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| author |   John Reiser <jreiser@bitwagon.com> | 2009-07-27 11:23:50 -0700 |
|---|---|---|
| committer |   Steven Rostedt <rostedt@goodmis.org> | 2009-09-12 21:57:29 -0400 |
| commit | 4b3b4c5e64ce26612646867ee354373620063534 (patch) | |
| tree | 048ff75a616c83c5bd64372f4140d53c9f79f169 | |
| parent | tracing: do not update tracing_max_latency when tracer is stopped (diff) | |
| download | linux-dev-4b3b4c5e64ce26612646867ee354373620063534.tar.xz linux-dev-4b3b4c5e64ce26612646867ee354373620063534.zip | |
ftrace: __start_mcount_loc should be .init.rodata
__start_mcount_loc[] is unused after init, yet occupies RAM forever
as part of .rodata. 152kiB is typical on a 64-bit architecture. Instead,
__start_mcount_loc should be in the interval [__init_begin, __init_end)
so that the space is reclaimed after init.
__start_mcount_loc[] is generated during the load portion
of kernel build, and is used only by ftrace_init(). ftrace_init is declared
'__init' and is in .init.text, which is freed after init.
__start_mcount_loc is placed into .rodata by a call to MCOUNT_REC inside
the RO_DATA macro of include/asm-generic/vmlinux.lds.h. The array *is*
read-only, but more importantly it is not used after init. So the call to
MCOUNT_REC should be moved from RO_DATA to INIT_DATA.
This patch has been tested on x86_64 with CONFIG_DEBUG_PAGEALLOC=y
which verifies that the address range never is accessed after init.
Signed-off-by: John Reiser <jreiser@BitWagon.com>
LKML-Reference: <4A6DF0B6.7080402@bitwagon.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
| -rw-r--r-- | include/asm-generic/vmlinux.lds.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 6ad76bf5fb40..98b37cf3ac6d 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -91,7 +91,8 @@ #endif #ifdef CONFIG_FTRACE_MCOUNT_RECORD -#define MCOUNT_REC() VMLINUX_SYMBOL(__start_mcount_loc) = .; \ +#define MCOUNT_REC() . = ALIGN(8); \ + VMLINUX_SYMBOL(__start_mcount_loc) = .; \ *(__mcount_loc) \ VMLINUX_SYMBOL(__stop_mcount_loc) = .; #else @@ -331,7 +332,6 @@ /* __*init sections */ \ __init_rodata : AT(ADDR(__init_rodata) - LOAD_OFFSET) { \ *(.ref.rodata) \ - MCOUNT_REC() \ DEV_KEEP(init.rodata) \ DEV_KEEP(exit.rodata) \ CPU_KEEP(init.rodata) \ @@ -455,6 +455,7 @@ MEM_DISCARD(init.data) \ KERNEL_CTORS() \ *(.init.rodata) \ + MCOUNT_REC() \ DEV_DISCARD(init.rodata) \ CPU_DISCARD(init.rodata) \ MEM_DISCARD(init.rodata) |