x86/Kconfig: Enable kernel IBT by default x86,pm: Force out-of-line memcpy() objtool: Fix weak hole vs prefix symbol objtool: Optimize elf_dirty_reloc_sym() x86/cfi: Add boot time hash randomization x86/cfi: Boot time selection of CFI scheme x86/ibt: Implement FineIBT objtool: Add --cfi to generate the .cfi_sites section x86: Add prefix symbols for function padding objtool: Add option to generate prefix symbols objtool: Avoid O(bloody terrible) behaviour -- an ode to libelf objtool: Slice up elf_create_section_symbol() kallsyms: Revert "Take callthunks into account" x86: Unconfuse CONFIG_ and X86_FEATURE_ namespaces x86/retpoline: Fix crash printing warning x86/paravirt: Fix a !PARAVIRT build warning ... 
Pull x86 core updates from Borislav Petkov:

 - Add the call depth tracking mitigation for Retbleed which has been
   long in the making. It is a lighterweight software-only fix for
   Skylake-based cores where enabling IBRS is a big hammer and causes a
   significant performance impact.

   What it basically does is, it aligns all kernel functions to 16 bytes
   boundary and adds a 16-byte padding before the function, objtool
   collects all functions' locations and when the mitigation gets
   applied, it patches a call accounting thunk which is used to track
   the call depth of the stack at any time.

   When that call depth reaches a magical, microarchitecture-specific
   value for the Return Stack Buffer, the code stuffs that RSB and
   avoids its underflow which could otherwise lead to the Intel variant
   of Retbleed.

   This software-only solution brings a lot of the lost performance
   back, as benchmarks suggest:

       https://lore.kernel.org/all/20220915111039.092790446@infradead.org/

   That page above also contains a lot more detailed explanation of the
   whole mechanism

 - Implement a new control flow integrity scheme called FineIBT which is
   based on the software kCFI implementation and uses hardware IBT
   support where present to annotate and track indirect branches using a
   hash to validate them

 - Other misc fixes and cleanups

* tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (80 commits)
  x86/paravirt: Use common macro for creating simple asm paravirt functions
  x86/paravirt: Remove clobber bitmask from .parainstructions
  x86/debug: Include percpu.h in debugreg.h to get DECLARE_PER_CPU() et al
  x86/cpufeatures: Move X86_FEATURE_CALL_DEPTH from bit 18 to bit 19 of word 11, to leave space for WIP X86_FEATURE_SGX_EDECCSSA bit
  x86/Kconfig: Enable kernel IBT by default
  x86,pm: Force out-of-line memcpy()
  objtool: Fix weak hole vs prefix symbol
  objtool: Optimize elf_dirty_reloc_sym()
  x86/cfi: Add boot time hash randomization
  x86/cfi: Boot time selection of CFI scheme
  x86/ibt: Implement FineIBT
  objtool: Add --cfi to generate the .cfi_sites section
  x86: Add prefix symbols for function padding
  objtool: Add option to generate prefix symbols
  objtool: Avoid O(bloody terrible) behaviour -- an ode to libelf
  objtool: Slice up elf_create_section_symbol()
  kallsyms: Revert "Take callthunks into account"
  x86: Unconfuse CONFIG_ and X86_FEATURE_ namespaces
  x86/retpoline: Fix crash printing warning
  x86/paravirt: Fix a !PARAVIRT build warning
  ...
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-11-18T02:30:39+00:00 Jakub Kicinski kuba@kernel.org 2022-11-18T00:19:14+00:00 224b744abf9f0663ca6762a79c7298b663fa4f04 include/linux/bpf.h 1f6e04a1c7b8 ("bpf: Fix offset calculation error in __copy_map_value and zero_map_value") aa3496accc41 ("bpf: Refactor kptr_off_tab into btf_record") f71b2f64177a ("bpf: Refactor map->off_arr handling") https://lore.kernel.org/all/20221114095000.67a73239@canb.auug.org.au/ Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
include/linux/bpf.h
  1f6e04a1c7b8 ("bpf: Fix offset calculation error in __copy_map_value and zero_map_value")
  aa3496accc41 ("bpf: Refactor kptr_off_tab into btf_record")
  f71b2f64177a ("bpf: Refactor map->off_arr handling")
https://lore.kernel.org/all/20221114095000.67a73239@canb.auug.org.au/

