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author | Sven Schnelle <svens@stackframe.org> | 2019-06-05 22:32:22 +0200 |
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committer | Helge Deller <deller@gmx.de> | 2019-06-08 12:56:29 +0200 |
commit | 6ca6366220ed285e29ee22f4cf5c68a0397cb005 (patch) | |
tree | e6ba9bb5f0eeab4e10205cbb479189237bee72c1 /arch/parisc/include | |
parent | 2809b392a62ae307da058a52d451b2fc3ce4de7e (diff) | |
download | linux-6ca6366220ed285e29ee22f4cf5c68a0397cb005.tar.gz linux-6ca6366220ed285e29ee22f4cf5c68a0397cb005.tar.bz2 linux-6ca6366220ed285e29ee22f4cf5c68a0397cb005.zip |
parisc: add dynamic ftrace
This patch implements dynamic ftrace for PA-RISC. The required mcount
call sequences can get pretty long, so instead of patching the
whole call sequence out of the functions, we are using
-fpatchable-function-entry from gcc. This puts a configurable amount of
NOPS before/at the start of the function. Taking do_sys_open() as example,
which would look like this when the call is patched out:
1036b248: 08 00 02 40 nop
1036b24c: 08 00 02 40 nop
1036b250: 08 00 02 40 nop
1036b254: 08 00 02 40 nop
1036b258 <do_sys_open>:
1036b258: 08 00 02 40 nop
1036b25c: 08 03 02 41 copy r3,r1
1036b260: 6b c2 3f d9 stw rp,-14(sp)
1036b264: 08 1e 02 43 copy sp,r3
1036b268: 6f c1 01 00 stw,ma r1,80(sp)
When ftrace gets enabled for this function the kernel will patch these
NOPs to:
1036b248: 10 19 57 20 <address of ftrace>
1036b24c: 6f c1 00 80 stw,ma r1,40(sp)
1036b250: 48 21 3f d1 ldw -18(r1),r1
1036b254: e8 20 c0 02 bv,n r0(r1)
1036b258 <do_sys_open>:
1036b258: e8 3f 1f df b,l,n .-c,r1
1036b25c: 08 03 02 41 copy r3,r1
1036b260: 6b c2 3f d9 stw rp,-14(sp)
1036b264: 08 1e 02 43 copy sp,r3
1036b268: 6f c1 01 00 stw,ma r1,80(sp)
So the first NOP in do_sys_open() will be patched to jump backwards into
some minimal trampoline code which pushes a stackframe, saves r1 which
holds the return address, loads the address of the real ftrace function,
and branches to that location. For 64 Bit things are getting a bit more
complicated (and longer) because we must make sure that the address of
ftrace location is 8 byte aligned, and the offset passed to ldd for
fetching the address is 8 byte aligned as well.
Note that gcc has a bug which misplaces the function label, and needs a
patch to make dynamic ftrace work. See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90751 for details.
Signed-off-by: Sven Schnelle <svens@stackframe.org>
Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to 'arch/parisc/include')
-rw-r--r-- | arch/parisc/include/asm/ftrace.h | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/arch/parisc/include/asm/ftrace.h b/arch/parisc/include/asm/ftrace.h index 42b2c75a1645..958c0aa5dbb2 100644 --- a/arch/parisc/include/asm/ftrace.h +++ b/arch/parisc/include/asm/ftrace.h @@ -5,12 +5,23 @@ #ifndef __ASSEMBLY__ extern void mcount(void); -#define MCOUNT_INSN_SIZE 4 - +#define MCOUNT_ADDR ((unsigned long)mcount) +#define MCOUNT_INSN_SIZE 4 +#define CC_USING_NOP_MCOUNT extern unsigned long sys_call_table[]; extern unsigned long return_address(unsigned int); +#ifdef CONFIG_DYNAMIC_FTRACE +extern void ftrace_caller(void); + +struct dyn_arch_ftrace { +}; + +unsigned long ftrace_call_adjust(unsigned long addr); + +#endif + #define ftrace_return_address(n) return_address(n) #endif /* __ASSEMBLY__ */ |