mmap() bpf_arena right after creation, since the kernel needs to
remember the address returned from mmap. This is user_vm_start.
LLVM will generate bpf_arena_cast_user() instructions where
necessary and JIT will add upper 32-bit of user_vm_start
to such pointers.

Fix up bpf_map_mmap_sz() to compute mmap size as
map->value_size * map->max_entries for arrays and
PAGE_SIZE * map->max_entries for arena.

Don't set BTF at arena creation time, since it doesn't support it.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240308010812.89848-9-alexei.starovoitov@gmail.com

Add __arg_arena to bpf_helpers.h
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240308010812.89848-8-alexei.starovoitov@gmail.com

In global bpf functions recognize btf_decl_tag("arg:arena") as PTR_TO_ARENA.

Note, when the verifier sees:

__weak void foo(struct bar *p)

it recognizes 'p' as PTR_TO_MEM and 'struct bar' has to be a struct with scalars.
Hence the only way to use arena pointers in global functions is to tag them with "arg:arena".
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/20240308010812.89848-7-alexei.starovoitov@gmail.com

rY = addr_space_cast(rX, 0, 1) tells the verifier that rY->type = PTR_TO_ARENA.
Any further operations on PTR_TO_ARENA register have to be in 32-bit domain.

The verifier will mark load/store through PTR_TO_ARENA with PROBE_MEM32.
JIT will generate them as kern_vm_start + 32bit_addr memory accesses.

rY = addr_space_cast(rX, 1, 0) tells the verifier that rY->type = unknown scalar.
If arena->map_flags has BPF_F_NO_USER_CONV set then convert cast_user to mov32 as well.
Otherwise JIT will convert it to:
  rY = (u32)rX;
  if (rY)
     rY |= arena->user_vm_start & ~(u64)~0U;
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240308010812.89848-6-alexei.starovoitov@gmail.com

LLVM generates bpf_addr_space_cast instruction while translating
pointers between native (zero) address space and
__attribute__((address_space(N))).
The addr_space=1 is reserved as bpf_arena address space.

rY = addr_space_cast(rX, 0, 1) is processed by the verifier and
converted to normal 32-bit move: wX = wY

rY = addr_space_cast(rX, 1, 0) has to be converted by JIT:

aux_reg = upper_32_bits of arena->user_vm_start
aux_reg <<= 32
wX = wY // clear upper 32 bits of dst register
if (wX) // if not zero add upper bits of user_vm_start
  wX |= aux_reg

JIT can do it more efficiently:

mov dst_reg32, src_reg32  // 32-bit move
shl dst_reg, 32
or dst_reg, user_vm_start
rol dst_reg, 32
xor r11, r11
test dst_reg32, dst_reg32 // check if lower 32-bit are zero
cmove r11, dst_reg	  // if so, set dst_reg to zero
			  // Intel swapped src/dst register encoding in CMOVcc
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240308010812.89848-5-alexei.starovoitov@gmail.com

Add support for [LDX | STX | ST], PROBE_MEM32, [B | H | W | DW] instructions.
They are similar to PROBE_MEM instructions with the following differences:
- PROBE_MEM has to check that the address is in the kernel range with
  src_reg + insn->off >= TASK_SIZE_MAX + PAGE_SIZE check
- PROBE_MEM doesn't support store
- PROBE_MEM32 relies on the verifier to clear upper 32-bit in the register
- PROBE_MEM32 adds 64-bit kern_vm_start address (which is stored in %r12 in the prologue)
  Due to bpf_arena constructions such %r12 + %reg + off16 access is guaranteed
  to be within arena virtual range, so no address check at run-time.
- PROBE_MEM32 allows STX and ST. If they fault the store is a nop.
  When LDX faults the destination register is zeroed.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/20240308010812.89848-4-alexei.starovoitov@gmail.com

LLVM generates rX = addr_space_cast(rY, dst_addr_space, src_addr_space)
instruction when pointers in non-zero address space are used by the bpf
program. Recognize this insn in uapi and in bpf disassembler.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/20240308010812.89848-3-alexei.starovoitov@gmail.com

Introduce bpf_arena, which is a sparse shared memory region between the bpf
program and user space.