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
bpf: Revert ("Fix dispatcher patchable function entry to 5 bytes nop") 2022-11-04T22:13:08+00:00 Peter Zijlstra peterz@infradead.org 2022-11-03T12:00:13+00:00 18acb7fac22ff7b36c7ea5a76b12996e7b7dbaba Because __attribute__((patchable_function_entry)) is only available since GCC-8 this solution fails to build on the minimum required GCC version. Undo these changes so we might try again -- without cluttering up the patches with too many changes. This is an almost complete revert of: dbe69b299884 ("bpf: Fix dispatcher patchable function entry to 5 bytes nop") ceea991a019c ("bpf: Move bpf_dispatcher function out of ftrace locations") (notably the arch/x86/Kconfig hunk is kept). Reported-by: David Laight <David.Laight@aculab.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Tested-by: Björn Töpel <bjorn@kernel.org> Tested-by: Jiri Olsa <jolsa@kernel.org> Acked-by: Björn Töpel <bjorn@kernel.org> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lkml.kernel.org/r/439d8dc735bb4858875377df67f1b29a@AcuMS.aculab.com Link: https://lore.kernel.org/bpf/20221103120647.728830733@infradead.org 
Because __attribute__((patchable_function_entry)) is only available
since GCC-8 this solution fails to build on the minimum required GCC
version.

Undo these changes so we might try again -- without cluttering up the
patches with too many changes.

This is an almost complete revert of:

  dbe69b299884 ("bpf: Fix dispatcher patchable function entry to 5 bytes nop")
  ceea991a019c ("bpf: Move bpf_dispatcher function out of ftrace locations")

(notably the arch/x86/Kconfig hunk is kept).

Reported-by: David Laight <David.Laight@aculab.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Björn Töpel <bjorn@kernel.org>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lkml.kernel.org/r/439d8dc735bb4858875377df67f1b29a@AcuMS.aculab.com
Link: https://lore.kernel.org/bpf/20221103120647.728830733@infradead.org
Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2022-11-02T15:18:27+00:00 Jakub Kicinski kuba@kernel.org 2022-11-02T15:18:26+00:00 b54a0d4094f5c94eda1cafad44323306afe8f807 Daniel Borkmann says: ==================== bpf-next 2022-11-02 We've added 70 non-merge commits during the last 14 day(s) which contain a total of 96 files changed, 3203 insertions(+), 640 deletions(-). The main changes are: 1) Make cgroup local storage available to non-cgroup attached BPF programs such as tc BPF ones, from Yonghong Song. 2) Avoid unnecessary deadlock detection and failures wrt BPF task storage helpers, from Martin KaFai Lau. 3) Add LLVM disassembler as default library for dumping JITed code in bpftool, from Quentin Monnet. 4) Various kprobe_multi_link fixes related to kernel modules, from Jiri Olsa. 5) Optimize x86-64 JIT with emitting BMI2-based shift instructions, from Jie Meng. 6) Improve BPF verifier's memory type compatibility for map key/value arguments, from Dave Marchevsky. 7) Only create mmap-able data section maps in libbpf when data is exposed via skeletons, from Andrii Nakryiko. 8) Add an autoattach option for bpftool to load all object assets, from Wang Yufen. 9) Various memory handling fixes for libbpf and BPF selftests, from Xu Kuohai. 10) Initial support for BPF selftest's vmtest.sh on arm64, from Manu Bretelle. 11) Improve libbpf's BTF handling to dedup identical structs, from Alan Maguire. 12) Add BPF CI and denylist documentation for BPF selftests, from Daniel Müller. 13) Check BPF cpumap max_entries before doing allocation work, from Florian Lehner. * tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (70 commits) samples/bpf: Fix typo in README bpf: Remove the obsolte u64_stats_fetch_*_irq() users. bpf: check max_entries before allocating memory bpf: Fix a typo in comment for DFS algorithm bpftool: Fix spelling mistake "disasembler" -> "disassembler" selftests/bpf: Fix bpftool synctypes checking failure selftests/bpf: Panic on hard/soft lockup docs/bpf: Add documentation for new cgroup local storage selftests/bpf: Add test cgrp_local_storage to DENYLIST.s390x selftests/bpf: Add selftests for new cgroup local storage selftests/bpf: Fix test test_libbpf_str/bpf_map_type_str bpftool: Support new cgroup local storage libbpf: Support new cgroup local storage bpf: Implement cgroup storage available to non-cgroup-attached bpf progs bpf: Refactor some inode/task/sk storage functions for reuse bpf: Make struct cgroup btf id global selftests/bpf: Tracing prog can still do lookup under busy lock selftests/bpf: Ensure no task storage failure for bpf_lsm.s prog due to deadlock detection bpf: Add new bpf_task_storage_delete proto with no deadlock detection bpf: bpf_task_storage_delete_recur does lookup first before the deadlock check ... ==================== Link: https://lore.kernel.org/r/20221102062120.5724-1-daniel@iogearbox.net Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Daniel Borkmann says:

====================
bpf-next 2022-11-02

We've added 70 non-merge commits during the last 14 day(s) which contain
a total of 96 files changed, 3203 insertions(+), 640 deletions(-).

The main changes are:

1) Make cgroup local storage available to non-cgroup attached BPF programs
   such as tc BPF ones, from Yonghong Song.

2) Avoid unnecessary deadlock detection and failures wrt BPF task storage
   helpers, from Martin KaFai Lau.

3) Add LLVM disassembler as default library for dumping JITed code
   in bpftool, from Quentin Monnet.

4) Various kprobe_multi_link fixes related to kernel modules,
   from Jiri Olsa.

5) Optimize x86-64 JIT with emitting BMI2-based shift instructions,
   from Jie Meng.

6) Improve BPF verifier's memory type compatibility for map key/value
   arguments, from Dave Marchevsky.

7) Only create mmap-able data section maps in libbpf when data is exposed
   via skeletons, from Andrii Nakryiko.

8) Add an autoattach option for bpftool to load all object assets,
   from Wang Yufen.

9) Various memory handling fixes for libbpf and BPF selftests,
   from Xu Kuohai.

10) Initial support for BPF selftest's vmtest.sh on arm64,
    from Manu Bretelle.

11) Improve libbpf's BTF handling to dedup identical structs,
    from Alan Maguire.

12) Add BPF CI and denylist documentation for BPF selftests,
    from Daniel Müller.

13) Check BPF cpumap max_entries before doing allocation work,
    from Florian Lehner.

* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (70 commits)
  samples/bpf: Fix typo in README
  bpf: Remove the obsolte u64_stats_fetch_*_irq() users.
  bpf: check max_entries before allocating memory
  bpf: Fix a typo in comment for DFS algorithm
  bpftool: Fix spelling mistake "disasembler" -> "disassembler"
  selftests/bpf: Fix bpftool synctypes checking failure
  selftests/bpf: Panic on hard/soft lockup
  docs/bpf: Add documentation for new cgroup local storage
  selftests/bpf: Add test cgrp_local_storage to DENYLIST.s390x
  selftests/bpf: Add selftests for new cgroup local storage
  selftests/bpf: Fix test test_libbpf_str/bpf_map_type_str
  bpftool: Support new cgroup local storage
  libbpf: Support new cgroup local storage
  bpf: Implement cgroup storage available to non-cgroup-attached bpf progs
  bpf: Refactor some inode/task/sk storage functions for reuse
  bpf: Make struct cgroup btf id global
  selftests/bpf: Tracing prog can still do lookup under busy lock
  selftests/bpf: Ensure no task storage failure for bpf_lsm.s prog due to deadlock detection
  bpf: Add new bpf_task_storage_delete proto with no deadlock detection
  bpf: bpf_task_storage_delete_recur does lookup first before the deadlock check
  ...
====================

