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Eric Dumazet 7de0869093 powerpc/bpf: Fix tail call implementation 
We have seen many crashes on powerpc hosts while loading bpf programs.

The problem here is that bpf_int_jit_compile() does a first pass
to compute the program length.

Then it allocates memory to store the generated program and
calls bpf_jit_build_body() a second time (and a third time
later)

What I have observed is that the second bpf_jit_build_body()
could end up using few more words than expected.

If bpf_jit_binary_alloc() put the space for the program
at the end of the allocated page, we then write on
a non mapped memory.

It appears that bpf_jit_emit_tail_call() calls
bpf_jit_emit_common_epilogue() while ctx->seen might not
be stable.

Only after the second pass we can be sure ctx->seen wont be changed.

Trying to avoid a second pass seems quite complex and probably
not worth it.

Fixes: ce0761419f ("powerpc/bpf: Implement support for tail calls")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Sandipan Das <sandipan@linux.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20191101033444.143741-1-edumazet@google.com
2019-11-02 00:32:26 +01:00
arch powerpc/bpf: Fix tail call implementation 2019-11-02 00:32:26 +01:00
block
certs
crypto
Documentation
drivers cxgb4: request the TX CIDX updates to status page 2019-10-25 20:20:50 -07:00
fs
include bpf: Change size to u64 for bpf_map_{area_alloc, charge_init}() 2019-10-31 21:41:33 +01:00
init
ipc
kernel bpf: Change size to u64 for bpf_map_{area_alloc, charge_init}() 2019-10-31 21:41:33 +01:00
lib
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net Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf 2019-10-27 12:13:16 -07:00
samples samples/bpf: fix build by setting HAVE_ATTR_TEST to zero 2019-10-31 21:39:15 +01:00
scripts
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tools perf tools: Make usage of test_attr__* optional for perf-sys.h 2019-10-31 21:38:41 +01:00
usr
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MAINTAINERS bpf, doc: Add Andrii as official reviewer to BPF subsystem 2019-10-29 15:51:59 +01:00
Makefile
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.