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Daniel Borkmann d2e4c1e6c2 bpf: Constant map key tracking for prog array pokes 
Add tracking of constant keys into tail call maps. The signature of
bpf_tail_call_proto is that arg1 is ctx, arg2 map pointer and arg3
is a index key. The direct call approach for tail calls can be enabled
if the verifier asserted that for all branches leading to the tail call
helper invocation, the map pointer and index key were both constant
and the same.

Tracking of map pointers we already do from prior work via c93552c443
("bpf: properly enforce index mask to prevent out-of-bounds speculation")
and 09772d92cd ("bpf: avoid retpoline for lookup/update/ delete calls
on maps").

Given the tail call map index key is not on stack but directly in the
register, we can add similar tracking approach and later in fixup_bpf_calls()
add a poke descriptor to the progs poke_tab with the relevant information
for the JITing phase.

We internally reuse insn->imm for the rewritten BPF_JMP | BPF_TAIL_CALL
instruction in order to point into the prog's poke_tab, and keep insn->imm
as 0 as indicator that current indirect tail call emission must be used.
Note that publishing to the tracker must happen at the end of fixup_bpf_calls()
since adding elements to the poke_tab reallocates its memory, so we need
to wait until its in final state.

Future work can generalize and add similar approach to optimize plain
array map lookups. Difference there is that we need to look into the key
value that sits on stack. For clarity in bpf_insn_aux_data, map_state
has been renamed into map_ptr_state, so we get map_{ptr,key}_state as
trackers.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/e8db37f6b2ae60402fa40216c96738ee9b316c32.1574452833.git.daniel@iogearbox.net
2019-11-24 17:04:11 -08:00
arch bpf, x86: Generalize and extend bpf_arch_text_poke for direct jumps 2019-11-24 16:58:47 -08:00
block iocost: check active_list of all the ancestors in iocg_activate() 2019-11-14 13:56:54 -07:00
certs
crypto
Documentation docs: networking: nfc: change to rst format 2019-11-23 11:00:19 -08:00
drivers bnxt_en: Add support for flashing the device via devlink 2019-11-24 14:48:03 -08:00
fs afs: Fix large file support 2019-11-22 14:19:26 -08:00
include bpf: Constant map key tracking for prog array pokes 2019-11-24 17:04:11 -08:00
init
ipc
kernel bpf: Constant map key tracking for prog array pokes 2019-11-24 17:04:11 -08:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-11-16 21:51:42 -08:00
LICENSES
mm Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-11-22 16:27:24 -08:00
net xsk: Fix xsk_poll()'s return type 2019-11-24 16:58:44 -08:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2019-11-20 18:11:23 -08:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-11-16 21:51:42 -08:00
security
sound ALSA: usb-audio: Fix incorrect size check for processing/extension units 2019-11-14 18:01:22 +01:00
tools selftests/bpf: Add BPF trampoline performance test 2019-11-24 16:58:46 -08:00
usr
virt KVM: Add a comment describing the /dev/kvm no_compat handling 2019-11-15 10:14:04 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
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MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-11-22 16:27:24 -08:00
Makefile Linux 5.4-rc8 2019-11-17 14:47:30 -08:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.