On Thu, Aug 07, 2014 at 11:25:14PM +0200, Ralf Baechle wrote:
> On Wed, Aug 06, 2014 at 01:12:06PM -0400, Alan Cooper wrote:
>
> > Actually , there's no reason to write the second NOP when nop'ing the
> > mcount call site in a module. This was done to remove the stack adjust
> > instruction which only exists at this location for internal kernel
> > routines. The following diff seems like a simpler way to solve issue
> > #1:
>
> Oh?
>
> $ mips-linux-objdump -d --reloc net/sctp/sctp.ko
> [...]
> 00000000 <sctp_sm_lookup_event>:
> 0: 27bdffe8 addiu sp,sp,-24
> 4: afbf0014 sw ra,20(sp)
> 8: 3c030000 lui v1,0x0
> 8: R_MIPS_HI16 _mcount
> c: 24630000 addiu v1,v1,0
> c: R_MIPS_LO16 _mcount
> 10: 03e00821 move at,ra
> 14: 27ac0014 addiu t4,sp,20
> 18: 0060f809 jalr v1
> 1c: 27bdfff8 addiu sp,sp,-8 <====
> [...]
> 64: 27bd0018 addiu sp,sp,24
> 68: 03e00008 jr ra
> [...]
>
> So the stack adjustment also exists for modules.
>
> Or am I missunderstanding something?
>
> Ralf
>
We have a workaround for dynamic ftrace under 32bit mode back in Feburary. I thought
it is not good enough but maybe this is the right solution for issue #1 ?
Tony
commit d3167328b1bd63c22abb129a17fcb658e11c2a7b
Author: Jun-Ru Chang <jrjang@xxxxxxxxx>
Date: Thu Feb 27 15:23:34 2014 +0800
mips: ftrace: fix ftrace_make_call long call restore
In case of long call under 32bit mode, two instructions,
lui and addiu, are required to load the mcount address into
the jump register.
In ftrace_make_nop, both instructions are marked as nop, so
in ftrace_make_call, we have to restore both of them.
Signed-off-by: Jun-Ru Chang <jrjang@xxxxxxxxx>
Signed-off-by: Tony Wu <tung7970@xxxxxxxxx>
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 9bb8bcd..b12858c 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -61,6 +61,9 @@ static inline int in_kernel_space(unsigned long ip)
static unsigned int insn_jal_ftrace_caller __read_mostly;
static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
+#ifndef CONFIG_64BIT
+static unsigned int insn_add_v1_lo16_mcount __read_mostly;
+#endif
static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
static inline void ftrace_dyn_arch_init_insns(void)
@@ -73,6 +76,12 @@ static inline void ftrace_dyn_arch_init_insns(void)
buf = (u32 *)&insn_lui_v1_hi16_mcount;
UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
+#ifndef CONFIG_64BIT
+ /* addiu v1, vi, lo16_mcount */
+ buf = (u32 *)&insn_add_v1_lo16_mcount;
+ UASM_i_LA(&buf, v1, MCOUNT_ADDR);
+#endif
+
/* jal (ftrace_caller + 8), jump over the first two instruction */
buf = (u32 *)&insn_jal_ftrace_caller;
uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
@@ -180,7 +189,10 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
insn_lui_v1_hi16_mcount;
- return ftrace_modify_code(ip, new);
+ if (IS_BUILTIN(CONFIG_64BIT) || new == insn_jal_ftrace_caller)
+ return ftrace_modify_code(ip, new);
+ else
+ return ftrace_modify_code_2(ip, new, insn_add_v1_lo16_mcount);
}
#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