Use cases:
1. User space mmap-s bpf_arena and uses it as a traditional mmap-ed
   anonymous region, like memcached or any key/value storage. The bpf
   program implements an in-kernel accelerator. XDP prog can search for
   a key in bpf_arena and return a value without going to user space.
2. The bpf program builds arbitrary data structures in bpf_arena (hash
   tables, rb-trees, sparse arrays), while user space consumes it.
3. bpf_arena is a "heap" of memory from the bpf program's point of view.
   The user space may mmap it, but bpf program will not convert pointers
   to user base at run-time to improve bpf program speed.

Initially, the kernel vm_area and user vma are not populated. User space
can fault in pages within the range. While servicing a page fault,
bpf_arena logic will insert a new page into the kernel and user vmas. The
bpf program can allocate pages from that region via
bpf_arena_alloc_pages(). This kernel function will insert pages into the
kernel vm_area. The subsequent fault-in from user space will populate that
page into the user vma. The BPF_F_SEGV_ON_FAULT flag at arena creation time
can be used to prevent fault-in from user space. In such a case, if a page
is not allocated by the bpf program and not present in the kernel vm_area,
the user process will segfault. This is useful for use cases 2 and 3 above.

bpf_arena_alloc_pages() is similar to user space mmap(). It allocates pages
either at a specific address within the arena or allocates a range with the
maple tree. bpf_arena_free_pages() is analogous to munmap(), which frees
pages and removes the range from the kernel vm_area and from user process
vmas.

bpf_arena can be used as a bpf program "heap" of up to 4GB. The speed of
bpf program is more important than ease of sharing with user space. This is
use case 3. In such a case, the BPF_F_NO_USER_CONV flag is recommended.
It will tell the verifier to treat the rX = bpf_arena_cast_user(rY)
instruction as a 32-bit move wX = wY, which will improve bpf prog
performance. Otherwise, bpf_arena_cast_user is translated by JIT to
conditionally add the upper 32 bits of user vm_start (if the pointer is not
NULL) to arena pointers before they are stored into memory. This way, user
space sees them as valid 64-bit pointers.

Diff https://github.com/llvm/llvm-project/pull/84410 enables LLVM BPF
backend generate the bpf_addr_space_cast() instruction to cast pointers
between address_space(1) which is reserved for bpf_arena pointers and
default address space zero. All arena pointers in a bpf program written in
C language are tagged as __attribute__((address_space(1))). Hence, clang
provides helpful diagnostics when pointers cross address space. Libbpf and
the kernel support only address_space == 1. All other address space
identifiers are reserved.

rX = bpf_addr_space_cast(rY, /* dst_as */ 1, /* src_as */ 0) tells the
verifier that rX->type = PTR_TO_ARENA. Any further operations on
PTR_TO_ARENA register have to be in the 32-bit domain. The verifier will
mark load/store through PTR_TO_ARENA with PROBE_MEM32. JIT will generate
them as kern_vm_start + 32bit_addr memory accesses. The behavior is similar
to copy_from_kernel_nofault() except that no address checks are necessary.
The address is guaranteed to be in the 4GB range. If the page is not
present, the destination register is zeroed on read, and the operation is
ignored on write.

rX = bpf_addr_space_cast(rY, 0, 1) tells the verifier that rX->type =
unknown scalar. If arena->map_flags has BPF_F_NO_USER_CONV set, then the
verifier converts such cast instructions to mov32. Otherwise, JIT will emit
native code equivalent to:
rX = (u32)rY;
if (rY)
  rX |= clear_lo32_bits(arena->user_vm_start); /* replace hi32 bits in rX */

After such conversion, the pointer becomes a valid user pointer within
bpf_arena range. The user process can access data structures created in
bpf_arena without any additional computations. For example, a linked list
built by a bpf program can be walked natively by user space.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Barret Rhoden <brho@google.com>
Link: https://lore.kernel.org/bpf/20240308010812.89848-2-alexei.starovoitov@gmail.com

We already have kprobe and fentry benchmarks. Let's add kretprobe and
fexit ones for completeness.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20240309005124.3004446-1-andrii@kernel.org

ioremap_page_range() should be used for ranges within vmalloc range only.
The vmalloc ranges are allocated by get_vm_area(). PCI has "resource"
allocator that manages PCI_IOBASE, IO_SPACE_LIMIT address range, hence
introduce vmap_page_range() to be used exclusively to map pages
in PCI address space.

