Messages in this thread | | | Date | Mon, 21 Jan 2019 16:23:55 -0500 (EST) | From | Mathieu Desnoyers <> | Subject | Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at C startup and thread creation (v5) |
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----- On Jan 18, 2019, at 12:41 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
> ----- On Jan 14, 2019, at 8:51 PM, Mathieu Desnoyers > mathieu.desnoyers@efficios.com wrote: > > [...] > >> diff --git a/sysdeps/unix/sysv/linux/rseq-sym.c >> b/sysdeps/unix/sysv/linux/rseq-sym.c >> new file mode 100644 >> index 0000000000..6856d0388a > [...] >> +/* volatile because fields can be read/updated by the kernel. */ >> +__thread volatile struct rseq __rseq_abi = { >> + .cpu_id = RSEQ_CPU_ID_UNINITIALIZED, >> +}; >> + >> +/* volatile because refcount can be read/updated by signal handlers. */ >> +__thread volatile uint32_t __rseq_refcount; > > Back to the weak vs non-weak question about those two symbols. I understand > that tagging them as weak symbols has little effect on the dynamic loader > when it loads libc.so. However, I'm worried about that happens when > libc is statically linked into an application, and there happens to > be more than one instance of those symbols (e.g. libc and another library > define the same symbols, and both are statically linked into the same > application). Isn't it a situation where tagging those symbols as "weak" > becomes useful ?
Testing shows that it seems fine to statically link two archives within an executable in a scenario where each .a defines the same symbol, without using "weak", so I won't worry about this further.
Thanks,
Mathieu
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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