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v2: Fixes as per review comments. The only code changes are the #error in 0004 and the removal of the #ifdef in 0009. The rest are comments and commit message rewording/expansion. This series contains fixes and improvements to the ARM ftrace support. It adds Thumb-2 support and re-implements the dynamic ftrace support. "ftrace: allow building without frame pointers" and "ftrace: pass KBUILD_CFLAGS to record_mcount.pl" are non-ARM-specific ftrace patches which are required to support the ARM functionality. Cleanups / docs: ARM: ftrace: clean up mcount assembly indentation ARM: ftrace: document mcount formats Thumb-2: ftrace: allow building without frame pointers ARM: ftrace: allow building without frame pointers ARM: ftrace: add ENDPROC annotations ARM: ftrace: add Thumb-2 support Dynamic ftrace: ftrace: pass KBUILD_CFLAGS to record_mcount.pl ARM: ftrace: fix and update dynamic ftrace ARM: ftrace: add Thumb-2 support to dynamic ftrace ARM: ftrace: enable dynamic ftrace Makefile | 7 ++ arch/arm/Kconfig | 2 + arch/arm/Kconfig.debug | 5 + arch/arm/include/asm/ftrace.h | 20 ++++- arch/arm/kernel/armksyms.c | 2 + arch/arm/kernel/entry-common.S | 178 +++++++++++++++++++++++++++----------- arch/arm/kernel/ftrace.c | 188 +++++++++++++++++++++++++++++---------- kernel/trace/Kconfig | 2 +- scripts/Makefile.build | 3 +- scripts/recordmcount.pl | 2 + 10 files changed, 307 insertions(+), 102 deletions(-) --
When building as Thumb-2, the ".type foo, %function" annotation in
ENDPROC seems to be required in order for the assembly routines to be
recognized as Thumb-2 code. If the ENDPROC annotations are not present,
calls to these routines are generated as BLX instead of BL.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Rabin Vincent <rabin@rab.in>
---
arch/arm/kernel/entry-common.S | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 6805a72..c3bdb05 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -146,6 +146,7 @@ mcount_call:
bl ftrace_stub
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
+ENDPROC(mcount)
ENTRY(ftrace_caller)
stmdb sp!, {r0-r3, lr}
@@ -158,6 +159,7 @@ ftrace_call:
bl ftrace_stub
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
+ENDPROC(ftrace_caller)
#else
@@ -179,6 +181,7 @@ gnu_trace:
mov pc, r2
ldmia sp!, {r0-r3, ip, lr}
mov pc, ip
+ENDPROC(__gnu_mcount_nc)
#ifdef CONFIG_OLD_MCOUNT
/*
@@ -204,13 +207,15 @@ trace:
mov pc, r2
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
+ENDPROC(mcount)
#endif
#endif /* CONFIG_DYNAMIC_FTRACE */
.globl ftrace_stub
-ftrace_stub:
+ENTRY(ftrace_stub)
mov pc, lr
+ENDPROC(ftrace_stub)
#endif /* CONFIG_FUNCTION_TRACER */
--
1.7.0
--
ENTRY does the .globl for you, so please kill your own version. --
Updated patch below.
