Paul:
I noticed that when passing a zero address to kallsyms_lookup(), the kernel
thought it was a valid kernel address, even if it was not for the specific
architecture I was running things on.
This was because is_kernel_extratext() was checking against labels that don't
exist on many archs. Since PPC is the only kernel which defines _extra_text,
(which doesn't seem to be used anymore?) there are three options:
- make the check dependant on PPC
- make the check dependant on extratext being populated
- remove _extra_text support from:
linux-2.6.x/arch/ppc/kernel/vmlinux.lds.S
linux-2.6.x/include/asm-generic/sections.h
linux-2.6.x/kernel/kallsyms.c
linux-2.6.x/scripts/kallsyms.c
Since I don't know the history on that label I thought I would ask (since you
seem to be the only arch using it) before I sent a patch.
-Robin
Because #1 & #2 are trivial, here is what I was thinking:
- make the check dependant on PPC
===================================================================
--- linux-2.6.x/kernel/kallsyms.c (revision 3760)
+++ linux-2.6.x/kernel/kallsyms.c (working copy)
@@ -51,7 +51,8 @@
static inline int is_kernel_extratext(unsigned long addr)
{
+ #ifdef CONFIG_PPC
if (addr >= (unsigned long)_sextratext
&& addr <= (unsigned long)_eextratext)
return 1;
+ #endif
return 0;
}
OR
- make the check dependant on extratext being populated
===================================================================
--- linux-2.6.x/kernel/kallsyms.c (revision 3760)
+++ linux-2.6.x/kernel/kallsyms.c (working copy)
@@ -51,7 +51,8 @@
static inline int is_kernel_extratext(unsigned long addr)
{
if (addr >= (unsigned long)_sextratext
- && addr <= (unsigned long)_eextratext)
+ && addr <= (unsigned long)_eextratext
+ && _sextratext && _eextratext)
return 1;
return 0;
}
On 10/24/07, Robin Getz <[email protected]> wrote:
> - make the check dependant on extratext being populated
> ===================================================================
> --- linux-2.6.x/kernel/kallsyms.c (revision 3760)
> +++ linux-2.6.x/kernel/kallsyms.c (working copy)
> @@ -51,7 +51,8 @@
> static inline int is_kernel_extratext(unsigned long addr)
> {
> if (addr >= (unsigned long)_sextratext
> - && addr <= (unsigned long)_eextratext)
> + && addr <= (unsigned long)_eextratext
> + && _sextratext && _eextratext)
> return 1;
> return 0;
> }
i think you'd want:
if (_sextratext && _eextratext &&
... everything else ...
-mike
On Wed 24 Oct 2007 08:36, Robin Getz pondered:
> Paul:
>
> I noticed that when passing a zero address to kallsyms_lookup(), the
> kernel thought it was a valid kernel address, even if it was not for the
> specific architecture it was running on.
>
> This was because is_kernel_extratext() was checking against labels that
> don't exist on many archs. Since PPC is the only kernel which defines
> _extra_text, (which doesn't seem to be used anymore?) there are three options:
> - make the check dependant on PPC
> - make the check dependant on extratext being populated
> - remove _extra_text support from:
> linux-2.6.x/arch/ppc/kernel/vmlinux.lds.S
> linux-2.6.x/include/asm-generic/sections.h
> linux-2.6.x/kernel/kallsyms.c
> linux-2.6.x/scripts/kallsyms.c
>
> Since I don't know the history on that label I thought I would ask
> (since PPC seem to be the only arch using it) before I sent a patch.
OK, it looks like:
David Woodhouse added this functionality 5 May 2005:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=075d6eb16d273dab7b7b4b83fcee8bce4ee387ed
and then Jon Loeliger removed everything in this section 17 Sep 2005
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=6c45ab992e4299c869fb26427944a8f8ea177024
David/Jon:
Is this section still used on PPC, or can the entire support for extratext be removed?
Thanks
On Fri, 2007-10-26 at 05:57 -0400, Robin Getz wrote:
> Is this section still used on PPC, or can the entire support for
> extratext be removed?
I think it can die.
--
dwmw2
David Woodhouse wrote:
> On Fri, 2007-10-26 at 05:57 -0400, Robin Getz wrote:
>> Is this section still used on PPC, or can the entire support for
>> extratext be removed?
>
> I think it can die.
>
Agreed. For history, see this:
http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019734.html
and
http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019736.html
where Arnd says:
> The users of the ppc64 function in_kernel_text() can probably be converted
> to the generic is_kernel_text() function.
