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Author SHA1 Message Date
Yonghong Song e3d8ee35e4 reland "[DebugInfo] Support to emit debugInfo for extern variables" 
Commit d77ae1552f
("[DebugInfo] Support to emit debugInfo for extern variables")
added deebugInfo for extern variables for BPF target.
The commit is reverted by 891e25b02d
as the committed tests using %clang instead of %clang_cc1 causing
test failed in certain scenarios as reported by Reid Kleckner.

This patch fixed the tests by using %clang_cc1.

Differential Revision: https://reviews.llvm.org/D71818
 2019-12-22 18:28:50 -08:00
Reid Kleckner 891e25b02d Revert "[DebugInfo] Support to emit debugInfo for extern variables" 
This reverts commit d77ae1552f.

The tests committed along with this change do not pass, and should be
changed to use %clang_cc1.
 2019-12-22 12:54:06 -08:00
Yonghong Song d77ae1552f [DebugInfo] Support to emit debugInfo for extern variables 
Extern variable usage in BPF is different from traditional
pure user space application. Recent discussion in linux bpf
mailing list has two use cases where debug info types are
required to use extern variables:
  - extern types are required to have a suitable interface
    in libbpf (bpf loader) to provide kernel config parameters
    to bpf programs.
    https://lore.kernel.org/bpf/CAEf4BzYCNo5GeVGMhp3fhysQ=_axAf=23PtwaZs-yAyafmXC9g@mail.gmail.com/T/#t
  - extern types are required so kernel bpf verifier can
    verify program which uses external functions more precisely.
    This will make later link with actual external function no
    need to reverify.
    https://lore.kernel.org/bpf/87eez4odqp.fsf@toke.dk/T/#m8d5c3e87ffe7f2764e02d722cb0d8cbc136880ed

This patch added clang support to emit debuginfo for extern variables
with a TargetInfo hook to enable it. The debuginfo for the
extern variable is emitted only if that extern variable is
referenced in the current compilation unit.

Currently, only BPF target enables to generate debug info for
extern variables. The emission of such debuginfo is disabled for C++
 at this moment since BPF only supports a subset of C language.
Emission with C++ can be enabled later if an appropriate use case
is identified.

-fstandalone-debug permits us to see more debuginfo with the cost
of bloated binary size. This patch did not add emission of extern
variable debug info with -fstandalone-debug. This can be
re-evaluated if there is a real need.

Differential Revision: https://reviews.llvm.org/D70696
 2019-12-10 08:09:51 -08:00
Yonghong Song 05e46979d2 [BPF] do compile-once run-everywhere relocation for bitfields 
A bpf specific clang intrinsic is introduced:
   u32 __builtin_preserve_field_info(member_access, info_kind)
Depending on info_kind, different information will
be returned to the program. A relocation is also
recorded for this builtin so that bpf loader can
patch the instruction on the target host.
This clang intrinsic is used to get certain information
to facilitate struct/union member relocations.

The offset relocation is extended by 4 bytes to
include relocation kind.
Currently supported relocation kinds are
 enum {
    FIELD_BYTE_OFFSET = 0,
    FIELD_BYTE_SIZE,
    FIELD_EXISTENCE,
    FIELD_SIGNEDNESS,
    FIELD_LSHIFT_U64,
    FIELD_RSHIFT_U64,
 };
for __builtin_preserve_field_info. The old
access offset relocation is covered by
    FIELD_BYTE_OFFSET = 0.

An example:
struct s {
    int a;
    int b1:9;
    int b2:4;
};
enum {
    FIELD_BYTE_OFFSET = 0,
    FIELD_BYTE_SIZE,
    FIELD_EXISTENCE,
    FIELD_SIGNEDNESS,
    FIELD_LSHIFT_U64,
    FIELD_RSHIFT_U64,
};

