Thanks for the update, for the patch, ack.
Thanks,
Tao Liu
On Wed, Jul 24, 2024 at 7:55 PM <cb126yx@xxxxxxx> wrote:
>
> 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 By checking the raw data below, will see the lr (fp+8) data show the pointer which already been replaced by PAC prefix.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.kachhap@xxxxxxx/
> Link: https://cs.android.com/android/_/android/kernel/common/+/689eae42afd7a916634146edca38463769969184
>
>
> Signed-off-by: bevis_chen <bevis_chen@xxxxxxxx>
> ---
> 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
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