>
> Arnd <><
and
http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019751.html
Where Paul said:
>> And I assume that the obvious mappings can take place (ie, that
>> "pmac.text" can just be placed in regular .text, etc), right?
>
> Yes.
>
> Paul.
HTH,
jdl
From: Robin Getz <[email protected]>
when passing a zero address to kallsyms_lookup(), the kernel thought it was a
valid kernel address, even if it is not. This is because is_ksym_addr() called
is_kernel_extratext() and checked against labels that don't exist on many
archs (which default as zero). Since PPC was the only kernel which defines
_extra_text, (in 2005), and no longer needs it, this patch removes _extra_text
support.
arch/ppc/kernel/vmlinux.lds.S | 5 -----
include/asm-generic/sections.h | 2 --
kernel/kallsyms.c | 11 +----------
scripts/kallsyms.c | 12 +++---------
4 files changed, 4 insertions(+), 26 deletions(-)
Signed-off-by: Robin Getz <[email protected]>
cc: David Woodhouse <[email protected]>
cc: Jon Loeliger <[email protected]>
cc: Paul Mackerras <[email protected]>
----
For some history (provided by Jon):
http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019734.html
http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019736.html
http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019751.html
Index: kernel/kallsyms.c
===================================================================
--- kernel/kallsyms.c (revision 3780)
+++ kernel/kallsyms.c (working copy)
@@ -48,14 +48,6 @@
return 0;
}
-static inline int is_kernel_extratext(unsigned long addr)
-{
- if (addr >= (unsigned long)_sextratext
- && addr <= (unsigned long)_eextratext)
- return 1;
- return 0;
-}
-
static inline int is_kernel_text(unsigned long addr)
{
if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)
@@ -79,8 +71,7 @@
if (all_var)
return is_kernel(addr);
- return is_kernel_text(addr) || is_kernel_inittext(addr) ||
- is_kernel_extratext(addr);
+ return is_kernel_text(addr) || is_kernel_inittext(addr);
}
/* expand a compressed symbol data into the resulting uncompressed string,
Index: include/asm-generic/sections.h
===================================================================
--- include/asm-generic/sections.h (revision 3780)
+++ include/asm-generic/sections.h (working copy)
@@ -8,8 +8,6 @@
extern char __bss_start[], __bss_stop[];
extern char __init_begin[], __init_end[];
extern char _sinittext[], _einittext[];
-extern char _sextratext[] __attribute__((weak));
-extern char _eextratext[] __attribute__((weak));
extern char _end[];
extern char __per_cpu_start[], __per_cpu_end[];
extern char __kprobes_text_start[], __kprobes_text_end[];
Index: scripts/kallsyms.c
===================================================================
--- scripts/kallsyms.c (revision 3780)
+++ scripts/kallsyms.c (working copy)
@@ -45,7 +45,7 @@
static struct sym_entry *table;
static unsigned int table_size, table_cnt;
-static unsigned long long _text, _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext;
+static unsigned long long _text, _stext, _etext, _sinittext, _einittext;
static unsigned long long _stext_l1, _etext_l1;
static int all_symbols = 0;
static char symbol_prefix_char = '\0';
@@ -104,10 +104,6 @@
_sinittext = s->addr;
else if (strcmp(sym, "_einittext") == 0)
_einittext = s->addr;
- else if (strcmp(sym, "_sextratext") == 0)
- _sextratext = s->addr;
- else if (strcmp(sym, "_eextratext") == 0)
- _eextratext = s->addr;
else if (strcmp(sym, "_stext_l1" ) == 0)
_stext_l1 = s->addr;
else if (strcmp(sym, "_etext_l1" ) == 0)
@@ -175,18 +171,16 @@
if (!all_symbols) {
if ((s->addr < _stext || s->addr > _etext)
&& (s->addr < _sinittext || s->addr > _einittext)
- && (s->addr < _sextratext || s->addr > _eextratext)
&& (s->addr < _stext_l1 || s->addr > _etext_l1))
return 0;
/* Corner case. Discard any symbols with the same value as
- * _etext _einittext or _eextratext; they can move between pass
+ * _etext; they can move between pass
* 1 and 2 when the kallsyms data are added. If these symbols
* move then they may get dropped in pass 2, which breaks the
* kallsyms rules.
