[PATCH] kernel/crash: make parse_crashkernel()'s return value more indicant

[PATCH] kernel/crash: make parse_crashkernel()'s return value more indicant

[Pingfan Liu]

At present, both return and crash_size should be checked to guarantee the
success of parse_crashkernel().
Simplify the way by returning negative if fail, positive if success. In
case of failure, -EINVAL for bad syntax, -1 for the parsing results in
crash_size=0.

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Julien Thierry <julien.thierry@arm.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Greg Hackmann <ghackmann@android.com>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Yangtao Li <tiny.windzz@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: x86@kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
---
 arch/arm/kernel/setup.c             |  2 +-
 arch/arm64/mm/init.c                |  2 +-
 arch/ia64/kernel/setup.c            |  2 +-
 arch/mips/kernel/setup.c            |  2 +-
 arch/powerpc/kernel/fadump.c        |  2 +-
 arch/powerpc/kernel/machine_kexec.c |  2 +-
 arch/s390/kernel/setup.c            |  2 +-
 arch/sh/kernel/machine_kexec.c      |  2 +-
 arch/x86/kernel/setup.c             |  4 ++--
 kernel/crash_core.c                 | 12 ++++++++++--
 10 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 5d78b6a..2feab13 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -997,7 +997,7 @@ static void __init reserve_crashkernel(void)
 	total_mem = get_total_mem();
 	ret = parse_crashkernel(boot_command_line, total_mem,
 				&crash_size, &crash_base);
-	if (ret)
+	if (ret < 0)
 		return;
 
 	if (crash_base <= 0) {
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 6bc1350..240918c 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -79,7 +79,7 @@ static void __init reserve_crashkernel(void)
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&crash_size, &crash_base);
 	/* no crashkernel= or invalid value specified */
-	if (ret || !crash_size)
+	if (ret < 0)
 		return;
 
 	crash_size = PAGE_ALIGN(crash_size);
diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c
index 583a374..99cae33 100644
--- a/arch/ia64/kernel/setup.c
+++ b/arch/ia64/kernel/setup.c
@@ -277,7 +277,7 @@ static void __init setup_crashkernel(unsigned long total, int *n)
 
 	ret = parse_crashkernel(boot_command_line, total,
 			&size, &base);
-	if (ret == 0 && size > 0) {
+	if (ret >= 0) {
 		if (!base) {
 			sort_regions(rsvd_region, *n);
 			*n = merge_regions(rsvd_region, *n);
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 8d1dc6c..168571b 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -715,7 +715,7 @@ static void __init mips_parse_crashkernel(void)
 	total_mem = get_total_mem();
 	ret = parse_crashkernel(boot_command_line, total_mem,
 				&crash_size, &crash_base);
-	if (ret != 0 || crash_size <= 0)
+	if (ret < 0)
 		return;
 
 	if (!memory_region_available(crash_base, crash_size)) {
diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 45a8d0b..0b626e2 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -376,7 +376,7 @@ static inline unsigned long fadump_calculate_reserve_size(void)
 	 */
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&size, &base);
-	if (ret == 0 && size > 0) {
+	if (ret >= 0) {
 		unsigned long max_size;
 
 		if (fw_dump.reserve_bootvar)
diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
index 63f5a93..9f3e61a 100644
--- a/arch/powerpc/kernel/machine_kexec.c
+++ b/arch/powerpc/kernel/machine_kexec.c
@@ -122,7 +122,7 @@ void __init reserve_crashkernel(void)
 	/* use common parsing */
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 			&crash_size, &crash_base);
-	if (ret == 0 && crash_size > 0) {
+	if (ret >= 0) {
 		crashk_res.start = crash_base;
 		crashk_res.end = crash_base + crash_size - 1;
 	}
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 2c642af..d4bd61b 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -671,7 +671,7 @@ static void __init reserve_crashkernel(void)
 
 	crash_base = ALIGN(crash_base, KEXEC_CRASH_MEM_ALIGN);
 	crash_size = ALIGN(crash_size, KEXEC_CRASH_MEM_ALIGN);
-	if (rc || crash_size == 0)
+	if (rc < 0)
 		return;
 
 	if (memblock.memory.regions[0].size < crash_size) {
diff --git a/arch/sh/kernel/machine_kexec.c b/arch/sh/kernel/machine_kexec.c
index 63d63a3..612b21e 100644
--- a/arch/sh/kernel/machine_kexec.c
+++ b/arch/sh/kernel/machine_kexec.c
@@ -157,7 +157,7 @@ void __init reserve_crashkernel(void)
 
