RISC-V: take text_mutex during alternative patching

commit 9493e6f upstream.

Guenter reported a splat during boot, that Samuel pointed out was the
lockdep assertion failing in patch_insn_write():

WARNING: CPU: 0 PID: 0 at arch/riscv/kernel/patch.c:63 patch_insn_write+0x222/0x2f6
epc : patch_insn_write+0x222/0x2f6
 ra : patch_insn_write+0x21e/0x2f6
epc : ffffffff800068c6 ra : ffffffff800068c2 sp : ffffffff81803df0
 gp : ffffffff81a1ab78 tp : ffffffff81814f80 t0 : ffffffffffffe000
 t1 : 0000000000000001 t2 : 4c45203a76637369 s0 : ffffffff81803e40
 s1 : 0000000000000004 a0 : 0000000000000000 a1 : ffffffffffffffff
 a2 : 0000000000000004 a3 : 0000000000000000 a4 : 0000000000000001
 a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000052464e43
 s2 : ffffffff80b4889c s3 : 000000000000082c s4 : ffffffff80b48828
 s5 : 0000000000000828 s6 : ffffffff8131a0a0 s7 : 0000000000000fff
 s8 : 0000000008000200 s9 : ffffffff8131a520 s10: 0000000000000018
 s11: 000000000000000b t3 : 0000000000000001 t4 : 000000000000000d
 t5 : ffffffffd8180000 t6 : ffffffff81803bc8
status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003
[<ffffffff800068c6>] patch_insn_write+0x222/0x2f6
[<ffffffff80006a36>] patch_text_nosync+0xc/0x2a
[<ffffffff80003b86>] riscv_cpufeature_patch_func+0x52/0x98
[<ffffffff80003348>] _apply_alternatives+0x46/0x86
[<ffffffff80c02d36>] apply_boot_alternatives+0x3c/0xfa
[<ffffffff80c03ad8>] setup_arch+0x584/0x5b8
[<ffffffff80c0075a>] start_kernel+0xa2/0x8f8

This issue was exposed by 702e645 ("riscv: fpu: switch has_fpu() to
riscv_has_extension_likely()"), as it is the patching in has_fpu() that
triggers the splats in Guenter's report.

Take the text_mutex before doing any code patching to satisfy lockdep.

Fixes: ff689fd ("riscv: add RISC-V Svpbmt extension support")
Fixes: a35707c ("riscv: add memory-type errata for T-Head")
Fixes: 1a0e5db ("riscv: sifive: Add SiFive alternative ports")
Reported-by: Guenter Roeck <[email protected]>
Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Conor Dooley <[email protected]>
Reviewed-by: Samuel Holland <[email protected]>
Tested-by: Guenter Roeck <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Cc: [email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

Author: ConchuOD

arch/riscv/errata/sifive/errata.c

@@ -4,6 +4,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/memory.h>
 #include <linux/module.h>
 #include <linux/string.h>
 #include <linux/bug.h>
@@ -107,7 +108,9 @@ void __init_or_module sifive_errata_patch_func(struct alt_entry *begin,
 
 		tmp = (1U << alt->errata_id);
 		if (cpu_req_errata & tmp) {
+			mutex_lock(&text_mutex);
 			patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
+			mutex_lock(&text_mutex);
 			cpu_apply_errata |= tmp;
 		}
 	}

arch/riscv/errata/thead/errata.c

@@ -5,6 +5,7 @@
 
 #include <linux/bug.h>
 #include <linux/kernel.h>
+#include <linux/memory.h>
 #include <linux/module.h>
 #include <linux/string.h>
 #include <linux/uaccess.h>
@@ -78,11 +79,14 @@ void __init_or_module thead_errata_patch_func(struct alt_entry *begin, struct al
 		tmp = (1U << alt->errata_id);
 		if (cpu_req_errata & tmp) {
 			/* On vm-alternatives, the mmu isn't running yet */
-			if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+			if (stage == RISCV_ALTERNATIVES_EARLY_BOOT) {
 				memcpy((void *)__pa_symbol(alt->old_ptr),
 				       (void *)__pa_symbol(alt->alt_ptr), alt->alt_len);
-			else
+			} else {
+				mutex_lock(&text_mutex);
 				patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
+				mutex_unlock(&text_mutex);
+			}
 		}
 	}
 

arch/riscv/kernel/cpufeature.c

@@ -9,6 +9,7 @@
 #include <linux/bitmap.h>
 #include <linux/ctype.h>
 #include <linux/libfdt.h>
+#include <linux/memory.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <asm/alternative.h>
@@ -316,8 +317,11 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin,
 		}
 
 		tmp = (1U << alt->errata_id);
-		if (cpu_req_feature & tmp)
+		if (cpu_req_feature & tmp) {
+			mutex_lock(&text_mutex);
 			patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
+			mutex_unlock(&text_mutex);
+		}
 	}
 }
 #endif