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Message-Id: <20220405031859.17673-1-ccross@google.com>
Date: Mon, 4 Apr 2022 20:18:59 -0700
From: Colin Cross <ccross@...gle.com>
To: musl@...ts.openwall.com
Cc: Colin Cross <ccross@...gle.com>
Subject: [PATCH] dl_iterate_phdr: return empty string for the name of the main program
The glibc man page for dl_iterate_phdr states:
The first object visited by callback is the main program. For the main program, the
dlpi_name field will be an empty string.
This is relied upon by the LLVM ASAN runtime:
https://github.com/llvm/llvm-project/blob/72ec2f76396fe5de5397bfb898993fdb22e2b0da/compiler-rt/lib/asan/asan_linux.cpp#L135
Without this patch, running a binary that has been instrumented with
ASAN fails with:
==4156919==ASan runtime does not come first in initial library list; you should either link runtime to your application or manually preload it with LD_PRELOAD.
Use a constant empty string instead of the DSO name field for the first
entry in the DSO list.
---
This has come up previously on the mailing list at
https://www.openwall.com/lists/musl/2018/05/28/1.
ldso/dynlink.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index fd0d38e9..d2e22a0b 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -2323,12 +2323,15 @@ no_redir:
int dl_iterate_phdr(int(*callback)(struct dl_phdr_info *info, size_t size, void *data), void *data)
{
+ static const char* empty_string = "";
struct dso *current;
struct dl_phdr_info info;
int ret = 0;
for(current = head; current;) {
info.dlpi_addr = (uintptr_t)current->base;
- info.dlpi_name = current->name;
+ /* glibc uses an empty string for the main program */
+ info.dlpi_name = (current == head) ? empty_string :
+ current->name;
info.dlpi_phdr = current->phdr;
info.dlpi_phnum = current->phnum;
info.dlpi_adds = gencnt;
--
2.35.1.1094.g7c7d902a7c-goog
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