linux-kernel - [PATCH v3 1/2] vmcore: remove dependency with is_kdump

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Message-ID: <20230912082950.856977-1-hbathini@linux.ibm.com>
Date:   Tue, 12 Sep 2023 13:59:49 +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 v3 1/2] vmcore: remove dependency with is_kdump_kernel() for exporting vmcore

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. Since, is_kdump_kernel() is used to restrict resources in
crash dump capture kernel and 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, remove unnecessary dependency with is_kdump_kernel(), for
exporting vmcore.

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

Suggested-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Hari Bathini <hbathini@...ux.ibm.com>
---

Changes in v3:
* Decoupled is_vmcore_usable() & vmcore_unusable() from is_kdump_kernel()
  as suggested here: 
    https://lore.kernel.org/linuxppc-dev/ZP7si3UMVpPfYV+w@MiWiFi-R3L-srv/T/#m13ae5a7e4ba6f4d8397f0f66581832292eee3a85


 include/linux/crash_dump.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 0f3a656293b0..acc55626afdc 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 +65,7 @@ static inline bool is_kdump_kernel(void)
 {
 	return elfcorehdr_addr != ELFCORE_ADDR_MAX;
 }
+#endif
 
 /* is_vmcore_usable() checks if the kernel is booting after a panic and
  * the vmcore region is usable.
@@ -75,7 +77,8 @@ 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 elfcorehdr_addr != ELFCORE_ADDR_ERR &&
+		elfcorehdr_addr != ELFCORE_ADDR_MAX ? 1 : 0;
 }
 
 /* vmcore_unusable() marks the vmcore as unusable,
@@ -84,8 +87,7 @@ static inline int is_vmcore_usable(void)
 
 static inline void vmcore_unusable(void)
 {
-	if (is_kdump_kernel())
-		elfcorehdr_addr = ELFCORE_ADDR_ERR;
+	elfcorehdr_addr = ELFCORE_ADDR_ERR;
 }
 
 /**
-- 
2.41.0