Link: https://lore.kernel.org/r/20221102062120.5724-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
bpf: Remove prog->active check for bpf_lsm and bpf_iter 2022-10-26T06:11:46+00:00 Martin KaFai Lau martin.lau@kernel.org 2022-10-25T18:45:16+00:00 271de525e1d7f564e88a9d212c50998b49a54476 The commit 64696c40d03c ("bpf: Add __bpf_prog_{enter,exit}_struct_ops for struct_ops trampoline") removed prog->active check for struct_ops prog. The bpf_lsm and bpf_iter is also using trampoline. Like struct_ops, the bpf_lsm and bpf_iter have fixed hooks for the prog to attach. The kernel does not call the same hook in a recursive way. This patch also removes the prog->active check for bpf_lsm and bpf_iter. A later patch has a test to reproduce the recursion issue for a sleepable bpf_lsm program. This patch appends the '_recur' naming to the existing enter and exit functions that track the prog->active counter. New __bpf_prog_{enter,exit}[_sleepable] function are added to skip the prog->active tracking. The '_struct_ops' version is also removed. It also moves the decision on picking the enter and exit function to the new bpf_trampoline_{enter,exit}(). It returns the '_recur' ones for all tracing progs to use. For bpf_lsm, bpf_iter, struct_ops (no prog->active tracking after 64696c40d03c), and bpf_lsm_cgroup (no prog->active tracking after 69fd337a975c7), it will return the functions that don't track the prog->active. Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Link: https://lore.kernel.org/r/20221025184524.3526117-2-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
The commit 64696c40d03c ("bpf: Add __bpf_prog_{enter,exit}_struct_ops for struct_ops trampoline")
removed prog->active check for struct_ops prog.  The bpf_lsm
and bpf_iter is also using trampoline.  Like struct_ops, the bpf_lsm
and bpf_iter have fixed hooks for the prog to attach.  The
kernel does not call the same hook in a recursive way.
This patch also removes the prog->active check for
bpf_lsm and bpf_iter.

A later patch has a test to reproduce the recursion issue
for a sleepable bpf_lsm program.

This patch appends the '_recur' naming to the existing
enter and exit functions that track the prog->active counter.
New __bpf_prog_{enter,exit}[_sleepable] function are
added to skip the prog->active tracking. The '_struct_ops'
version is also removed.

It also moves the decision on picking the enter and exit function to
the new bpf_trampoline_{enter,exit}().  It returns the '_recur' ones
for all tracing progs to use.  For bpf_lsm, bpf_iter,
struct_ops (no prog->active tracking after 64696c40d03c), and
bpf_lsm_cgroup (no prog->active tracking after 69fd337a975c7),
it will return the functions that don't track the prog->active.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20221025184524.3526117-2-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-10-24T20:44:11+00:00 Jakub Kicinski kuba@kernel.org 2022-10-24T20:44:11+00:00 96917bb3a377e1ed103fd5c420a95e5fb25ca104 include/linux/net.h a5ef058dc4d9 ("net: introduce and use custom sockopt socket flag") e993ffe3da4b ("net: flag sockets supporting msghdr originated zerocopy") Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
include/linux/net.h
  a5ef058dc4d9 ("net: introduce and use custom sockopt socket flag")
  e993ffe3da4b ("net: flag sockets supporting msghdr originated zerocopy")

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
bpf: Fix dispatcher patchable function entry to 5 bytes nop 2022-10-21T01:57:51+00:00 Jiri Olsa jolsa@kernel.org 2022-10-18T07:59:34+00:00 dbe69b29988465b011f198f2797b1c2b6980b50e The patchable_function_entry(5) might output 5 single nop instructions (depends on toolchain), which will clash with bpf_arch_text_poke check for 5 bytes nop instruction. Adding early init call for dispatcher that checks and change the patchable entry into expected 5 nop instruction if needed. There's no need to take text_mutex, because we are using it in early init call which is called at pre-smp time. Fixes: ceea991a019c ("bpf: Move bpf_dispatcher function out of ftrace locations") Signed-off-by: Jiri Olsa <jolsa@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20221018075934.574415-1-jolsa@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
The patchable_function_entry(5) might output 5 single nop
instructions (depends on toolchain), which will clash with
bpf_arch_text_poke check for 5 bytes nop instruction.

