[PATCH] arm64: Fix bt command show wrong stacktrace on ramdump source

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If we use crash to parse ramdump(Qcom phone device) rathen than vmcore.
Start command should be like: crash vmlinux --kaslr=xxx DDRCS0_0.BIN@0x0000000080000000,... --machdep vabits_actual=39
Then We will see bt command show misleading backtrace information below:

crash> bt 16930
PID: 16930    TASK: ffffff89b3eada00  CPU: 2    COMMAND: "Firebase Backgr"
 #0 [ffffffc034c437f0] __switch_to at ffffffe0036832d4
 #1 [ffffffc034c43850] __kvm_nvhe_$d.2314 at 6be732e004cf05a0
 #2 [ffffffc034c438b0] __kvm_nvhe_$d.2314 at 86c54c6004ceff80
 #3 [ffffffc034c43950] __kvm_nvhe_$d.2314 at 55d6f96003a7b120
 #4 [ffffffc034c439f0] __kvm_nvhe_$d.2314 at 9ccec46003a80a64
 #5 [ffffffc034c43ac0] __kvm_nvhe_$d.2314 at 8cf41e6003a945c4
 #6 [ffffffc034c43b10] __kvm_nvhe_$d.2314 at a8f181e00372c818
 #7 [ffffffc034c43b40] __kvm_nvhe_$d.2314 at 6dedde600372c0d0
 #8 [ffffffc034c43b90] __kvm_nvhe_$d.2314 at 62cc07e00373d0ac
 #9 [ffffffc034c43c00] __kvm_nvhe_$d.2314 at 72fb1de00373bedc
...
     PC: 00000073f5294840   LR: 00000070d8f39ba4   SP: 00000070d4afd5d0
    X29: 00000070d4afd600  X28: b4000071efcda7f0  X27: 00000070d4afe000
    X26: 0000000000000000  X25: 00000070d9616000  X24: 0000000000000000
    X23: 0000000000000000  X22: 0000000000000000  X21: 0000000000000000
    X20: b40000728fd27520  X19: b40000728fd27550  X18: 000000702daba000
    X17: 00000073f5294820  X16: 00000070d940f9d8  X15: 00000000000000bf
    X14: 0000000000000000  X13: 00000070d8ad2fac  X12: b40000718fce5040
    X11: 0000000000000000  X10: 0000000000000070   X9: 0000000000000001
     X8: 0000000000000062   X7: 0000000000000020   X6: 0000000000000000
     X5: 0000000000000000   X4: 0000000000000000   X3: 0000000000000000
     X2: 0000000000000002   X1: 0000000000000080   X0: b40000728fd27550
    ORIG_X0: b40000728fd27550  SYSCALLNO: ffffffff  PSTATE: 40001000

By checking the raw data below, will see the lr (fp+8) data show the pointer which already been replaced by PAC prefix.

crash> bt -f
PID: 16930    TASK: ffffff89b3eada00  CPU: 2    COMMAND: "Firebase Backgr"
 #0 [ffffffc034c437f0] __switch_to at ffffffe0036832d4
    ffffffc034c437f0: ffffffc034c43850 6be732e004cf05a4
    ffffffc034c43800: ffffffe006186108 a0ed07e004cf09c4
    ffffffc034c43810: ffffff8a1a340000 ffffff8a8d343c00
    ffffffc034c43820: ffffff89b3eada00 ffffff8b780db540
    ffffffc034c43830: ffffff89b3eada00 0000000000000000
    ffffffc034c43840: 0000000000000004 712b828118484a00
 #1 [ffffffc034c43850] __kvm_nvhe_$d.2314 at 6be732e004cf05a0
    ffffffc034c43850: ffffffc034c438b0 86c54c6004ceff84
    ffffffc034c43860: 000000708070f000 ffffffc034c43938
    ffffffc034c43870: ffffff88bd822878 ffffff89b3eada00
...