Fixes: 3e49a866 ("mm: Enforce VM_IOREMAP flag and range in ioremap_page_range.")
Reported-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/bpf/CANiq72ka4rir+RTN2FQoT=Vvprp_Ao-CvoYEkSNqtSY+RZj+AA@mail.gmail.com

We used bpf_prog_pack to aggregate bpf programs into huge page to
relieve the iTLB pressure on the system. This was merged for ARM64[1]
We can apply it to bpf trampoline as well. This would increase the
preformance of fentry and struct_ops programs.

[1] https://lore.kernel.org/bpf/20240228141824.119877-1-puranjay12@gmail.com/Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Message-ID: <20240304202803.31400-1-puranjay12@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Toke Høiland-Jørgensen says:

====================
Fix hash bucket overflow checks for 32-bit arches

Syzbot managed to trigger a crash by creating a DEVMAP_HASH map with a
large number of buckets because the overflow check relies on
well-defined behaviour that is only correct on 64-bit arches.

Fix the overflow checks to happen before values are rounded up in all
the affected map types.

v3:
- Keep the htab->n_buckets > U32_MAX / sizeof(struct bucket) check
- Use 1UL << 31 instead of U32_MAX / 2 + 1 as the constant to check
  against
- Add patch to fix stackmap.c
v2:
- Fix off-by-one error in overflow check
- Apply the same fix to hashtab, where the devmap_hash code was copied
  from (John)

Toke Høiland-Jørgensen (3):
  bpf: Fix DEVMAP_HASH overflow check on 32-bit arches
  bpf: Fix hashtab overflow check on 32-bit arches
  bpf: Fix stackmap overflow check on 32-bit arches

 kernel/bpf/devmap.c   | 11 ++++++-----
 kernel/bpf/hashtab.c  | 14 +++++++++-----
 kernel/bpf/stackmap.c |  9 ++++++---
 3 files changed, 21 insertions(+), 13 deletions(-)
====================

Link: https://lore.kernel.org/r/20240307120340.99577-1-toke@redhat.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

The stackmap code relies on roundup_pow_of_two() to compute the number
of hash buckets, and contains an overflow check by checking if the
resulting value is 0. However, on 32-bit arches, the roundup code itself
can overflow by doing a 32-bit left-shift of an unsigned long value,
which is undefined behaviour, so it is not guaranteed to truncate
neatly. This was triggered by syzbot on the DEVMAP_HASH type, which
contains the same check, copied from the hashtab code.

The commit in the fixes tag actually attempted to fix this, but the fix
did not account for the UB, so the fix only works on CPUs where an
overflow does result in a neat truncation to zero, which is not
guaranteed. Checking the value before rounding does not have this
problem.

Fixes: 6183f4d3 ("bpf: Check for integer overflow when using roundup_pow_of_two()")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Reviewed-by: Bui Quang Minh <minhquangbui99@gmail.com>
Message-ID: <20240307120340.99577-4-toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

The hashtab code relies on roundup_pow_of_two() to compute the number of
hash buckets, and contains an overflow check by checking if the
resulting value is 0. However, on 32-bit arches, the roundup code itself
can overflow by doing a 32-bit left-shift of an unsigned long value,
which is undefined behaviour, so it is not guaranteed to truncate
neatly. This was triggered by syzbot on the DEVMAP_HASH type, which
contains the same check, copied from the hashtab code. So apply the same
fix to hashtab, by moving the overflow check to before the roundup.

Fixes: daaf427c ("bpf: fix arraymap NULL deref and missing overflow and zero size checks")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Message-ID: <20240307120340.99577-3-toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

The devmap code allocates a number hash buckets equal to the next power
of two of the max_entries value provided when creating the map. When
rounding up to the next power of two, the 32-bit variable storing the
number of buckets can overflow, and the code checks for overflow by
checking if the truncated 32-bit value is equal to 0. However, on 32-bit
arches the rounding up itself can overflow mid-way through, because it
ends up doing a left-shift of 32 bits on an unsigned long value. If the
size of an unsigned long is four bytes, this is undefined behaviour, so
there is no guarantee that we'll end up with a nice and tidy 0-value at
the end.

Syzbot managed to turn this into a crash on arm32 by creating a
DEVMAP_HASH with max_entries > 0x80000000 and then trying to update it.
Fix this by moving the overflow check to before the rounding up
operation.

Fixes: 6f9d451a ("xdp: Add devmap_hash map type for looking up devices by hashed index")
Link: https://lore.kernel.org/r/000000000000ed666a0611af6818@google.com
Reported-and-tested-by: syzbot+8cd36f6b65f3cafd400a@syzkaller.appspotmail.com
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Message-ID: <20240307120340.99577-2-toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Alexei Starovoitov says:

====================
These are bpf_arena prerequisite patches.
Useful on its own.

Alexei Starovoitov (5):
  bpf: Allow kfuncs return 'void *'
  bpf: Recognize '__map' suffix in kfunc arguments
  bpf: Plumb get_unmapped_area() callback into bpf_map_ops
  libbpf: Allow specifying 64-bit integers in map BTF.
  bpf: Tell bpf programs kernel's PAGE_SIZE
====================
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

vmlinux BTF includes all kernel enums.
Add __PAGE_SIZE = PAGE_SIZE enum, so that bpf programs
that include vmlinux.h can easily access it.
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20240307031228.42896-7-alexei.starovoitov@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

It's not restricted to working with "internal" maps, it cares about any
map that can be mmap'ed. Reflect that in more succinct and generic name.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20240307031228.42896-6-alexei.starovoitov@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

__uint() macro that is used to specify map attributes like:
  __uint(type, BPF_MAP_TYPE_ARRAY);
  __uint(map_flags, BPF_F_MMAPABLE);
It is limited to 32-bit, since BTF_KIND_ARRAY has u32 "number of elements"
field in "struct btf_array".

Introduce __ulong() macro that allows specifying values bigger than 32-bit.
In map definition "map_extra" is the only u64 field, so far.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20240307031228.42896-5-alexei.starovoitov@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

Subsequent patches introduce bpf_arena that imposes special alignment
requirements on address selection.
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20240307031228.42896-4-alexei.starovoitov@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

Recognize 'void *p__map' kfunc argument as 'struct bpf_map *p__map'.
It allows kfunc to have 'void *' argument for maps, since bpf progs
will call them as:
struct {
        __uint(type, BPF_MAP_TYPE_ARENA);
	...
} arena SEC(".maps");

bpf_kfunc_with_map(... &arena ...);

Underneath libbpf will load CONST_PTR_TO_MAP into the register via ld_imm64
insn. If kfunc was defined with 'struct bpf_map *' it would pass the
verifier as well, but bpf prog would need to type cast the argument
(void *)&arena, which is not clean.
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20240307031228.42896-3-alexei.starovoitov@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

Recognize return of 'void *' from kfunc as returning unknown scalar.
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20240307031228.42896-2-alexei.starovoitov@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

The riscv BPF JIT doesn't emit proper kCFI prologues for BPF programs
and struct_ops trampolines when CONFIG_CFI_CLANG is enabled.

This causes CFI failures when calling BPF programs and can even crash
the kernel due to invalid memory accesses.

