diff mbox

[6/7] x86: kexec_file: clean up prepare_elf64_headers()

Message ID 20180227044814.24808-7-takahiro.akashi@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

AKASHI Takahiro Feb. 27, 2018, 4:48 a.m. UTC 
removing bufp variable in prepare_elf64_headers() makes the code simpler
and more understandable.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
---
 arch/x86/kernel/crash.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

Comments

Dave Young March 2, 2018, 5:39 a.m. UTC | #1 
On 02/27/18 at 01:48pm, AKASHI Takahiro wrote:
> removing bufp variable in prepare_elf64_headers() makes the code simpler
> and more understandable.
> 
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> Cc: Dave Young <dyoung@redhat.com>
> Cc: Vivek Goyal <vgoyal@redhat.com>
> Cc: Baoquan He <bhe@redhat.com>
> ---
>  arch/x86/kernel/crash.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index bfc37ad20d4a..a842fd847684 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -334,7 +334,7 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
>  	Elf64_Ehdr *ehdr;
>  	Elf64_Phdr *phdr;
>  	unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
> -	unsigned char *buf, *bufp;
> +	unsigned char *buf;
>  	unsigned int cpu, i;
>  	unsigned long long notes_addr;
>  	unsigned long mstart, mend;
> @@ -359,9 +359,8 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
>  	if (!buf)
>  		return -ENOMEM;
>  
> -	bufp = buf;
> -	ehdr = (Elf64_Ehdr *)bufp;
> -	bufp += sizeof(Elf64_Ehdr);
> +	ehdr = (Elf64_Ehdr *)buf;
> +	phdr = (Elf64_Phdr *)(ehdr + 1);

phdr should start with ehdr + sizeof(Elf64_Ehdr);

>  	memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
>  	ehdr->e_ident[EI_CLASS] = ELFCLASS64;
>  	ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
> @@ -377,33 +376,30 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
>  
>  	/* Prepare one phdr of type PT_NOTE for each present cpu */
>  	for_each_present_cpu(cpu) {
> -		phdr = (Elf64_Phdr *)bufp;
> -		bufp += sizeof(Elf64_Phdr);
>  		phdr->p_type = PT_NOTE;
>  		notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
>  		phdr->p_offset = phdr->p_paddr = notes_addr;
>  		phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
>  		(ehdr->e_phnum)++;
> +		phdr++;
>  	}
>  
>  	/* Prepare one PT_NOTE header for vmcoreinfo */
> -	phdr = (Elf64_Phdr *)bufp;
> -	bufp += sizeof(Elf64_Phdr);
>  	phdr->p_type = PT_NOTE;
>  	phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
>  	phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
>  	(ehdr->e_phnum)++;
> +	phdr++;
>  
>  	/* Prepare PT_LOAD type program header for kernel text region */
>  	if (kernel_map) {
> -		phdr = (Elf64_Phdr *)bufp;
> -		bufp += sizeof(Elf64_Phdr);
>  		phdr->p_type = PT_LOAD;
>  		phdr->p_flags = PF_R|PF_W|PF_X;
>  		phdr->p_vaddr = (Elf64_Addr)_text;
>  		phdr->p_filesz = phdr->p_memsz = _end - _text;
>  		phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
> -		(ehdr->e_phnum)++;
> +		ehdr->e_phnum++;
> +		phdr++;
>  	}
>  
>  	/* Go through all the ranges in cmem->ranges[] and prepare phdr */
> -- 
> 2.16.2
> 

Thanks
Dave
AKASHI Takahiro March 2, 2018, 5:58 a.m. UTC | #2 
On Fri, Mar 02, 2018 at 01:39:45PM +0800, Dave Young wrote:
> On 02/27/18 at 01:48pm, AKASHI Takahiro wrote:
> > removing bufp variable in prepare_elf64_headers() makes the code simpler
> > and more understandable.
> > 
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > Cc: Dave Young <dyoung@redhat.com>
> > Cc: Vivek Goyal <vgoyal@redhat.com>
> > Cc: Baoquan He <bhe@redhat.com>
> > ---
> >  arch/x86/kernel/crash.c | 18 +++++++-----------
> >  1 file changed, 7 insertions(+), 11 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> > index bfc37ad20d4a..a842fd847684 100644
> > --- a/arch/x86/kernel/crash.c
> > +++ b/arch/x86/kernel/crash.c
> > @@ -334,7 +334,7 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> >  	Elf64_Ehdr *ehdr;
> >  	Elf64_Phdr *phdr;
> >  	unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
> > -	unsigned char *buf, *bufp;
> > +	unsigned char *buf;
> >  	unsigned int cpu, i;
> >  	unsigned long long notes_addr;
> >  	unsigned long mstart, mend;
> > @@ -359,9 +359,8 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> >  	if (!buf)
> >  		return -ENOMEM;
> >  
> > -	bufp = buf;
> > -	ehdr = (Elf64_Ehdr *)bufp;
> > -	bufp += sizeof(Elf64_Ehdr);
> > +	ehdr = (Elf64_Ehdr *)buf;
> > +	phdr = (Elf64_Phdr *)(ehdr + 1);
> 
> phdr should start with ehdr + sizeof(Elf64_Ehdr);

