If we use crash to parse ramdump(Qcom phone device) rather 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 as: 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ffffffff PSTATE: 40001000 By checking the raw data below, will see the lr (fp+8) data show the pointer which already been replaced by PAC prefix.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 may search the CONFIG_ARM64_PTR_AUTH_KERNEL to double check if pac mechanism has been enabled on this ramdump. Luckily, lijiang and tao give some valuable suggestion: As IKCONFIG may not available in most distributions. So we could check if the "struct ptrauth_keys_kernel" has already been embeded into arm's thread structure. struct thread_struct { struct cpu_context cpu_context; /* cpu context */ ... #ifdef CONFIG_ARM64_PTR_AUTH struct ptrauth_keys_user keys_user; #ifdef CONFIG_ARM64_PTR_AUTH_KERNEL struct ptrauth_keys_kernel keys_kernel; #endif ... }; PAC feature should be enabled when "struct ptrauth_keys_kernel" exist, and we can use vabits to figure out pac bitmask. The fix backtrace is shown 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 Here is gki's PAC related original commit: Link: https://lore.kernel.org/all/1584090304-18043-12-git-send-email-amit.kachh... Link: https://cs.android.com/android/_/android/kernel/common/+/689eae42afd7a916... Signed-off-by: bevis_chen <bevis_chen(a)asus.com&gt; --- arm64.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/arm64.c b/arm64.c index b3040d7..50dd458 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 +582,17 @@ 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 we check if the "sturct ptrauth_keys_kernel" exits + * as a basis for whether PAC feature is enabled or not. + * If yes, then we use vabits to figure out pac bitmask. + */ + if(!machdep->machspec->CONFIG_ARM64_KERNELPACMASK) + arm64_recalc_KERNELPACMASK(); + + arm64_irq_stack_init(); arm64_overflow_stack_init(); arm64_stackframe_init(); @@ -4921,6 +4933,21 @@ 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){ + /* arm64: check if pac already enabled yet from related structure.*/ + if (STRUCT_EXISTS("ptrauth_keys_kernel") && 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 */ -- 2.27.0 -- Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki