From e859cfc75076eeaf798c440a4aba40f79536839c Mon Sep 17 00:00:00 2001 From: Heiko Stuebner Date: Fri, 10 Dec 2021 16:19:19 +0100 Subject: [PATCH 01/14] riscv: prevent null-pointer dereference with sbi_remote_fence_i The callback used inside sbi_remote_fence_i is set at sbi probe time to the needed variant. Before that it is a NULL pointer. flush_icache_all is from its name a pretty generic functionality so probably shoudln't get a "only call after boot-step X" limit. To prevent running into a null pointer dereference, add a default __sbi_rfence_none returning an error code and adapt flush_icache_all to check for an error from the remote fence to then fall back to a simple local_icache_flush(), as that could really only happen if called before other cpu cores are brought up. Signed-off-by: Heiko Stuebner --- arch/riscv/kernel/sbi.c | 10 +++++++++- arch/riscv/mm/cacheflush.c | 15 ++++++++++++--- 2 files changed, 21 insertions(+), 4 deletions(-) diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c index 2438d6fdb788..7f7a9630dc89 100644 --- a/arch/riscv/kernel/sbi.c +++ b/arch/riscv/kernel/sbi.c @@ -14,11 +14,19 @@ unsigned long sbi_spec_version __ro_after_init = SBI_SPEC_VERSION_DEFAULT; EXPORT_SYMBOL(sbi_spec_version); +static int __sbi_rfence_none(int fid, const struct cpumask *cpu_mask, + unsigned long start, unsigned long size, + unsigned long arg4, unsigned long arg5) +{ + return -EOPNOTSUPP; +} + static void (*__sbi_set_timer)(uint64_t stime) __ro_after_init; static int (*__sbi_send_ipi)(const struct cpumask *cpu_mask) __ro_after_init; static int (*__sbi_rfence)(int fid, const struct cpumask *cpu_mask, unsigned long start, unsigned long size, - unsigned long arg4, unsigned long arg5) __ro_after_init; + unsigned long arg4, unsigned long arg5) + __ro_after_init = __sbi_rfence_none; struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0, unsigned long arg1, unsigned long arg2, diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c index 6cb7d96ad9c7..ea9634450557 100644 --- a/arch/riscv/mm/cacheflush.c +++ b/arch/riscv/mm/cacheflush.c @@ -18,10 +18,19 @@ void flush_icache_all(void) { local_flush_icache_all(); - if (IS_ENABLED(CONFIG_RISCV_SBI)) - sbi_remote_fence_i(NULL); - else + if (IS_ENABLED(CONFIG_RISCV_SBI)) { + int ret = sbi_remote_fence_i(NULL); + + /* + * Only fails when sbi-init hasn't run yet, so the kernel + * also is before SMP init, so flushing the local cpu + * is enough. + */ + if (ret) + local_flush_icache_all(); + } else { on_each_cpu(ipi_remote_fence_i, NULL, 1); + } } EXPORT_SYMBOL(flush_icache_all); -- 2.30.2