Example crash:

root@rv-selftester:~/bpf# ./test_progs -a dummy_st_ops

 Unable to handle kernel paging request at virtual address ffffffff78204ffc
 Oops [#1]
 Modules linked in: bpf_testmod(OE) [....]
 CPU: 3 PID: 356 Comm: test_progs Tainted: P           OE      6.8.0-rc1 #1
 Hardware name: riscv-virtio,qemu (DT)
 epc : bpf_struct_ops_test_run+0x28c/0x5fc
  ra : bpf_struct_ops_test_run+0x26c/0x5fc
 epc : ffffffff82958010 ra : ffffffff82957ff0 sp : ff200000007abc80
  gp : ffffffff868d6218 tp : ff6000008d87b840 t0 : 000000000000000f
  t1 : 0000000000000000 t2 : 000000002005793e s0 : ff200000007abcf0
  s1 : ff6000008a90fee0 a0 : 0000000000000000 a1 : 0000000000000000
  a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
  a5 : ffffffff868dba26 a6 : 0000000000000001 a7 : 0000000052464e43
  s2 : 00007ffffc0a95f0 s3 : ff6000008a90fe80 s4 : ff60000084c24c00
  s5 : ffffffff78205000 s6 : ff60000088750648 s7 : ff20000000035008
  s8 : fffffffffffffff4 s9 : ffffffff86200610 s10: 0000000000000000
  s11: 0000000000000000 t3 : ffffffff8483dc30 t4 : ffffffff8483dc10
  t5 : ffffffff8483dbf0 t6 : ffffffff8483dbd0
 status: 0000000200000120 badaddr: ffffffff78204ffc cause: 000000000000000d
 [<ffffffff82958010>] bpf_struct_ops_test_run+0x28c/0x5fc
 [<ffffffff805083ee>] bpf_prog_test_run+0x170/0x548
 [<ffffffff805029c8>] __sys_bpf+0x2d2/0x378
 [<ffffffff804ff570>] __riscv_sys_bpf+0x5c/0x120
 [<ffffffff8000e8fe>] syscall_handler+0x62/0xe4
 [<ffffffff83362df6>] do_trap_ecall_u+0xc6/0x27c
 [<ffffffff833822c4>] ret_from_exception+0x0/0x64
 Code: b603 0109 b683 0189 b703 0209 8493 0609 157d 8d65 (a303) ffca
 ---[ end trace 0000000000000000 ]---
 Kernel panic - not syncing: Fatal exception
 SMP: stopping secondary CPUs

Implement proper kCFI prologues for the BPF programs and callbacks and
drop __nocfi for riscv64. Fix the trampoline generation code to emit kCFI
prologue when a struct_ops trampoline is being prepared.
Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/bpf/20240303170207.82201-2-puranjay12@gmail.com

Eduard Zingerman says:

====================
libbpf: type suffixes and autocreate flag for struct_ops maps

Tweak struct_ops related APIs to allow the following features:
- specify version suffixes for stuct_ops map types;
- share same BPF program between several map definitions with
  different local BTF types, assuming only maps with same
  kernel BTF type would be selected for load;
- toggle autocreate flag for struct_ops maps;
- automatically toggle autoload for struct_ops programs referenced
  from struct_ops maps, depending on autocreate status of the
  corresponding map;
- use SEC("?.struct_ops") and SEC("?.struct_ops.link")
  to define struct_ops maps with autocreate == false after object open.

This would allow loading programs like below:

    SEC("struct_ops/foo") int BPF_PROG(foo) { ... }
    SEC("struct_ops/bar") int BPF_PROG(bar) { ... }

    struct bpf_testmod_ops___v1 {
        int (*foo)(void);
    };

    struct bpf_testmod_ops___v2 {
        int (*foo)(void);
        int (*bar)(void);
    };

    /* Assume kernel type name to be 'test_ops' */
    SEC(".struct_ops.link")
    struct test_ops___v1 map_v1 = {
        /* Program 'foo' shared by maps with
         * different local BTF type
         */
        .foo = (void *)foo
    };

    SEC(".struct_ops.link")
    struct test_ops___v2 map_v2 = {
        .foo = (void *)foo,
        .bar = (void *)bar
    };

Assuming the following tweaks are done before loading:

    /* to load v1 */
    bpf_map__set_autocreate(skel->maps.map_v1, true);
    bpf_map__set_autocreate(skel->maps.map_v2, false);

    /* to load v2 */
    bpf_map__set_autocreate(skel->maps.map_v1, false);
    bpf_map__set_autocreate(skel->maps.map_v2, true);

Patch #8 ties autocreate and autoload flags for struct_ops maps and
programs.

