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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/livepatch/module-elf-format.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to 'Documentation/livepatch/module-elf-format.rst')
-rw-r--r-- | Documentation/livepatch/module-elf-format.rst | 309 |
1 files changed, 309 insertions, 0 deletions
diff --git a/Documentation/livepatch/module-elf-format.rst b/Documentation/livepatch/module-elf-format.rst new file mode 100644 index 000000000..734763889 --- /dev/null +++ b/Documentation/livepatch/module-elf-format.rst @@ -0,0 +1,309 @@ +=========================== +Livepatch module Elf format +=========================== + +This document outlines the Elf format requirements that livepatch modules must follow. + + +.. Table of Contents + +.. contents:: :local: + + +1. Background and motivation +============================ + +Formerly, livepatch required separate architecture-specific code to write +relocations. However, arch-specific code to write relocations already +exists in the module loader, so this former approach produced redundant +code. So, instead of duplicating code and re-implementing what the module +loader can already do, livepatch leverages existing code in the module +loader to perform the all the arch-specific relocation work. Specifically, +livepatch reuses the apply_relocate_add() function in the module loader to +write relocations. The patch module Elf format described in this document +enables livepatch to be able to do this. The hope is that this will make +livepatch more easily portable to other architectures and reduce the amount +of arch-specific code required to port livepatch to a particular +architecture. + +Since apply_relocate_add() requires access to a module's section header +table, symbol table, and relocation section indices, Elf information is +preserved for livepatch modules (see section 5). Livepatch manages its own +relocation sections and symbols, which are described in this document. The +Elf constants used to mark livepatch symbols and relocation sections were +selected from OS-specific ranges according to the definitions from glibc. + +Why does livepatch need to write its own relocations? +----------------------------------------------------- +A typical livepatch module contains patched versions of functions that can +reference non-exported global symbols and non-included local symbols. +Relocations referencing these types of symbols cannot be left in as-is +since the kernel module loader cannot resolve them and will therefore +reject the livepatch module. Furthermore, we cannot apply relocations that +affect modules not yet loaded at patch module load time (e.g. a patch to a +driver that is not loaded). Formerly, livepatch solved this problem by +embedding special "dynrela" (dynamic rela) sections in the resulting patch +module Elf output. Using these dynrela sections, livepatch could resolve +symbols while taking into account its scope and what module the symbol +belongs to, and then manually apply the dynamic relocations. However this +approach required livepatch to supply arch-specific code in order to write +these relocations. In the new format, livepatch manages its own SHT_RELA +relocation sections in place of dynrela sections, and the symbols that the +relas reference are special livepatch symbols (see section 2 and 3). The +arch-specific livepatch relocation code is replaced by a call to +apply_relocate_add(). + +2. Livepatch modinfo field +========================== + +Livepatch modules are required to have the "livepatch" modinfo attribute. +See the sample livepatch module in samples/livepatch/ for how this is done. + +Livepatch modules can be identified by users by using the 'modinfo' command +and looking for the presence of the "livepatch" field. This field is also +used by the kernel module loader to identify livepatch modules. + +Example: +-------- + +**Modinfo output:** + +:: + + % modinfo livepatch-meminfo.ko + filename: livepatch-meminfo.ko + livepatch: Y + license: GPL + depends: + vermagic: 4.3.0+ SMP mod_unload + +3. Livepatch relocation sections +================================ + +A livepatch module manages its own Elf relocation sections to apply +relocations to modules as well as to the kernel (vmlinux) at the +appropriate time. For example, if a patch module patches a driver that is +not currently loaded, livepatch will apply the corresponding livepatch +relocation section(s) to the driver once it loads. + +Each "object" (e.g. vmlinux, or a module) within a patch module