Unverified Commit edf2d546 authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Palmer Dabbelt
Browse files

riscv: patch: Flush the icache right after patching to avoid illegal insns 



We cannot delay the icache flush after patching some functions as we may
have patched a function that will get called before the icache flush.

The only way to completely avoid such scenario is by flushing the icache
as soon as we patch a function. This will probably be costly as we don't
batch the icache maintenance anymore.

Fixes: 6ca445d8 ("riscv: Fix early ftrace nop patching")
Reported-by: default avatarConor Dooley <conor.dooley@microchip.com>
Closes: https://lore.kernel.org/linux-riscv/20240613-lubricant-breath-061192a9489a@wendy/


Signed-off-by: default avatarAlexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: default avatarAndy Chiu <andy.chiu@sifive.com>
Link: https://lore.kernel.org/r/20240624082141.153871-1-alexghiti@rivosinc.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 04a2aef5

arch/riscv/kernel/ftrace.c

+2 −5
Original line number Diff line number Diff line
@@ -120,9 +120,6 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) 
	out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);

	mutex_unlock(&text_mutex);



	if (!mod)

		local_flush_icache_range(rec->ip, rec->ip + MCOUNT_INSN_SIZE);



	return out;

}
@@ -156,9 +153,9 @@ static int __ftrace_modify_code(void *data) 
	} else {

		while (atomic_read(&param->cpu_count) <= num_online_cpus())

			cpu_relax();

	}



		local_flush_icache_all();

	}



	return 0;

}

arch/riscv/kernel/patch.c

+18 −8
Original line number Diff line number Diff line
@@ -89,6 +89,14 @@ static int __patch_insn_set(void *addr, u8 c, size_t len) 


	memset(waddr, c, len);



	/*

	 * We could have just patched a function that is about to be

	 * called so make sure we don't execute partially patched

	 * instructions by flushing the icache as soon as possible.

	 */

	local_flush_icache_range((unsigned long)waddr,

				 (unsigned long)waddr + len);



	patch_unmap(FIX_TEXT_POKE0);



	if (across_pages)
@@ -135,6 +143,14 @@ static int __patch_insn_write(void *addr, const void *insn, size_t len) 


	ret = copy_to_kernel_nofault(waddr, insn, len);



	/*

	 * We could have just patched a function that is about to be

	 * called so make sure we don't execute partially patched

	 * instructions by flushing the icache as soon as possible.

	 */

	local_flush_icache_range((unsigned long)waddr,

				 (unsigned long)waddr + len);



	patch_unmap(FIX_TEXT_POKE0);



	if (across_pages)
@@ -189,9 +205,6 @@ int patch_text_set_nosync(void *addr, u8 c, size_t len) 


	ret = patch_insn_set(tp, c, len);



	if (!ret)

		flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len);



	return ret;

}

NOKPROBE_SYMBOL(patch_text_set_nosync);
@@ -224,9 +237,6 @@ int patch_text_nosync(void *addr, const void *insns, size_t len) 


	ret = patch_insn_write(tp, insns, len);



	if (!ret)

		flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len);



	return ret;

}

NOKPROBE_SYMBOL(patch_text_nosync);
@@ -253,9 +263,9 @@ static int patch_text_cb(void *data) 
	} else {

		while (atomic_read(&patch->cpu_count) <= num_online_cpus())

			cpu_relax();

	}



		local_flush_icache_all();

	}



	return ret;

}