void bpf_probe_read(void *, unsigned, const void *);
int field_read(struct s *arg) {
  unsigned long long ull = 0;
  unsigned offset = __builtin_preserve_field_info(arg->b2, FIELD_BYTE_OFFSET);
  unsigned size = __builtin_preserve_field_info(arg->b2, FIELD_BYTE_SIZE);
 #ifdef USE_PROBE_READ
  bpf_probe_read(&ull, size, (const void *)arg + offset);
  unsigned lshift = __builtin_preserve_field_info(arg->b2, FIELD_LSHIFT_U64);
 #if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
  lshift = lshift + (size << 3) - 64;
 #endif
 #else
  switch(size) {
  case 1:
    ull = *(unsigned char *)((void *)arg + offset); break;
  case 2:
    ull = *(unsigned short *)((void *)arg + offset); break;
  case 4:
    ull = *(unsigned int *)((void *)arg + offset); break;
  case 8:
    ull = *(unsigned long long *)((void *)arg + offset); break;
  }
  unsigned lshift = __builtin_preserve_field_info(arg->b2, FIELD_LSHIFT_U64);
 #endif
  ull <<= lshift;
  if (__builtin_preserve_field_info(arg->b2, FIELD_SIGNEDNESS))
    return (long long)ull >> __builtin_preserve_field_info(arg->b2, FIELD_RSHIFT_U64);
  return ull >> __builtin_preserve_field_info(arg->b2, FIELD_RSHIFT_U64);
}

There is a minor overhead for bpf_probe_read() on big endian.

The code and relocation generated for field_read where bpf_probe_read() is
used to access argument data on little endian mode:
        r3 = r1
        r1 = 0
        r1 = 4  <=== relocation (FIELD_BYTE_OFFSET)
        r3 += r1
        r1 = r10
        r1 += -8
        r2 = 4  <=== relocation (FIELD_BYTE_SIZE)
        call bpf_probe_read
        r2 = 51 <=== relocation (FIELD_LSHIFT_U64)
        r1 = *(u64 *)(r10 - 8)
        r1 <<= r2
        r2 = 60 <=== relocation (FIELD_RSHIFT_U64)
        r0 = r1
        r0 >>= r2
        r3 = 1  <=== relocation (FIELD_SIGNEDNESS)
        if r3 == 0 goto LBB0_2
        r1 s>>= r2
        r0 = r1
LBB0_2:
        exit

Compare to the above code between relocations FIELD_LSHIFT_U64 and
FIELD_LSHIFT_U64, the code with big endian mode has four more
instructions.
        r1 = 41   <=== relocation (FIELD_LSHIFT_U64)
        r6 += r1
        r6 += -64
        r6 <<= 32
        r6 >>= 32
        r1 = *(u64 *)(r10 - 8)
        r1 <<= r6
        r2 = 60   <=== relocation (FIELD_RSHIFT_U64)

The code and relocation generated when using direct load.
        r2 = 0
        r3 = 4
        r4 = 4
        if r4 s> 3 goto LBB0_3
        if r4 == 1 goto LBB0_5
        if r4 == 2 goto LBB0_6
        goto LBB0_9
LBB0_6:                                 # %sw.bb1
        r1 += r3
        r2 = *(u16 *)(r1 + 0)
        goto LBB0_9
LBB0_3:                                 # %entry
        if r4 == 4 goto LBB0_7
        if r4 == 8 goto LBB0_8
        goto LBB0_9
LBB0_8:                                 # %sw.bb9
        r1 += r3
        r2 = *(u64 *)(r1 + 0)
        goto LBB0_9
LBB0_5:                                 # %sw.bb
        r1 += r3
        r2 = *(u8 *)(r1 + 0)
        goto LBB0_9
LBB0_7:                                 # %sw.bb5
        r1 += r3
        r2 = *(u32 *)(r1 + 0)
LBB0_9:                                 # %sw.epilog
        r1 = 51
        r2 <<= r1
        r1 = 60
        r0 = r2
        r0 >>= r1
        r3 = 1
        if r3 == 0 goto LBB0_11
        r2 s>>= r1
        r0 = r2
LBB0_11:                                # %sw.epilog
        exit

Considering verifier is able to do limited constant
propogation following branches. The following is the
code actually traversed.
        r2 = 0
        r3 = 4   <=== relocation
        r4 = 4   <=== relocation
        if r4 s> 3 goto LBB0_3
LBB0_3:                                 # %entry
        if r4 == 4 goto LBB0_7
LBB0_7:                                 # %sw.bb5
        r1 += r3
        r2 = *(u32 *)(r1 + 0)
LBB0_9:                                 # %sw.epilog
        r1 = 51   <=== relocation
        r2 <<= r1
        r1 = 60   <=== relocation
        r0 = r2
        r0 >>= r1
        r3 = 1
        if r3 == 0 goto LBB0_11
        r2 s>>= r1
        r0 = r2
LBB0_11:                                # %sw.epilog
        exit

For native load case, the load size is calculated to be the
same as the size of load width LLVM otherwise used to load
the value which is then used to extract the bitfield value.

