Unverified Commit e3f16d63 authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Palmer Dabbelt
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riscv: ftrace: Properly acquire text_mutex to fix a race condition 



As reported by lockdep, some patching was done without acquiring
text_mutex, so there could be a race when mapping the page to patch
since we use the same fixmap entry.

Reported-by: default avatarHan Gao <rabenda.cn@gmail.com>
Reported-by: default avatarVivian Wang <wangruikang@iscas.ac.cn>
Reported-by: default avatarYao Zi <ziyao@disroot.org>
Closes: https://lore.kernel.org/linux-riscv/aGODMpq7TGINddzM@pie.lan/


Tested-by: default avatarYao Zi <ziyao@disroot.org>
Tested-by: default avatarHan Gao <rabenda.cn@gmail.com>
Reviewed-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarAlexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20250711-alex-fixes-v2-1-d85a5438da6c@rivosinc.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@dabbelt.com>
parent 16d74360

arch/riscv/kernel/ftrace.c

+14 −4
Original line number Diff line number Diff line
@@ -14,6 +14,18 @@ 
#include <asm/text-patching.h>



#ifdef CONFIG_DYNAMIC_FTRACE

void ftrace_arch_code_modify_prepare(void)

	__acquires(&text_mutex)

{

	mutex_lock(&text_mutex);

}



void ftrace_arch_code_modify_post_process(void)

	__releases(&text_mutex)

{

	mutex_unlock(&text_mutex);

}



unsigned long ftrace_call_adjust(unsigned long addr)

{

	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
@@ -29,10 +41,8 @@ unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip) 


void arch_ftrace_update_code(int command)

{

	mutex_lock(&text_mutex);

	command |= FTRACE_MAY_SLEEP;

	ftrace_modify_all_code(command);

	mutex_unlock(&text_mutex);

	flush_icache_all();

}
@@ -149,6 +159,8 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) 
	unsigned int nops[2], offset;

	int ret;



	guard(mutex)(&text_mutex);



	ret = ftrace_rec_set_nop_ops(rec);

	if (ret)

		return ret;
@@ -157,9 +169,7 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) 
	nops[0] = to_auipc_t0(offset);

	nops[1] = RISCV_INSN_NOP4;



	mutex_lock(&text_mutex);

	ret = patch_insn_write((void *)pc, nops, 2 * MCOUNT_INSN_SIZE);

	mutex_unlock(&text_mutex);



	return ret;

}