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 			&crash_size, &crash_base);
-	if (ret == 0 && crash_size > 0) {
+	if (ret >= 0) {
 		crashk_res.start = crash_base;
 		crashk_res.end = crash_base + crash_size - 1;
 	}
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 3d872a5..62d07d4 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -526,11 +526,11 @@ static void __init reserve_crashkernel(void)
 
 	/* crashkernel=XM */
 	ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
-	if (ret != 0 || crash_size <= 0) {
+	if (ret == -EINVAL) {
 		/* crashkernel=X,high */
 		ret = parse_crashkernel_high(boot_command_line, total_mem,
 					     &crash_size, &crash_base);
-		if (ret != 0 || crash_size <= 0)
+		if (ret < 0)
 			return;
 		high = true;
 	}
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 093c9f9..563d86d 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -87,7 +87,7 @@ static int __init parse_crashkernel_mem(char *cmdline,
 		cur = tmp;
 		if (size >= system_ram) {
 			pr_warn("crashkernel: invalid size\n");
-			return -EINVAL;
+			return -1;
 		}
 
 		/* match ? */
@@ -108,8 +108,10 @@ static int __init parse_crashkernel_mem(char *cmdline,
 				return -EINVAL;
 			}
 		}
-	} else
+	} else {
 		pr_info("crashkernel size resulted in zero bytes\n");
+		return -1;
+	}
 
 	return 0;
 }
@@ -139,6 +141,8 @@ static int __init parse_crashkernel_simple(char *cmdline,
 		pr_warn("crashkernel: unrecognized char: %c\n", *cur);
 		return -EINVAL;
 	}
+	if (*crash_size == 0)
+		return -1;
 
 	return 0;
 }
@@ -181,6 +185,8 @@ static int __init parse_crashkernel_suffix(char *cmdline,
 		pr_warn("crashkernel: unrecognized char: %c\n", *cur);
 		return -EINVAL;
 	}
+	if (*crash_size == 0)
+		return -1;
 
 	return 0;
 }
@@ -266,6 +272,8 @@ static int __init __parse_crashkernel(char *cmdline,
 /*
  * That function is the entry point for command line parsing and should be
  * called from the arch-specific code.
+ * On success 0 or 1 if @offset is given. On error -EINVAL if bad syntax,
+ * or -1 if the parsing results in crash_size=0.
  */
 int __init parse_crashkernel(char *cmdline,
 			     unsigned long long system_ram,
-- 
2.7.4

Re: [PATCH] kernel/crash: make parse_crashkernel()'s return value more indicant

[Thomas Gleixner]

On Fri, 19 Apr 2019, Pingfan Liu wrote:

> At present, both return and crash_size should be checked to guarantee the
> success of parse_crashkernel().
> Simplify the way by returning negative if fail, positive if success. In
> case of failure, -EINVAL for bad syntax, -1 for the parsing results in
> crash_size=0.

I'm not entirely sure what you are trying to say here, but '-1' is not an
improvement at all. We surely are not short of proper error codes, right?

Also I don't see any positive return value > 0. So what is this about:

> --- a/arch/ia64/kernel/setup.c
> +++ b/arch/ia64/kernel/setup.c
> @@ -277,7 +277,7 @@ static void __init setup_crashkernel(unsigned long total, int *n)
>  
>  	ret = parse_crashkernel(boot_command_line, total,
>  			&size, &base);
> -	if (ret == 0 && size > 0) {
> +	if (ret >= 0) {

  ^^^^^^^^^^^^^^^^^^^^^^^^^^^  ????

