linux-kernel - [PATCH v2] RISC-V: Don't mark init section as non-executable

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Date:   Mon,  1 Jun 2020 10:36:56 +0530
From:   Anup Patel <anup.patel@....com>
To:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>
Cc:     Atish Patra <atish.patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        Anup Patel <anup@...infault.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Anup Patel <anup.patel@....com>, stable@...r.kernel.org
Subject: [PATCH v2] RISC-V: Don't mark init section as non-executable

The head text section (i.e. _start, secondary_start_sbi, etc) and the
init section fall under same page table level-1 mapping.

Currently, the runtime CPU hotplug is broken because we are marking
init section as non-executable which in-turn marks head text section
as non-executable.

Further investigating other architectures, it seems marking the init
section as non-executable is redundant because the init section pages
are anyway poisoned and freed.

To fix broken runtime CPU hotplug, we simply remove the code marking
the init section as non-executable.

Fixes: d27c3c90817e ("riscv: add STRICT_KERNEL_RWX support")
Cc: stable@...r.kernel.org
Signed-off-by: Anup Patel <anup.patel@....com>
---
Changes since v1:
 - Updated free_initmem() is same as generic free_initmem() defined in
   init/main.c so we completely remove free_initmem() from arch/riscv
---
 arch/riscv/mm/init.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 736de6c8739f..fdc772f57edc 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -479,17 +479,6 @@ static void __init setup_vm_final(void)
 	csr_write(CSR_SATP, PFN_DOWN(__pa_symbol(swapper_pg_dir)) | SATP_MODE);
 	local_flush_tlb_all();
 }
-
-void free_initmem(void)
-{
-	unsigned long init_begin = (unsigned long)__init_begin;
-	unsigned long init_end = (unsigned long)__init_end;
-
-	/* Make the region as non-execuatble. */
-	set_memory_nx(init_begin, (init_end - init_begin) >> PAGE_SHIFT);
-	free_initmem_default(POISON_FREE_INITMEM);
-}
-
 #else
 asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 {
-- 
2.25.1