So we check the CONFIG_ARM64_PTR_AUTH and CONFIG_ARM64_PTR_AUTH_KERNEL to double check if pac mechanism been enabled on this ramdump.
Then we use vabits to figure it out.
Fix then show the right backtrace below:
crash> bt 16930
PID: 16930    TASK: ffffff89b3eada00  CPU: 2    COMMAND: "Firebase Backgr"
 #0 [ffffffc034c437f0] __switch_to at ffffffe0036832d4
 #1 [ffffffc034c43850] __schedule at ffffffe004cf05a0
 #2 [ffffffc034c438b0] preempt_schedule_common at ffffffe004ceff80
 #3 [ffffffc034c43950] unmap_page_range at ffffffe003a7b120
 #4 [ffffffc034c439f0] unmap_vmas at ffffffe003a80a64
 #5 [ffffffc034c43ac0] exit_mmap at ffffffe003a945c4
 #6 [ffffffc034c43b10] __mmput at ffffffe00372c818
 #7 [ffffffc034c43b40] mmput at ffffffe00372c0d0
 #8 [ffffffc034c43b90] exit_mm at ffffffe00373d0ac
 #9 [ffffffc034c43c00] do_exit at ffffffe00373bedc
     PC: 00000073f5294840   LR: 00000070d8f39ba4   SP: 00000070d4afd5d0
    X29: 00000070d4afd600  X28: b4000071efcda7f0  X27: 00000070d4afe000
    X26: 0000000000000000  X25: 00000070d9616000  X24: 0000000000000000
    X23: 0000000000000000  X22: 0000000000000000  X21: 0000000000000000
    X20: b40000728fd27520  X19: b40000728fd27550  X18: 000000702daba000
    X17: 00000073f5294820  X16: 00000070d940f9d8  X15: 00000000000000bf
    X14: 0000000000000000  X13: 00000070d8ad2fac  X12: b40000718fce5040
    X11: 0000000000000000  X10: 0000000000000070   X9: 0000000000000001
     X8: 0000000000000062   X7: 0000000000000020   X6: 0000000000000000
     X5: 0000000000000000   X4: 0000000000000000   X3: 0000000000000000
     X2: 0000000000000002   X1: 0000000000000080   X0: b40000728fd27550
    ORIG_X0: b40000728fd27550  SYSCALLNO: ffffffff  PSTATE: 40001000

Let's use GENMASK to replace the pac pointer to fix it.
gki related commit url here:
https://lore.kernel.org/all/20230412160134.306148-4-mark.rutland@xxxxxxx/

Signed-off-by: bevis_chen <bevis_chen@xxxxxxxx>
---
 arm64.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/arm64.c b/arm64.c
index b3040d7..d8ce98f 100644
--- a/arm64.c
+++ b/arm64.c
@@ -92,6 +92,7 @@ static void arm64_get_crash_notes(void);
 static void arm64_calc_VA_BITS(void);
 static int arm64_is_uvaddr(ulong, struct task_context *);
 static void arm64_calc_KERNELPACMASK(void);
+static void arm64_recalc_KERNELPACMASK(void);
 static int arm64_get_vmcoreinfo(unsigned long *vaddr, const char *label, int base);

 struct kernel_range {
@@ -581,6 +582,18 @@ arm64_init(int when)
                if (!machdep->hz)
                        machdep->hz = 100;

+               /*
+               * In the case of using ramdump rather than vmcore,
+               * Will fail to parse out KERNELPAC.
+               * So let's try again from kconfig to ensure if PAC enabled.
+               * If yes, then we use vabits to figure it out.
+               * gki related commit url:
+               * https://lore.kernel.org/all/20230412160134.306148-4-mark.rutland@xxxxxxx/
+               */
+               if(!machdep->machspec->CONFIG_ARM64_KERNELPACMASK)
+                       arm64_recalc_KERNELPACMASK();
+
+
                arm64_irq_stack_init();
                arm64_overflow_stack_init();
                arm64_stackframe_init();
@@ -4921,6 +4934,26 @@ static void arm64_calc_KERNELPACMASK(void)
        }
 }

+
+#define GENMASK_UL(h, l) \
+    (((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
+
+static void arm64_recalc_KERNELPACMASK(void){
+       if (kt->ikconfig_flags & IKCONFIG_AVAIL){
+               /* arm64: check pac already enabled yet.*/
+               if ((get_kernel_config("CONFIG_ARM64_PTR_AUTH", NULL) == IKCONFIG_Y)
+                       && (get_kernel_config("CONFIG_ARM64_PTR_AUTH_KERNEL", NULL) == IKCONFIG_Y)){
+                       if (machdep->machspec->VA_BITS_ACTUAL){
+                               machdep->machspec->CONFIG_ARM64_KERNELPACMASK =
+                                       GENMASK_UL(63, machdep->machspec->VA_BITS_ACTUAL);
+                               if (CRASHDEBUG(1))
+                                       fprintf(fp, "CONFIG_ARM64_KERNELPACMASK: %lx\n",
+                                               machdep->machspec->CONFIG_ARM64_KERNELPACMASK);
+                       }
+               }
+       }
+}
+
 #endif  /* ARM64 */


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2.27.0
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