| From cb4ae699b10e57c1c7185cefff39857e624a347c Mon Sep 17 00:00:00 2001 |
| From: Vasily Gorbik <gor@linux.ibm.com> |
| Date: Tue, 10 Dec 2019 14:33:39 +0100 |
| Subject: [PATCH] s390/ftrace: generate traced function stack frame |
| |
| commit 45f7a0da600d3c409b5ad8d5ddddacd98ddc8840 upstream. |
| |
| Currently backtrace from ftraced function does not contain ftraced |
| function itself. e.g. for "path_openat": |
| |
| arch_stack_walk+0x15c/0x2d8 |
| stack_trace_save+0x50/0x68 |
| stack_trace_call+0x15e/0x3d8 |
| ftrace_graph_caller+0x0/0x1c <-- ftrace code |
| do_filp_open+0x7c/0xe8 <-- ftraced function caller |
| do_open_execat+0x76/0x1b8 |
| open_exec+0x52/0x78 |
| load_elf_binary+0x180/0x1160 |
| search_binary_handler+0x8e/0x288 |
| load_script+0x2a8/0x2b8 |
| search_binary_handler+0x8e/0x288 |
| __do_execve_file.isra.39+0x6fa/0xb40 |
| __s390x_sys_execve+0x56/0x68 |
| system_call+0xdc/0x2d8 |
| |
| Ftraced function is expected in the backtrace by ftrace kselftests, which |
| are now failing. It would also be nice to have it for clarity reasons. |
| |
| "ftrace_caller" itself is called without stack frame allocated for it |
| and does not store its caller (ftraced function). Instead it simply |
| allocates a stack frame for "ftrace_trace_function" and sets backchain |
| to point to ftraced function stack frame (which contains ftraced function |
| caller in saved r14). |
| |
| To fix this issue make "ftrace_caller" allocate a stack frame |
| for itself just to store ftraced function for the stack unwinder. |
| As a result backtrace looks like the following: |
| |
| arch_stack_walk+0x15c/0x2d8 |
| stack_trace_save+0x50/0x68 |
| stack_trace_call+0x15e/0x3d8 |
| ftrace_graph_caller+0x0/0x1c <-- ftrace code |
| path_openat+0x6/0xd60 <-- ftraced function |
| do_filp_open+0x7c/0xe8 <-- ftraced function caller |
| do_open_execat+0x76/0x1b8 |
| open_exec+0x52/0x78 |
| load_elf_binary+0x180/0x1160 |
| search_binary_handler+0x8e/0x288 |
| load_script+0x2a8/0x2b8 |
| search_binary_handler+0x8e/0x288 |
| __do_execve_file.isra.39+0x6fa/0xb40 |
| __s390x_sys_execve+0x56/0x68 |
| system_call+0xdc/0x2d8 |
| |
| Reported-by: Sven Schnelle <sven.schnelle@ibm.com> |
| Tested-by: Sven Schnelle <sven.schnelle@ibm.com> |
| Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> |
| Signed-off-by: Vasily Gorbik <gor@linux.ibm.com> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S |
| index 9e1660a6b9db..3431b2d5e334 100644 |
| --- a/arch/s390/kernel/mcount.S |
| +++ b/arch/s390/kernel/mcount.S |
| @@ -26,6 +26,12 @@ ENDPROC(ftrace_stub) |
| #define STACK_PTREGS (STACK_FRAME_OVERHEAD) |
| #define STACK_PTREGS_GPRS (STACK_PTREGS + __PT_GPRS) |
| #define STACK_PTREGS_PSW (STACK_PTREGS + __PT_PSW) |
| +#ifdef __PACK_STACK |
| +/* allocate just enough for r14, r15 and backchain */ |
| +#define TRACED_FUNC_FRAME_SIZE 24 |
| +#else |
| +#define TRACED_FUNC_FRAME_SIZE STACK_FRAME_OVERHEAD |
| +#endif |
| |
| ENTRY(_mcount) |
| BR_EX %r14 |
| @@ -39,9 +45,16 @@ ENTRY(ftrace_caller) |
| #if !(defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT)) |
| aghi %r0,MCOUNT_RETURN_FIXUP |
| #endif |
| - aghi %r15,-STACK_FRAME_SIZE |
| + # allocate stack frame for ftrace_caller to contain traced function |
| + aghi %r15,-TRACED_FUNC_FRAME_SIZE |
| stg %r1,__SF_BACKCHAIN(%r15) |
| + stg %r0,(__SF_GPRS+8*8)(%r15) |
| + stg %r15,(__SF_GPRS+9*8)(%r15) |
| + # allocate pt_regs and stack frame for ftrace_trace_function |
| + aghi %r15,-STACK_FRAME_SIZE |
| stg %r1,(STACK_PTREGS_GPRS+15*8)(%r15) |
| + aghi %r1,-TRACED_FUNC_FRAME_SIZE |
| + stg %r1,__SF_BACKCHAIN(%r15) |
| stg %r0,(STACK_PTREGS_PSW+8)(%r15) |
| stmg %r2,%r14,(STACK_PTREGS_GPRS+2*8)(%r15) |
| #ifdef CONFIG_HAVE_MARCH_Z196_FEATURES |
| -- |
| 2.7.4 |
| |