From 87b70ed633da00fe9873a5819c6d24e57368de43 Mon Sep 17 00:00:00 2001
From: Rabin Vincent <rabin@rab.in>
Date: Sun, 14 Feb 2010 01:18:33 +0530
Subject: [PATCH] ARM: ftrace: add ENDPROC annotations
When building as Thumb-2, the ".type foo, %function" annotation in
ENDPROC seems to be required in order for the assembly routines to be
recognized as Thumb-2 code. If the ENDPROC annotations are not present,
calls to these routines are generated as BLX instead of BL.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Rabin Vincent <rabin@rab.in>
---
arch/arm/kernel/entry-common.S | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 6805a72..c7a8c20 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -146,6 +146,7 @@ mcount_call:
bl ftrace_stub
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
+ENDPROC(mcount)
ENTRY(ftrace_caller)
stmdb sp!, {r0-r3, lr}
@@ -158,6 +159,7 @@ ftrace_call:
bl ftrace_stub
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
+ENDPROC(ftrace_caller)
#else
@@ -179,6 +181,7 @@ gnu_trace:
mov pc, r2
ldmia sp!, {r0-r3, ip, lr}
mov pc, ip
+ENDPROC(__gnu_mcount_nc)
#ifdef CONFIG_OLD_MCOUNT
/*
@@ -204,13 +207,14 @@ trace:
mov pc, r2
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
+ENDPROC(mcount)
#endif
#endif /* CONFIG_DYNAMIC_FTRACE */
- .globl ftrace_stub
-ftrace_stub:
+ENTRY(ftrace_stub)
mov pc, lr
+ENDPROC(ftrace_stub)
#endif /* CONFIG_FUNCTION_TRACER */
--
1.7.0.4
--
Hi Rabin, What's the status of these patches? I haven't seen them in mainline. Thanks. -- Catalin --
Hi Catalin, On Tue, Aug 10, 2010 at 10:37 PM, Catalin Marinas They're in the patch tracker now. I'd forgotten about them for a while, and there was one patch missing an ack, but that's sorted out now. Rabin --
On ARM, we have two ABIs, and the ABI used is controlled via a config option. Object files built with one ABI can't be merged with object files built with the other ABI. So, record_mcount.pl needs to use the same compiler flags as the kernel when generating the object file with the mcount locations. Ensure this by passing CFLAGS to the script. Signed-off-by: Rabin Vincent <rabin@rab.in> --- scripts/Makefile.build | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 0b94d2f..2535c11 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -209,7 +209,8 @@ ifdef CONFIG_FTRACE_MCOUNT_RECORD cmd_record_mcount = set -e ; perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \ "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \ "$(if $(CONFIG_64BIT),64,32)" \ - "$(OBJDUMP)" "$(OBJCOPY)" "$(CC)" "$(LD)" "$(NM)" "$(RM)" "$(MV)" \ + "$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CFLAGS)" \ + "$(LD)" "$(NM)" "$(RM)" "$(MV)" \ "$(if $(part-of-module),1,0)" "$(@)"; endif -- 1.7.0 --
Again, I'll have to test this on other archs, just to make sure its does not cause any side effects. Oh, I forgot I now have a MIPS board I can test on too. I'll probably do this on Monday. Thanks, --
Again, I'll have to test this on other archs, just to make sure its does not cause any side effects. Oh, I forgot I now have a MIPS board I can test on too. I'll probably do this on Monday. Thanks, --
I've now built PowerPC, SH, and MIPS kernels with dynamic ftrace enabled and checked that the obj files don't change as the result of this series. I've run the MIPS kernel on QEMU and x86_64 on my PC. Rabin --
Steven, Frederic, I'd like to resurrect this old ARM dynamic ftrace patchset. It still applies on next except for a small merge conflict in one of the ARM-specific patches. This is the only non-arch/arm/ patch in the series which doesn't have either of your Acked-bys, so if you'd be willing to ack it, I'll send in the lot via rmk's ARM patch system for .37. Alternatively, this one and "[PATCH 03/10] ftrace: allow building without frame pointers" could go in via the tracing tree for .36? Then I'll send in the ARM specific stuff for .37 via the ARM tree. Thanks, --
I'll let Steve handling this one as I have few skills with things that touch scripts/recordmcount.pl :) --
Sorry for the late reply, just got back from vacation. Hmm, this changes the number of parameters passed to the recordmcount.pl. shouldn't this be part of the change to recordmcount.pl? Otherwise, we can break a bisect. --
No, this doesn't change the number of parameters. KBUILD_CFLAGS is included inside the CC argument. Rabin --
Sorry for top post. Sent from phone. Argh! We had this discussion before. I must be getting old. Acked-by: Steven Rostedt <rostedt@goodmis.org> -- Steve -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. --
This adds mcount recording and updates dynamic ftrace for ARM to work
with the new ftrace dyamic tracing implementation. It also adds support
for the mcount format used by newer ARM compilers.