Changelog:
- v3 [3] -> v4:
  - changes for multiple styling suggestions from Andrii;
  - patch #5: libbpf log capture now happens for LIBBPF_INFO and
    LIBBPF_WARN messages and does not depend on verbosity flags
    (Andrii);
  - patch #6: fixed runtime crash caused by conflict with newly added
    test case struct_ops_multi_pages;
  - patch #7: fixed free of possibly uninitialized pointer (Daniel)
  - patch #8: simpler algorithm to detect which programs to autoload
    (Andrii);
  - patch #9: added assertions for autoload flag after object load
    (Andrii);
  - patch #12: DATASEC name rewrite in libbpf is now done inplace, no
    new strings added to BTF (Andrii);
  - patch #14: allow any printable characters in DATASEC names when
    kernel validates BTF (Andrii)
- v2 [2] -> v3:
  - moved patch #8 logic to be fully done on load
    (requested by Andrii in offlist discussion);
  - in patch #9 added test case for shadow vars and
    autocreate/autoload interaction.
- v1 [1] -> v2:
  - fixed memory leak in patch #1 (Kui-Feng);
  - improved error messages in patch #2 (Martin, Andrii);
  - in bad_struct_ops selftest from patch #6 added .test_2
    map member setup (David);
  - added utility functions to capture libbpf log from selftests (David)
  - in selftests replaced usage of ...__open_and_load by separate
    calls to ..._open() and ..._load() (Andrii);
  - removed serial_... in selftest definitions (Andrii);
  - improved comments in selftest struct_ops_autocreate
    from patch #7 (David);
  - removed autoload toggling logic incompatible with shadow variables
    from bpf_map__set_autocreate(), instead struct_ops programs
    autoload property is computed at struct_ops maps load phase,
    see patch #8 (Kui-Feng, Martin, Andrii);
  - added support for SEC("?.struct_ops") and SEC("?.struct_ops.link")
    (Andrii).

[1] https://lore.kernel.org/bpf/20240227204556.17524-1-eddyz87@gmail.com/
[2] https://lore.kernel.org/bpf/20240302011920.15302-1-eddyz87@gmail.com/
[3] https://lore.kernel.org/bpf/20240304225156.24765-1-eddyz87@gmail.com/
====================

Link: https://lore.kernel.org/r/20240306104529.6453-1-eddyz87@gmail.comSigned-off-by: Andrii Nakryiko <andrii@kernel.org>

Two test cases to verify that '?' and other printable characters are
allowed in BTF DATASEC names:
- DATASEC with name "?.foo bar:buz" should be accepted;
- type with name "?foo" should be rejected.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-16-eddyz87@gmail.com

The intent is to allow libbpf to use SEC("?.struct_ops") to identify
struct_ops maps that are optional, e.g. like in the following BPF code:

    SEC("?.struct_ops")
    struct test_ops optional_map = { ... };

Which yields the following BTF:

    ...
    [13] DATASEC '?.struct_ops' size=0 vlen=...
    ...

To load such BTF libbpf rewrites DATASEC name before load.
After this patch the rewrite won't be necessary.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-15-eddyz87@gmail.com

Check that "?.struct_ops" and "?.struct_ops.link" section names define
struct_ops maps with autocreate == false after open.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-14-eddyz87@gmail.com

Optional struct_ops maps are defined using question mark at the start
of the section name, e.g.:

    SEC("?.struct_ops")
    struct test_ops optional_map = { ... };

This commit teaches libbpf to detect if kernel allows '?' prefix
in datasec names, and if it doesn't then to rewrite such names
by replacing '?' with '_', e.g.:

    DATASEC ?.struct_ops -> DATASEC _.struct_ops
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-13-eddyz87@gmail.com

Allow using two new section names for struct_ops maps:
- SEC("?.struct_ops")
- SEC("?.struct_ops.link")

To specify maps that have bpf_map->autocreate == false after open.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-12-eddyz87@gmail.com

