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86ed4be68f
To verify fix ("bpf: sock_ops ctx access may stomp registers in corner case")
we want to force compiler to generate the following code when accessing a
field with BPF_TCP_SOCK_GET_COMMON,
r1 = *(u32 *)(r1 + 96) // r1 is skops ptr
Rather than depend on clang to do this we add the test with inline asm to
the tcpbpf test. This saves us from having to create another runner and
ensures that if we break this again test_tcpbpf will crash.
With above code we get the xlated code,
11: (7b) *(u64 *)(r1 +32) = r9
12: (61) r9 = *(u32 *)(r1 +28)
13: (15) if r9 == 0x0 goto pc+4
14: (79) r9 = *(u64 *)(r1 +32)
15: (79) r1 = *(u64 *)(r1 +0)
16: (61) r1 = *(u32 *)(r1 +2348)
17: (05) goto pc+1
18: (79) r9 = *(u64 *)(r1 +32)
We also add the normal case where src_reg != dst_reg so we can compare
code generation easily from llvm-objdump and ensure that case continues
to work correctly. The normal code is xlated to,
20: (b7) r1 = 0
21: (61) r1 = *(u32 *)(r3 +28)
22: (15) if r1 == 0x0 goto pc+2
23: (79) r1 = *(u64 *)(r3 +0)
24: (61) r1 = *(u32 *)(r1 +2348)
Where the temp variable is not used.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/159718351457.4728.3295119261717842496.stgit@john-Precision-5820-Tower
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.