Well, it's a matter of rhetoric :)
The values from both expressions are the same.
Or do you mean my expression is confusing?

-Takahiro AKASHI


> >  	memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
> >  	ehdr->e_ident[EI_CLASS] = ELFCLASS64;
> >  	ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
> > @@ -377,33 +376,30 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> >  
> >  	/* Prepare one phdr of type PT_NOTE for each present cpu */
> >  	for_each_present_cpu(cpu) {
> > -		phdr = (Elf64_Phdr *)bufp;
> > -		bufp += sizeof(Elf64_Phdr);
> >  		phdr->p_type = PT_NOTE;
> >  		notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
> >  		phdr->p_offset = phdr->p_paddr = notes_addr;
> >  		phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
> >  		(ehdr->e_phnum)++;
> > +		phdr++;
> >  	}
> >  
> >  	/* Prepare one PT_NOTE header for vmcoreinfo */
> > -	phdr = (Elf64_Phdr *)bufp;
> > -	bufp += sizeof(Elf64_Phdr);
> >  	phdr->p_type = PT_NOTE;
> >  	phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
> >  	phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
> >  	(ehdr->e_phnum)++;
> > +	phdr++;
> >  
> >  	/* Prepare PT_LOAD type program header for kernel text region */
> >  	if (kernel_map) {
> > -		phdr = (Elf64_Phdr *)bufp;
> > -		bufp += sizeof(Elf64_Phdr);
> >  		phdr->p_type = PT_LOAD;
> >  		phdr->p_flags = PF_R|PF_W|PF_X;
> >  		phdr->p_vaddr = (Elf64_Addr)_text;
> >  		phdr->p_filesz = phdr->p_memsz = _end - _text;
> >  		phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
> > -		(ehdr->e_phnum)++;
> > +		ehdr->e_phnum++;
> > +		phdr++;
> >  	}
> >  
> >  	/* Go through all the ranges in cmem->ranges[] and prepare phdr */
> > -- 
> > 2.16.2
> > 
> 
> Thanks
> Dave
Dave Young March 2, 2018, 6:04 a.m. UTC | #3 
On 03/02/18 at 02:58pm, AKASHI Takahiro wrote:
> On Fri, Mar 02, 2018 at 01:39:45PM +0800, Dave Young wrote:
> > On 02/27/18 at 01:48pm, AKASHI Takahiro wrote:
> > > removing bufp variable in prepare_elf64_headers() makes the code simpler
> > > and more understandable.
> > > 
> > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > > Cc: Dave Young <dyoung@redhat.com>
> > > Cc: Vivek Goyal <vgoyal@redhat.com>
> > > Cc: Baoquan He <bhe@redhat.com>
> > > ---
> > >  arch/x86/kernel/crash.c | 18 +++++++-----------
> > >  1 file changed, 7 insertions(+), 11 deletions(-)
> > > 
> > > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> > > index bfc37ad20d4a..a842fd847684 100644
> > > --- a/arch/x86/kernel/crash.c
> > > +++ b/arch/x86/kernel/crash.c
> > > @@ -334,7 +334,7 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> > >  	Elf64_Ehdr *ehdr;
> > >  	Elf64_Phdr *phdr;
> > >  	unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
> > > -	unsigned char *buf, *bufp;
> > > +	unsigned char *buf;
> > >  	unsigned int cpu, i;
> > >  	unsigned long long notes_addr;
> > >  	unsigned long mstart, mend;
> > > @@ -359,9 +359,8 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> > >  	if (!buf)
> > >  		return -ENOMEM;
> > >  
> > > -	bufp = buf;
> > > -	ehdr = (Elf64_Ehdr *)bufp;
> > > -	bufp += sizeof(Elf64_Ehdr);
> > > +	ehdr = (Elf64_Ehdr *)buf;
> > > +	phdr = (Elf64_Phdr *)(ehdr + 1);
> > 
> > phdr should start with ehdr + sizeof(Elf64_Ehdr);
> 
> Well, it's a matter of rhetoric :)
> The values from both expressions are the same.
> Or do you mean my expression is confusing?

