mips, uasm: Add workaround for Loongson-2F nop CPU errata

This patch implements a workaround for the Loongson-2F nop in generated,
code, if the existing option CONFIG_CPU_NOP_WORKAROUND is set. Before,
the binutils option -mfix-loongson2f-nop was enabled, but no workaround
was done when emitting MIPS code. Now, the nop pseudo instruction is
emitted as "or ax,ax,zero" instead of the default "sll zero,zero,0". This
is consistent with the workaround implemented by binutils.

Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Link: https://sourceware.org/legacy-ml/binutils/2009-11/msg00387.html
Link: https://lore.kernel.org/bpf/20211005165408.2305108-3-johan.almbladh@anyfinetworks.com

diff --git a/arch/mips/include/asm/uasm.h b/arch/mips/include/asm/uasm.h
index 5efa4e2dc9abb6e2ba9d5ea2b97bba5cd38f97d7..296bcf31abb57176fc1e195a231ceff4da10dd5c 100644 (file)
--- a/arch/mips/include/asm/uasm.h
+++ b/arch/mips/include/asm/uasm.h
@@ -249,7 +249,11 @@ static inline void uasm_l##lb(struct uasm_label **lab, u32 *addr)  \
 #define uasm_i_bnezl(buf, rs, off) uasm_i_bnel(buf, rs, 0, off)
 #define uasm_i_ehb(buf) uasm_i_sll(buf, 0, 0, 3)
 #define uasm_i_move(buf, a, b) UASM_i_ADDU(buf, a, 0, b)
+#ifdef CONFIG_CPU_NOP_WORKAROUNDS
+#define uasm_i_nop(buf) uasm_i_or(buf, 1, 1, 0)
+#else
 #define uasm_i_nop(buf) uasm_i_sll(buf, 0, 0, 0)
+#endif
 #define uasm_i_ssnop(buf) uasm_i_sll(buf, 0, 0, 1)
 
 static inline void uasm_i_drotr_safe(u32 **p, unsigned int a1,