Re: [PATCH] perf syscalltbl: Add syscalltbl__id_at_idx() with no syscall table support

[Charlie Jenkins <charlie@rivosinc.com>]

On Fri, Aug 30, 2024 at 09:30:50PM -0700, Charlie Jenkins wrote:
> When HAVE_SYSCALL_TABLE_SUPPORT is not defined, neither is
> syscalltbl__id_at_idx(). However, this function is expected to be
> defined when HAVE_BPF_SKEL is defined.
> 
> Return -1 from syscalltbl__id_at_idx() to match the other functions when
> HAVE_SYSCALL_TABLE_SUPPORT is not defined.
> 
> Without this, compiling perf on riscv when libtraceevents, libelf, and
> clang are available will cause the functions trying to call
> syscalltbl__id_at_idx() to be compiled. This results in the following
> error:
> 
> /usr/bin/ld: perf-in.o: in function `.L0 ':
> builtin-trace.c:(.text+0x60b14): undefined reference to `syscalltbl__id_at_idx'
> /usr/bin/ld: builtin-trace.c:(.text+0x60c6c): undefined reference to `syscalltbl__id_at_idx'
> /usr/bin/ld: perf-in.o: in function `.L2564':
> builtin-trace.c:(.text+0x60cb6): undefined reference to `syscalltbl__id_at_idx'
> collect2: error: ld returned 1 exit status
> make[2]: *** [Makefile.perf:793: perf] Error 1
> make[1]: *** [Makefile.perf:290: sub-make] Error 2
> make: *** [Makefile:70: all] Error 2
> make: Leaving directory '/src/linux-6.11-rc5/tools/perf'
> 
> This patch resolves this issue for all architectures which do not define
> HAVE_SYSCALL_TABLE_SUPPORT.
> 
> $ ./perf trace -e syscalls:sys_enter_mmap --max-events=1 ls
> 0.000 ls/287 syscalls:sys_enter_mmap(__syscall_nr: 222, len: 9939, prot: READ, flags: PRIVATE, fd: 3)
> 
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> Reported-by: David Abdurachmanov <davidlt@rivosinc.com>
> Suggested-by: David Abdurachmanov <davidlt@rivosinc.com>
> Fixes: 7a2fb5619cc1 ("perf trace: Fix iteration of syscall ids in syscalltbl->entries")
> ---
>  tools/perf/util/syscalltbl.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/tools/perf/util/syscalltbl.c b/tools/perf/util/syscalltbl.c
> index 0dd26b991b3f..12654460428f 100644
> --- a/tools/perf/util/syscalltbl.c
> +++ b/tools/perf/util/syscalltbl.c
> @@ -188,4 +188,9 @@ int syscalltbl__strglobmatch_first(struct syscalltbl *tbl, const char *syscall_g
>  {
>  	return syscalltbl__strglobmatch_next(tbl, syscall_glob, idx);
>  }
> +
> +int syscalltbl__id_at_idx(struct syscalltbl *tbl __always_unused, int idx __always_unused)
> +{
> +	return -1;
> +}
>  #endif /* HAVE_SYSCALL_TABLE_SUPPORT */
> 
> ---
> base-commit: 985bf40edf4343dcb04c33f58b40b4a85c1776d4
> change-id: 20240830-perf_syscalltbl_fix-4f586221795e
> -- 
> - Charlie
> 

Can this please be picked up? Compilation on riscv (along with any of
the other architectures that don't have syscall table support) is
broken. The long term solution is to add support for the syscall table
on riscv. I will send out a patch for that, but in the meantime it would
be great to have this in the tree.

- Charlie