Re: [PATCH 1/7] kexec_file: add kexec_file flag to control debug printing
From: Joe Perches <joe@perches.com>
Date: 2023-11-14 16:03:30
Also in:
kexec, linux-arm-kernel, linux-riscv, lkml
On Tue, 2023-11-14 at 23:32 +0800, Baoquan He wrote:
When specifying 'kexec -c -d', kexec_load interface will print loading information, e.g the regions where kernel/initrd/purgatory/cmdline are put, the memmap passed to 2nd kernel taken as system RAM ranges, and printing all contents of struct kexec_segment, etc. These are very helpful for analyzing or positioning what's happening when kexec/kdump itself failed. The debugging printing for kexec_load interface is made in user space utility kexec-tools. Whereas, with kexec_file_load interface, 'kexec -s -d' print nothing. Because kexec_file code is mostly implemented in kernel space, and the debugging printing functionality is missed. It's not convenient when debugging kexec/kdump loading and jumping with kexec_file_load interface. Now add KEXEC_FILE_DEBUG to kexec_file flag to control the debugging message printing. And add global variable kexec_file_dbg_print and macro kexec_dprintk() to facilitate the printing. This is a preparation, later kexec_dprintk() will be used to replace the existing pr_debug(). Once 'kexec -s -d' is specified, it will print out kexec/kdump loading information. If '-d' is not specified, it regresses to pr_debug().
Not quite as pr_debug is completely eliminated with zero object size when DEBUG is not #defined. Now the object size will be larger and contain the formats in .text. []
quoted hunk ↗ jump to hunk
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
[]
quoted hunk ↗ jump to hunk
@@ -264,6 +264,18 @@ arch_kexec_apply_relocations(struct purgatory_info *pi, Elf_Shdr *section, return -ENOEXEC; } #endif + +extern bool kexec_file_dbg_print; + +#define kexec_dprintk(fmt, args...) \ + do { \ + if (kexec_file_dbg_print) \ + printk(KERN_INFO fmt, ##args); \ + else \ + printk(KERN_DEBUG fmt, ##args); \ + } while (0) + +
I don't know how many of these printks exist and if
overall object size matters but using
#define kexec_dprintkfmt, ...) \
printk("%s" fmt, \
kexec_file_dbg_print ? KERN_INFO : KERN_DEBUG, \
##__VA_ARGS__)
should reduce overall object size by eliminating the
mostly duplicated format in .text which differs only
by the KERN_<PREFIX>