With dynamic tracing, mcount() is implemented as a nop. Callsites are
patched on startup with nops, and dynamically patched to call to the
ftrace_caller() routine as needed.
Signed-off-by: Rabin Vincent <rabin@rab.in>
---
arch/arm/include/asm/ftrace.h | 19 +++++-
arch/arm/kernel/entry-common.S | 37 +++++++---
arch/arm/kernel/ftrace.c | 155 +++++++++++++++++++++++++++------------
scripts/recordmcount.pl | 2 +
4 files changed, 155 insertions(+), 58 deletions(-)
diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index 103f7ee..4a56a2e 100644
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -2,12 +2,29 @@
#define _ASM_ARM_FTRACE
#ifdef CONFIG_FUNCTION_TRACER
-#define MCOUNT_ADDR ((long)(mcount))
+#define MCOUNT_ADDR ((unsigned long)(__gnu_mcount_nc))
#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */
#ifndef __ASSEMBLY__
extern void mcount(void);
extern void __gnu_mcount_nc(void);
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+struct dyn_arch_ftrace {
+#ifdef CONFIG_OLD_MCOUNT
+ bool old_mcount;
+#endif
+};
+
+static inline unsigned long ftrace_call_adjust(unsigned long addr)
+{
+ return addr;
+}
+
+extern void ftrace_caller_old(void);
+extern void ftrace_call_old(void);
+#endif
+
#endif
#endif
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 573ed3b..9931a02 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -127,6 +127,10 @@ ENDPROC(ret_from_fork)
* clobber the ip register. This is OK because the ARM calling convention
* allows it to be clobbered in subroutines and doesn't use it to hold
* parameters.)
+ *
+ * When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0"
+ * for the mcount ...Acked-by: Steven Rostedt <rostedt@goodmis.org> -- Steve --
Acked-by: Steven Rostedt <rostedt@goodmis.org> -- Steve --
Dynamic ftrace for ARM has been disabled since 07c4cc1cdaa08f ("ftrace: disable dynamic ftrace for all archs that use daemon"). Now that the code has been updated, re-enable it. Signed-off-by: Rabin Vincent <rabin@rab.in> --- arch/arm/Kconfig | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index cadfe2e..a264837 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -18,6 +18,8 @@ config ARM select HAVE_KPROBES if (!XIP_KERNEL) select HAVE_KRETPROBES if (HAVE_KPROBES) select HAVE_FUNCTION_TRACER if (!XIP_KERNEL) + select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL) + select HAVE_DYNAMIC_FTRACE if (!XIP_KERNEL) select HAVE_GENERIC_DMA_COHERENT select HAVE_KERNEL_GZIP select HAVE_KERNEL_LZO -- 1.7.0 --
Handle the different nop and call instructions for Thumb-2. Also, we
need to adjust the recorded mcount_loc addresses because they have the
lsb set.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org> [recordmcount.pl change]
Signed-off-by: Rabin Vincent <rabin@rab.in>
---
v2: #ifdef in ftrace_call_adjust replaced with comment.
