| Message ID | 1488588672-21865-1-git-send-email-abelvesa@linux.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, Mar 04, 2017 at 12:51:12AM +0000, Abel Vesa wrote: > diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S > index c73c403..93f9abb 100644 > --- a/arch/arm/kernel/entry-ftrace.S > +++ b/arch/arm/kernel/entry-ftrace.S > @@ -92,12 +92,78 @@ > 2: mcount_exit > .endm > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > + > +.macro __ftrace_regs_caller > + > + sub sp, sp, #8 @ space for CPSR and OLD_R0 (not used) > + > + add ip, sp, #12 @ move in IP the value of SP as it was > + @ before the push {lr} of the mcount mechanism > + stmdb sp!, {ip,lr,pc} This doesn't build with CONFIG_THUMB2_KERNEL: entry-ftrace.S:285: Error: PC not allowed in register list -- `stmdb sp!,{ip,lr,pc}' Saving PC in STMDB is prohibited in Thumb and deprecated in ARM. > + stmdb sp!, {r0-r11,lr} > + > + ldr r0, [sp, #S_LR] @ replace PC with LR > + str r0, [sp, #S_PC] @ into pt_regs > + > + ldr r1, [sp, #PT_REGS_SIZE] @ replace new LR with > + str r1, [sp, #S_LR] @ previous LR into pt_regs > + > + @ stack content at this point: > + @ 0 4 48 52 56 60 64 68 72 > + @ R0 | R1 | ... | LR | SP + 4 | previous LR | LR | PSR | OLD_R0 | previous LR | So this code only adjust the SP by 72 bytes. Since the stack is not aligned to 8 bytes at entry to mcount, this code calls into C functions with a misaligned stack. This is a violation of the procedure call standard. Also, I believe this should have unwind annotations to indicate where it saved the registers. See mcount_enter for an example. > + > + mov r3, sp @ struct pt_regs* > + ldr r2, =function_trace_op > + ldr r2, [r2] @ pointer to the current > + @ function tracing op > + ldr r1, [sp, #PT_REGS_SIZE] @ lr of instrumented func > + mcount_adjust_addr r0, lr @ instrumented function > + > + .globl ftrace_regs_call > +ftrace_regs_call: > + bl ftrace_stub > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > + .globl ftrace_graph_regs_call > +ftrace_graph_regs_call: > + mov r0, r0 > +#endif > + @ pop saved regs > + ldmia sp, {r0-r15} This doesn't build either: entry-ftrace.S:285: Error: LR and PC should not both be in register list -- `ldmia sp,{r0-r15}' Restoring LR and PC together is prohibited in Thumb and deprecated in ARM. It's the same case with SP. > +.endm > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > +.macro __ftrace_graph_regs_caller > + > + sub r0, fp, #4 @ lr of instrumented routine (parent) > + > + @ called from __ftrace_regs_caller > + ldr r1, [sp, #S_PC] @ instrumented routine (func) > + mcount_adjust_addr r1, r1 > + > + mov r2, fp @ frame pointer > + bl prepare_ftrace_return > + > + @ pop registers saved in ftrace_regs_caller > + ldmia sp, {r0-r15} This doesn't get built on CONFIG_THUMB2_KERNEL since there's no suppport for CONFIG_FUNCTION_GRAPH_TRACER there, but this is also using deprecated operands. > +.endm > +#endif > +#endif ... > diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c > index 3f17594..f165265 100644 > --- a/arch/arm/kernel/ftrace.c > +++ b/arch/arm/kernel/ftrace.c > @@ -29,11 +29,6 @@ > #endif > > #ifdef CONFIG_DYNAMIC_FTRACE > -#ifdef CONFIG_OLD_MCOUNT > -#define OLD_MCOUNT_ADDR ((unsigned long) mcount) > -#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) > - > -#define OLD_NOP 0xe1a00000 /* mov r0, r0 */ > > static int __ftrace_modify_code(void *data) > { > @@ -51,6 +46,12 @@ void arch_ftrace_update_code(int command) > stop_machine(__ftrace_modify_code, &command, NULL); > } > > +#ifdef CONFIG_OLD_MCOUNT > +#define OLD_MCOUNT_ADDR ((unsigned long) mcount) > +#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) > + > +#define OLD_NOP 0xe1a00000 /* mov r0, r0 */ > + > static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) This