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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/kernel/entry.S | |
parent | 2809b392a62ae307da058a52d451b2fc3ce4de7e (diff) | |
download | linux-stable-6ca6366220ed285e29ee22f4cf5c68a0397cb005.tar.gz linux-stable-6ca6366220ed285e29ee22f4cf5c68a0397cb005.tar.bz2 linux-stable-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/kernel/entry.S')
-rw-r--r-- | arch/parisc/kernel/entry.S | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index 89c801c2b5d1..3e430590c1e1 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -2012,6 +2012,70 @@ ftrace_stub: #endif ENDPROC_CFI(mcount) +#ifdef CONFIG_DYNAMIC_FTRACE + +#ifdef CONFIG_64BIT +#define FTRACE_FRAME_SIZE (2*FRAME_SIZE) +#else +#define FTRACE_FRAME_SIZE FRAME_SIZE +#endif +ENTRY_CFI(ftrace_caller, caller,frame=FTRACE_FRAME_SIZE,CALLS,SAVE_RP,SAVE_SP) +ftrace_caller: + .global ftrace_caller + + STREG %r3, -FTRACE_FRAME_SIZE+1*REG_SZ(%sp) + ldo -FTRACE_FRAME_SIZE(%sp), %r3 + STREG %rp, -RP_OFFSET(%r3) + + /* Offset 0 is already allocated for %r1 */ + STREG %r23, 2*REG_SZ(%r3) + STREG %r24, 3*REG_SZ(%r3) + STREG %r25, 4*REG_SZ(%r3) + STREG %r26, 5*REG_SZ(%r3) + STREG %r28, 6*REG_SZ(%r3) + STREG %r29, 7*REG_SZ(%r3) +#ifdef CONFIG_64BIT + STREG %r19, 8*REG_SZ(%r3) + STREG %r20, 9*REG_SZ(%r3) + STREG %r21, 10*REG_SZ(%r3) + STREG %r22, 11*REG_SZ(%r3) + STREG %r27, 12*REG_SZ(%r3) + STREG %r31, 13*REG_SZ(%r3) + loadgp + ldo -16(%sp),%r29 +#endif + LDREG 0(%r3), %r25 + copy %rp, %r26 + ldo -8(%r25), %r25 + b,l ftrace_function_trampoline, %rp + copy %r3, %r24 + + LDREG -RP_OFFSET(%r3), %rp + LDREG 2*REG_SZ(%r3), %r23 + LDREG 3*REG_SZ(%r3), %r24 + LDREG 4*REG_SZ(%r3), %r25 + LDREG 5*REG_SZ(%r3), %r26 + LDREG 6*REG_SZ(%r3), %r28 + LDREG 7*REG_SZ(%r3), %r29 +#ifdef CONFIG_64BIT + LDREG 8*REG_SZ(%r3), %r19 + LDREG 9*REG_SZ(%r3), %r20 + LDREG 10*REG_SZ(%r3), %r21 + LDREG 11*REG_SZ(%r3), %r22 + LDREG 12*REG_SZ(%r3), %r27 + LDREG 13*REG_SZ(%r3), %r31 +#endif + LDREG 1*REG_SZ(%r3), %r3 + + LDREGM -FTRACE_FRAME_SIZE(%sp), %r1 + /* Adjust return point to jump back to beginning of traced function */ + ldo -4(%r1), %r1 + bv,n (%r1) + +ENDPROC_CFI(ftrace_caller) + +#endif + #ifdef CONFIG_FUNCTION_GRAPH_TRACER .align 8 ENTRY_CFI(return_to_handler, caller,frame=FRAME_SIZE) |