[musl] [PATCH] riscv: correct symbol version of __vdso_flush_icache

[musl] [PATCH] riscv: correct symbol version of __vdso_flush_icache

[Ignotas "gns" WANG]

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Hi,

I'm porting LuaJIT to RISC-V, our binary built with musl would occasionally SIGILL at patched JIT insns. It looks that musl's __riscv_flush_icache is faulty, which may be the cause of this cache coherency issue.

For the patch, see the attachments.

Since I'm not a subscriber to the musl list, CC me please.

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From e427fd578a8de3220e72ab31b9eb18b412195a93 Mon Sep 17 00:00:00 2001
From: gns <infiwang@proton.me>
Date: Thu, 25 Jan 2024 23:59:52 +0800
Subject: [PATCH] riscv: correct symbol version of __vdso_flush_icache

Previously, __riscv_flush_icache would not work correctly as __vdso_flush_icache
had a wrong symbol version. Fix this by correcting symbol version.

Fixes: 0a48860c27a8 ("add riscv64 architecture support")
---
 src/linux/cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/linux/cache.c b/src/linux/cache.c
index 0eb051c2..45024309 100644
--- a/src/linux/cache.c
+++ b/src/linux/cache.c
@@ -21,7 +21,7 @@ weak_alias(__cachectl, cachectl);
 #ifdef SYS_riscv_flush_icache
 
 #define VDSO_FLUSH_ICACHE_SYM "__vdso_flush_icache"
-#define VDSO_FLUSH_ICACHE_VER "LINUX_4.5"
+#define VDSO_FLUSH_ICACHE_VER "LINUX_4.15"
 
 static void *volatile vdso_func;
 
-- 
2.39.2

Re: [musl] [PATCH] riscv: correct symbol version of __vdso_flush_icache

[Rich Felker]

On Thu, Jan 25, 2024 at 04:55:16PM +0000, Ignotas "gns" WANG wrote:
> Hi,
> 
> I'm porting LuaJIT to RISC-V, our binary built with musl would
> occasionally SIGILL at patched JIT insns. It looks that musl's
> __riscv_flush_icache is faulty, which may be the cause of this cache
> coherency issue.
> 
> For the patch, see the attachments.
> 
> Since I'm not a subscriber to the musl list, CC me please.

Just to be clear, this was always wrong, not a change on the kernel
side where either symbol version might be seen depending on kernel
version, right?

Rich

Re: [musl] [PATCH] riscv: correct symbol version of __vdso_flush_icache

[Rich Felker]

On Thu, Jan 25, 2024 at 02:05:34PM -0500, Rich Felker wrote:
> On Thu, Jan 25, 2024 at 04:55:16PM +0000, Ignotas "gns" WANG wrote:
> > Hi,
> > 
> > I'm porting LuaJIT to RISC-V, our binary built with musl would
> > occasionally SIGILL at patched JIT insns. It looks that musl's
> > __riscv_flush_icache is faulty, which may be the cause of this cache
> > coherency issue.
> > 
> > For the patch, see the attachments.
> > 
> > Since I'm not a subscriber to the musl list, CC me please.
> 
> Just to be clear, this was always wrong, not a change on the kernel
> side where either symbol version might be seen depending on kernel
> version, right?

OK, answering my own question. The original Linux commit introducing
riscv vdso, e2c0cdfba7f69925afc92b20cd9835d81e11a4f1, has:

+VERSION
+{
+       LINUX_4.15 {

and 921ebd8f2c081b3cf6c3b29ef4103eef3ff26054 adds
__riscv_flush_icache under that. So apparently the version was just
miscopied/typo when added to musl.

I'll apply this right away and it'll be in the upcoming release.

Rich