netdev - [PATCH bpf 1/3] bpf: show real jited prog address in /proc/kallsyms

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Message-ID: <20181101070058.2760251-2-songliubraving@fb.com>
Date:   Thu, 1 Nov 2018 00:00:56 -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 bpf 1/3] bpf: show real jited prog address in /proc/kallsyms

Currently, /proc/kallsyms shows page address of jited bpf program. This
is not ideal for detailed profiling (find hot instructions from stack
traces). This patch replaces the page address with real prog start
address.

Signed-off-by: Song Liu <songliubraving@...com>
---
 kernel/bpf/core.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 6377225b2082..1a796e0799ec 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -553,7 +553,6 @@ bool is_bpf_text_address(unsigned long addr)
 int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 		    char *sym)
 {
-	unsigned long symbol_start, symbol_end;
 	struct bpf_prog_aux *aux;
 	unsigned int it = 0;
 	int ret = -ERANGE;
@@ -566,10 +565,9 @@ int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 		if (it++ != symnum)
 			continue;
 
-		bpf_get_prog_addr_region(aux->prog, &symbol_start, &symbol_end);
 		bpf_get_prog_name(aux->prog, sym);
 
-		*value = symbol_start;
+		*value = (unsigned long)aux->prog->bpf_func;
 		*type  = BPF_SYM_ELF_TYPE;
 
 		ret = 0;
-- 
2.17.1