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Jean-Philippe Brucker 4fda26d2f7 libbpf: Fix BTF dump of pointer-to-array-of-struct
[ Upstream commit 901ee1d750f29a335423eeb9463c3ca461ca18c2 ]

The vmlinux.h generated from BTF is invalid when building
drivers/phy/ti/phy-gmii-sel.c with clang:

vmlinux.h:61702:27: error: array type has incomplete element type ‘struct reg_field’
61702 |  const struct reg_field (*regfields)[3];
      |                           ^~~~~~~~~

bpftool generates a forward declaration for this struct regfield, which
compilers aren't happy about. Here's a simplified reproducer:

	struct inner {
		int val;
	};
	struct outer {
		struct inner (*ptr_to_array)[2];
	} A;

After build with clang -> bpftool btf dump c -> clang/gcc:
./def-clang.h:11:23: error: array has incomplete element type 'struct inner'
        struct inner (*ptr_to_array)[2];

Member ptr_to_array of struct outer is a pointer to an array of struct
inner. In the DWARF generated by clang, struct outer appears before
struct inner, so when converting BTF of struct outer into C, bpftool
issues a forward declaration to struct inner. With GCC the DWARF info is
reversed so struct inner gets fully defined.

That forward declaration is not sufficient when compilers handle an
array of the struct, even when it's only used through a pointer. Note
that we can trigger the same issue with an intermediate typedef:

	struct inner {
	        int val;
	};
	typedef struct inner inner2_t[2];
	struct outer {
	        inner2_t *ptr_to_array;
	} A;

Becomes:

	struct inner;
	typedef struct inner inner2_t[2];

And causes:

./def-clang.h:10:30: error: array has incomplete element type 'struct inner'
	typedef struct inner inner2_t[2];

To fix this, clear through_ptr whenever we encounter an intermediate
array, to make the inner struct part of a strong link and force full
declaration.

Fixes: 351131b51c ("libbpf: add btf_dump API for BTF-to-C conversion")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210319112554.794552-2-jean-philippe@linaro.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-03-30 14:35:27 +02:00
arch ARM: dts: at91-sama5d27_som1: fix phy address to 7 2021-03-30 14:35:24 +02:00
block block: Suppress uevent for hidden device when removed 2021-03-30 14:35:23 +02:00
certs
crypto crypto: x86 - Regularize glue function prototypes 2021-03-20 10:39:47 +01:00
Documentation KVM: arm64: Reject VM creation when the default IPA size is unsupported 2021-03-17 17:03:57 +01:00
drivers net: stmmac: dwmac-sun8i: Provide TX and RX fifo sizes 2021-03-30 14:35:27 +02:00
fs squashfs: fix xattr id and id lookup sanity checks 2021-03-30 14:35:23 +02:00
include tcp: relookup sock for RST+ACK packets handled by obsolete req sock 2021-03-30 14:35:26 +02:00
init
ipc
kernel gcov: fix clang-11+ support 2021-03-30 14:35:23 +02:00
lib
LICENSES
mm hugetlbfs: hugetlb_fault_mutex_hash() cleanup 2021-03-30 14:35:19 +02:00
net mac80211: fix rate mask reset 2021-03-30 14:35:26 +02:00
samples
scripts
security integrity: double check iint_cache was initialized 2021-03-30 14:35:24 +02:00
sound ALSA: hda: ignore invalid NHLT table 2021-03-30 14:35:20 +02:00
tools libbpf: Fix BTF dump of pointer-to-array-of-struct 2021-03-30 14:35:27 +02:00
usr
virt KVM: arm64: Ensure I-cache isolation between vcpus of a same VM 2021-03-17 17:03:57 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
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COPYING
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Makefile Linux 5.4.108 2021-03-24 11:26:46 +01:00
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.