arch/arm/include/asm/ftrace.h | 3 ++-
arch/arm/kernel/ftrace.c | 33 +++++++++++++++++++++++++++++++++
scripts/recordmcount.pl | 2 +-
3 files changed, 36 insertions(+), 2 deletions(-)
diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index 4a56a2e..f89515a 100644
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -18,7 +18,8 @@ struct dyn_arch_ftrace {
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
- return addr;
+ /* With Thumb-2, the recorded addresses have the lsb set */
+ return addr & ~1;
}
extern void ftrace_caller_old(void);
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index f09014c..971ac8c 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -18,7 +18,11 @@
#include <asm/cacheflush.h>
#include <asm/ftrace.h>
+#ifdef CONFIG_THUMB2_KERNEL
+#define NOP 0xeb04f85d /* pop.w {lr} */
+#else
#define NOP 0xe8bd4000 /* pop {lr} */
+#endif
#ifdef CONFIG_OLD_MCOUNT
#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
@@ -56,6 +60,34 @@ static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
#endif
/* construct a branch (BL) instruction to addr */
+#ifdef CONFIG_THUMB2_KERNEL
+static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
+{
+ unsigned long s, j1, j2, i1, i2, imm10, imm11;
+ unsigned long first, second;
+ long offset;
+
+ offset = (long)addr - (long)(pc + 4);
+ if (offset < -16777216 || offset > 16777214) {
+ WARN_ON_ONCE(1);
+ return 0;
+ }
+
+ s = (offset >> 24) & 0x1;
+ i1 = ...Add a comment describing the mcount variants and how the callsites look
like.
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Rabin Vincent <rabin@rab.in>
---
v2: Reword/expand comment.
arch/arm/kernel/entry-common.S | 36 ++++++++++++++++++++++++++++++++++++
1 files changed, 36 insertions(+), 0 deletions(-)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 0b042bd..f05a35a 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -92,6 +92,42 @@ ENDPROC(ret_from_fork)
#define CALL(x) .long x
#ifdef CONFIG_FUNCTION_TRACER
+/*
+ * When compiling with -pg, gcc inserts a call to the mcount routine at the
+ * start of every function. In mcount, apart from the function's address (in
+ * lr), we need to get hold of the function's caller's address.
+ *
+ * Older GCCs (pre-4.4) inserted a call to a routine called mcount like this:
+ *
+ * bl mcount
+ *
+ * These versions have the limitation that in order for the mcount routine to
+ * be able to determine the function's caller's address, an APCS-style frame
+ * pointer (which is set up with something like the code below) is required.
+ *
+ * mov ip, sp
+ * push {fp, ip, lr, pc}
+ * sub fp, ip, #4
+ *
+ * With EABI, these frame pointers are not available unless -mapcs-frame is
+ * specified, and if building as Thumb-2, not even then.
+ *
+ * Newer GCCs (4.4+) solve this problem by introducing a new version of mcount,
+ * with call sites like:
+ *
+ * push {lr}
+ * bl __gnu_mcount_nc
+ *
+ * With these compilers, frame pointers are not necessary.
+ *
+ * mcount can be thought of as a function called in the middle of a subroutine
+ * call. As such, it needs to be transparent for both the caller and the
+ * callee: the original lr needs to be restored when leaving mcount, and no
+ * registers should be clobbered. (In the __gnu_mcount_nc implementation, we
+ * clobber the ip register. This is OK because the ARM calling ...With current gcc, compiling with both -pg and -fomit-frame-pointer is not allowed. However, -pg can be used to build without actually specying -fno-omit-frame-pointer, upon which the defaut behaviour for the target will be used. On ARM, it is not possible to build a Thumb-2 kernel with -fno-omit-frame-pointer (FRAME_POINTERS depends on !THUMB2_KERNEL). In order to support ftrace for Thumb-2, we need to be able to allow a combination of FUNCTION_TRACER and !FRAME_POINTER. We do this by omitting -fomit-frame-pointer if ftrace is enabled. Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Rabin Vincent <rabin@rab.in> --- v2: Better comment. Makefile | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/Makefile b/Makefile index 08ff02d..61404e0 100644 --- a/Makefile +++ b/Makefile @@ -546,8 +546,15 @@ endif ifdef CONFIG_FRAME_POINTER KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls else +# Some targets (ARM with Thumb2, for example), can't be built with frame +# pointers. For those, we don't have FUNCTION_TRACER automatically +# select FRAME_POINTER. However, FUNCTION_TRACER adds -pg, and this is +# incompatible with -fomit-frame-pointer with current GCC, so we don't use +# -fomit-frame-pointer with FUNCTION_TRACER. +ifndef CONFIG_FUNCTION_TRACER KBUILD_CFLAGS += -fomit-frame-pointer endif +endif ifdef CONFIG_DEBUG_INFO KBUILD_CFLAGS += -g -- 1.7.0 --
I believe this is correct, but have you tested this on other archs other than ARM? I can do it for x86 and PPC, but it will need to wait as those machines are currently performing stress tests. --
I've tested the series on x86-64. Note that this particular change will not currently affect other archs since they still have the "select FRAME_POINTER" in FUNCTION_TRACER. Rabin --
I believe this is correct, but have you tested this on other archs other than ARM? I can do it for x86 and PPC, but it will need to wait as those machines are currently performing stress tests. --
With a new enough GCC, ARM function tracing can be supported without the
need for frame pointers. This is essential for Thumb-2 support, since
frame pointers aren't available then.