>  	if (!memory_region_available(crash_base, crash_size)) {
> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> index 45a8d0b..0b626e2 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -376,7 +376,7 @@ static inline unsigned long fadump_calculate_reserve_size(void)
>  	 */
>  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>  				&size, &base);
> -	if (ret == 0 && size > 0) {
> +	if (ret >= 0) {

and this ?

>  		unsigned long max_size;
>  
>  		if (fw_dump.reserve_bootvar)
> diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> index 63f5a93..9f3e61a 100644
> --- a/arch/powerpc/kernel/machine_kexec.c
> +++ b/arch/powerpc/kernel/machine_kexec.c
> @@ -122,7 +122,7 @@ void __init reserve_crashkernel(void)
>  	/* use common parsing */
>  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>  			&crash_size, &crash_base);
> -	if (ret == 0 && crash_size > 0) {
> +	if (ret >= 0) {

Again.

>  		crashk_res.start = crash_base;
>  		crashk_res.end = crash_base + crash_size - 1;
>  	}
> --- a/arch/sh/kernel/machine_kexec.c
> +++ b/arch/sh/kernel/machine_kexec.c
> @@ -157,7 +157,7 @@ void __init reserve_crashkernel(void)
>  
>  	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
>  			&crash_size, &crash_base);
> -	if (ret == 0 && crash_size > 0) {
> +	if (ret >= 0) {

And some more.

>  		crashk_res.start = crash_base;
>  		crashk_res.end = crash_base + crash_size - 1;
>  	}
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 3d872a5..62d07d4 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -526,11 +526,11 @@ static void __init reserve_crashkernel(void)
>  
>  	/* crashkernel=XM */
>  	ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
> -	if (ret != 0 || crash_size <= 0) {
> +	if (ret == -EINVAL) {

Without an explanation why this proceedes on error codes other than EINVAL
this is uncomprehensible. Comments exist for a reason.

>  		/* crashkernel=X,high */
>  		ret = parse_crashkernel_high(boot_command_line, total_mem,
>  					     &crash_size, &crash_base);
> -		if (ret != 0 || crash_size <= 0)
> +		if (ret < 0)
>  			return;
>  		high = true;

> @@ -87,7 +87,7 @@ static int __init parse_crashkernel_mem(char *cmdline,
>  		cur = tmp;
>  		if (size >= system_ram) {
>  			pr_warn("crashkernel: invalid size\n");
> -			return -EINVAL;
> +			return -1;

Well, this is incomprehensible as well. The pr_warn() says invalid and then
you change the error code to something magic.

Thanks,

	tglx

Re: [PATCH] kernel/crash: make parse_crashkernel()'s return value more indicant

[Pingfan Liu]

On Fri, Apr 19, 2019 at 4:19 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Fri, 19 Apr 2019, Pingfan Liu wrote:
>
> > At present, both return and crash_size should be checked to guarantee the
> > success of parse_crashkernel().
> > Simplify the way by returning negative if fail, positive if success. In
> > case of failure, -EINVAL for bad syntax, -1 for the parsing results in
> > crash_size=0.
>
> I'm not entirely sure what you are trying to say here, but '-1' is not an
> improvement at all. We surely are not short of proper error codes, right?
>
The different negative return values are only used by x86. The option
"crashkernel=X,high", which is only used on x86, causes parse_kernel()
to return -EINVAL, then let parse_crashkernel_high() have a try.

When parsing crashkernel=size@offset and crashkernel=range1:size1,
there are other cases of failure, which is not worth to call
parse_crashkernel_high() to have a try. That is "-1" aiming for.

First, in parse_crashkernel_mem(), if demanded size is bigger than
system ram, this one looks like -ENOMEM, but -ENOMEM normally is used
for allocation. Second, in parse_crashkernel_mem(), if system ram is
not inside the range listed by "crashkernel=". Third, crashkernel=0MB
is given in the option (not in practice, but can not forbid user to do
so).

