Unverified Commit 6ca445d8 authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Palmer Dabbelt
Browse files

riscv: Fix early ftrace nop patching 



Commit c97bf629 ("riscv: Fix text patching when IPI are used")
converted ftrace_make_nop() to use patch_insn_write() which does not
emit any icache flush relying entirely on __ftrace_modify_code() to do
that.

But we missed that ftrace_make_nop() was called very early directly when
converting mcount calls into nops (actually on riscv it converts 2B nops
emitted by the compiler into 4B nops).

This caused crashes on multiple HW as reported by Conor and Björn since
the booting core could have half-patched instructions in its icache
which would trigger an illegal instruction trap: fix this by emitting a
local flush icache when early patching nops.

Fixes: c97bf629 ("riscv: Fix text patching when IPI are used")
Signed-off-by: default avatarAlexandre Ghiti <alexghiti@rivosinc.com>
Reported-by: default avatarConor Dooley <conor.dooley@microchip.com>
Tested-by: default avatarConor Dooley <conor.dooley@microchip.com>
Reviewed-by: default avatarBjörn Töpel <bjorn@rivosinc.com>
Tested-by: default avatarBjörn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20240523115134.70380-1-alexghiti@rivosinc.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 46cad6cd

arch/riscv/include/asm/cacheflush.h

+6 −0
Original line number Diff line number Diff line
@@ -13,6 +13,12 @@ static inline void local_flush_icache_all(void) 
	asm volatile ("fence.i" ::: "memory");

}



static inline void local_flush_icache_range(unsigned long start,

					    unsigned long end)

{

	local_flush_icache_all();

}



#define PG_dcache_clean PG_arch_1



static inline void flush_dcache_folio(struct folio *folio)

arch/riscv/kernel/ftrace.c

+3 −0
Original line number Diff line number Diff line
@@ -120,6 +120,9 @@ 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;

}