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authorLinus Torvalds <torvalds@linux-foundation.org>2018-02-07 06:00:42 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-02-07 06:00:42 +0300
commit0dc400f41f0d589a7d4defabdc537ec7e0640039 (patch)
treefbe4455726d97e64eca353ab516e5833940ced21 /Documentation
parentcbd7b8a76b79a2ff6112ef2e77031b694843b8a1 (diff)
parent176bfb406d735655f9a69d868a7af0c3da959d51 (diff)
downloadlinux-0dc400f41f0d589a7d4defabdc537ec7e0640039.tar.xz
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Pull networking fixes from David Miller: 1) Fix error path in netdevsim, from Jakub Kicinski. 2) Default values listed in tcp_wmem and tcp_rmem documentation were inaccurate, from Tonghao Zhang. 3) Fix route leaks in SCTP, both for ipv4 and ipv6. From Alexey Kodanev and Tommi Rantala. 4) Fix "MASK < Y" meant to be "MASK << Y" in xgbe driver, from Wolfram Sang. 5) Use after free in u32_destroy_key(), from Paolo Abeni. 6) Fix two TX issues in be2net driver, from Suredh Reddy. * git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (25 commits) be2net: Handle transmit completion errors in Lancer be2net: Fix HW stall issue in Lancer RDS: IB: Fix null pointer issue nfp: fix kdoc warnings on nested structures sample/bpf: fix erspan metadata net: erspan: fix erspan config overwrite net: erspan: fix metadata extraction cls_u32: fix use after free in u32_destroy_key() net: amd-xgbe: fix comparison to bitshift when dealing with a mask net: phy: Handle not having GPIO enabled in the kernel ibmvnic: fix empty firmware version and errors cleanup sctp: fix dst refcnt leak in sctp_v4_get_dst sctp: fix dst refcnt leak in sctp_v6_get_dst() dwc-xlgmac: remove Jie Deng as co-maintainer doc: Change the min default value of tcp_wmem/tcp_rmem. samples/bpf: use bpf_set_link_xdp_fd libbpf: add missing SPDX-License-Identifier libbpf: add error reporting in XDP libbpf: add function to setup XDP tools: add netlink.h and if_link.h in tools uapi ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/bpf/bpf_devel_QA.txt31
-rw-r--r--Documentation/networking/ip-sysctl.txt4
2 files changed, 33 insertions, 2 deletions
diff --git a/Documentation/bpf/bpf_devel_QA.txt b/Documentation/bpf/bpf_devel_QA.txt
index cefef855dea4..84cbb302f2b5 100644
--- a/Documentation/bpf/bpf_devel_QA.txt
+++ b/Documentation/bpf/bpf_devel_QA.txt
@@ -516,4 +516,35 @@ A: LLVM has a -mcpu selector for the BPF back end in order to allow the
By the way, the BPF kernel selftests run with -mcpu=probe for better
test coverage.
+Q: In some cases clang flag "-target bpf" is used but in other cases the
+ default clang target, which matches the underlying architecture, is used.
+ What is the difference and when I should use which?
+
+A: Although LLVM IR generation and optimization try to stay architecture
+ independent, "-target <arch>" still has some impact on generated code:
+
+ - BPF program may recursively include header file(s) with file scope
+ inline assembly codes. The default target can handle this well,
+ while bpf target may fail if bpf backend assembler does not
+ understand these assembly codes, which is true in most cases.
+
+ - When compiled without -g, additional elf sections, e.g.,
+ .eh_frame and .rela.eh_frame, may be present in the object file
+ with default target, but not with bpf target.
+
+ - The default target may turn a C switch statement into a switch table
+ lookup and jump operation. Since the switch table is placed
+ in the global readonly section, the bpf program will fail to load.
+ The bpf target does not support switch table optimization.
+ The clang option "-fno-jump-tables" can be used to disable
+ switch table generation.
+
+ You should use default target when:
+
+ - Your program includes a header file, e.g., ptrace.h, which eventually
+ pulls in some header files containing file scope host assembly codes.
+ - You can add "-fno-jump-tables" to work around the switch table issue.
+
+ Otherwise, you can use bpf target.
+
Happy BPF hacking!
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 3f2c40d8e6aa..a553d4e4a0fb 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -508,7 +508,7 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max
min: Minimal size of receive buffer used by TCP sockets.
It is guaranteed to each TCP socket, even under moderate memory
pressure.
- Default: 1 page
+ Default: 4K
default: initial size of receive buffer used by TCP sockets.
This value overrides net.core.rmem_default used by other protocols.
@@ -667,7 +667,7 @@ tcp_window_scaling - BOOLEAN
tcp_wmem - vector of 3 INTEGERs: min, default, max
min: Amount of memory reserved for send buffers for TCP sockets.
Each TCP socket has rights to use it due to fact of its birth.
- Default: 1 page
+ Default: 4K
default: initial size of send buffer used by TCP sockets. This
value overrides net.core.wmem_default used by other protocols.