netdev - [PATCH v2 bpf 2/3] bpf: show real jited address in bpf_prog_info->jited

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Message-ID: <20181102171617.310178-3-songliubraving@fb.com>
Date:   Fri, 2 Nov 2018 10:16:16 -0700
From:   Song Liu <songliubraving@...com>
To:     <netdev@...r.kernel.org>
CC:     <kernel-team@...com>, Song Liu <songliubraving@...com>,
        <ast@...nel.org>, <daniel@...earbox.net>,
        <sandipan@...ux.vnet.ibm.com>
Subject: [PATCH  v2 bpf 2/3] bpf: show real jited address in bpf_prog_info->jited_ksyms

Currently, jited_ksyms in bpf_prog_info shows page addresses of jited
bpf program. The main reason here is to not expose randomized start
address. However, this is not ideal for detailed profiling (find hot
instructions from stack traces). This patch replaces the page address
with real prog start address.

This change is OK because bpf_prog_get_info_by_fd() is only available
to root.

Signed-off-by: Song Liu <songliubraving@...com>
---
 kernel/bpf/syscall.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index ccb93277aae2..34a9eef5992c 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2172,7 +2172,6 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 			user_ksyms = u64_to_user_ptr(info.jited_ksyms);
 			for (i = 0; i < ulen; i++) {
 				ksym_addr = (ulong) prog->aux->func[i]->bpf_func;
-				ksym_addr &= PAGE_MASK;
 				if (put_user((u64) ksym_addr, &user_ksyms[i]))
 					return -EFAULT;
 			}
-- 
2.17.1