From: Jeremy Linton <jeremy.linton@arm.com> To: linux-arm-kernel@lists.infradead.org Cc: catalin.marinas@arm.com, will@kernel.org, keescook@chromium.org, Jason@zx2c4.com, gustavoars@kernel.org, mark.rutland@arm.com, rostedt@goodmis.org, arnd@arndb.de, broonie@kernel.org, guohui@uniontech.com, Manoj.Iyer@arm.com, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Jeremy Linton <jeremy.linton@arm.com> Subject: [PATCH 0/1] Bring kstack randomized perf closer to unrandomized Date: Tue, 5 Mar 2024 16:18:23 -0600 [thread overview] Message-ID: <20240305221824.3300322-1-jeremy.linton@arm.com> (raw) Currently with kstack randomization there is somewhere on the order of 5x worse variation in response latencies vs unrandomized syscalls. This is down from ~10x on pre 6.2 kernels where the RNG reseeding was moved out of the syscall path, but get_random_uXX() still contains a fair amount of additional global state manipulation which is problematic. So, lets replace the full get_random_u16 in the syscall path with prandom_u32_state(). This also has the advantage of bringing the randomized and unrandomized overall syscall performace much closer together. Although in the syscall path, prandom_u32_state() remains measurably worse than other architectures relying on non-random functions (cycle counters) with respect to perf/latency measurements. By comparison, the algorithm presented in the RFC which had basically no impact given recent OoO cores are able to hide all of the overhead from the the handful of additional instructions. I'm still looking for suggestions reseeding prandom_u32_state() if needed or improving the performace of get_random_u16. so consider this somewhate more than an RFC and maybe less of a full patch request. RFC->V1: Replace custom inline RNG with prandom_u32_state Jeremy Linton (1): arm64: syscall: Direct PRNG kstack randomization arch/arm64/kernel/syscall.c | 42 ++++++++++++++++++++++++++++++++++++- 1 file changed, 41 insertions(+), 1 deletion(-) -- 2.43.0
WARNING: multiple messages have this Message-ID (diff)
From: Jeremy Linton <jeremy.linton@arm.com> To: linux-arm-kernel@lists.infradead.org Cc: catalin.marinas@arm.com, will@kernel.org, keescook@chromium.org, Jason@zx2c4.com, gustavoars@kernel.org, mark.rutland@arm.com, rostedt@goodmis.org, arnd@arndb.de, broonie@kernel.org, guohui@uniontech.com, Manoj.Iyer@arm.com, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Jeremy Linton <jeremy.linton@arm.com> Subject: [PATCH 0/1] Bring kstack randomized perf closer to unrandomized Date: Tue, 5 Mar 2024 16:18:23 -0600 [thread overview] Message-ID: <20240305221824.3300322-1-jeremy.linton@arm.com> (raw) Currently with kstack randomization there is somewhere on the order of 5x worse variation in response latencies vs unrandomized syscalls. This is down from ~10x on pre 6.2 kernels where the RNG reseeding was moved out of the syscall path, but get_random_uXX() still contains a fair amount of additional global state manipulation which is problematic. So, lets replace the full get_random_u16 in the syscall path with prandom_u32_state(). This also has the advantage of bringing the randomized and unrandomized overall syscall performace much closer together. Although in the syscall path, prandom_u32_state() remains measurably worse than other architectures relying on non-random functions (cycle counters) with respect to perf/latency measurements. By comparison, the algorithm presented in the RFC which had basically no impact given recent OoO cores are able to hide all of the overhead from the the handful of additional instructions. I'm still looking for suggestions reseeding prandom_u32_state() if needed or improving the performace of get_random_u16. so consider this somewhate more than an RFC and maybe less of a full patch request. RFC->V1: Replace custom inline RNG with prandom_u32_state Jeremy Linton (1): arm64: syscall: Direct PRNG kstack randomization arch/arm64/kernel/syscall.c | 42 ++++++++++++++++++++++++++++++++++++- 1 file changed, 41 insertions(+), 1 deletion(-) -- 2.43.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2024-03-05 22:18 UTC|newest] Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-03-05 22:18 Jeremy Linton [this message] 2024-03-05 22:18 ` [PATCH 0/1] Bring kstack randomized perf closer to unrandomized Jeremy Linton 2024-03-05 22:18 ` [PATCH 1/1] arm64: syscall: Direct PRNG kstack randomization Jeremy Linton 2024-03-05 22:18 ` Jeremy Linton 2024-03-05 23:33 ` Kees Cook 2024-03-05 23:33 ` Kees Cook 2024-03-06 20:46 ` Arnd Bergmann 2024-03-06 20:46 ` Arnd Bergmann 2024-03-06 21:54 ` Jeremy Linton 2024-03-06 21:54 ` Jeremy Linton 2024-03-07 11:10 ` Arnd Bergmann 2024-03-07 11:10 ` Arnd Bergmann 2024-03-07 19:10 ` Kees Cook 2024-03-07 19:10 ` Kees Cook 2024-03-07 21:56 ` Arnd Bergmann 2024-03-07 21:56 ` Arnd Bergmann 2024-03-07 19:15 ` Kees Cook 2024-03-07 19:15 ` Kees Cook 2024-03-07 22:02 ` Arnd Bergmann 2024-03-07 22:02 ` Arnd Bergmann 2024-03-08 16:49 ` Jeremy Linton 2024-03-08 16:49 ` Jeremy Linton 2024-03-08 20:29 ` Arnd Bergmann 2024-03-08 20:29 ` Arnd Bergmann 2024-03-22 23:40 ` Jeremy Linton 2024-03-22 23:40 ` Jeremy Linton 2024-03-23 12:47 ` Arnd Bergmann 2024-03-23 12:47 ` Arnd Bergmann 2024-03-07 19:05 ` kernel test robot 2024-03-07 19:05 ` kernel test robot
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20240305221824.3300322-1-jeremy.linton@arm.com \ --to=jeremy.linton@arm.com \ --cc=Jason@zx2c4.com \ --cc=Manoj.Iyer@arm.com \ --cc=arnd@arndb.de \ --cc=broonie@kernel.org \ --cc=catalin.marinas@arm.com \ --cc=guohui@uniontech.com \ --cc=gustavoars@kernel.org \ --cc=keescook@chromium.org \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=linux-hardening@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=mark.rutland@arm.com \ --cc=rostedt@goodmis.org \ --cc=will@kernel.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.