Differential Revision: https://reviews.llvm.org/D67980

llvm-svn: 374099
 2019-10-08 18:23:17 +00:00
Chandler Carruth 2946cd7010 Update the file headers across all of the LLVM projects in the monorepo 
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
 2019-01-19 08:50:56 +00:00
Yonghong Song 6927cf0c2a bpf: recognize target specific option -mattr=dwarfris in clang 
The following is the usage example with clang:
  bash-4.2$ clang -target bpf -O2 -g -c -Xclang -target-feature -Xclang +dwarfris t.c
  bash-4.2$ llvm-objdump -S -d t.o

  t.o:    file format ELF64-BPF

  Disassembly of section .text:
  test:
  ; int test(void) {
       0:       b7 00 00 00 00 00 00 00         r0 = 0
  ; return 0;
         1:       95 00 00 00 00 00 00 00         exit
  bash-4.2$ cat t.c
  int test(void) {
    return 0;
  }
  bash-4.2$

Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 334839
 2018-06-15 15:53:31 +00:00
Yonghong Song 2ad75f7410 bpf: accept all asm register names 
Sometimes when people compile bpf programs with
"clang ... -target bpf ...", the kernel header
files may contain host arch inline assembly codes
as in the patch https://patchwork.kernel.org/patch/10119683/
by Arnaldo Carvaldo de Melo.

The current workaround in the above patch
is to guard the inline assembly with "#ifndef __BPF__"
marco. So when __BPF__ is defined, these macros will
have no use.

Such a method is not extensible. As a matter of fact,
most of these inline assembly codes will be thrown away
at the end of clang compilation.

So for bpf target, this patch accepts all asm register
names in clang AST stage. The name will be checked
again during llc code generation if the inline assembly
code is indeed for bpf programs.

With this patch, the above "#ifndef __BPF__" is not needed
any more in https://patchwork.kernel.org/patch/10119683/.

Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 329823
 2018-04-11 16:08:00 +00:00
Yonghong Song 8b1e93b7d6 bpf: Hook target feature "alu32" with LLVM 
LLVM has supported a new target feature "alu32" which could be enabled or
disabled by "-mattr=[+|-]alu32" when using llc.

This patch link Clang with it, so it could be also done by passing related
options to Clang, for example:

  -Xclang -target-feature -Xclang +alu32

Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Yonghong Song <yhs@fb.com>
llvm-svn: 325996
 2018-02-23 23:55:29 +00:00
Erich Keane e44bdb3f70 Add Rest of Targets Support to ValidCPUList (enabling march notes) 
A followup to: https://reviews.llvm.org/D42978

Most of the rest of the Targets were pretty rote, so this
patch knocks them all out at once. 

Differential Revision: https://reviews.llvm.org/D43057

llvm-svn: 324676
 2018-02-08 23:16:55 +00:00
Yonghong Song c4ea1010c1 bpf: add -mcpu=# support for bpf 
-mcpu=# will support:
  . generic: the default insn set
  . v1: insn set version 1, the same as generic
  . v2: insn set version 2, version 1 + additional jmp insns
  . probe: the compiler will probe the underlying kernel to
           decide proper version of insn set.

Examples:
$ clang -target bpf -mcpu=v1 -c t.c
$ clang -target bpf -mcpu=v2 -c t.c
$ clang -target bpf -mcpu=generic -c t.c
$ clang -target bpf -mcpu=probe -c t.c
$ clang -target bpf -mcpu=v3 -c t.c
error: unknown target CPU 'v3'

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 311523
 2017-08-23 04:26:17 +00:00
Erich Keane ebba592682 Break up Targets.cpp into a header/impl pair per target type[NFCI] 
Targets.cpp is getting unwieldy, and even minor changes cause the entire thing 
to cause recompilation for everyone. This patch bites the bullet and breaks 
it up into a number of files.

I tended to keep function definitions in the class declaration unless it 
caused additional includes to be necessary. In those cases, I pulled it 
over into the .cpp file. Content is copy/paste for the most part, 
besides includes/format/etc.


Differential Revision: https://reviews.llvm.org/D35701

llvm-svn: 308791
 2017-07-21 22:37:03 +00:00