All of these cases can be treated as -EINVAL, but hard to define the
error codes.
> Also I don't see any positive return value > 0. So what is this about:
>
Yes. 0 is enough for success.  I had thought about returning 1 if
@offset is specified in crashkernel. But at present, no use case for
it.

> > --- a/arch/ia64/kernel/setup.c
> > +++ b/arch/ia64/kernel/setup.c
> > @@ -277,7 +277,7 @@ static void __init setup_crashkernel(unsigned long total, int *n)
> >
> >       ret = parse_crashkernel(boot_command_line, total,
> >                       &size, &base);
> > -     if (ret == 0 && size > 0) {
> > +     if (ret >= 0) {
>
>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^  ????
>
> >       if (!memory_region_available(crash_base, crash_size)) {
> > diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> > index 45a8d0b..0b626e2 100644
> > --- a/arch/powerpc/kernel/fadump.c
> > +++ b/arch/powerpc/kernel/fadump.c
> > @@ -376,7 +376,7 @@ static inline unsigned long fadump_calculate_reserve_size(void)
> >        */
> >       ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
> >                               &size, &base);
> > -     if (ret == 0 && size > 0) {
> > +     if (ret >= 0) {
>
> and this ?
>
> >               unsigned long max_size;
> >
> >               if (fw_dump.reserve_bootvar)
> > diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> > index 63f5a93..9f3e61a 100644
> > --- a/arch/powerpc/kernel/machine_kexec.c
> > +++ b/arch/powerpc/kernel/machine_kexec.c
> > @@ -122,7 +122,7 @@ void __init reserve_crashkernel(void)
> >       /* use common parsing */
> >       ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
> >                       &crash_size, &crash_base);
> > -     if (ret == 0 && crash_size > 0) {
> > +     if (ret >= 0) {
>
> Again.
>
> >               crashk_res.start = crash_base;
> >               crashk_res.end = crash_base + crash_size - 1;
> >       }
> > --- a/arch/sh/kernel/machine_kexec.c
> > +++ b/arch/sh/kernel/machine_kexec.c
> > @@ -157,7 +157,7 @@ void __init reserve_crashkernel(void)
> >
> >       ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
> >                       &crash_size, &crash_base);
> > -     if (ret == 0 && crash_size > 0) {
> > +     if (ret >= 0) {
>
> And some more.
>
> >               crashk_res.start = crash_base;
> >               crashk_res.end = crash_base + crash_size - 1;
> >       }
> > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> > index 3d872a5..62d07d4 100644
> > --- a/arch/x86/kernel/setup.c
> > +++ b/arch/x86/kernel/setup.c
> > @@ -526,11 +526,11 @@ static void __init reserve_crashkernel(void)
> >
> >       /* crashkernel=XM */
> >       ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
> > -     if (ret != 0 || crash_size <= 0) {
> > +     if (ret == -EINVAL) {
>
> Without an explanation why this proceedes on error codes other than EINVAL
> this is uncomprehensible. Comments exist for a reason.
>
As explained above, deciding whether to let parse_crashkernel_high() try.

> >               /* crashkernel=X,high */
> >               ret = parse_crashkernel_high(boot_command_line, total_mem,
> >                                            &crash_size, &crash_base);
> > -             if (ret != 0 || crash_size <= 0)
> > +             if (ret < 0)
> >                       return;
> >               high = true;
>
> > @@ -87,7 +87,7 @@ static int __init parse_crashkernel_mem(char *cmdline,
> >               cur = tmp;
> >               if (size >= system_ram) {
> >                       pr_warn("crashkernel: invalid size\n");
> > -                     return -EINVAL;
> > +                     return -1;
>
> Well, this is incomprehensible as well. The pr_warn() says invalid and then
> you change the error code to something magic.
>
As explained above, want to know whether worth to let
parse_crashkernel_high() try.

What about the following alternative method? Treating crash_size=0 as
-EINVAL. Then on x86, just call parse_crashkernel_high() blindly to
have a try. Thanks for your review.

Regards,
Pingfan