From 9de52a755cfb6da5ee21a07e3a868bdc8fbfccb3 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Thu, 30 Nov 2017 11:56:37 +0000 Subject: [PATCH] arm64: fpsimd: Fix failure to restore FPSIMD state after signals MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The fpsimd_update_current_state() function is responsible for loading the FPSIMD state from the user signal frame into the current task during sigreturn. When implementing support for SVE, conditional code was added to this function in order to handle the case where SVE state need to be loaded for the task and merged with the FPSIMD data from the signal frame; however, the FPSIMD-only case was unintentionally dropped. As a result of this, sigreturn does not currently restore the FPSIMD state of the task, except in the case where the system supports SVE and the signal frame contains SVE state in addition to FPSIMD state. This patch fixes this bug by making the copy-in of the FPSIMD data from the signal frame to thread_struct unconditional. This remains a performance regression from v4.14, since the FPSIMD state is now copied into thread_struct and then loaded back, instead of _only_ being loaded into the CPU FPSIMD registers. However, it is essential to call task_fpsimd_load() here anyway in order to ensure that the SVE enable bit in CPACR_EL1 is set correctly before returning to userspace. This could use some refactoring, but since sigreturn is not a fast path I have kept this patch as a pure fix and left the refactoring for later. Cc: Catalin Marinas Cc: Ard Biesheuvel Fixes: 8cd969d28fd2 ("arm64/sve: Signal handling support") Reported-by: Alex Bennée Tested-by: Alex Bennée Reviewed-by: Alex Bennée Signed-off-by: Dave Martin Signed-off-by: Will Deacon --- arch/arm64/kernel/fpsimd.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 143b3e72c25e..5084e699447a 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -1026,10 +1026,10 @@ void fpsimd_update_current_state(struct fpsimd_state *state) local_bh_disable(); - if (system_supports_sve() && test_thread_flag(TIF_SVE)) { - current->thread.fpsimd_state = *state; + current->thread.fpsimd_state = *state; + if (system_supports_sve() && test_thread_flag(TIF_SVE)) fpsimd_to_sve(current); - } + task_fpsimd_load(); if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) { -- 2.30.2