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FAILED: patch "[PATCH] RISC-V: take text_mutex during alternative patching" failed to apply to 6.2-stable tree

PATCH [email protected] 1 participant 1 message Mar 7, 2023

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The patch below does not apply to the 6.2-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.2.y
git checkout FETCH_HEAD
git cherry-pick -x 9493e6f3ce02f44c21aa19f3cbf3b9aa05479d06
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '[email protected]' --subject-prefix 'PATCH 6.2.y' HEAD^..

Possible dependencies:

9493e6f3ce02 ("RISC-V: take text_mutex during alternative patching") bfd6fc5d8014 ("riscv: Fix early alternative patching")
8d23e94a4433 ("riscv: switch to relative alternative entries")
4bf8860760d9 ("riscv: cpufeature: extend riscv_cpufeature_patch_func to all ISA extensions") abcc445acdbe ("riscv: move riscv_noncoherent_supported() out of ZICBOM probe") 61a9b7129070 ("Merge patch series "Putting some basic order on isa extension lists"")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9493e6f3ce02f44c21aa19f3cbf3b9aa05479d06 Mon Sep 17 00:00:00 2001
From: Conor Dooley <[email protected]>
Date: Sun, 12 Feb 2023 19:47:36 +0000
Subject: [PATCH] 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 702e64550b12 ("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 ff689fd21cb1 ("riscv: add RISC-V Svpbmt extension support")
Fixes a35707c3d850 ("riscv: add memory-type errata for T-Head")
Fixes 1a0e5dbd3723 ("riscv: sifive: Add SiFive alternative ports")
Reported-by Guenter Roeck <[email protected]>
Link https://lore.kernel.org/all/[email protected]/ open here
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] open here
Cc [email protected]
Signed-off-by Palmer Dabbelt <[email protected]>
arch/riscv/errata/sifive/errata.c +3 -0
index ef9a4eec0dba..da55cb247e89 100644
@@ -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;
 		}
 	}
arch/riscv/errata/thead/errata.c +6 -2
index 1dd90a5f86f0..3b96a06d3c54 100644
@@ -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);
+			}
 		}
 	}
arch/riscv/kernel/cpufeature.c +4 -0
index 21fb567e1b22..59d58ee0f68d 100644
@@ -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