Messages in this thread | | | Subject | Re: [PATCH 1/7] kexec_file: add kexec_file flag to control debug printing | From | Joe Perches <> | Date | Tue, 14 Nov 2023 08:03:17 -0800 |
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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.
[] > diff --git a/include/linux/kexec.h b/include/linux/kexec.h [] > @@ -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>
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