may have +multiple livepatch relocation sections associated with it (e.g. patches to +multiple functions within the same object). There is a 1-1 correspondence +between a livepatch relocation section and the target section (usually the +text section of a function) to which the relocation(s) apply. It is +also possible for a livepatch module to have no livepatch relocation +sections, as in the case of the sample livepatch module (see +samples/livepatch). + +Since Elf information is preserved for livepatch modules (see Section 5), a +livepatch relocation section can be applied simply by passing in the +appropriate section index to apply_relocate_add(), which then uses it to +access the relocation section and apply the relocations. + +Every symbol referenced by a rela in a livepatch relocation section is a +livepatch symbol. These must be resolved before livepatch can call +apply_relocate_add(). See Section 3 for more information. + +3.1 Livepatch relocation section format +======================================= + +Livepatch relocation sections must be marked with the SHF_RELA_LIVEPATCH +section flag. See include/uapi/linux/elf.h for the definition. The module +loader recognizes this flag and will avoid applying those relocation sections +at patch module load time. These sections must also be marked with SHF_ALLOC, +so that the module loader doesn't discard them on module load (i.e. they will +be copied into memory along with the other SHF_ALLOC sections). + +The name of a livepatch relocation section must conform to the following +format:: + + .klp.rela.objname.section_name + ^ ^^ ^ ^ ^ + |________||_____| |__________| + [A] [B] [C] + +[A] + The relocation section name is prefixed with the string ".klp.rela." + +[B] + The name of the object (i.e. "vmlinux" or name of module) to + which the relocation section belongs follows immediately after the prefix. + +[C] + The actual name of the section to which this relocation section applies. + +Examples: +--------- + +**Livepatch relocation section names:** + +:: + + .klp.rela.ext4.text.ext4_attr_store + .klp.rela.vmlinux.text.cmdline_proc_show + +**`readelf --sections` output for a patch +module that patches vmlinux and modules 9p, btrfs, ext4:** + +:: + + Section Headers: + [Nr] Name Type Address Off Size ES Flg Lk Inf Al + [ snip ] + [29] .klp.rela.9p.text.caches.show RELA 0000000000000000 002d58 0000c0 18 AIo 64 9 8 + [30] .klp.rela.btrfs.text.btrfs.feature.attr.show RELA 0000000000000000 002e18 000060 18 AIo 64 11 8 + [ snip ] + [34] .klp.rela.ext4.text.ext4.attr.store RELA 0000000000000000 002fd8 0000d8 18 AIo 64 13 8 + [35] .klp.rela.ext4.text.ext4.attr.show RELA 0000000000000000 0030b0 000150 18 AIo 64 15 8 + [36] .klp.rela.vmlinux.text.cmdline.proc.show RELA 0000000000000000 003200 000018 18 AIo 64 17 8 + [37] .klp.rela.vmlinux.text.meminfo.proc.show RELA 0000000000000000 003218 0000f0 18 AIo 64 19 8 + [ snip ] ^ ^ + | | + [*] [*] + +[*] + Livepatch relocation sections are SHT_RELA sections but with a few special + characteristics. Notice that they are marked SHF_ALLOC ("A") so that they will + not be discarded when the module is loaded into memory, as well as with the + SHF_RELA_LIVEPATCH flag ("o" - for OS-specific). + +**`readelf --relocs` output for a patch module:** + +:: + + Relocation section '.klp.rela.btrfs.text.btrfs_feature_attr_show' at offset 0x2ba0 contains 4 entries: + Offset Info Type Symbol's Value Symbol's Name + Addend + 000000000000001f 0000005e00000002 R_X86_64_PC32 0000000000000000 .klp.sym.vmlinux.printk,0 - 4 + 0000000000000028 0000003d0000000b R_X86_64_32S 0000000000000000 .klp.sym.btrfs.btrfs_ktype,0 + 0 + 0000000000000036 0000003b00000002 R_X86_64_PC32 0000000000000000 .klp.sym.btrfs.can_modify_feature.isra.3,0 - 4 + 000000000000004c 0000004900000002 R_X86_64_PC32 0000000000000000 .klp.sym.vmlinux.snprintf,0 - 4 + [ snip ] ^ + | + [*] + +[*] + Every symbol referenced by a relocation is a livepatch symbol. + +4. Livepatch symbols +==================== + +Livepatch symbols are symbols referred to by livepatch relocation sections. +These are symbols accessed from new versions of functions for patched +objects, whose addresses cannot be resolved by the module loader (because +they are local or unexported global syms). Since the module loader only +resolves exported syms, and not every symbol referenced by the new patched +functions is exported, livepatch symbols were introduced. They are used +also in cases where we cannot immediately know the address of a symbol when +a patch module loads. For example, this is