> Hi Cuper.
> OK. Thanks for the patch.
This commit is breaking the BPF build, because libgcc emits libcalls to
__builtin_abort. We need to rethink this.
Please revert:
commit faf5b148588bd7fbb60ec669aefa704044037cdc
Author: Cupertino Miranda <cupertino.mira...@oracle.com>
Date: Thu Nov 23 22:28:01 2023 +0000
Thanks!
>
>> Hi everyone,
>>
>> The attached patch is a temporary solution for the lack of proper linker
>> and external library linking of the eBPF platform.
>> Any calls created by the compiler, that would usually be defined within
>> libgcc, will endup being undefined in bpftool, when GCC the compiled
>> code is passed.
>>
>> This patch anticipates that error to the compiler, by verifiying if
>> any of those calls are being generated, and reporting as an error.
>>
>> Looking forward to your comments.
>>
>> Cheers,
>> Cupertino
>>
>> commit c2110ae497c7ff83c309f172bc265973652b760d
>> Author: Cupertino Miranda <cupertino.mira...@oracle.com>
>> Date: Thu Nov 23 22:28:01 2023 +0000
>>
>> This patch enables errors when external calls are created.
>>
>> When architectural limitations or usage of builtins implies the compiler
>> to create function calls to external libraries that implement the
>> functionality, GCC will now report an error claiming that this function
>> calls are not compatible with eBPF target.
>> Examples of those are the usage of __builtin_memmove and a sign division
>> in BPF ISA v3 or below that will require to call __divdi3.
>> This is currently an eBPF limitation which does not support linking of
>> object files but rather "raw" non linked ones. Those object files are
>> loaded and relocated by libbpf and the kernel.
>>
>> gcc/ChangeLog:
>> * config/bpf/bpf.cc (bpf_output_call): Report error in case the
>> function call is for a builtin.
>> (bpf_external_libcall): Added target hook to detect and report
>> error when other external calls that are not builtins.
>>
>> diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
>> index 0c9d5257c384..1c84113055b1 100644
>> --- a/gcc/config/bpf/bpf.cc
>> +++ b/gcc/config/bpf/bpf.cc
>> @@ -744,6 +744,15 @@ bpf_output_call (rtx target)
>> xops[0] = GEN_INT (TREE_INT_CST_LOW (TREE_VALUE (attr_args)));
>> output_asm_insn ("call\t%0", xops);
>> }
>> + else if (fndecl_built_in_p (decl))
>> + {
>> + /* For now lets report this as an error while we are not able to
>> + link eBPF object files. In particular with libgcc. */
>> + tree name = DECL_NAME (decl);
>> + error ("call to external builtin %s in function, which is not
>> supported by "
>> + "eBPF", name != NULL_TREE ? IDENTIFIER_POINTER (name) :
>> "(anon)");
>> + output_asm_insn ("call 0", NULL);
>> + }
>> else
>> output_asm_insn ("call\t%0", &target);
>>
>> @@ -763,6 +772,18 @@ bpf_output_call (rtx target)
>> return "";
>> }
>>
>> +static void
>> +bpf_external_libcall (rtx fun)
>> +{
>> + tree decl = SYMBOL_REF_DECL (fun);
>> + tree name = DECL_NAME (decl);
>> + error ("call to external libcall %s in function, which is not supported
>> by "
>> + "eBPF", name != NULL_TREE ? IDENTIFIER_POINTER (name) : "(anon)");
>> +}
>> +
>> +#undef TARGET_ASM_EXTERNAL_LIBCALL
>> +#define TARGET_ASM_EXTERNAL_LIBCALL bpf_external_libcall
>> +
>> /* Print register name according to assembly dialect. In normal
>> syntax registers are printed like %rN where N is the register
>> number.
