On Fri, Nov 08, 2024 at 10:43:54AM -0800, Andrii Nakryiko wrote:
On Sun, Nov 3, 2024 at 9:00 PM Saket Kumar Bhaskar skb99@linux.ibm.com wrote:
Since commit 94746890202cf ("powerpc: Don't add __powerpc_ prefix to syscall entry points") drops _powerpc prefix to syscall entry points, even though powerpc now supports syscall wrapper, so /proc/kallsyms have symbols for syscall entry without powerpc prefix(sys_*).
For this reason, arch specific prefix for syscall functions in powerpc is dropped.
Signed-off-by: Saket Kumar Bhaskar skb99@linux.ibm.com
tools/lib/bpf/libbpf.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 219facd0e66e..3a370fa37d8a 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11110,9 +11110,7 @@ static const char *arch_specific_syscall_pfx(void) #elif defined(__riscv) return "riscv"; #elif defined(__powerpc__)
return "powerpc";-#elif defined(__powerpc64__)
return "powerpc64";
return "";#else return NULL; #endif @@ -11127,7 +11125,11 @@ int probe_kern_syscall_wrapper(int token_fd) if (!ksys_pfx) return 0;
+#if defined(__powerpc__)
snprintf(syscall_name, sizeof(syscall_name), "sys_bpf");+#else snprintf(syscall_name, sizeof(syscall_name), "__%s_sys_bpf", ksys_pfx); +#endif
The problem is that on older versions of kernel it will have this prefix, while on newer ones it won't. So to not break anything on old kernels, we'd need to do feature detection and pick whether to use prefix or not, right?
So it seems like this change needs a bit more work.
pw-bot: cr
Hi Andrii,
IMO since both the patches 7e92e01b7245(powerpc: Provide syscall wrapper) and 94746890202cf(powerpc: Don't add __powerpc_ prefix to syscall entry points) went into the same kernel version v6.1-rc1, there won't me much kernel versions that has only one of these patches.
Also, to test more I tried this patch with ARCH_HAS_SYSCALL_WRAPPER disabled, and it the test passed in this case too.
Thanks, Saket
if (determine_kprobe_perf_type() >= 0) { int pfd;@@ -11272,8 +11274,12 @@ struct bpf_link *bpf_program__attach_ksyscall(const struct bpf_program *prog, * compiler does not know that we have an explicit conditional * as well. */ +#if defined(__powerpc__)
snprintf(func_name, sizeof(func_name), "sys_%s", syscall_name);+#else snprintf(func_name, sizeof(func_name), "__%s_sys_%s", arch_specific_syscall_pfx() ? : "", syscall_name); +#endif } else { snprintf(func_name, sizeof(func_name), "__se_sys_%s", syscall_name); } -- 2.43.5