Signed-off-by: Rabin Vincent <rabin@rab.in>
---
v2: #error if incompatible GCC.
arch/arm/Kconfig.debug | 5 +++++
arch/arm/kernel/armksyms.c | 2 ++
arch/arm/kernel/entry-common.S | 14 ++++++++++++++
kernel/trace/Kconfig | 2 +-
4 files changed, 22 insertions(+), 1 deletions(-)
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 91344af..4dbce53 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -27,6 +27,11 @@ config ARM_UNWIND
the performance is not affected. Currently, this feature
only works with EABI compilers. If unsure say Y.
+config OLD_MCOUNT
+ bool
+ depends on FUNCTION_TRACER && FRAME_POINTER
+ default y
+
config DEBUG_USER
bool "Verbose user fault messages"
help
diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
index 8214bfe..e5e1e53 100644
--- a/arch/arm/kernel/armksyms.c
+++ b/arch/arm/kernel/armksyms.c
@@ -165,6 +165,8 @@ EXPORT_SYMBOL(_find_next_bit_be);
#endif
#ifdef CONFIG_FUNCTION_TRACER
+#ifdef CONFIG_OLD_MCOUNT
EXPORT_SYMBOL(mcount);
+#endif
EXPORT_SYMBOL(__gnu_mcount_nc);
#endif
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index f05a35a..6805a72 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -128,6 +128,13 @@ ENDPROC(ret_from_fork)
* allows it to be clobbered in subroutines and doesn't use it to hold
* parameters.)
*/
+
+#ifndef CONFIG_OLD_MCOUNT
+#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4))
+#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0.
+#endif
+#endif
+
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(mcount)
stmdb sp!, {r0-r3, lr}
@@ -173,6 +180,12 @@ gnu_trace:
ldmia sp!, {r0-r3, ip, lr}
mov pc, ip
+#ifdef ...I'm fine with this if the ARM maintainers are. Acked-by: Steven Rostedt <rostedt@goodmis.org> --
I'm fine with this if the ARM maintainers are. Acked-by: Steven Rostedt <rostedt@goodmis.org> --
I think we did this already in other places, so: Acked-by: Catalin Marinas <catalin.marinas@arm.com> --
Fix the mcount routines to build and run on a kernel built with the
Thumb-2 instruction set:
- Without the BSYM, the following assembler errors appear:
entry-common.S: Assembler messages:
entry-common.S:179: Error: invalid immediate for address calculation (value = 0x00000004)
- Without the orr, the lsb is not set on the pointer loaded from
ftrace_trace_function, but is set on BSYM(ftrace_stub), leading to the
comparison failing even when the pointer is pointing to ftrace_stub.
