linux-kernel - [PATCH 1/2] vmcore: allow alternate dump capturing methods to export vmcore without is_kdump

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Message-ID: <20230901190438.375678-1-hbathini@linux.ibm.com>
Date:   Sat,  2 Sep 2023 00:34:37 +0530
From:   Hari Bathini <hbathini@...ux.ibm.com>
To:     lkml <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Kexec-ml <kexec@...ts.infradead.org>
Cc:     Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Sourabh Jain <sourabhjain@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 1/2] vmcore: allow alternate dump capturing methods to export vmcore without is_kdump_kernel()

Currently, is_kdump_kernel() returns true when elfcorehdr_addr is set.
While elfcorehdr_addr is set for kexec based kernel dump mechanism,
alternate dump capturing methods like fadump [1] also set it to export
the vmcore. is_kdump_kernel() is used to restrict resources in crash
dump capture kernel but such restrictions may not be desirable for
fadump. Allow is_kdump_kernel() to be defined differently for such
scenarios. With this, is_kdump_kernel() could be false while vmcore
is usable. So, introduce is_crashdump_kernel() to return true when
elfcorehdr_addr is set and use it for vmcore related checks.

[1] https://docs.kernel.org/powerpc/firmware-assisted-dump.html

Signed-off-by: Hari Bathini <hbathini@...ux.ibm.com>
---
 include/linux/crash_dump.h | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 0f3a656293b0..1052a0faf0dd 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -50,6 +50,7 @@ void vmcore_cleanup(void);
 #define vmcore_elf64_check_arch(x) (elf_check_arch(x) || vmcore_elf_check_arch_cross(x))
 #endif
 
+#ifndef is_kdump_kernel
 /*
  * is_kdump_kernel() checks whether this kernel is booting after a panic of
  * previous kernel or not. This is determined by checking if previous kernel
@@ -64,6 +65,19 @@ static inline bool is_kdump_kernel(void)
 {
 	return elfcorehdr_addr != ELFCORE_ADDR_MAX;
 }
+#endif
+
+/*
+ * Return true if this is a dump capture kernel, where vmcore needs to be
+ * exported, irrespective of the dump capture mechanism in use.
+ *
+ * Same as is_kdump_kernel() unless arch specific code defines is_kdump_kernel()
+ * differently while supporting other dump capturing mechanisms.
+ */
+static inline bool is_crashdump_kernel(void)
+{
+	return elfcorehdr_addr != ELFCORE_ADDR_MAX;
+}
 
 /* is_vmcore_usable() checks if the kernel is booting after a panic and
  * the vmcore region is usable.
@@ -75,7 +89,7 @@ static inline bool is_kdump_kernel(void)
 
 static inline int is_vmcore_usable(void)
 {
-	return is_kdump_kernel() && elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0;
+	return is_crashdump_kernel() && elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0;
 }
 
 /* vmcore_unusable() marks the vmcore as unusable,
@@ -84,7 +98,7 @@ static inline int is_vmcore_usable(void)
 
 static inline void vmcore_unusable(void)
 {
-	if (is_kdump_kernel())
+	if (is_crashdump_kernel())
 		elfcorehdr_addr = ELFCORE_ADDR_ERR;
 }
 
-- 
2.41.0