Messages in this thread | | | Subject | Re: [PATCH V2 2/4] powerpc: add helper to check if offset is within rel branch range | From | Anju T Sudhakar <> | Date | Fri, 16 Dec 2016 22:01:03 +0530 |
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Hi Masami,
Thank you for reviewing the patch set.
On Friday 16 December 2016 05:22 PM, Masami Hiramatsu wrote: > On Wed, 14 Dec 2016 21:48:30 +0530 > Anju T Sudhakar <anju@linux.vnet.ibm.com> wrote: > >> From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> >> > The coding is OK to me. Please add a description for this patch > here, e.g. what is done by this patch, what kind of branch > instruction will be covered, and why thse checks are needed etc.
Sure. I will give a description for this patch.
Thanks and Regards,
-Anju
> > Thank you, > >> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> >> Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com> >> --- >> arch/powerpc/include/asm/code-patching.h | 1 + >> arch/powerpc/lib/code-patching.c | 24 +++++++++++++++++++++++- >> 2 files changed, 24 insertions(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h >> index 2015b07..75ee4f4 100644 >> --- a/arch/powerpc/include/asm/code-patching.h >> +++ b/arch/powerpc/include/asm/code-patching.h >> @@ -22,6 +22,7 @@ >> #define BRANCH_SET_LINK 0x1 >> #define BRANCH_ABSOLUTE 0x2 >> >> +bool is_offset_in_branch_range(long offset); >> unsigned int create_branch(const unsigned int *addr, >> unsigned long target, int flags); >> unsigned int create_cond_branch(const unsigned int *addr, >> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c >> index d5edbeb..f643451 100644 >> --- a/arch/powerpc/lib/code-patching.c >> +++ b/arch/powerpc/lib/code-patching.c >> @@ -32,6 +32,28 @@ int patch_branch(unsigned int *addr, unsigned long target, int flags) >> return patch_instruction(addr, create_branch(addr, target, flags)); >> } >> >> +bool is_offset_in_branch_range(long offset) >> +{ >> + /* >> + * Powerpc branch instruction is : >> + * >> + * 0 6 30 31 >> + * +---------+----------------+---+---+ >> + * | opcode | LI |AA |LK | >> + * +---------+----------------+---+---+ >> + * Where AA = 0 and LK = 0 >> + * >> + * LI is a signed 24 bits integer. The real branch offset is computed >> + * by: imm32 = SignExtend(LI:'0b00', 32); >> + * >> + * So the maximum forward branch should be: >> + * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc >> + * The maximum backward branch should be: >> + * (0xff800000 << 2) = 0xfe000000 = -0x2000000 >> + */ >> + return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3)); >> +} >> + >> unsigned int create_branch(const unsigned int *addr, >> unsigned long target, int flags) >> { >> @@ -43,7 +65,7 @@ unsigned int create_branch(const unsigned int *addr, >> offset = offset - (unsigned long)addr; >> >> /* Check we can represent the target in the instruction format */ >> - if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3) >> + if (!is_offset_in_branch_range(offset)) >> return 0; >> >> /* Mask out the flags and target, so they don't step on each other. */ >> -- >> 2.7.4 >> >
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