- The problem with the "mov lr, pc", is that it does not set the lsb when
storing the pc in lr. The called function returns with "bx lr", and the
mode changes to ARM. The blx is to avoid this.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Rabin Vincent <rabin@rab.in>
---
arch/arm/kernel/entry-common.S | 8 +++++---
1 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index c3bdb05..573ed3b 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -167,7 +167,8 @@ ENTRY(__gnu_mcount_nc)
stmdb sp!, {r0-r3, lr}
ldr r0, =ftrace_trace_function
ldr r2, [r0]
- adr r0, ftrace_stub
+ THUMB( orr r2, r2, #1 )
+ adr r0, BSYM(ftrace_stub)
cmp r0, r2
bne gnu_trace
ldmia sp!, {r0-r3, ip, lr}
@@ -177,8 +178,9 @@ gnu_trace:
ldr r1, [sp, #20] @ lr of instrumented routine
mov r0, lr
sub r0, r0, #MCOUNT_INSN_SIZE
- mov lr, pc
- mov pc, r2
+ ARM( mov lr, pc )
+ ARM( mov pc, r2 )
+ THUMB( blx r2 )
ldmia sp!, {r0-r3, ip, lr}
mov pc, ip
ENDPROC(__gnu_mcount_nc)
--
1.7.0
--
Hi Rabin,
I'm still confused by this. I think that's a compiler problem but need
If the ftrace_stub isn't .globl, the code compiles fine. My approach
would be something like this:
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index d085033..5f5aef6 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -122,7 +122,7 @@ ENTRY(__gnu_mcount_nc)
stmdb sp!, {r0-r3, lr}
ldr r0, =ftrace_trace_function
ldr r2, [r0]
- adr r0, ftrace_stub
+ adr r0, 1f
cmp r0, r2
bne gnu_trace
ldmia sp!, {r0-r3, ip, lr}
@@ -132,8 +132,9 @@ gnu_trace:
ldr r1, [sp, #20] @ lr of instrumented routine
mov r0, lr
sub r0, r0, #MCOUNT_INSN_SIZE
- mov lr, pc
+ adr lr, BSYM(2f)
mov pc, r2
+2:
ldmia sp!, {r0-r3, ip, lr}
mov pc, ip
@@ -141,7 +142,7 @@ ENTRY(mcount)
stmdb sp!, {r0-r3, lr}
ldr r0, =ftrace_trace_function
ldr r2, [r0]
- adr r0, ftrace_stub
+ adr r0, 1f
cmp r0, r2
bne trace
ldr lr, [fp, #-4] @ restore lr
@@ -160,6 +161,7 @@ trace:
.globl ftrace_stub
ftrace_stub:
+1:
mov pc, lr
#endif /* CONFIG_FUNCTION_TRACER */
--
Catalin
--
I'm not familiar with ftrace but why does the called function returns using "bx lr". Is this generated by the compiler? I had the impression that if we don't enable interworking, we wouldn't get this instruction (but haven't tried this yet). -- Catalin --
There's nothing special about the called function: it's just a regular C function. GCC uses "bx lr" for the return. Rabin --
New patch below:
From bf828a0c069b1bb3f6bf4e68f1dceecab396c286 Mon Sep 17 00:00:00 2001
From: Rabin Vincent <rabin@rab.in>
Date: Sun, 14 Feb 2010 01:18:34 +0530
Subject: [PATCH 06/10] ARM: ftrace: add Thumb-2 support
Fix the mcount routines to build and run on a kernel built with the
Thumb-2 instruction set by correcting the following errors using the
fixes suggested by Catalin Marinas:
- Problem: The following assembler errors appear at the "adr r0,
ftrace_stub" instruction:
entry-common.S: Assembler messages:
entry-common.S:179: Error: invalid immediate for address calculation (value = 0x00000004)
Fix: The errors don't occur with a non-global symbol, so use one.
- Problem: The "mov lr, pc" does not set the lsb when storing the pc in
lr. The called function returns with "bx lr", and the mode changes
to ARM.
Fix: Add a label on the return address and use "adr lr, BSYM(label)".
