6.6-stable review patch. If anyone has any objections, please let me know.
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From: Alexandre Ghiti alexghiti@rivosinc.com
[ Upstream commit c97bf629963e52b205ed5fbaf151e5bd342f9c63 ]
For now, we use stop_machine() to patch the text and when we use IPIs for remote icache flushes (which is emitted in patch_text_nosync()), the system hangs.
So instead, make sure every CPU executes the stop_machine() patching function and emit a local icache flush there.
Co-developed-by: Björn Töpel bjorn@rivosinc.com Signed-off-by: Björn Töpel bjorn@rivosinc.com Signed-off-by: Alexandre Ghiti alexghiti@rivosinc.com Reviewed-by: Andrea Parri parri.andrea@gmail.com Link: https://lore.kernel.org/r/20240229121056.203419-3-alexghiti@rivosinc.com Signed-off-by: Palmer Dabbelt palmer@rivosinc.com Stable-dep-of: 13134cc94914 ("riscv: kprobes: Fix incorrect address calculation") Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/include/asm/patch.h | 1 + arch/riscv/kernel/ftrace.c | 44 ++++++++++++++++++++++++++++++---- arch/riscv/kernel/patch.c | 16 +++++++++---- 3 files changed, 53 insertions(+), 8 deletions(-)
diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h index e88b52d39eac..9f5d6e14c405 100644 --- a/arch/riscv/include/asm/patch.h +++ b/arch/riscv/include/asm/patch.h @@ -6,6 +6,7 @@ #ifndef _ASM_RISCV_PATCH_H #define _ASM_RISCV_PATCH_H
+int patch_insn_write(void *addr, const void *insn, size_t len); int patch_text_nosync(void *addr, const void *insns, size_t len); int patch_text_set_nosync(void *addr, u8 c, size_t len); int patch_text(void *addr, u32 *insns, int ninsns); diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c index 03a6434a8cdd..6ede2bcce238 100644 --- a/arch/riscv/kernel/ftrace.c +++ b/arch/riscv/kernel/ftrace.c @@ -8,6 +8,7 @@ #include <linux/ftrace.h> #include <linux/uaccess.h> #include <linux/memory.h> +#include <linux/stop_machine.h> #include <asm/cacheflush.h> #include <asm/patch.h>
@@ -75,8 +76,7 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target, make_call_t0(hook_pos, target, call);
/* Replace the auipc-jalr pair at once. Return -EPERM on write error. */ - if (patch_text_nosync - ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE)) + if (patch_insn_write((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE)) return -EPERM;
return 0; @@ -88,7 +88,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
make_call_t0(rec->ip, addr, call);
- if (patch_text_nosync((void *)rec->ip, call, MCOUNT_INSN_SIZE)) + if (patch_insn_write((void *)rec->ip, call, MCOUNT_INSN_SIZE)) return -EPERM;
return 0; @@ -99,7 +99,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, { unsigned int nops[2] = {NOP4, NOP4};
- if (patch_text_nosync((void *)rec->ip, nops, MCOUNT_INSN_SIZE)) + if (patch_insn_write((void *)rec->ip, nops, MCOUNT_INSN_SIZE)) return -EPERM;
return 0; @@ -134,6 +134,42 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
return ret; } + +struct ftrace_modify_param { + int command; + atomic_t cpu_count; +}; + +static int __ftrace_modify_code(void *data) +{ + struct ftrace_modify_param *param = data; + + if (atomic_inc_return(¶m->cpu_count) == num_online_cpus()) { + ftrace_modify_all_code(param->command); + /* + * Make sure the patching store is effective *before* we + * increment the counter which releases all waiting CPUs + * by using the release variant of atomic increment. The + * release pairs with the call to local_flush_icache_all() + * on the waiting CPU. + */ + atomic_inc_return_release(¶m->cpu_count); + } else { + while (atomic_read(¶m->cpu_count) <= num_online_cpus()) + cpu_relax(); + } + + local_flush_icache_all(); + + return 0; +} + +void arch_ftrace_update_code(int command) +{ + struct ftrace_modify_param param = { command, ATOMIC_INIT(0) }; + + stop_machine(__ftrace_modify_code, ¶m, cpu_online_mask); +} #endif
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 30e12b310cab..78387d843aa5 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -196,7 +196,7 @@ int patch_text_set_nosync(void *addr, u8 c, size_t len) } NOKPROBE_SYMBOL(patch_text_set_nosync);
-static int patch_insn_write(void *addr, const void *insn, size_t len) +int patch_insn_write(void *addr, const void *insn, size_t len) { size_t patched = 0; size_t size; @@ -240,16 +240,24 @@ static int patch_text_cb(void *data) if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) { for (i = 0; ret == 0 && i < patch->ninsns; i++) { len = GET_INSN_LENGTH(patch->insns[i]); - ret = patch_text_nosync(patch->addr + i * len, - &patch->insns[i], len); + ret = patch_insn_write(patch->addr + i * len, &patch->insns[i], len); } - atomic_inc(&patch->cpu_count); + /* + * Make sure the patching store is effective *before* we + * increment the counter which releases all waiting CPUs + * by using the release variant of atomic increment. The + * release pairs with the call to local_flush_icache_all() + * on the waiting CPU. + */ + atomic_inc_return_release(&patch->cpu_count); } else { while (atomic_read(&patch->cpu_count) <= num_online_cpus()) cpu_relax(); smp_mb(); }
+ local_flush_icache_all(); + return ret; } NOKPROBE_SYMBOL(patch_text_cb);