The next patch would add two new section names for struct_ops maps.
To make working with multiple struct_ops sections more convenient:
- remove fields like elf_state->st_ops_{shndx,link_shndx};
- mark section descriptions hosting struct_ops as
  elf_sec_desc->sec_type == SEC_ST_OPS;

After these changes struct_ops sections could be processed uniformly
by iterating bpf_object->efile.secs entries.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-11-eddyz87@gmail.com

Check that autocreate flags of struct_ops map cause autoload of
struct_ops corresponding programs:
- when struct_ops program is referenced only from a map for which
  autocreate is set to false, that program should not be loaded;
- when struct_ops program with autoload == false is set to be used
  from a map with autocreate == true using shadow var,
  that program should be loaded;
- when struct_ops program is not referenced from any map object load
  should fail.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-10-eddyz87@gmail.com

Automatically select which struct_ops programs to load depending on
which struct_ops maps are selected for automatic creation.
E.g. for the BPF code below:

    SEC("struct_ops/test_1") int BPF_PROG(foo) { ... }
    SEC("struct_ops/test_2") int BPF_PROG(bar) { ... }

    SEC(".struct_ops.link")
    struct test_ops___v1 A = {
        .foo = (void *)foo
    };

    SEC(".struct_ops.link")
    struct test_ops___v2 B = {
        .foo = (void *)foo,
        .bar = (void *)bar,
    };

And the following libbpf API calls:

    bpf_map__set_autocreate(skel->maps.A, true);
    bpf_map__set_autocreate(skel->maps.B, false);

The autoload would be enabled for program 'foo' and disabled for
program 'bar'.

During load, for each struct_ops program P, referenced from some
struct_ops map M:
- set P.autoload = true if M.autocreate is true for some M;
- set P.autoload = false if M.autocreate is false for all M;
- don't change P.autoload, if P is not referenced from any map.

Do this after bpf_object__init_kern_struct_ops_maps()
to make sure that shadow vars assignment is done.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-9-eddyz87@gmail.com

Check that bpf_map__set_autocreate() can be used to disable automatic
creation for struct_ops maps.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-8-eddyz87@gmail.com

When loading struct_ops programs kernel requires BTF id of the
struct_ops type and member index for attachment point inside that
type. This makes impossible to use same BPF program in several
struct_ops maps that have different struct_ops type.
Check if libbpf rejects such BPF objects files.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-7-eddyz87@gmail.com

Several test_progs tests already capture libbpf log in order to check
for some expected output, e.g bpf_tcp_ca.c, kfunc_dynptr_param.c,
log_buf.c and a few others.

This commit provides a, hopefully, simple API to capture libbpf log
w/o necessity to define new print callback in each test:

    /* Creates a global memstream capturing INFO and WARN level output
     * passed to libbpf_print_fn.
     * Returns 0 on success, negative value on failure.
     * On failure the description is printed using PRINT_FAIL and
     * current test case is marked as fail.
     */
    int start_libbpf_log_capture(void)

    /* Destroys global memstream created by start_libbpf_log_capture().
     * Returns a pointer to captured data which has to be freed.
     * Returned buffer is null terminated.
     */
    char *stop_libbpf_log_capture(void)

The intended usage is as follows:

    if (start_libbpf_log_capture())
            return;
    use_libbpf();
    char *log = stop_libbpf_log_capture();
    ASSERT_HAS_SUBSTR(log, "... expected ...", "expected some message");
    free(log);

As a safety measure, free(start_libbpf_log_capture()) is invoked in the
epilogue of the test_progs.c:run_one_test().
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-6-eddyz87@gmail.com

Extend struct_ops_module test case to check if it is possible to use
'___' suffixes for struct_ops type specification.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20240306104529.6453-5-eddyz87@gmail.com

Skip load steps for struct_ops maps not marked for automatic creation.
This should allow to load bpf object in situations like below:

    SEC("struct_ops/foo") int BPF_PROG(foo) { ... }
    SEC("struct_ops/bar") int BPF_PROG(bar) { ... }

    struct test_ops___v1 {
    	int (*foo)(void);
    };

    struct test_ops___v2 {
    	int (*foo)(void);
    	int (*does_not_exist)(void);
    };