We don't modify the old mcount because it won't be built when using
Thumb-2.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Rabin Vincent <rabin@rab.in>
---
arch/arm/kernel/entry-common.S | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index c7a8c20..f5e75de 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -167,7 +167,7 @@ ENTRY(__gnu_mcount_nc)
stmdb sp!, {r0-r3, lr}
ldr r0, =ftrace_trace_function
ldr r2, [r0]
- adr r0, ftrace_stub
+ adr r0, .Lftrace_stub
cmp r0, r2
bne gnu_trace
ldmia sp!, {r0-r3, ip, lr}
@@ -177,8 +177,9 @@ gnu_trace:
ldr r1, [sp, #20] @ lr of instrumented routine
mov r0, lr
sub r0, r0, #MCOUNT_INSN_SIZE
- mov lr, pc
+ adr lr, BSYM(1f)
mov pc, r2
+1:
ldmia sp!, {r0-r3, ip, lr}
mov pc, ip
ENDPROC(__gnu_mcount_nc)
@@ -213,6 +214,7 @@ ENDPROC(mcount)
#endif /* CONFIG_DYNAMIC_FTRACE */
ENTRY(ftrace_stub)
+.Lftrace_stub:
mov pc, lr
...Acked-by: Catalin Marinas <catalin.marinas@arm.com> -- Catalin --
The mcount implementation currently uses a different indentation style
from the rest of the file (and the rest of the ARM assembly in the
kernel). Clean it up.
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Rabin Vincent <rabin@rab.in>
---
arch/arm/kernel/entry-common.S | 88 ++++++++++++++++++++--------------------
1 files changed, 44 insertions(+), 44 deletions(-)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 2c1db77..0b042bd 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -94,73 +94,73 @@ ENDPROC(ret_from_fork)
#ifdef CONFIG_FUNCTION_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(mcount)
- stmdb sp!, {r0-r3, lr}
- mov r0, lr
- sub r0, r0, #MCOUNT_INSN_SIZE
+ stmdb sp!, {r0-r3, lr}
+ mov r0, lr
+ sub r0, r0, #MCOUNT_INSN_SIZE
.globl mcount_call
mcount_call:
- bl ftrace_stub
- ldr lr, [fp, #-4] @ restore lr
- ldmia sp!, {r0-r3, pc}
+ bl ftrace_stub
+ ldr lr, [fp, #-4] @ restore lr
+ ldmia sp!, {r0-r3, pc}
ENTRY(ftrace_caller)
- stmdb sp!, {r0-r3, lr}
- ldr r1, [fp, #-4]
- mov r0, lr
- sub r0, r0, #MCOUNT_INSN_SIZE
+ stmdb sp!, {r0-r3, lr}
+ ldr r1, [fp, #-4]
+ mov r0, lr
+ sub r0, r0, #MCOUNT_INSN_SIZE
.globl ftrace_call
ftrace_call:
- bl ftrace_stub
- ldr lr, [fp, #-4] @ restore lr
- ldmia sp!, {r0-r3, pc}
+ bl ftrace_stub
+ ldr lr, [fp, #-4] @ restore lr
+ ldmia sp!, {r0-r3, pc}
#else
ENTRY(__gnu_mcount_nc)
- stmdb sp!, {r0-r3, lr}
- ldr r0, =ftrace_trace_function
- ldr r2, [r0]
- adr r0, ftrace_stub
- cmp r0, r2
- bne gnu_trace
- ldmia sp!, {r0-r3, ip, lr}
- mov pc, ip
+ stmdb sp!, {r0-r3, lr}
+ ldr r0, =ftrace_trace_function
+ ldr r2, [r0]
+ adr r0, ftrace_stub
+ cmp r0, r2
+ bne gnu_trace
+ ldmia sp!, {r0-r3, ip, lr}
+ mov pc, ip
gnu_trace:
- ldr r1, [sp, #20] @ lr of instrumented routine
- mov r0, lr
- sub r0, r0, #MCOUNT_INSN_SIZE
- mov lr, ...Hi Steven, Do you have any further concerns about this patchset? If not, do you mind if I try to send in the series (v2 + the two updated patches) via the ARM patch system, since most of the patches only touch code under arch/arm/? Rabin --
