[Crash-utility] [PATCH] arm64: fix regression for the determination of VA_BITS and section_size_bits

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1. The commit f02c8e87 will cause a regression issue for the determination of VA_BITS
on Linux 4.19 and earlier kernels, the crash session fails during initialization with
the error message due to get a wrong vabits_actual:
vmcoreinfo : vabits_actual: 27
crash: invalid kernel virtual address: ffffffa890a41318  type: "kernel_config_data"
WARNING: cannot read kernel_config_data
crash: invalid kernel virtual address: ffffffa89106db50  type: "possible"
WARNING: cannot read cpu_possible_map
crash: invalid kernel virtual address: ffffffa89106db48  type: "present"
WARNING: cannot read cpu_present_map
crash: invalid kernel virtual address: ffffffa89106db40  type: "online"
WARNING: cannot read cpu_online_map
crash: invalid kernel virtual address: ffffffa89106db58  type: "active"
WARNING: cannot read cpu_active_map
crash: invalid kernel virtual address: ffffffa89143cb80  type: "shadow_timekeeper xtime_sec"
crash: invalid kernel virtual address: ffffffa89107b76c  type: "init_uts_ns"
WARNING: invalid linux_banner pointer: ffffffa890a30018
crash: vmlinux and SYS_COREDUMP do not match!

Fix it by remove arm64_set_va_bits_by_tcr() if vabits_actual is missing.

2. The commit 568c6f04 will cause a regression issue for the determination of section_size_bits
on Linux 5.12 and earlier kernels. The section_size_bits compatible with linux upstream and
android GKI changes should be:
Before android-12-GKI or Linux 5.12:
	SECTION_SIZE_BITS = 30

After android-12-gki:
    SECTION_SIZE_BITS = 27 when defined 4K_PAGES or 16K_PAGES.
    SECTION_SIZE_BITS = 29 when defined 64K_PAGES.

Fixes: f02c8e87 ("arm64: use TCR_EL1_T1SZ to get the correct info if vabits_actual is missing")
Fixes: 568c6f04 ("arm64: section_size_bits compatible with macro definitions")
Signed-off-by: qiwu.chen <qiwu.chen@xxxxxxxxxxxxx>
---
 arm64.c | 37 ++++++++++++++++++-------------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/arm64.c b/arm64.c
index b3040d7..176c465 100644
--- a/arm64.c
+++ b/arm64.c
@@ -1613,8 +1613,15 @@ arm64_get_section_size_bits(void)
 {
 	int ret;
 	char *string;
+	bool is_ikconfig_avail;
 
-	if (THIS_KERNEL_VERSION >= LINUX(5,12,0)) {
+	if (arm64_get_vmcoreinfo(&machdep->section_size_bits, "NUMBER(SECTION_SIZE_BITS)", NUM_DEC))
+		goto exit;
+
+	is_ikconfig_avail = kt->ikconfig_flags & IKCONFIG_AVAIL ? TRUE : FALSE;
+	/* The commit reduce section size for arm64 sparsemem is introduced on linux-v5.12 and android-12-GKI */
+	if (THIS_KERNEL_VERSION >= LINUX(5,12,0) || (is_ikconfig_avail &&
+		get_kernel_config("CONFIG_ANDROID_KABI_RESERVE", NULL) == IKCONFIG_Y)) {
 		if (machdep->pagesize == 65536)
 			machdep->section_size_bits = _SECTION_SIZE_BITS_5_12_64K;
 		else
@@ -1622,24 +1629,18 @@ arm64_get_section_size_bits(void)
 	} else
 		machdep->section_size_bits = _SECTION_SIZE_BITS;
 
-	if (arm64_get_vmcoreinfo(&machdep->section_size_bits, "NUMBER(SECTION_SIZE_BITS)", NUM_DEC)) {
-		/* nothing */
-	} else if (kt->ikconfig_flags & IKCONFIG_AVAIL) {
-		if ((ret = get_kernel_config("CONFIG_MEMORY_HOTPLUG", NULL)) == IKCONFIG_Y) {
-			if ((ret = get_kernel_config("CONFIG_HOTPLUG_SIZE_BITS", &string)) == IKCONFIG_STR)
-				machdep->section_size_bits = atol(string);
-		}
-
-		/* arm64: reduce section size for sparsemem */
-		if ((ret = get_kernel_config("CONFIG_ARM64_4K_PAGES", NULL)) == IKCONFIG_Y
-			|| (ret = get_kernel_config("CONFIG_ARM64_16K_PAGES", NULL)) == IKCONFIG_Y)
-			machdep->section_size_bits = _SECTION_SIZE_BITS_5_12;
-		else if ((ret = get_kernel_config("CONFIG_ARM64_64K_PAGES", NULL)) == IKCONFIG_Y)
-			machdep->section_size_bits = _SECTION_SIZE_BITS_5_12_64K;
+	/* section_size_bits for arm64 vendor special case */
+	if (is_ikconfig_avail && get_kernel_config("CONFIG_MEMORY_HOTPLUG", NULL) == IKCONFIG_Y) {
+		if (get_kernel_config("CONFIG_HOTPLUG_SIZE_BITS", &string) == IKCONFIG_STR)
+			machdep->section_size_bits = atol(string);
 	}
 
-	if (CRASHDEBUG(1))
-		fprintf(fp, "SECTION_SIZE_BITS: %ld\n", machdep->section_size_bits);
+exit:
+	if (machdep->section_size_bits) {
+		if (CRASHDEBUG(1))
+			fprintf(fp, "SECTION_SIZE_BITS: %ld\n", machdep->section_size_bits);
+	} else
+		error(FATAL, "cannot determine SECTION_SIZE_BITS\n");
 }
 
 /*
@@ -4733,8 +4734,6 @@ arm64_calc_VA_BITS(void)
 		 */
 		machdep->flags |= FLIPPED_VM;
 		return;
-	} else if (arm64_set_va_bits_by_tcr()) {
-		return;
 	} 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);
-- 
2.25.1
--
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