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| author | Michael Ellerman <mpe@ellerman.id.au> | 2016-03-24 14:04:05 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2016-04-14 08:48:06 +0300 |
| commit | 85baa095497f3e590df9f6c8932121f123efca5c (patch) | |
| tree | e05e3f82a00772249694c361a77efb593ac5781c /arch/powerpc/kernel/asm-offsets.c | |
| parent | 5d31a96e6c0187f2c5d7004e005fd094a1277e9e (diff) | |
| download | linux-85baa095497f3e590df9f6c8932121f123efca5c.tar.xz | |
powerpc/livepatch: Add live patching support on ppc64le
Add the kconfig logic & assembly support for handling live patched
functions. This depends on DYNAMIC_FTRACE_WITH_REGS, which in turn
depends on the new -mprofile-kernel ftrace ABI, which is only supported
currently on ppc64le.
Live patching is handled by a special ftrace handler. This means it runs
from ftrace_caller(). The live patch handler modifies the NIP so as to
redirect the return from ftrace_caller() to the new patched function.
However there is one particularly tricky case we need to handle.
If a function A calls another function B, and it is known at link time
that they share the same TOC, then A will not save or restore its TOC,
and will call the local entry point of B.
When we live patch B, we replace it with a new function C, which may
not have the same TOC as A. At live patch time it's too late to modify A
to do the TOC save/restore, so the live patching code must interpose
itself between A and C, and do the TOC save/restore that A omitted.
An additionaly complication is that the livepatch code can not create a
stack frame in order to save the TOC. That is because if C takes > 8
arguments, or is varargs, A will have written the arguments for C in
A's stack frame.
To solve this, we introduce a "livepatch stack" which grows upward from
the base of the regular stack, and is used to store the TOC & LR when
calling a live patched function.
When the patched function returns, we retrieve the real LR & TOC from
the livepatch stack, restore them, and pop the livepatch "stack frame".
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
Diffstat (limited to 'arch/powerpc/kernel/asm-offsets.c')
| -rw-r--r-- | arch/powerpc/kernel/asm-offsets.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 07cebc3514f3..723efac2d917 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -86,6 +86,10 @@ int main(void) DEFINE(KSP_LIMIT, offsetof(struct thread_struct, ksp_limit)); #endif /* CONFIG_PPC64 */ +#ifdef CONFIG_LIVEPATCH + DEFINE(TI_livepatch_sp, offsetof(struct thread_info, livepatch_sp)); +#endif + DEFINE(KSP, offsetof(struct thread_struct, ksp)); DEFINE(PT_REGS, offsetof(struct thread_struct, regs)); #ifdef CONFIG_BOOKE |