From e3ccff0cab08c0487b8a3caa84ee0b46461fc38f Mon Sep 17 00:00:00 2001
From: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Date: Thu, 27 Jul 2017 12:56:00 +0530
Subject: [PATCH] kpatch-build: Support gcc-6 function prologue
With gcc-6 the function prologue is changeg by
moving the toc base resolution func - 0x8 bytes:
.globl my_func
.type my_func, @function
.quad .TOC.-my_func
my_func:
.reloc ., R_PPC64_ENTRY ; optional
ld r2,-8(r12)
add r2,r2,r12
.localentry my_func, .-my_func
Add support for function prologue, along with gcc-5.
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
---
kpatch-build/create-diff-object.c | 21 ++++++++++++
kpatch-build/create-klp-module.c | 14 +++++++-
kpatch-build/kpatch-elf.c | 53 +++++++++++++++++++++++++++++--
kpatch-build/kpatch-elf.h | 4 +++
4 files changed, 89 insertions(+), 3 deletions(-)
diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
index 0bc5cca..56cd166 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -2253,6 +2253,27 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
*/
sym_objname = objname;
+ /*
+ * function prologue generated by gcc6 on ppc64le has
+ * the sequence:
+ *
+ * .globl my_func
+ * .type my_func, @function
+ * .quad .TOC.-my_func
+ * my_func:
+ * .reloc ., R_PPC64_ENTRY ; optional
+ * ld r2,-8(r12)
+ * add r2,r2,r12
+ * .localentry my_func, .-my_func
+ *
+ * first entry past function global entry point is optional
+ * and has the relocation type R_PPC64_ENTRY. We should *not*
+ * skip this entry while building up the rela list, rather
+ * skip it's lookup.
+ */
+ if (rela->type == R_PPC64_ENTRY)
+ continue;
+
if (rela->sym->bind == STB_LOCAL) {
/* An unchanged local symbol */
ret = lookup_local_symbol(table,
diff --git a/kpatch-build/create-klp-module.c b/kpatch-build/create-klp-module.c
index 046f2f4..9c1187e 100644
--- a/kpatch-build/create-klp-module.c
+++ b/kpatch-build/create-klp-module.c
@@ -243,7 +243,19 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
rela->offset = toc_offset;
else
rela->offset = krelas[index].offset;
- rela->addend = krelas[index].addend;
+
+ /*
+ * gcc6 adds offset for 0x8 for every local function entry in
+ * .toc section, for avoiding setup of toc but when the previously
+ * local function becomes global, toc is anyways setup. So remove
+ * the wrong addend.
+ */
+ if (!strcmp(base->name, ".toc") &&
+ rela->sym->type == STT_FUNC && rela->sym->bind == STB_LOCAL) {
+ rela->addend = 0;
+ } else {
+ rela->addend = krelas[index].addend;
+ }
}
}
diff --git a/kpatch-build/kpatch-elf.c b/kpatch-build/kpatch-elf.c
index 9b80e14..bd249de 100644
--- a/kpatch-build/kpatch-elf.c
+++ b/kpatch-build/kpatch-elf.c
@@ -76,6 +76,50 @@ int is_debug_section(struct section *sec)
!strncmp(name, ".eh_frame", 9);
}
+#ifdef __powerpc__
+
+/* Symbol st_others value for powerpc */
+#define STO_PPC64_LOCAL_BIT 5
+#define STO_PPC64_LOCAL_MASK (7 << STO_PPC64_LOCAL_BIT)
+#define PPC64_LOCAL_ENTRY_OFFSET(other) \
+ (((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)
+
+/*
+ * function prologue generated by gcc6 on ppc64le has
+ * the sequence:
+ *
+ * .globl my_func
+ * .type my_func, @function
+ * .quad .TOC.-my_func
+ * my_func:
+ * .reloc ., R_PPC64_ENTRY ; optional
+ * ld r2,-8(r12)
+ * add r2,r2,r12
+ * .localentry my_func, .-my_func
+ *
+ * my_func is resolved by .TOC.-my_func to a 64-bit offset stored
+ * above the global entry point. my_func st_value is set 0x8, for
+ * calling into the .localentry of the function.
+ *
+ * Number of instructions between global and local entry point of a
+ * function is mostly 8 instructions. i.e st_other == 3. The count of
+ * instruction can be decoded only for local function symbols.
+ */
+static int is_localentry_sym(struct symbol *sym)
+{
+ if (sym->type != STT_FUNC || sym->sym.st_shndx == SHN_UNDEF)
+ return 0;
+
+ if (sym->sym.st_value != 0x8)
+ return 0;
+
+ if (!PPC64_LOCAL_ENTRY_OFFSET(sym->sym.st_other))
+ return 0;
+
+ return 1;
+}
+#endif
+
struct section *find_section_by_index(struct list_head *list, unsigned int index)
{
struct section *sec;
@@ -328,9 +372,14 @@ void kpatch_create_symbol_list(struct kpatch_elf *kelf)
sym->name);
if (is_bundleable(sym)) {
- if (sym->sym.st_value != 0)
+ if (sym->sym.st_value != 0) {
+#ifdef __powerpc__
+ if (!is_localentry_sym(sym))
+#endif
ERROR("symbol %s at offset %lu within section %s, expected 0",
- sym->name, sym->sym.st_value, sym->sec->name);
+ sym->name, sym->sym.st_value, sym->sec->name);
+ }
+
sym->sec->sym = sym;
} else if (sym->type == STT_SECTION) {
sym->sec->secsym = sym;
diff --git a/kpatch-build/kpatch-elf.h b/kpatch-build/kpatch-elf.h
index aa98688..e4b5b52 100644
--- a/kpatch-build/kpatch-elf.h
+++ b/kpatch-build/kpatch-elf.h
@@ -131,6 +131,10 @@ struct rela *find_rela_by_offset(struct section *relasec, unsigned int offset);
int offset_of_string(struct list_head *list, char *name);
+#ifndef R_PPC64_ENTRY
+#define R_PPC64_ENTRY 118
+#endif
+
/*************
* Functions
* **********/