*/
if ((s->addr == _etext && strcmp((char*)s->sym + offset, "_etext")) ||
- (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) ||
- (s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext")))
+ (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")))
return 0;
}
Index: arch/ppc/kernel/vmlinux.lds.S
===================================================================
--- arch/ppc/kernel/vmlinux.lds.S (revision 3780)
+++ arch/ppc/kernel/vmlinux.lds.S (working copy)
@@ -144,11 +144,6 @@
. = ALIGN(4096);
__init_end = .;
-
- . = ALIGN(4096);
- _sextratext = .;
- _eextratext = .;
-
__bss_start = .;
.bss :
{
On Fri, 26 Oct 2007 15:43:56 -0400
Robin Getz <[email protected]> wrote:
> From: Robin Getz <[email protected]>
>
> when passing a zero address to kallsyms_lookup(), the kernel thought it was a
> valid kernel address, even if it is not. This is because is_ksym_addr() called
> is_kernel_extratext() and checked against labels that don't exist on many
> archs (which default as zero). Since PPC was the only kernel which defines
> _extra_text, (in 2005), and no longer needs it, this patch removes _extra_text
> support.
I hit numerous rejects here. I am not sure which kernel you patched but I
suspect it was not an up-to-date one.
> --- kernel/kallsyms.c (revision 3780)
> +++ kernel/kallsyms.c (working copy)
Please prepare patches in `patch -p1' form. This should have been
--- foo/kernel/kallsyms.c (revision 3780)
+++ bar/kernel/kallsyms.c (working copy)
> */
> if ((s->addr == _etext && strcmp((char*)s->sym + offset, "_etext")) ||
> - (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) ||
> - (s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext")))
> + (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")))
> return 0;
> }
I don't understand why this hunk is changing _einittext handling, and I
suspect this was a mistake, so I left that bit out.
I ended up with this:
From: Robin Getz <[email protected]>
When passing a zero address to kallsyms_lookup(), the kernel thought it was
a valid kernel address, even if it is not. This is because is_ksym_addr()
called is_kernel_extratext() and checked against labels that don't exist on
many archs (which default as zero). Since PPC was the only kernel which
defines _extra_text, (in 2005), and no longer needs it, this patch removes
_extra_text support.
For some history (provided by Jon):
http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019734.html
http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019736.html
http://ozlabs.org/pipermail/linuxppc-dev/2005-September/019751.html
Signed-off-by: Robin Getz <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Jon Loeliger <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Sam Ravnborg <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
arch/ppc/kernel/vmlinux.lds.S | 5 -----
include/asm-generic/sections.h | 2 --
kernel/kallsyms.c | 11 +----------
scripts/kallsyms.c | 24 ++++++++++--------------
4 files changed, 11 insertions(+), 31 deletions(-)
diff -puN arch/ppc/kernel/vmlinux.lds.S~remove-support-for-un-needed-_extratext-section arch/ppc/kernel/vmlinux.lds.S
--- a/arch/ppc/kernel/vmlinux.lds.S~remove-support-for-un-needed-_extratext-section
+++ a/arch/ppc/kernel/vmlinux.lds.S
@@ -143,11 +143,6 @@ SECTIONS
. = ALIGN(4096);
__init_end = .;
-
- . = ALIGN(4096);
- _sextratext = .;
- _eextratext = .;
-
__bss_start = .;
.bss :
{
diff -puN include/asm-generic/sections.h~remove-support-for-un-needed-_extratext-section include/asm-generic/sections.h
--- a/include/asm-generic/sections.h~remove-support-for-un-needed-_extratext-section
+++ a/include/asm-generic/sections.h
@@ -8,8 +8,6 @@ extern char _data[], _sdata[], _edata[];
extern char __bss_start[], __bss_stop[];
extern char __init_begin[], __init_end[];
extern char _sinittext[], _einittext[];
-extern char _sextratext[] __attribute__((weak));
-extern char _eextratext[] __attribute__((weak));
extern char _end[];
extern char __per_cpu_start[], __per_cpu_end[];
extern char __kprobes_text_start[], __kprobes_text_end[];
diff -puN kernel/kallsyms.c~remove-support-for-un-needed-_extratext-section kernel/kallsyms.c
--- a/kernel/kallsyms.c~remove-support-for-un-needed-_extratext-section
+++ a/kernel/kallsyms.c
@@ -48,14 +48,6 @@ static inline int is_kernel_inittext(uns
return 0;
}
