Re: [Crash-utility] [PATCH] arm64: use TCR_EL1_T1SZ to get the correct info if vabits_actual is missing
On 2022/08/22 18:29, Huang Shijie wrote:
After kernel patch:
"0d9b1ffefabe arm64: mm: make vabits_actual a build time constant if
possible"
the "vabits_actual" is not compiled to kernel symbols when "VA_BITS >
48"
is false.
So the crash will not find the "vabits_actual" symbol, and it will
fail in the end.
This patch introduces the arm64_set_va_bits_by_tcr(), and if crash cannot
find "vabits_actual" symbol, it will use the TCR_EL1_T1SZ register to get
the correct VA_BITS_ACTUAL/VA_BITS/VA_START.
Tested this patch with:
1.) the live mode with /proc/kcore
2.) the kdump file with /proc/vmcore.
Signed-off-by: Huang Shijie <shijie(a)os.amperecomputing.com>
---
arm64.c | 50 +++++++++++++++++++++++++++++++++-----------------
1 file changed, 33 insertions(+), 17 deletions(-)
diff --git a/arm64.c b/arm64.c
index b6b7aa1..3a613f9 100644
--- a/arm64.c
+++ b/arm64.c
@@ -4586,6 +4586,35 @@ arm64_IS_VMALLOC_ADDR(ulong vaddr)
(vaddr >= ms->modules_vaddr && vaddr <=
ms->modules_end));
}
+/* Return TRUE if we succeed, return FALSE on failure. */
+static int arm64_set_va_bits_by_tcr()
$ make -j $(nproc) warn
...
arm64.c:4590:12: warning: function declaration isn't a prototype
[-Wstrict-prototypes]
static int arm64_set_va_bits_by_tcr()
^~~~~~~~~~~~~~~~~~~~~~~~
and please follow the style of the other functions as far as possible:
-static int arm64_set_va_bits_by_tcr()
+static int
+arm64_set_va_bits_by_tcr(void)
(hmm, some functions in arm64.c already don't follow it, though...)
But this can be fixed when merging, you don't need to respin only for this.
Otherwise, looks good to me. Thank you for the early fix.
Acked-by: Kazuhito Hagio <k-hagio-ab(a)nec.com>
Thanks,
Kazu
> +{
> + ulong value;
> + char *string;
> +
> + if ((string = pc->read_vmcoreinfo("NUMBER(TCR_EL1_T1SZ)")) ||
> + (string = pc->read_vmcoreinfo("NUMBER(tcr_el1_t1sz)"))) {
> + /* See ARMv8 ARM for the description of
> + * TCR_EL1.T1SZ and how it can be used
> + * to calculate the vabits_actual
> + * supported by underlying kernel.
> + *
> + * Basically:
> + * vabits_actual = 64 - T1SZ;
> + */
> + value = 64 - strtoll(string, NULL, 0);
> + if (CRASHDEBUG(1))
> + fprintf(fp, "vmcoreinfo : vabits_actual: %ld\n", value);
> + free(string);
> + machdep->machspec->VA_BITS_ACTUAL = value;
> + machdep->machspec->VA_BITS = value;
> + machdep->machspec->VA_START =
_VA_START(machdep->machspec->VA_BITS_ACTUAL);
> + return TRUE;
> + }
> +
> + return FALSE;
> +}
> +
> static void
> arm64_calc_VA_BITS(void)
> {
> @@ -4616,23 +4645,8 @@ arm64_calc_VA_BITS(void)
> } else if (ACTIVE())
> error(FATAL, "cannot determine VA_BITS_ACTUAL: please use
/proc/kcore\n");
> else {
> - if ((string = pc->read_vmcoreinfo("NUMBER(TCR_EL1_T1SZ)")) ||
> - (string = pc->read_vmcoreinfo("NUMBER(tcr_el1_t1sz)"))) {
> - /* See ARMv8 ARM for the description of
> - * TCR_EL1.T1SZ and how it can be used
> - * to calculate the vabits_actual
> - * supported by underlying kernel.
> - *
> - * Basically:
> - * vabits_actual = 64 - T1SZ;
> - */
> - value = 64 - strtoll(string, NULL, 0);
> - if (CRASHDEBUG(1))
> - fprintf(fp, "vmcoreinfo : vabits_actual: %ld\n", value);
> - free(string);
> - machdep->machspec->VA_BITS_ACTUAL = value;
> - machdep->machspec->VA_BITS = value;
> - machdep->machspec->VA_START =
_VA_START(machdep->machspec->VA_BITS_ACTUAL);
> + if (arm64_set_va_bits_by_tcr()) {
> + /* nothing */
> } else if (machdep->machspec->VA_BITS_ACTUAL) {
> machdep->machspec->VA_BITS = machdep->machspec->VA_BITS_ACTUAL;
> machdep->machspec->VA_START =
_VA_START(machdep->machspec->VA_BITS_ACTUAL);
> @@ -4654,6 +4668,8 @@ arm64_calc_VA_BITS(void)
> */
> machdep->flags |= FLIPPED_VM;
> return;
> + } else if (arm64_set_va_bits_by_tcr()) {
> + return;
> }
>
> if (!(sp = symbol_search("swapper_pg_dir")) &&