the case when livepatch patches +a module that is not loaded yet. In this case, the relevant livepatch +symbols are resolved simply when the target module loads. In any case, for +any livepatch relocation section, all livepatch symbols referenced by that +section must be resolved before livepatch can call apply_relocate_add() for +that reloc section. + +Livepatch symbols must be marked with SHN_LIVEPATCH so that the module +loader can identify and ignore them. Livepatch modules keep these symbols +in their symbol tables, and the symbol table is made accessible through +module->symtab. + +4.1 A livepatch module's symbol table +===================================== +Normally, a stripped down copy of a module's symbol table (containing only +"core" symbols) is made available through module->symtab (See layout_symtab() +in kernel/module/kallsyms.c). For livepatch modules, the symbol table copied +into memory on module load must be exactly the same as the symbol table produced +when the patch module was compiled. This is because the relocations in each +livepatch relocation section refer to their respective symbols with their symbol +indices, and the original symbol indices (and thus the symtab ordering) must be +preserved in order for apply_relocate_add() to find the right symbol. + +For example, take this particular rela from a livepatch module::: + + Relocation section '.klp.rela.btrfs.text.btrfs_feature_attr_show' at offset 0x2ba0 contains 4 entries: + Offset Info Type Symbol's Value Symbol's Name + Addend + 000000000000001f 0000005e00000002 R_X86_64_PC32 0000000000000000 .klp.sym.vmlinux.printk,0 - 4 + + This rela refers to the symbol '.klp.sym.vmlinux.printk,0', and the symbol index is encoded + in 'Info'. Here its symbol index is 0x5e, which is 94 in decimal, which refers to the + symbol index 94. + And in this patch module's corresponding symbol table, symbol index 94 refers to that very symbol: + [ snip ] + 94: 0000000000000000 0 NOTYPE GLOBAL DEFAULT OS [0xff20] .klp.sym.vmlinux.printk,0 + [ snip ] + +4.2 Livepatch symbol format +=========================== + +Livepatch symbols must have their section index marked as SHN_LIVEPATCH, so +that the module loader can identify them and not attempt to resolve them. +See include/uapi/linux/elf.h for the actual definitions. + +Livepatch symbol names must conform to the following format:: + + .klp.sym.objname.symbol_name,sympos + ^ ^^ ^ ^ ^ ^ + |_______||_____| |_________| | + [A] [B] [C] [D] + +[A] + The symbol name is prefixed with the string ".klp.sym." + +[B] + The name of the object (i.e. "vmlinux" or name of module) to + which the symbol belongs follows immediately after the prefix. + +[C] + The actual name of the symbol. + +[D] + The position of the symbol in the object (as according to kallsyms) + This is used to differentiate duplicate symbols within the same + object. The symbol position is expressed numerically (0, 1, 2...). + The symbol position of a unique symbol is 0. + +Examples: +--------- + +**Livepatch symbol names:** + +:: + + .klp.sym.vmlinux.snprintf,0 + .klp.sym.vmlinux.printk,0 + .klp.sym.btrfs.btrfs_ktype,0 + +**`readelf --symbols` output for a patch module:** + +:: + + Symbol table '.symtab' contains 127 entries: + Num: Value Size Type Bind Vis Ndx Name + [ snip ] + 73: 0000000000000000 0 NOTYPE GLOBAL DEFAULT OS [0xff20] .klp.sym.vmlinux.snprintf,0 + 74: 0000000000000000 0 NOTYPE GLOBAL DEFAULT OS [0xff20] .klp.sym.vmlinux.capable,0 + 75: 0000000000000000 0 NOTYPE GLOBAL DEFAULT OS [0xff20] .klp.sym.vmlinux.find_next_bit,0 + 76: 0000000000000000 0 NOTYPE GLOBAL DEFAULT OS [0xff20] .klp.sym.vmlinux.si_swapinfo,0 + [ snip ] ^ + | + [*] + +[*] + Note that the 'Ndx' (Section index) for these symbols is SHN_LIVEPATCH (0xff20). + "OS" means OS-specific. + +5. Symbol table and Elf section access +====================================== +A livepatch module's symbol table is accessible through module->symtab. + +Since apply_relocate_add() requires access to a module's section headers, +symbol table, and relocation section indices, Elf information is preserved for +livepatch modules and is made accessible by the module loader through +module->klp_info, which is a klp_modinfo struct. When a livepatch module loads, +this struct is filled in by the module loader. Its fields are documented below:: + + struct klp_modinfo { + Elf_Ehdr hdr; /* Elf header */ + Elf_Shdr *sechdrs; /* Section header table */ + char *secstrings; /* String table for the section headers */ + unsigned int symndx; /* The symbol table section index */ + }; |