linux-kernel - [PATCH v3 2/3] powerpc/module32: Use symbolic instructions names.

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Date:   Fri,  3 May 2019 06:40:16 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v3 2/3] powerpc/module32: Use symbolic instructions names.

To increase readability/maintainability, replace hard coded
instructions values by symbolic names.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
v3: no change
v2: Remove the ENTRY_JMP0 and ENTRY_JMP1 macros ; left real instructions as a comment.

 arch/powerpc/kernel/module_32.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/kernel/module_32.c b/arch/powerpc/kernel/module_32.c
index 88d83771f462..9cf201111d6c 100644
--- a/arch/powerpc/kernel/module_32.c
+++ b/arch/powerpc/kernel/module_32.c
@@ -172,10 +172,12 @@ int module_frob_arch_sections(Elf32_Ehdr *hdr,
 
 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 {
-	if (entry->jump[0] == 0x3d800000 + ((val + 0x8000) >> 16)
-	    && entry->jump[1] == 0x398c0000 + (val & 0xffff))
-		return 1;
-	return 0;
+	if (entry->jump[0] != (PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val)))
+		return 0;
+	if (entry->jump[1] != (PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) |
+			       PPC_LO(val)))
+		return 0;
+	return 1;
 }
 
 /* Set up a trampoline in the PLT to bounce us to the distant function */
@@ -200,10 +202,16 @@ static uint32_t do_plt_call(void *location,
 		entry++;
 	}
 
-	entry->jump[0] = 0x3d800000+((val+0x8000)>>16); /* lis r12,sym@ha */
-	entry->jump[1] = 0x398c0000 + (val&0xffff);     /* addi r12,r12,sym@l*/
-	entry->jump[2] = 0x7d8903a6;                    /* mtctr r12 */
-	entry->jump[3] = 0x4e800420;			/* bctr */
+	/*
+	 * lis r12, sym@ha
+	 * addi r12, r12, sym@l
+	 * mtctr r12
+	 * bctr
+	 */
+	entry->jump[0] = PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val);
+	entry->jump[1] = PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) | PPC_LO(val);
+	entry->jump[2] = PPC_INST_MTCTR | __PPC_RS(R12);
+	entry->jump[3] = PPC_INST_BCTR;
 
 	pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
 	return (uint32_t)entry;
-- 
2.13.3