6.1-stable patches

added patches:
	loongarch-fix-and-simplify-fcsr-initialization-on-execve.patch

diff --git a/queue-6.1/loongarch-fix-and-simplify-fcsr-initialization-on-execve.patch b/queue-6.1/loongarch-fix-and-simplify-fcsr-initialization-on-execve.patch
new file mode 100644 (file)
index 0000000..0583017
--- /dev/null
+++ b/queue-6.1/loongarch-fix-and-simplify-fcsr-initialization-on-execve.patch
@@ -0,0 +1,117 @@
+From c2396651309eba291c15e32db8fbe44c738b5921 Mon Sep 17 00:00:00 2001
+From: Xi Ruoyao <xry111@xry111.site>
+Date: Wed, 17 Jan 2024 12:43:08 +0800
+Subject: LoongArch: Fix and simplify fcsr initialization on execve()
+
+From: Xi Ruoyao <xry111@xry111.site>
+
+commit c2396651309eba291c15e32db8fbe44c738b5921 upstream.
+
+There has been a lingering bug in LoongArch Linux systems causing some
+GCC tests to intermittently fail (see Closes link).  I've made a minimal
+reproducer:
+
+    zsh% cat measure.s
+    .align 4
+    .globl _start
+    _start:
+        movfcsr2gr  $a0, $fcsr0
+        bstrpick.w  $a0, $a0, 16, 16
+        beqz        $a0, .ok
+        break       0
+    .ok:
+        li.w        $a7, 93
+        syscall     0
+    zsh% cc mesaure.s -o measure -nostdlib
+    zsh% echo $((1.0/3))
+    0.33333333333333331
+    zsh% while ./measure; do ; done
+
+This while loop should not stop as POSIX is clear that execve must set
+fenv to the default, where FCSR should be zero.  But in fact it will
+just stop after running for a while (normally less than 30 seconds).
+Note that "$((1.0/3))" is needed to reproduce this issue because it
+raises FE_INVALID and makes fcsr0 non-zero.
+
+The problem is we are currently relying on SET_PERSONALITY2() to reset
+current->thread.fpu.fcsr.  But SET_PERSONALITY2() is executed before
+start_thread which calls lose_fpu(0).  We can see if kernel preempt is
+enabled, we may switch to another thread after SET_PERSONALITY2() but
+before lose_fpu(0).  Then bad thing happens: during the thread switch
+the value of the fcsr0 register is stored into current->thread.fpu.fcsr,
+making it dirty again.
+
+The issue can be fixed by setting current->thread.fpu.fcsr after
+lose_fpu(0) because lose_fpu() clears TIF_USEDFPU, then the thread
+switch won't touch current->thread.fpu.fcsr.
+
+The only other architecture setting FCSR in SET_PERSONALITY2() is MIPS.
+I've ran a similar test on MIPS with mainline kernel and it turns out
+MIPS is buggy, too.  Anyway MIPS do this for supporting different FP
+flavors (NaN encodings, etc.) which do not exist on LoongArch.  So for
+LoongArch, we can simply remove the current->thread.fpu.fcsr setting
+from SET_PERSONALITY2() and do it in start_thread(), after lose_fpu(0).
+
+The while loop failing with the mainline kernel has survived one hour
+after this change on LoongArch.
+
+Fixes: 803b0fc5c3f2baa ("LoongArch: Add process management")
+Closes: https://github.com/loongson-community/discussions/issues/7
+Link: https://lore.kernel.org/linux-mips/7a6aa1bbdbbe2e63ae96ff163fab0349f58f1b9e.camel@xry111.site/
+Cc: stable@vger.kernel.org
+Signed-off-by: Xi Ruoyao <xry111@xry111.site>
+Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/loongarch/include/asm/elf.h |    5 -----
+ arch/loongarch/kernel/elf.c      |    5 -----
+ arch/loongarch/kernel/process.c  |    1 +
+ 3 files changed, 1 insertion(+), 10 deletions(-)
+
+--- a/arch/loongarch/include/asm/elf.h
++++ b/arch/loongarch/include/asm/elf.h
+@@ -241,8 +241,6 @@ void loongarch_dump_regs64(u64 *uregs, c
+ do {                                                                  \
+       current->thread.vdso = &vdso_info;                              \
+                                                                       \
+-      loongarch_set_personality_fcsr(state);                          \
+-                                                                      \
+       if (personality(current->personality) != PER_LINUX)             \
+               set_personality(PER_LINUX);                             \
+ } while (0)
+@@ -259,7 +257,6 @@ do {                                                                       \
+       clear_thread_flag(TIF_32BIT_ADDR);                              \
+                                                                       \
+       current->thread.vdso = &vdso_info;                              \
+-      loongarch_set_personality_fcsr(state);                          \
+                                                                       \
+       p = personality(current->personality);                          \
+       if (p != PER_LINUX32 && p != PER_LINUX)                         \
+@@ -340,6 +337,4 @@ extern int arch_elf_pt_proc(void *ehdr,
+ extern int arch_check_elf(void *ehdr, bool has_interpreter, void *interp_ehdr,
+                         struct arch_elf_state *state);
+ 
+-extern void loongarch_set_personality_fcsr(struct arch_elf_state *state);
+-
+ #endif /* _ASM_ELF_H */
+--- a/arch/loongarch/kernel/elf.c
++++ b/arch/loongarch/kernel/elf.c
+@@ -23,8 +23,3 @@ int arch_check_elf(void *_ehdr, bool has
+ {
+       return 0;
+ }
+-
+-void loongarch_set_personality_fcsr(struct arch_elf_state *state)
+-{
+-      current->thread.fpu.fcsr = boot_cpu_data.fpu_csr0;
+-}
+--- a/arch/loongarch/kernel/process.c
++++ b/arch/loongarch/kernel/process.c
+@@ -82,6 +82,7 @@ void start_thread(struct pt_regs *regs,
+       euen = regs->csr_euen & ~(CSR_EUEN_FPEN);
+       regs->csr_euen = euen;
+       lose_fpu(0);
++      current->thread.fpu.fcsr = boot_cpu_data.fpu_csr0;
+ 
+       clear_thread_flag(TIF_LSX_CTX_LIVE);
+       clear_thread_flag(TIF_LASX_CTX_LIVE);

diff --git a/queue-6.1/series b/queue-6.1/series
index 6a76ea8a22e11acabe82b929a8d581fddfa08a03..04d37bbbb8ff7710f56b0c642f1bea2c8b8e0e89 100644 (file)
--- a/queue-6.1/series
+++ b/queue-6.1/series
@@ -301,3 +301,4 @@ md-raid1-use-blk_opf_t-for-read-and-write-operations.patch
 rootfs-fix-support-for-rootfstype-when-root-is-given.patch
 bluetooth-fix-atomicity-violation-in-min-max-_key_size_set.patch
 bpf-fix-re-attachment-branch-in-bpf_tracing_prog_attach.patch
+loongarch-fix-and-simplify-fcsr-initialization-on-execve.patch