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Re: [PATCH 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v8)
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- Cc: Will Deacon <will dot deacon at arm dot com>, carlos <carlos at redhat dot com>, Florian Weimer <fweimer at redhat dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, libc-alpha <libc-alpha at sourceware dot org>, Thomas Gleixner <tglx at linutronix dot de>, Ben Maurer <bmaurer at fb dot com>, Peter Zijlstra <peterz at infradead dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>, Boqun Feng <boqun dot feng at gmail dot com>, Dave Watson <davejwatson at fb dot com>, Paul Turner <pjt at google dot com>, Rich Felker <dalias at libc dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, linux-api <linux-api at vger dot kernel dot org>
- Date: Thu, 18 Apr 2019 14:48:34 +0000
- Subject: Re: [PATCH 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v8)
- References: <20190416173216.9028-1-mathieu.desnoyers@efficios.com> <20190416173216.9028-2-mathieu.desnoyers@efficios.com> <364803063.586.1555516769056.JavaMail.zimbra@efficios.com> <alpine.DEB.2.21.1904171601540.32123@digraph.polyomino.org.uk> <1770787324.668.1555530989646.JavaMail.zimbra@efficios.com> <1066731871.915.1555593471194.JavaMail.zimbra@efficios.com>
On Thu, 18 Apr 2019, Mathieu Desnoyers wrote:
> The approach above should work for arm32 be8 vs be32 linker weirdness.
>
> For aarch64, I think we can simply do:
>
> /*
> * aarch64 -mbig-endian generates mixed endianness code vs data:
> * little-endian code and big-endian data. Ensure the RSEQ_SIG signature
> * matches code endianness.
> */
> #define RSEQ_SIG_CODE 0xd428bc00 /* BRK #0x45E0. */
>
> #ifdef __ARM_BIG_ENDIAN
> #define RSEQ_SIG_DATA 0x00bc28d4 /* BRK #0x45E0. */
> #else
> #define RSEQ_SIG_DATA RSEQ_SIG_CODE
> #endif
>
> #define RSEQ_SIG RSEQ_SIG_DATA
>
> Feedback is most welcome,
You'll also need __ASSEMBLER__ conditionals in the installed sys/rseq.h
header so that it only defines constants and doesn't include any C
declarations in that case, if RSEQ_SIG_CODE is meant to be usable in .S
files rather than just inline asm in C files.
--
Joseph S. Myers
joseph@codesourcery.com