On Thu, Nov 12, 2020 at 09:45:45AM +0000, Vincenzo Frascino wrote:

On 11/12/20 9:39 AM, Catalin Marinas wrote:

quoted

On Tue, Nov 10, 2020 at 11:10:29PM +0100, Andrey Konovalov wrote:

quoted

diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 664c968dc43c..dbda6598c19d 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c

@@ -129,6 +131,26 @@ void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
 	return ptr;
 }
 
+void mte_init_tags(u64 max_tag)
+{
+	static bool gcr_kernel_excl_initialized = false;
+
+	if (!gcr_kernel_excl_initialized) {
+		/*
+		 * The format of the tags in KASAN is 0xFF and in MTE is 0xF.
+		 * This conversion extracts an MTE tag from a KASAN tag.
+		 */
+		u64 incl = GENMASK(FIELD_GET(MTE_TAG_MASK >> MTE_TAG_SHIFT,
+					     max_tag), 0);
+
+		gcr_kernel_excl = ~incl & SYS_GCR_EL1_EXCL_MASK;
+		gcr_kernel_excl_initialized = true;
+	}
+
+	/* Enable the kernel exclude mask for random tags generation. */
+	write_sysreg_s(SYS_GCR_EL1_RRND | gcr_kernel_excl, SYS_GCR_EL1);
+}

I don't think this function belongs to this patch. There is an earlier
patch that talks about mte_init_tags() but no trace of it until this
patch.

Could you please point out to which patch are you referring to?

I replied to it already (or you can search ;)). But this patch is about
switching GCR_EL1 on exception entry/exit rather than setting up the
initial kernel GCR_EL1 value.

-- 
Catalin

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