chunk above fixes the problem which Nicolai pointed out earlier. Since it's a bug fix for the current dynamic ftrace code, it should really be submitted as a separate patch. Feel free to use some variant of this commit message which I wrote when I ran into this yesterday: ARM: ftrace: fix dynamic ftrace with DEBUG_RODATA and !FRAME_POINTER The support for dynamic ftrace with CONFIG_DEBUG_RODATA involves overriding the weak arch_ftrace_update_code() with a variant which makes the kernel text writable around the patching. This override was however added under the CONFIG_OLD_MCOUNT ifdef, and CONFIG_OLD_MCOUNT is only enabled if frame pointers are enabled. This leads to non-functional dynamic ftrace (ftrace triggers a WARN_ON()) when CONFIG_DEBUG_RODATA is enabled and CONFIG_FRAME_POINTER is not. Move the override out of that ifdef and into the CONFIG_DYNAMIC_FTRACE ifdef where it belongs. Fixes: 80d6b0c2eed2a ("ARM: mm: allow text and rodata sections to be read-only") > { > return rec->arch.old_mcount ? OLD_NOP : NOP; > @@ -139,6 +140,15 @@ int ftrace_update_ftrace_func(ftrace_func_t func) > > ret = ftrace_modify_code(pc, 0, new, false); > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS This code (and the rest of your additions to this file below), are already under CONFIG_DYNAMIC_FTRACE and afaics CONFIG_DYNAMIC_FTRACE_WITH_REGS is always enabled when the former is enabled, so could you please drop these ifdefs? The code in entry-ftrace.S under CONFIG_DYNAMIC_FTRACE_WITH_REGS would also benefit from just using CONFIG_DYNAMIC_FTRACE everywhere instead.
On Sat, Mar 04, 2017 at 02:02:17PM +0100, Rabin Vincent wrote: > On Sat, Mar 04, 2017 at 12:51:12AM +0000, Abel Vesa wrote: > > diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S > > index c73c403..93f9abb 100644 > > --- a/arch/arm/kernel/entry-ftrace.S > > +++ b/arch/arm/kernel/entry-ftrace.S > > @@ -92,12 +92,78 @@ > > 2: mcount_exit > > .endm > > > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > > + > > +.macro __ftrace_regs_caller > > + > > + sub sp, sp, #8 @ space for CPSR and OLD_R0 (not used) > > + > > + add ip, sp, #12 @ move in IP the value of SP as it was > > + @ before the push {lr} of the mcount mechanism > > + stmdb sp!, {ip,lr,pc} > > This doesn't build with CONFIG_THUMB2_KERNEL: > > entry-ftrace.S:285: Error: PC not allowed in register list -- `stmdb sp!,{ip,lr,pc}' > > Saving PC in STMDB is prohibited in Thumb and deprecated in ARM. > > > + stmdb sp!, {r0-r11,lr} > > + > > + ldr r0, [sp, #S_LR] @ replace PC with LR > > + str r0, [sp, #S_PC] @ into pt_regs > > + > > + ldr r1, [sp, #PT_REGS_SIZE] @ replace new LR with > > + str r1, [sp, #S_LR] @ previous LR into pt_regs > > + > > + @ stack content at this point: > > + @ 0 4 48 52 56 60 64 68 72 > > + @ R0 | R1 | ... | LR | SP + 4 | previous LR | LR | PSR | OLD_R0 | previous LR | > > So this code only adjust the SP by 72 bytes. Since the stack is not > aligned to 8 bytes at entry to mcount, this code calls into C functions > with a misaligned stack. This is a violation of the procedure call > standard. > > Also, I believe this should have unwind annotations to indicate where it > saved the registers. See mcount_enter for an example. > > > + > > + mov r3, sp @ struct pt_regs* > > + ldr r2, =function_trace_op > > + ldr r2, [r2] @ pointer to the current > > + @ function tracing op > > + ldr r1, [sp, #PT_REGS_SIZE] @ lr of instrumented func > > + mcount_adjust_addr r0, lr @ instrumented function > > + > > + .globl ftrace_regs_call > > +ftrace_regs_call: > > + bl ftrace_stub > > + > > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > > + .globl ftrace_graph_regs_call > > +ftrace_graph_regs_call: > > + mov r0, r0 > > +#endif > > + @ pop saved regs > > + ldmia sp, {r0-r15} > > This