Adding early init call for dispatcher that checks and change
the patchable entry into expected 5 nop instruction if needed.

There's no need to take text_mutex, because we are using it
in early init call which is called at pre-smp time.

Fixes: ceea991a019c ("bpf: Move bpf_dispatcher function out of ftrace locations")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221018075934.574415-1-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf,x64: use shrx/sarx/shlx when available 2022-10-19T23:53:51+00:00 Jie Meng jmeng@fb.com 2022-10-07T20:23:48+00:00 77d8f5d47bfbb5f0a8630102838ffb22cd70d6f5 BMI2 provides 3 shift instructions (shrx, sarx and shlx) that use VEX encoding but target general purpose registers [1]. They allow the shift count in any general purpose register and have the same performance as non BMI2 shift instructions [2]. Instead of shr/sar/shl that implicitly use %cl (lowest 8 bit of %rcx), emit their more flexible alternatives provided in BMI2 when advantageous; keep using the non BMI2 instructions when shift count is already in BPF_REG_4/%rcx as non BMI2 instructions are shorter. To summarize, when BMI2 is available: ------------------------------------------------- | arbitrary dst ================================================= src == ecx | shl dst, cl ------------------------------------------------- src != ecx | shlx dst, dst, src ------------------------------------------------- And no additional register shuffling is needed. A concrete example between non BMI2 and BMI2 codegen. To shift %rsi by %rdi: Without BMI2: ef3: push %rcx 51 ef4: mov %rdi,%rcx 48 89 f9 ef7: shl %cl,%rsi 48 d3 e6 efa: pop %rcx 59 With BMI2: f0b: shlx %rdi,%rsi,%rsi c4 e2 c1 f7 f6 [1] https://en.wikipedia.org/wiki/X86_Bit_manipulation_instruction_set [2] https://www.agner.org/optimize/instruction_tables.pdf Signed-off-by: Jie Meng <jmeng@fb.com> Link: https://lore.kernel.org/r/20221007202348.1118830-3-jmeng@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
BMI2 provides 3 shift instructions (shrx, sarx and shlx) that use VEX
encoding but target general purpose registers [1]. They allow the shift
count in any general purpose register and have the same performance as
non BMI2 shift instructions [2].

Instead of shr/sar/shl that implicitly use %cl (lowest 8 bit of %rcx),
emit their more flexible alternatives provided in BMI2 when advantageous;
keep using the non BMI2 instructions when shift count is already in
BPF_REG_4/%rcx as non BMI2 instructions are shorter.

To summarize, when BMI2 is available:
-------------------------------------------------
            |   arbitrary dst
=================================================
src == ecx  |   shl dst, cl
-------------------------------------------------
src != ecx  |   shlx dst, dst, src
-------------------------------------------------

And no additional register shuffling is needed.

A concrete example between non BMI2 and BMI2 codegen.  To shift %rsi by
%rdi:

Without BMI2:

 ef3:   push   %rcx
        51
 ef4:   mov    %rdi,%rcx
        48 89 f9
 ef7:   shl    %cl,%rsi
        48 d3 e6
 efa:   pop    %rcx
        59

With BMI2:

 f0b:   shlx   %rdi,%rsi,%rsi
        c4 e2 c1 f7 f6

[1] https://en.wikipedia.org/wiki/X86_Bit_manipulation_instruction_set
[2] https://www.agner.org/optimize/instruction_tables.pdf