Oops, I interpret it as (Elf64_Phdr *)ehdr + 1;

Please ignore this comment then.

> 
> -Takahiro AKASHI
> 
> 
> > >  	memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
> > >  	ehdr->e_ident[EI_CLASS] = ELFCLASS64;
> > >  	ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
> > > @@ -377,33 +376,30 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> > >  
> > >  	/* Prepare one phdr of type PT_NOTE for each present cpu */
> > >  	for_each_present_cpu(cpu) {
> > > -		phdr = (Elf64_Phdr *)bufp;
> > > -		bufp += sizeof(Elf64_Phdr);
> > >  		phdr->p_type = PT_NOTE;
> > >  		notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
> > >  		phdr->p_offset = phdr->p_paddr = notes_addr;
> > >  		phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
> > >  		(ehdr->e_phnum)++;
> > > +		phdr++;
> > >  	}
> > >  
> > >  	/* Prepare one PT_NOTE header for vmcoreinfo */
> > > -	phdr = (Elf64_Phdr *)bufp;
> > > -	bufp += sizeof(Elf64_Phdr);
> > >  	phdr->p_type = PT_NOTE;
> > >  	phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
> > >  	phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
> > >  	(ehdr->e_phnum)++;
> > > +	phdr++;
> > >  
> > >  	/* Prepare PT_LOAD type program header for kernel text region */
> > >  	if (kernel_map) {
> > > -		phdr = (Elf64_Phdr *)bufp;
> > > -		bufp += sizeof(Elf64_Phdr);
> > >  		phdr->p_type = PT_LOAD;
> > >  		phdr->p_flags = PF_R|PF_W|PF_X;
> > >  		phdr->p_vaddr = (Elf64_Addr)_text;
> > >  		phdr->p_filesz = phdr->p_memsz = _end - _text;
> > >  		phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
> > > -		(ehdr->e_phnum)++;
> > > +		ehdr->e_phnum++;
> > > +		phdr++;
> > >  	}
> > >  
> > >  	/* Go through all the ranges in cmem->ranges[] and prepare phdr */
> > > -- 
> > > 2.16.2
> > > 
> > 
> > Thanks
> > Dave
diff mbox

Patch

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index bfc37ad20d4a..a842fd847684 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -334,7 +334,7 @@  static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
 	Elf64_Ehdr *ehdr;
 	Elf64_Phdr *phdr;
 	unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
-	unsigned char *buf, *bufp;
+	unsigned char *buf;
 	unsigned int cpu, i;
 	unsigned long long notes_addr;
 	unsigned long mstart, mend;
@@ -359,9 +359,8 @@  static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
 	if (!buf)
 		return -ENOMEM;
 
-	bufp = buf;
-	ehdr = (Elf64_Ehdr *)bufp;
-	bufp += sizeof(Elf64_Ehdr);
+	ehdr = (Elf64_Ehdr *)buf;
+	phdr = (Elf64_Phdr *)(ehdr + 1);
 	memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
 	ehdr->e_ident[EI_CLASS] = ELFCLASS64;
 	ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
@@ -377,33 +376,30 @@  static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
 
 	/* Prepare one phdr of type PT_NOTE for each present cpu */
 	for_each_present_cpu(cpu) {
-		phdr = (Elf64_Phdr *)bufp;
-		bufp += sizeof(Elf64_Phdr);
 		phdr->p_type = PT_NOTE;
 		notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
 		phdr->p_offset = phdr->p_paddr = notes_addr;
 		phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
 		(ehdr->e_phnum)++;
+		phdr++;
 	}
 
 	/* Prepare one PT_NOTE header for vmcoreinfo */
-	phdr = (Elf64_Phdr *)bufp;
-	bufp += sizeof(Elf64_Phdr);
 	phdr->p_type = PT_NOTE;
 	phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
 	phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
 	(ehdr->e_phnum)++;
+	phdr++;
 
 	/* Prepare PT_LOAD type program header for kernel text region */
 	if (kernel_map) {
-		phdr = (Elf64_Phdr *)bufp;
-		bufp += sizeof(Elf64_Phdr);
 		phdr->p_type = PT_LOAD;
 		phdr->p_flags = PF_R|PF_W|PF_X;
 		phdr->p_vaddr = (Elf64_Addr)_text;
 		phdr->p_filesz = phdr->p_memsz = _end - _text;
 		phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
-		(ehdr->e_phnum)++;
+		ehdr->e_phnum++;
+		phdr++;
 	}
 
 	/* Go through all the ranges in cmem->ranges[] and prepare phdr */