doesn't build either: > > entry-ftrace.S:285: Error: LR and PC should not both be in register list -- `ldmia sp,{r0-r15}' > > Restoring LR and PC together is prohibited in Thumb and deprecated in > ARM. It's the same case with SP. > We could do it in separate instructions, something like: @ pop saved regs ldmia sp!, {r0-r12} ldr ip, [sp, #8] ldr lr, [sp, #4] ldr sp, [sp, #0] mov pc, ip Same goes for saving the regs, except I need to replace the LR stored outside of ftrace_regs_caller with OLD_R0 so that the stack would become aligned to 8 bytes. > > +.endm > > + > > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > > +.macro __ftrace_graph_regs_caller > > + > > + sub r0, fp, #4 @ lr of instrumented routine (parent) > > + > > + @ called from __ftrace_regs_caller > > + ldr r1, [sp, #S_PC] @ instrumented routine (func) > > + mcount_adjust_addr r1, r1 > > + > > + mov r2, fp @ frame pointer > > + bl prepare_ftrace_return > > + > > + @ pop registers saved in ftrace_regs_caller > > + ldmia sp, {r0-r15} > > This doesn't get built on CONFIG_THUMB2_KERNEL since there's no suppport > for CONFIG_FUNCTION_GRAPH_TRACER there, but this is also using > deprecated operands. > > > +.endm > > +#endif > > +#endif > ... > > diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c > > index 3f17594..f165265 100644 > > --- a/arch/arm/kernel/ftrace.c > > +++ b/arch/arm/kernel/ftrace.c > > @@ -29,11 +29,6 @@ > > #endif > > > > #ifdef CONFIG_DYNAMIC_FTRACE > > -#ifdef CONFIG_OLD_MCOUNT > > -#define OLD_MCOUNT_ADDR ((unsigned long) mcount) > > -#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) > > - > > -#define OLD_NOP 0xe1a00000 /* mov r0, r0 */ > > > > static int __ftrace_modify_code(void *data) > > { > > @@ -51,6 +46,12 @@ void arch_ftrace_update_code(int command) > > stop_machine(__ftrace_modify_code, &command, NULL); > > } > > > > +#ifdef CONFIG_OLD_MCOUNT > > +#define OLD_MCOUNT_ADDR ((unsigned long) mcount) > > +#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) > > + > > +#define OLD_NOP 0xe1a00000 /* mov r0, r0 */ > > + > > static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) > > This chunk above fixes the problem which Nicolai pointed out earlier. Since > it's a bug fix for the current dynamic ftrace code, it should really be > submitted as a separate patch. Feel free to use some variant of this > commit message which I wrote when I ran into this yesterday: > > ARM: ftrace: fix dynamic ftrace with DEBUG_RODATA and !FRAME_POINTER > > The support for dynamic ftrace with CONFIG_DEBUG_RODATA involves > overriding the weak arch_ftrace_update_code() with a variant which makes > the kernel text writable around the patching. > > This override was however added under the CONFIG_OLD_MCOUNT ifdef, and > CONFIG_OLD_MCOUNT is only enabled if frame pointers are enabled. > > This leads to non-functional dynamic ftrace (ftrace triggers a > WARN_ON()) when CONFIG_DEBUG_RODATA is enabled and CONFIG_FRAME_POINTER > is not. > > Move the override out of that ifdef and into the CONFIG_DYNAMIC_FTRACE > ifdef where it belongs. > > Fixes: 80d6b0c2eed2a ("ARM: mm: allow text and rodata sections to be read-only") > Sent as a separate patch already. > > { > > return rec->arch.old_mcount ? OLD_NOP : NOP; > > @@ -139,6 +140,15 @@ int ftrace_update_ftrace_func(ftrace_func_t func) > > > > ret = ftrace_modify_code(pc, 0, new, false); > > > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > > This code (and the rest of your additions to this file below), are already > under CONFIG_DYNAMIC_FTRACE and afaics CONFIG_DYNAMIC_FTRACE_WITH_REGS is > always enabled when the former is enabled, so could you please drop > these ifdefs? > > The code in entry-ftrace.S under CONFIG_DYNAMIC_FTRACE_WITH_REGS would > also benefit from just using CONFIG_DYNAMIC_FTRACE everywhere instead. I believe this is incorrect, I think it is worth being compiled in only if CONFIG_DYNAMIC_FTRACE_WITH_REGS, but this is dependent on CONFIG_DYNAMIC_FTRACE and the first one is not necessarily enabled if the second one is. Otherwise, what's the point of having two CONFIGs ?