Signed-off-by: Jie Meng <jmeng@fb.com>
Link: https://lore.kernel.org/r/20221007202348.1118830-3-jmeng@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf,x64: avoid unnecessary instructions when shift dest is ecx 2022-10-19T23:53:51+00:00 Jie Meng jmeng@fb.com 2022-10-07T20:23:47+00:00 81b35e7cad790eecf9f359662804bb26055ac7e8 x64 JIT produces redundant instructions when a shift operation's destination register is BPF_REG_4/ecx and this patch removes them. Specifically, when dest reg is BPF_REG_4 but the src isn't, we needn't push and pop ecx around shift only to get it overwritten by r11 immediately afterwards. In the rare case when both dest and src registers are BPF_REG_4, a single shift instruction is sufficient and we don't need the two MOV instructions around the shift. To summarize using shift left as an example, without patch: ------------------------------------------------- | dst == ecx | dst != ecx ================================================= src == ecx | mov r11, ecx | shl dst, cl | shl r11, ecx | | mov ecx, r11 | ------------------------------------------------- src != ecx | mov r11, ecx | push ecx | push ecx | mov ecx, src | mov ecx, src | shl dst, cl | shl r11, cl | pop ecx | pop ecx | | mov ecx, r11 | ------------------------------------------------- With patch: ------------------------------------------------- | dst == ecx | dst != ecx ================================================= src == ecx | shl ecx, cl | shl dst, cl ------------------------------------------------- src != ecx | mov r11, ecx | push ecx | mov ecx, src | mov ecx, src | shl r11, cl | shl dst, cl | mov ecx, r11 | pop ecx ------------------------------------------------- Signed-off-by: Jie Meng <jmeng@fb.com> Link: https://lore.kernel.org/r/20221007202348.1118830-2-jmeng@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
x64 JIT produces redundant instructions when a shift operation's
destination register is BPF_REG_4/ecx and this patch removes them.

Specifically, when dest reg is BPF_REG_4 but the src isn't, we
needn't push and pop ecx around shift only to get it overwritten
by r11 immediately afterwards.

In the rare case when both dest and src registers are BPF_REG_4,
a single shift instruction is sufficient and we don't need the
two MOV instructions around the shift.

To summarize using shift left as an example, without patch:
-------------------------------------------------
            |   dst == ecx     |    dst != ecx
=================================================
src == ecx  |   mov r11, ecx   |    shl dst, cl
            |   shl r11, ecx   |
            |   mov ecx, r11   |
-------------------------------------------------
src != ecx  |   mov r11, ecx   |    push ecx
            |   push ecx       |    mov ecx, src
            |   mov ecx, src   |    shl dst, cl
            |   shl r11, cl    |    pop ecx
            |   pop ecx        |
            |   mov ecx, r11   |
-------------------------------------------------

With patch:
-------------------------------------------------
            |   dst == ecx     |    dst != ecx
=================================================
src == ecx  |   shl ecx, cl    |    shl dst, cl
-------------------------------------------------
src != ecx  |   mov r11, ecx   |    push ecx
            |   mov ecx, src   |    mov ecx, src
            |   shl r11, cl    |    shl dst, cl
            |   mov ecx, r11   |    pop ecx
-------------------------------------------------

Signed-off-by: Jie Meng <jmeng@fb.com>
Link: https://lore.kernel.org/r/20221007202348.1118830-2-jmeng@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
x86/ftrace: Make it call depth tracking aware 2022-10-17T14:41:19+00:00 Peter Zijlstra peterz@infradead.org 2022-09-15T11:11:37+00:00 ee3e2469b3463d28ca4cde20e0283319ac6a562d Since ftrace has trampolines, don't use thunks for the __fentry__ site but instead require that every function called from there includes accounting. This very much includes all the direct-call functions. Additionally, ftrace uses ROP tricks in two places: - return_to_handler(), and - ftrace_regs_caller() when pt_regs->orig_ax is set by a direct-call. return_to_handler() already uses a retpoline to replace an indirect-jump to defeat IBT, since this is a jump-type retpoline, make sure there is no accounting done and ALTERNATIVE the RET into a ret. ftrace_regs_caller() does much the same and gets the same treatment. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20220915111148.927545073@infradead.org 
Since ftrace has trampolines, don't use thunks for the __fentry__ site
but instead require that every function called from there includes
accounting. This very much includes all the direct-call functions.

Additionally, ftrace uses ROP tricks in two places:

 - return_to_handler(), and
 - ftrace_regs_caller() when pt_regs->orig_ax is set by a direct-call.

return_to_handler() already uses a retpoline to replace an
indirect-jump to defeat IBT, since this is a jump-type retpoline, make
sure there is no accounting done and ALTERNATIVE the RET into a ret.

ftrace_regs_caller() does much the same and gets the same treatment.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111148.927545073@infradead.org