[Crash-utility] [PATCHv2] crash-utility/arm64: store phy_offset and memstart_addr separately

[Pingfan Liu]

Crash encounters a bug like the following:
    ...
    License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
    This is free software: you are free to change and redistribute it.
    There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
    and "show warranty" for details.
    This GDB was configured as "aarch64-unknown-linux-gnu"...

    crash: read error: kernel virtual address: ffff000f789c0050  type: "IRQ stack pointer"
    crash: read error: kernel virtual address: ffff000f78a60050  type: "IRQ stack pointer"
    crash: read error: kernel virtual address: ffff000f78b00050  type: "IRQ stack pointer"
    ...

This bug connects with kernel commit 7bc1a0f9e176 ("arm64: mm: use
single quantity to represent the PA to VA translation"), memstart_addr
can be negative, which makes it different from real phy_offset.

In crash utility, PTOV() needs memstart_addr to calculate VA from PA,
while getting PFN offset in a dumpfile, phy_offset is required. So
storing them separately for different purpose.

Signed-off-by: Pingfan Liu <piliu at redhat.com>
Cc: HAGIO KAZUHITO <k-hagio-ab at nec.com>
Cc: Lianbo Jiang <lijiang at redhat.com>
Cc: Mark Salter <msalter at redhat.com>
Cc: Mark Langsdorf <mlangsdo at redhat.com>
Cc: Jeremy Linton <jlinton at redhat.com>
To: crash-utility at redhat.com
---
 arm64.c | 25 ++++++++++++++++++++++---
 defs.h  |  1 +
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/arm64.c b/arm64.c
index 37aed07..a0bee62 100644
--- a/arm64.c
+++ b/arm64.c
@@ -24,6 +24,9 @@
 
 #define NOT_IMPLEMENTED(X) error((X), "%s: function not implemented\n", __func__)
 
+#define MEMSTART_ADDR_OFFSET \
+	(0xffffffffffffffff << 48 - 0xffffffffffffffff << 56)
+
 static struct machine_specific arm64_machine_specific = { 0 };
 static int arm64_verify_symbol(const char *, ulong, char);
 static void arm64_parse_cmdline_args(void);
@@ -687,6 +690,7 @@ arm64_dump_machdep_table(ulong arg)
 		fprintf(fp, "        kimage_voffset: %016lx\n", ms->kimage_voffset);
 	}
 	fprintf(fp, "           phys_offset: %lx\n", ms->phys_offset);
+	fprintf(fp, "         memstart_addr: %lx\n", ms->memstart_addr);
 	fprintf(fp, "__exception_text_start: %lx\n", ms->__exception_text_start);
 	fprintf(fp, "  __exception_text_end: %lx\n", ms->__exception_text_end);
 	fprintf(fp, " __irqentry_text_start: %lx\n", ms->__irqentry_text_start);
@@ -987,7 +991,7 @@ arm64_calc_physvirt_offset(void)
 	ulong physvirt_offset;
 	struct syment *sp;
 
-	ms->physvirt_offset = ms->phys_offset - ms->page_offset;
+	ms->physvirt_offset = ms->memstart_addr - ms->page_offset;
 
 	if ((sp = kernel_symbol_search("physvirt_offset")) &&
 			machdep->machspec->kimage_voffset) {
@@ -1028,7 +1032,11 @@ arm64_calc_phys_offset(void)
 		    ms->kimage_voffset && (sp = kernel_symbol_search("memstart_addr"))) {
 			if (pc->flags & PROC_KCORE) {
 				if ((string = pc->read_vmcoreinfo("NUMBER(PHYS_OFFSET)"))) {
-					ms->phys_offset = htol(string, QUIET, NULL);
+					ms->memstart_addr = htol(string, QUIET, NULL);
+					if (ms->memstart_addr < 0)
+						ms->phys_offset = ms->memstart_addr + MEMSTART_ADDR_OFFSET;
+					else
+						ms->phys_offset = ms->memstart_addr;
 					free(string);
 					return;
 				}
@@ -1080,7 +1088,18 @@ arm64_calc_phys_offset(void)
 	} else if (DISKDUMP_DUMPFILE() && diskdump_phys_base(&phys_offset)) {
 		ms->phys_offset = phys_offset;
 	} else if (KDUMP_DUMPFILE() && arm64_kdump_phys_base(&phys_offset)) {
-		ms->phys_offset = phys_offset;
+		/*
+		 * When running a 52bits kernel on 48bits hardware. Kernel plays a trick:
+		 * if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52))
+                 *       memstart_addr -= _PAGE_OFFSET(48) - _PAGE_OFFSET(52);
+		 *
+		 * In crash, this should be detected to get a real physical start address.
+		 */
+		ms->memstart_addr = phys_offset;
+		if ((long)phys_offset < 0)
+			ms->phys_offset = phys_offset + MEMSTART_ADDR_OFFSET;
+		else
+			ms->phys_offset = phys_offset;
 	} else {
 		error(WARNING,
 			"phys_offset cannot be determined from the dumpfile.\n");
diff --git a/defs.h b/defs.h
index 35b983a..64f2bcb 100644
--- a/defs.h
+++ b/defs.h
@@ -3290,6 +3290,7 @@ struct machine_specific {
 	ulong modules_vaddr;
 	ulong modules_end;
 	ulong phys_offset;
+	long memstart_addr;
 	ulong __exception_text_start;
 	ulong __exception_text_end;
 	struct arm64_pt_regs *panic_task_regs;
-- 
2.29.2