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[77.2.153.175]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47f63ec7c69sm11186363f8f.17.2026.07.18.02.17.40 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 18 Jul 2026 02:17:41 -0700 (PDT) From: Karl Mehltretter To: Russell King Cc: Karl Mehltretter , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] ARM: smp: set current pointer in assembly before jumping into C Date: Sat, 18 Jul 2026 11:16:00 +0200 Message-Id: <20260718091600.92021-1-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" With CONFIG_KCOV_INSTRUMENT_ALL=3Dy, secondary CPUs fail to come online on ARMv6K/ARMv7 SMP: CPU1: failed to boot: -38 The compiler inserts a call to __sanitizer_cov_trace_pc() at the entry of secondary_start_kernel(), before set_current(task). The KCOV hook dereferences current while TPIDRURO is still uninitialized, causing a data abort before cpu_init() has installed the exception stacks. The secondary CPU consequently never completes startup. Initialize current in the secondary assembly handoff, as __mmap_switched already does for the boot CPU. Fixes: 50596b7559bf ("ARM: smp: Store current pointer in TPIDRURO register = if available") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-fable-5 Signed-off-by: Karl Mehltretter --- Tested on QEMU vexpress-a15 (mainline and v6.12) and realview-eb-mpcore with and without CONFIG_KCOV_INSTRUMENT_ALL. The head-nommu.S change is untested because no currently reachable Kconfig combination enables non-MMU SMP. The redundant set_current(task) is retained to keep the fix minimal. arch/arm/kernel/head-nommu.S | 1 + arch/arm/kernel/head.S | 1 + 2 files changed, 2 insertions(+) diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S index b9d6818f1ee1..f80bbfbd3a6f 100644 --- a/arch/arm/kernel/head-nommu.S +++ b/arch/arm/kernel/head-nommu.S @@ -116,6 +116,7 @@ ENTRY(secondary_startup) ldr r7, __secondary_data @ reload r7 ldr sp, [r7, #12] @ set up the stack pointer ldr r0, [r7, #16] @ set up task pointer + set_current r0, r1 mov fp, #0 b secondary_start_kernel ENDPROC(secondary_startup) diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S index f22c50d4bd41..a22403a629ef 100644 --- a/arch/arm/kernel/head.S +++ b/arch/arm/kernel/head.S @@ -442,6 +442,7 @@ ENTRY(__secondary_switched) adr_l r7, secondary_data + 12 @ get secondary_data.stack ldr sp, [r7] ldr r0, [r7, #4] @ get secondary_data.task + set_current r0, r1 mov fp, #0 b secondary_start_kernel ENDPROC(__secondary_switched) -- 2.43.0