[Crash-utility] [PATCH] arm64: add tag_ignore machdep option

[Vinayak Menon]

Raw ramdumps without vmcoreinfo does not work currently
with pointer authentication or memory tagging enabled.
The arm capability array can be queried but that creates
a dependency on the bits identifying the capabilities.
Add a machdep option instead to ignore the tags when any
feature using the tag bits is enabled.

Signed-off-by: Vinayak Menon <vinayakm.list at gmail.com>
---
 arm64.c | 26 +++++++++++++++++++-------
 crash.8 |  1 +
 defs.h  |  1 +
 help.c  |  1 +
 4 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/arm64.c b/arm64.c
index 37aed07..3ed6795 100644
--- a/arm64.c
+++ b/arm64.c
@@ -745,7 +745,8 @@ arm64_parse_machdep_arg_l(char *argstring, char *param, ulong *value)
 	char *p;
 
 	len = strlen(param);
-	if (!STRNEQ(argstring, param) || (argstring[len] != '='))
+	if (!STRNEQ(argstring, param) || (!STRNEQ(argstring, "tag_ignore") &&
+				(argstring[len] != '=')))
 		return FALSE;
 
 	if ((LASTCHAR(argstring) == 'm') ||
@@ -763,6 +764,8 @@ arm64_parse_machdep_arg_l(char *argstring, char *param, ulong *value)
 			*value = dtol(p, flags, &err);
 		} else if (STRNEQ(argstring, "vabits_actual")) {
 			*value = dtol(p, flags, &err);
+		} else if (STRNEQ(argstring, "tag_ignore")) {
+			*value = 1;
 		} else if (megabytes) {
 			*value = dtol(p, flags, &err);
 			if (!err)
@@ -797,12 +800,6 @@ arm64_parse_cmdline_args(void)
 		if (!machdep->cmdline_args[index])
 			break;
 
-		if (!strstr(machdep->cmdline_args[index], "=")) {
-			error(WARNING, "ignoring --machdep option: %x\n",
-				machdep->cmdline_args[index]);
-			continue;
-		}
-
 		strcpy(buf, machdep->cmdline_args[index]);
 
 		for (p = buf; *p; p++) {
@@ -838,6 +835,11 @@ arm64_parse_cmdline_args(void)
 					"setting vabits_actual to: %ld\n\n",
 					machdep->machspec->VA_BITS_ACTUAL);
 				continue;
+			} else if (arm64_parse_machdep_arg_l(arglist[i], "tag_ignore",
+			        &machdep->machspec->tag_ignore)) {
+				error(NOTE,
+					"setting tag_ignore\n\n");
+				continue;
 			}
 
 			error(WARNING, "ignoring --machdep option: %s\n",
@@ -4122,6 +4124,9 @@ arm64_swp_offset(ulong pte)
 	return pte;
 }
 
+#define __GENMASK_ULL(h, l) \
+        (((~0ULL) - (1ULL << (l)) + 1) & \
+         (~0ULL >> (64 - 1 - (h))))
 static void arm64_calc_KERNELPACMASK(void)
 {
 	ulong value;
@@ -4133,6 +4138,13 @@ static void arm64_calc_KERNELPACMASK(void)
 		machdep->machspec->CONFIG_ARM64_KERNELPACMASK = value;
 		if (CRASHDEBUG(1))
 			fprintf(fp, "CONFIG_ARM64_KERNELPACMASK: %lx\n", value);
+	} else if (machdep->machspec->VA_BITS_ACTUAL &&
+				machdep->machspec->tag_ignore) {
+		machdep->machspec->CONFIG_ARM64_KERNELPACMASK =
+			__GENMASK_ULL(63, machdep->machspec->VA_BITS_ACTUAL);
+		if (CRASHDEBUG(1))
+			fprintf(fp, "CONFIG_ARM64_KERNELPACMASK: %lx\n",
+				machdep->machspec->CONFIG_ARM64_KERNELPACMASK);
 	}
 }
 
diff --git a/crash.8 b/crash.8
index 5020ce1..91f01fc 100644
--- a/crash.8
+++ b/crash.8
@@ -289,6 +289,7 @@ ARM64:
   kimage_voffset=<kimage_voffset-value>
   max_physmem_bits=<value>
   vabits_actual=<value>
+  tag_ignore
 X86:
   page_offset=<CONFIG_PAGE_OFFSET-value>
 .fi
diff --git a/defs.h b/defs.h
index 35b983a..cd3bcf9 100644
--- a/defs.h
+++ b/defs.h
@@ -3331,6 +3331,7 @@ struct machine_specific {
 	ulong VA_START;
 	ulong CONFIG_ARM64_KERNELPACMASK;
 	ulong physvirt_offset;
+	ulong tag_ignore;
 };
 
 struct arm64_stackframe {
diff --git a/help.c b/help.c
index 531f50a..d66125b 100644
--- a/help.c
+++ b/help.c
@@ -182,6 +182,7 @@ char *program_usage_info[] = {
     "      kimage_voffset=<kimage_voffset-value>",
     "      max_physmem_bits=<value>",
     "      vabits_actual=<value>",
+    "      tag_ignore",
     "    X86:",
     "      page_offset=<CONFIG_PAGE_OFFSET-value>",
     "",
--