RISC-V: take text_mutex during alternative patching

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 <linux@roeck-us.net> Link: https://lore.kernel.org/all/20230212154333.GA3760469@roeck-us.net/ Signed-off-by: Conor Dooley <conor.dooley@microchip.com> Reviewed-by: Samuel Holland <samuel@sholland.org> Tested-by: Guenter Roeck <linux@roeck-us.net> Link: https://lore.kernel.org/r/20230212194735.491785-1-conor@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
torvalds · Feb 22, 2023 · 9493e6f · 9493e6f
1 parent dac8bf1
commit 9493e6f
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Showing 3 changed files with 13 additions and 2 deletions.
diff --git a/arch/riscv/errata/sifive/errata.c b/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>
@@ -107,8 +108,10 @@ 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_ALT_PTR(alt),
 					  alt->alt_len);
+			mutex_lock(&text_mutex);
 			cpu_apply_errata |= tmp;
 		}
 	}

diff --git a/arch/riscv/errata/thead/errata.c b/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>
@@ -101,10 +102,13 @@ void __init_or_module thead_errata_patch_func(struct alt_entry *begin, struct al
 			altptr = ALT_ALT_PTR(alt);
 
 			/* On vm-alternatives, the mmu isn't running yet */
-			if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+			if (stage == RISCV_ALTERNATIVES_EARLY_BOOT) {
 				memcpy(oldptr, altptr, alt->alt_len);
-			else
+			} else {
+				mutex_lock(&text_mutex);
 				patch_text_nosync(oldptr, altptr, alt->alt_len);
+				mutex_unlock(&text_mutex);
+			}
 		}
 	}
 

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
@@ -10,6 +10,7 @@
 #include <linux/ctype.h>
 #include <linux/libfdt.h>
 #include <linux/log2.h>
+#include <linux/memory.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <asm/alternative.h>
@@ -292,8 +293,11 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin,
 
 		oldptr = ALT_OLD_PTR(alt);
 		altptr = ALT_ALT_PTR(alt);
+
+		mutex_lock(&text_mutex);
 		patch_text_nosync(oldptr, altptr, alt->alt_len);
 		riscv_alternative_fix_offsets(oldptr, alt->alt_len, oldptr - altptr);
+		mutex_unlock(&text_mutex);
 	}
 }
 #endif