If we use crash tool 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By checking the raw data below, will see the lr (fp+8) data show the pointer which already been replaced by PAC prefix.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 for reference:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Author: Amit Daniel Kachhap <amit.kachhap@xxxxxxx>
Date: Fri Mar 13 14:34:58 2020 +0530
arm64: mask PAC bits of __builtin_return_address
Functions like vmap() record how much memory has been allocated by their
callers, and callers are identified using __builtin_return_address(). Once
the kernel is using pointer-auth the return address will be signed. This
means it will not match any kernel symbol, and will vary between threads
even for the same caller.
The output of /proc/vmallocinfo in this case may look like,
0x(____ptrval____)-0x(____ptrval____) 20480 0x86e28000100e7c60 pages=4 vmalloc N0=4
0x(____ptrval____)-0x(____ptrval____) 20480 0x86e28000100e7c60 pages=4 vmalloc N0=4
0x(____ptrval____)-0x(____ptrval____) 20480 0xc5c78000100e7c60 pages=4 vmalloc N0=4
The above three 64bit values should be the same symbol name and not
different LR values.
Use the pre-processor to add logic to clear the PAC to
__builtin_return_address() callers. This patch adds a new file
asm/compiler.h and is transitively included via include/compiler_types.h on
the compiler command line so it is guaranteed to be loaded and the users of
this macro will not find a wrong version.
Helper macros ptrauth_kernel_pac_mask/ptrauth_clear_pac are created for
this purpose and added in this file. Existing macro ptrauth_user_pac_mask
moved from asm/pointer_auth.h.
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@xxxxxxx>
Reviewed-by: James Morse <james.morse@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 87e2cbb76930..115ceea0293e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -118,6 +118,7 @@ config ARM64
select HAVE_ALIGNED_STRUCT_PAGE if SLUB
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_BITREVERSE
+ select HAVE_ARCH_COMPILER_H
select HAVE_ARCH_HUGE_VMAP
select HAVE_ARCH_JUMP_LABEL
select HAVE_ARCH_JUMP_LABEL_RELATIVE
diff --git a/arch/arm64/include/asm/compiler.h b/arch/arm64/include/asm/compiler.h
new file mode 100644
index 000000000000..eece20d2c55f
--- /dev/null
+++ b/arch/arm64/include/asm/compiler.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_COMPILER_H
+#define __ASM_COMPILER_H
+
+#if defined(CONFIG_ARM64_PTR_AUTH)
+
+/*
+ * The EL0/EL1 pointer bits used by a pointer authentication code.
+ * This is dependent on TBI0/TBI1 being enabled, or bits 63:56 would also apply.
+ */
+#define ptrauth_user_pac_mask() GENMASK_ULL(54, vabits_actual)
+#define ptrauth_kernel_pac_mask() GENMASK_ULL(63, vabits_actual)
+
+/* Valid for EL0 TTBR0 and EL1 TTBR1 instruction pointers */
+#define ptrauth_clear_pac(ptr) \
+ ((ptr & BIT_ULL(55)) ? (ptr | ptrauth_kernel_pac_mask()) : \
+ (ptr & ~ptrauth_user_pac_mask()))
+
+#define __builtin_return_address(val) \
+ (void *)(ptrauth_clear_pac((unsigned long)__builtin_return_address(val)))
+
+#endif /* CONFIG_ARM64_PTR_AUTH */
+
+#endif /* __ASM_COMPILER_H */
diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index 833d3f948de0..70c47156e54b 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -68,16 +68,9 @@ static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kerne
extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
-/*
- * The EL0 pointer bits used by a pointer authentication code.
- * This is dependent on TBI0 being enabled, or bits 63:56 would also apply.
- */
-#define ptrauth_user_pac_mask() GENMASK(54, vabits_actual)
-
-/* Only valid for EL0 TTBR0 instruction pointers */
static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
{
- return ptr & ~ptrauth_user_pac_mask();
+ return ptrauth_clear_pac(ptr);
}
#define ptrauth_thread_init_user(tsk)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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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