From 853c35003abe5a1430a432f32fa325d6021f2d2f Mon Sep 17 00:00:00 2001 From: Khem Raj Date: Tue, 24 Sep 2019 23:57:04 -0700 Subject: musl: Fix riscv64 CAS functions Signed-off-by: Khem Raj Signed-off-by: Richard Purdie --- ...-operand-specifiers-in-the-riscv64-CAS-ro.patch | 55 ++++++++++++++++++++++ meta/recipes-core/musl/musl_git.bb | 1 + 2 files changed, 56 insertions(+) create mode 100644 meta/recipes-core/musl/musl/0001-correct-the-operand-specifiers-in-the-riscv64-CAS-ro.patch diff --git a/meta/recipes-core/musl/musl/0001-correct-the-operand-specifiers-in-the-riscv64-CAS-ro.patch b/meta/recipes-core/musl/musl/0001-correct-the-operand-specifiers-in-the-riscv64-CAS-ro.patch new file mode 100644 index 0000000000..09b71cb299 --- /dev/null +++ b/meta/recipes-core/musl/musl/0001-correct-the-operand-specifiers-in-the-riscv64-CAS-ro.patch @@ -0,0 +1,55 @@ +From 59f2954fcaacd9426827c69a729e2647cb9977e5 Mon Sep 17 00:00:00 2001 +From: Palmer Dabbelt +Date: Tue, 24 Sep 2019 20:30:15 -0700 +Subject: [PATCH] correct the operand specifiers in the riscv64 CAS routines + +The operand sepcifiers in a_cas and a_casp for riscv64 were incorrect: +there's a backwards branch in the routine, so despite tmp being written +at the end of the assembly fragment it cannot be allocated in one of the +input registers because the input values may be needed for another trip +around the loop. + +For code that follows the guarnteed forward progress requirements, he +backwards branch is rarely taken: SiFive's hardware only fails a store +conditional on execptional cases (ie, instruction cache misses inside +the loop), and until recently a bug in QEMU allowed back-to-back +store conditionals to succeed. The bug has been fixed in the latest +QEMU release, but it turns out that the fix caused this latent bug in +musl to manifest. + +Full disclosure: I haven't actually even compiled musl. I just guessed +this would fix a bug introducted by the new QEMU behavior, Alistair +(CC'd) actually checked it fixes the problem. The rest is just +conjecture. + +Upstream-Status: Submitted +Signed-off-by: Khem Raj +--- + arch/riscv64/atomic_arch.h | 4 ++-- + 1 file changed, 2 insertions(+), 2 deletions(-) + +diff --git a/arch/riscv64/atomic_arch.h b/arch/riscv64/atomic_arch.h +index c9765342..41ad4d04 100644 +--- a/arch/riscv64/atomic_arch.h ++++ b/arch/riscv64/atomic_arch.h +@@ -14,7 +14,7 @@ static inline int a_cas(volatile int *p, int t, int s) + " sc.w.aqrl %1, %4, (%2)\n" + " bnez %1, 1b\n" + "1:" +- : "=&r"(old), "=r"(tmp) ++ : "=&r"(old), "=&r"(tmp) + : "r"(p), "r"(t), "r"(s) + : "memory"); + return old; +@@ -31,7 +31,7 @@ static inline void *a_cas_p(volatile void *p, void *t, void *s) + " sc.d.aqrl %1, %4, (%2)\n" + " bnez %1, 1b\n" + "1:" +- : "=&r"(old), "=r"(tmp) ++ : "=&r"(old), "=&r"(tmp) + : "r"(p), "r"(t), "r"(s) + : "memory"); + return old; +-- +2.23.0 + diff --git a/meta/recipes-core/musl/musl_git.bb b/meta/recipes-core/musl/musl_git.bb index 87453be07f..335d53d42f 100644 --- a/meta/recipes-core/musl/musl_git.bb +++ b/meta/recipes-core/musl/musl_git.bb @@ -15,6 +15,7 @@ PV = "${BASEVER}+git${SRCPV}" SRC_URI = "git://git.musl-libc.org/musl \ file://0001-Make-dynamic-linker-a-relative-symlink-to-libc.patch \ file://0002-ldso-Use-syslibdir-and-libdir-as-default-pathes-to-l.patch \ + file://0001-correct-the-operand-specifiers-in-the-riscv64-CAS-ro.patch \ " S = "${WORKDIR}/git" -- cgit 1.2.3-korg