-static inline int is_kernel_extratext(unsigned long addr)
-{
- if (addr >= (unsigned long)_sextratext
- && addr <= (unsigned long)_eextratext)
- return 1;
- return 0;
-}
-
static inline int is_kernel_text(unsigned long addr)
{
if (addr >= (unsigned long)_stext && addr <= (unsigned long)_etext)
@@ -75,8 +67,7 @@ static int is_ksym_addr(unsigned long ad
if (all_var)
return is_kernel(addr);
- return is_kernel_text(addr) || is_kernel_inittext(addr) ||
- is_kernel_extratext(addr);
+ return is_kernel_text(addr) || is_kernel_inittext(addr);
}
/* expand a compressed symbol data into the resulting uncompressed string,
diff -puN scripts/kallsyms.c~remove-support-for-un-needed-_extratext-section scripts/kallsyms.c
--- a/scripts/kallsyms.c~remove-support-for-un-needed-_extratext-section
+++ a/scripts/kallsyms.c
@@ -41,7 +41,7 @@ struct sym_entry {
static struct sym_entry *table;
static unsigned int table_size, table_cnt;
-static unsigned long long _text, _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext;
+static unsigned long long _text, _stext, _etext, _sinittext, _einittext;
static int all_symbols = 0;
static char symbol_prefix_char = '\0';
@@ -99,10 +99,6 @@ static int read_symbol(FILE *in, struct
_sinittext = s->addr;
else if (strcmp(sym, "_einittext") == 0)
_einittext = s->addr;
- else if (strcmp(sym, "_sextratext") == 0)
- _sextratext = s->addr;
- else if (strcmp(sym, "_eextratext") == 0)
- _eextratext = s->addr;
else if (toupper(stype) == 'A')
{
/* Keep these useful absolute symbols */
@@ -165,18 +161,18 @@ static int symbol_valid(struct sym_entry
* and inittext sections are discarded */
if (!all_symbols) {
if ((s->addr < _stext || s->addr > _etext)
- && (s->addr < _sinittext || s->addr > _einittext)
- && (s->addr < _sextratext || s->addr > _eextratext))
+ && (s->addr < _sinittext || s->addr > _einittext))
return 0;
/* Corner case. Discard any symbols with the same value as
- * _etext _einittext or _eextratext; they can move between pass
- * 1 and 2 when the kallsyms data are added. If these symbols
- * move then they may get dropped in pass 2, which breaks the
- * kallsyms rules.
+ * _etext _einittext; they can move between pass 1 and 2 when
+ * the kallsyms data are added. If these symbols move then
+ * they may get dropped in pass 2, which breaks the kallsyms
+ * rules.
*/
- if ((s->addr == _etext && strcmp((char*)s->sym + offset, "_etext")) ||
- (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) ||
- (s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext")))
+ if ((s->addr == _etext &&
+ strcmp((char*)s->sym + offset, "_etext")) ||
+ (s->addr == _einittext &&
+ strcmp((char*)s->sym + offset, "_einittext")))
return 0;
}
_
On Mon 29 Oct 2007 18:22, Andrew Morton pondered:
> I hit numerous rejects here. I am not sure which kernel you patched but
> I suspect it was not an up-to-date one.
Sorry about that - I will do so in the future. Thanks for reviewing and fixing up.
> > --- kernel/kallsyms.c (revision 3780)
> > +++ kernel/kallsyms.c (working copy)
>
> Please prepare patches in `patch -p1' form. This should have been
>
> --- foo/kernel/kallsyms.c (revision 3780)
> +++ bar/kernel/kallsyms.c (working copy)
Sorry twice.
> > */
> > if ((s->addr == _etext && strcmp((char*)s->sym + offset, "_etext")) ||
> > - (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) ||
> > - (s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext")))
> > + (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")))
> > return 0;
> > }
>
> I don't understand why this hunk is changing _einittext handling, and I
> suspect this was a mistake, so I left that bit out.
I didn't think I did change the _einittext handling - just removed
_eextratext, and removed the trailing ||, and closed the parentheses for
the if statement.
- (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) ||
+ (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")))
I think this is the same as what you have here - isn't it?
> - if ((s->addr == _etext && strcmp((char*)s->sym + offset, "_etext")) ||
> - (s->addr == _einittext && strcmp((char*)s->sym + offset, "_einittext")) ||
> - (s->addr == _eextratext && strcmp((char*)s->sym + offset, "_eextratext")))
> + if ((s->addr == _etext &&
> + strcmp((char*)s->sym + offset, "_etext")) ||
> + (s->addr == _einittext &&
> + strcmp((char*)s->sym + offset, "_einittext")))
> return 0;
?