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 0d4e71b..bf5d8fa 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -56,6 +56,7 @@ config ARM select HAVE_DMA_API_DEBUG select HAVE_DMA_CONTIGUOUS if MMU select HAVE_DYNAMIC_FTRACE if (!XIP_KERNEL) && !CPU_ENDIAN_BE32 && MMU + select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU select HAVE_EXIT_THREAD select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL) diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h index 22b7311..f379881 100644 --- a/arch/arm/include/asm/ftrace.h +++ b/arch/arm/include/asm/ftrace.h @@ -1,6 +1,10 @@ #ifndef _ASM_ARM_FTRACE #define _ASM_ARM_FTRACE +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS +#define ARCH_SUPPORTS_FTRACE_OPS 1 +#endif + #ifdef CONFIG_FUNCTION_TRACER #define MCOUNT_ADDR ((unsigned long)(__gnu_mcount_nc)) #define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S index c73c403..93f9abb 100644 --- a/arch/arm/kernel/entry-ftrace.S +++ b/arch/arm/kernel/entry-ftrace.S @@ -92,12 +92,78 @@ 2: mcount_exit .endm +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + +.macro __ftrace_regs_caller + + sub sp, sp, #8 @ space for CPSR and OLD_R0 (not used) + + add ip, sp, #12 @ move in IP the value of SP as it was + @ before the push {lr} of the mcount mechanism + stmdb sp!, {ip,lr,pc} + stmdb sp!, {r0-r11,lr} + + ldr r0, [sp, #S_LR] @ replace PC with LR + str r0, [sp, #S_PC] @ into pt_regs + + ldr r1, [sp, #PT_REGS_SIZE] @ replace new LR with + str r1, [sp, #S_LR] @ previous LR into pt_regs + + @ stack content at this point: + @ 0 4 48 52 56 60 64 68 72 + @ R0 | R1 | ... | LR | SP + 4 | previous LR | LR | PSR | OLD_R0 | previous LR | + + mov r3, sp @ struct pt_regs* + ldr r2, =function_trace_op + ldr r2, [r2] @ pointer to the current + @ function tracing op + ldr r1, [sp, #PT_REGS_SIZE] @ lr of instrumented func + mcount_adjust_addr r0, lr @ instrumented function + + .globl ftrace_regs_call +ftrace_regs_call: + bl ftrace_stub + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + .globl ftrace_graph_regs_call +ftrace_graph_regs_call: + mov r0, r0 +#endif + @ pop saved regs + ldmia sp, {r0-r15} +.endm + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +.macro __ftrace_graph_regs_caller + + sub r0, fp, #4 @ lr of instrumented routine (parent) + + @ called from __ftrace_regs_caller + ldr r1, [sp, #S_PC] @ instrumented routine (func) + mcount_adjust_addr r1, r1 + + mov r2, fp @ frame pointer + bl prepare_ftrace_return + + @ pop registers saved in ftrace_regs_caller + ldmia sp, {r0-r15} +.endm +#endif +#endif + .macro __ftrace_caller suffix mcount_enter mcount_get_lr r1 @ lr of instrumented func mcount_adjust_addr r0, lr @ instrumented function +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + ldr r2, =function_trace_op + ldr r2, [r2] @ pointer to the current + @ function tracing op + mov r3, #0 @ regs is NULL +#endif + .globl ftrace_call\suffix ftrace_call\suffix: bl ftrace_stub @@ -212,6 +278,15 @@ UNWIND(.fnstart) __ftrace_caller UNWIND(.fnend) ENDPROC(ftrace_caller) + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS +ENTRY(ftrace_regs_caller) +UNWIND(.fnstart) + __ftrace_regs_caller +UNWIND(.fnend) +ENDPROC(ftrace_regs_caller) +#endif + #endif #ifdef CONFIG_FUNCTION_GRAPH_TRACER @@ -220,6 +295,14 @@ UNWIND(.fnstart) __ftrace_graph_caller UNWIND(.fnend) ENDPROC(ftrace_graph_caller) + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS +ENTRY(ftrace_graph_regs_caller) +UNWIND(.fnstart) + __ftrace_graph_regs_caller +UNWIND(.fnend) +ENDPROC(ftrace_graph_regs_caller) +#endif #endif .purgem mcount_enter diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c index 3f17594..f165265 100644 --- a/arch/arm/kernel/ftrace.c +++ b/arch/arm/kernel/ftrace.c @@ -29,11 +29,6 @@ #endif #ifdef CONFIG_DYNAMIC_FTRACE -#ifdef CONFIG_OLD_MCOUNT -#define OLD_MCOUNT_ADDR ((unsigned long) mcount) -#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) - -#define OLD_NOP 0xe1a00000 /* mov r0, r0 */ static int __ftrace_modify_code(void *data) { @@ -51,6 +46,12 @@ void arch_ftrace_update_code(int command) stop_machine(__ftrace_modify_code, &command, NULL); } +#ifdef CONFIG_OLD_MCOUNT +#define OLD_MCOUNT_ADDR ((unsigned long) mcount) +#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) + +#define OLD_NOP 0xe1a00000 /* mov r0, r0 */ + static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) { return rec->arch.old_mcount ? OLD_NOP : NOP; @@ -139,6 +140,15 @@ int ftrace_update_ftrace_func(ftrace_func_t func) ret = ftrace_modify_code(pc, 0, new, false); +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + if (!ret) { + pc = (unsigned long)&ftrace_regs_call; + new = ftrace_call_replace(pc, (unsigned long)func); + + ret = ftrace_modify_code(pc, 0, new, false); + } +#endif + #ifdef CONFIG_OLD_MCOUNT if (!ret) { pc = (unsigned long)&ftrace_call_old; @@ -157,11 +167,29 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) unsigned long ip = rec->ip; old = ftrace_nop_replace(rec); + new = ftrace_call_replace(ip, adjust_address(rec, addr)); return ftrace_modify_code(rec->ip, old, new, true); } +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, + unsigned long addr) +{ + unsigned long new, old; + unsigned long ip = rec->ip; + + old = ftrace_call_replace(ip, adjust_address(rec, old_addr)); + + new = ftrace_call_replace(ip, adjust_address(rec, addr)); + + return ftrace_modify_code(rec->ip, old, new, true); +} + +#endif + int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { @@ -229,6 +257,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, extern unsigned long ftrace_graph_call; extern unsigned long ftrace_graph_call_old; extern void ftrace_graph_caller_old(void); +extern unsigned long ftrace_graph_regs_call; +extern void ftrace_graph_regs_caller(void); static int __ftrace_modify_caller(unsigned long *callsite, void (*func) (void), bool enable) @@ -251,6 +281,14 @@ static int ftrace_modify_graph_caller(bool enable) ftrace_graph_caller, enable); +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + if (!ret) + ret = __ftrace_modify_caller(&ftrace_graph_regs_call, + ftrace_graph_regs_caller, + enable); +#endif + + #ifdef CONFIG_OLD_MCOUNT if (!ret) ret = __ftrace_modify_caller(&ftrace_graph_call_old,
The DYNAMIC_FTRACE_WITH_REGS configuration makes it possible for a ftrace operation to specify if registers need to saved/restored by the ftrace handler. This is needed by kgraft and possibly other ftrace-based tools, and the ARM architecture is currently lacking this feature. It would also be the first step to support the "Kprobes-on-ftrace" optimization on ARM. This patch introduces a new ftrace handler that stores the registers on the stack before calling the next stage. The registers are restored from the stack before going back to the instrumented function. A side-effect of this patch is to activate the support for ftrace_modify_call() as it defines ARCH_SUPPORTS_FTRACE_OPS for the ARM architecture. Signed-off-by: Abel Vesa <abelvesa@linux.com> --- arch/arm/Kconfig | 1 + arch/arm/include/asm/ftrace.h | 4 ++ arch/arm/kernel/entry-ftrace.S | 83 ++++++++++++++++++++++++++++++++++++++++++ arch/arm/kernel/ftrace.c | 48 +++++++++++++++++++++--- 4 files changed, 131 insertions(+), 5 deletions(-)