diff options
| author | Nicolas Pitre <nico@fluxnic.net> | 2010-08-26 23:10:50 -0400 |
|---|---|---|
| committer | Nicolas Pitre <nicolas.pitre@linaro.org> | 2010-10-01 22:35:19 -0400 |
| commit | ec706dab290c486837d4a825870ab052bf200279 (patch) | |
| tree | ba9437df27ea98feedb7409559a18d7870220688 /arch/arm/include/asm/elf.h | |
| parent | 70c70d97809c3cdb8ff04f38ee3718c5385a2a4d (diff) | |
ARM: add a vma entry for the user accessible vector page
The kernel makes the high vector page visible to user space. This page
contains (amongst others) small code segments that can be executed in
user space. Make this page visible through ptrace and /proc/<pid>/mem
in order to let gdb perform code parsing needed for proper unwinding.
For example, the ERESTART_RESTARTBLOCK handler actually has a stack
frame -- it returns to a PC value stored on the user's stack. To
unwind after a "sleep" system call was interrupted twice, GDB would
have to recognize this situation and understand that stack frame
layout -- which it currently cannot do.
We could fix this by hard-coding addresses in the vector page range into
GDB, but that isn't really portable as not all of those addresses are
guaranteed to remain stable across kernel releases. And having the gdb
process make an exception for this page and get content from its own
address space for it looks strange, and it is not future proof either.
Being located above PAGE_OFFSET, this vma cannot be deleted by
user space code.
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Diffstat (limited to 'arch/arm/include/asm/elf.h')
| -rw-r--r-- | arch/arm/include/asm/elf.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h index 5747a8baa413..8bb66bca2e3e 100644 --- a/arch/arm/include/asm/elf.h +++ b/arch/arm/include/asm/elf.h @@ -127,4 +127,8 @@ struct mm_struct; extern unsigned long arch_randomize_brk(struct mm_struct *mm); #define arch_randomize_brk arch_randomize_brk +extern int vectors_user_mapping(void); +#define arch_setup_additional_pages(bprm, uses_interp) vectors_user_mapping() +#define ARCH_HAS_SETUP_ADDITIONAL_PAGES + #endif |