>> diff --git a/gcc/testsuite/gcc.target/bpf/atomic-cmpxchg-2.c
>> b/gcc/testsuite/gcc.target/bpf/atomic-cmpxchg-2.c
>> index 4036570ac601..fec720584e48 100644
>> --- a/gcc/testsuite/gcc.target/bpf/atomic-cmpxchg-2.c
>> +++ b/gcc/testsuite/gcc.target/bpf/atomic-cmpxchg-2.c
>> @@ -6,7 +6,7 @@ foo (int *p, int *expected, int desired)
>> {
>> return __atomic_compare_exchange (p, expected, &desired, 0,
>> __ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
>> -}
>> +} /* { dg-error "call to external builtin" } */
>>
>> int
>> foo64 (long *p, long *expected, long desired)
>> diff --git a/gcc/testsuite/gcc.target/bpf/atomic-fetch-op-3.c
>> b/gcc/testsuite/gcc.target/bpf/atomic-fetch-op-3.c
>> index 044a2f76474b..ea1b8e48928a 100644
>> --- a/gcc/testsuite/gcc.target/bpf/atomic-fetch-op-3.c
>> +++ b/gcc/testsuite/gcc.target/bpf/atomic-fetch-op-3.c
>> @@ -9,7 +9,7 @@ long
>> test_atomic_fetch_add (long x)
>> {
>> return __atomic_fetch_add (&val, x, __ATOMIC_ACQUIRE);
>> -}
>> +} /* { dg-error "call to external builtin" } */
>>
>> long
>> test_atomic_fetch_sub (long x)
>> diff --git a/gcc/testsuite/gcc.target/bpf/atomic-op-3.c
>> b/gcc/testsuite/gcc.target/bpf/atomic-op-3.c
>> index b2ce28926347..fefafd6b748f 100644
>> --- a/gcc/testsuite/gcc.target/bpf/atomic-op-3.c
>> +++ b/gcc/testsuite/gcc.target/bpf/atomic-op-3.c
>> @@ -20,7 +20,7 @@ void
>> test_atomic_and (int x)
>> {
>> __atomic_and_fetch (&val, x, __ATOMIC_ACQUIRE);
>> -}
>> +} /* { dg-error "call to external builtin" } */
>>
>> void
>> test_atomic_nand (int x)
>> diff --git a/gcc/testsuite/gcc.target/bpf/atomic-xchg-2.c
>> b/gcc/testsuite/gcc.target/bpf/atomic-xchg-2.c
>> index 3b6324e966b8..eab695bf388c 100644
>> --- a/gcc/testsuite/gcc.target/bpf/atomic-xchg-2.c
>> +++ b/gcc/testsuite/gcc.target/bpf/atomic-xchg-2.c
>> @@ -7,7 +7,7 @@ int foo (int *p, int *new)
>> int old;
>> __atomic_exchange (p, new, &old, __ATOMIC_RELAXED);
>> return old;
>> -}
>> +} /* { dg-error "call to external builtin" } */
>>
>> int foo64 (long *p, long *new)
>> {
>> diff --git a/gcc/testsuite/gcc.target/bpf/diag-sdiv.c
>> b/gcc/testsuite/gcc.target/bpf/diag-sdiv.c
>> index c48bbf03df97..c3332558e7d2 100644
>> --- a/gcc/testsuite/gcc.target/bpf/diag-sdiv.c
>> +++ b/gcc/testsuite/gcc.target/bpf/diag-sdiv.c
>> @@ -7,6 +7,6 @@ foo ()
>> {
>> signed int x = 5;
>> signed int y = 2;
>> - signed int z = x / y;
>> + signed int z = x / y; /* { dg-error "call to external libcall" } */
>> }
>> /* { dg-final { scan-assembler-not "sdiv(32)?\t%r" } } */
>> diff --git a/gcc/testsuite/gcc.target/bpf/diag-smod.c
>> b/gcc/testsuite/gcc.target/bpf/diag-smod.c
>> index d3df308217f3..25bcb1e4ffdb 100644
>> --- a/gcc/testsuite/gcc.target/bpf/diag-smod.c
>> +++ b/gcc/testsuite/gcc.target/bpf/diag-smod.c
>> @@ -7,6 +7,6 @@ foo ()
>> {
>> signed int x = 5;
>> signed int y = 2;
>> - signed int z = x % y;
>> + signed int z = x % y; /* { dg-error "call to external libcall" } */
>> }
>> /* { dg-final { scan-assembler-not "smod(32)?\t%r" } } */
