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powerpc/lib: Add helper to check if offset is within conditional branch range

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Add a helper to check if a given offset is within the branch range for a
powerpc conditional branch instruction, and update some sites to use the
new helper.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/442b69a34ced32ca346a0d9a855f3f6cfdbbbd41.1633464148.git.naveen.n.rao@linux.vnet.ibm.com
This commit is contained in:
Naveen N. Rao 2021-10-06 01:55:20 +05:30 committed by Michael Ellerman
parent 23c216b335
commit 4549c3ea31
3 changed files with 8 additions and 7 deletions
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1
arch/powerpc/include/asm/code-patching.h
View File

@ -23,6 +23,7 @@
#define BRANCH_ABSOLUTE 0x2
bool is_offset_in_branch_range(long offset);
bool is_offset_in_cond_branch_range(long offset);
int create_branch(struct ppc_inst *instr, const u32 *addr,
unsigned long target, int flags);
int create_cond_branch(struct ppc_inst *instr, const u32 *addr,

7
arch/powerpc/lib/code-patching.c
View File

@ -228,6 +228,11 @@ bool is_offset_in_branch_range(long offset)
return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
}
bool is_offset_in_cond_branch_range(long offset)
{
return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3);
}
/*
* Helper to check if a given instruction is a conditional branch
* Derived from the conditional checks in analyse_instr()
@ -280,7 +285,7 @@ int create_cond_branch(struct ppc_inst *instr, const u32 *addr,
offset = offset - (unsigned long)addr;
/* Check we can represent the target in the instruction format */
if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
if (!is_offset_in_cond_branch_range(offset))
return 1;
/* Mask out the flags and target, so they don't step on each other. */

7
arch/powerpc/net/bpf_jit.h
View File

@ -78,11 +78,6 @@
#define PPC_FUNC_ADDR(d,i) do { PPC_LI32(d, i); } while(0)
#endif
static inline bool is_nearbranch(int offset)
{
return (offset < 32768) && (offset >= -32768);
}
/*
* The fly in the ointment of code size changing from pass to pass is
* avoided by padding the short branch case with a NOP. If code size differs
@ -91,7 +86,7 @@ static inline bool is_nearbranch(int offset)
* state.
*/
#define PPC_BCC(cond, dest) do { \
if (is_nearbranch((dest) - (ctx->idx * 4))) { \
if (is_offset_in_cond_branch_range((long)(dest) - (ctx->idx * 4))) { \
PPC_BCC_SHORT(cond, dest); \
EMIT(PPC_RAW_NOP()); \
} else { \