    SEC(".struct_ops.link")
    struct test_ops___v1 map_for_old = {
    	.test_1 = (void *)foo
    };

    SEC(".struct_ops.link")
    struct test_ops___v2 map_for_new = {
    	.test_1 = (void *)foo,
    	.does_not_exist = (void *)bar
    };

Suppose program is loaded on old kernel that does not have definition
for 'does_not_exist' struct_ops member. After this commit it would be
possible to load such object file after the following tweaks:

    bpf_program__set_autoload(skel->progs.bar, false);
    bpf_map__set_autocreate(skel->maps.map_for_new, false);
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20240306104529.6453-4-eddyz87@gmail.com

Enforce the following existing limitation on struct_ops programs based
on kernel BTF id instead of program-local BTF id:

    struct_ops BPF prog can be re-used between multiple .struct_ops &
    .struct_ops.link as long as it's the same struct_ops struct
    definition and the same function pointer field

This allows reusing same BPF program for versioned struct_ops map
definitions, e.g.:

    SEC("struct_ops/test")
    int BPF_PROG(foo) { ... }

    struct some_ops___v1 { int (*test)(void); };
    struct some_ops___v2 { int (*test)(void); };

    SEC(".struct_ops.link") struct some_ops___v1 a = { .test = foo }
    SEC(".struct_ops.link") struct some_ops___v2 b = { .test = foo }
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-3-eddyz87@gmail.com

E.g. allow the following struct_ops definitions:

    struct bpf_testmod_ops___v1 { int (*test)(void); };
    struct bpf_testmod_ops___v2 { int (*test)(void); };

    SEC(".struct_ops.link")
    struct bpf_testmod_ops___v1 a = { .test = ... }
    SEC(".struct_ops.link")
    struct bpf_testmod_ops___v2 b = { .test = ... }

Where both bpf_testmod_ops__v1 and bpf_testmod_ops__v2 would be
resolved as 'struct bpf_testmod_ops' from kernel BTF.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-2-eddyz87@gmail.com

Alexei Starovoitov says:

====================
bpf: Introduce may_goto and cond_break

From: Alexei Starovoitov <ast@kernel.org>

v5 -> v6:
- Rename BPF_JMA to BPF_JCOND
- Addressed Andrii's review comments

v4 -> v5:
- rewrote patch 1 to avoid fake may_goto_reg and use 'u32 may_goto_cnt' instead.
  This way may_goto handling is similar to bpf_loop() processing.
- fixed bug in patch 2 that RANGE_WITHIN should not use
  rold->type == NOT_INIT as a safe signal.
- patch 3 fixed negative offset computation in cond_break macro
- using bpf_arena and cond_break recompiled lib/glob.c as bpf prog
  and it works! It will be added as a selftest to arena series.

v3 -> v4:
- fix drained issue reported by John.
  may_goto insn could be implemented with sticky state (once
  reaches 0 it stays 0), but the verifier shouldn't assume that.
  It has to explore both branches.
  Arguably drained iterator state shouldn't be there at all.
  bpf_iter_css_next() is not sticky. Can be fixed, but auditing all
  iterators for stickiness. That's an orthogonal discussion.
- explained JMA name reasons in patch 1
- fixed test_progs-no_alu32 issue and added another test

v2 -> v3: Major change
- drop bpf_can_loop() kfunc and introduce may_goto instruction instead
  kfunc is a function call while may_goto doesn't consume any registers
  and LLVM can produce much better code due to less register pressure.
- instead of counting from zero to BPF_MAX_LOOPS start from it instead
  and break out of the loop when count reaches zero
- use may_goto instruction in cond_break macro
- recognize that 'exact' state comparison doesn't need to be truly exact.
  regsafe() should ignore precision and liveness marks, but range_within
  logic is safe to use while evaluating open coded iterators.
====================

Link: https://lore.kernel.org/r/20240306031929.42666-1-alexei.starovoitov@gmail.comSigned-off-by: Andrii Nakryiko <andrii@kernel.org>