On Thu, Jun 04, 2020 at 02:04:58AM +0530, Bhupesh Sharma wrote:

On Wed, Jun 3, 2020 at 4:50 PM Kamlakant Patel [off-list ref] wrote:

quoted

quoted

diff --git a/arch/arm64/kernel/crash_core.c b/arch/arm64/kernel/crash_core.c
index 1f646b07e3e9..314391a156ee 100644
--- a/arch/arm64/kernel/crash_core.c
+++ b/arch/arm64/kernel/crash_core.c

@@ -7,6 +7,14 @@
 #include <linux/crash_core.h>
 #include <asm/cpufeature.h>
 #include <asm/memory.h>
+#include <asm/pgtable-hwdef.h>
+
+static inline u64 get_tcr_el1_t1sz(void);
+
+static inline u64 get_tcr_el1_t1sz(void) {
+     return (read_sysreg(tcr_el1) & TCR_T1SZ_MASK) >> TCR_T1SZ_OFFSET; }

 void arch_crash_save_vmcoreinfo(void)
 {

@@ -16,6 +24,8 @@ void arch_crash_save_vmcoreinfo(void)
                                              kimage_voffset);
      vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%llx\n",
                                              PHYS_OFFSET);
+     vmcoreinfo_append_str("NUMBER(TCR_EL1_T1SZ)=0x%llx\n",
+                                             get_tcr_el1_t1sz());

I tested this patch on top of upstream kernel v5.7 and I am getting "crash: cannot determine VA_BITS_ACTUAL" error with crash tool.
I looked into crash-utility source and it is expecting tcr_el1_t1sz not TCR_EL1_T1SZ.
Could you please check.

Indeed. As per James comments on the v5 (see [1]) where he suggested
converting ttcr_el1_t1sz into TCR_EL1_T1SZ, I made the change in v6
accordingly.

This time I haven't sent out the v6 userspace changes
(makedumpfile/crash-utility) upstream first, since we are waiting for
kernel changes to be accepted first, as we have seen in the past that
while the userspace patches have been accepted, the kernel patches
required a respin cycle, thus leading to inconsistencies, as you also
pointed out with crash-utility.

Yes, and that';s the right way to do it. Userspace can't rely on the
stability of a kernel interface if it's no in the upstream kernel!

So doing with the ALL CAPS names is the right thing to do.

Will

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