[PATCH v2 0/4] Support new MIPSr6 relocations

[PATCH v2 0/4] Support new MIPSr6 relocations

[Paul Burton]

MIPSr6 introduced a few new relocations that may be present in loadable
kernel modules. This series introduces support for them in both their
rel & rela forms for MIPS32 & MIPS64 kernels respectively, and ensures
that any future missing relocs cause module loading to fail gracefully.

Paul Burton (3):
  MIPS: Bail on unsupported module relocs
  MIPS: Support R_MIPS_PC{21,26} rela-style relocs
  MIPS: Support R_MIPS_PC{16,21,26} rel-style relocs

Steven J. Hill (1):
  MIPS: module: Make consistent use of pr_*()

 arch/mips/include/asm/elf.h    |  5 +++
 arch/mips/kernel/module-rela.c | 75 +++++++++++++++++++++++++++++++++++-----
 arch/mips/kernel/module.c      | 77 +++++++++++++++++++++++++++++++++++++-----
 3 files changed, 140 insertions(+), 17 deletions(-)

-- 
2.7.0

[PATCH v2 1/4] MIPS: Bail on unsupported module relocs

[Paul Burton]

When an unsupported reloc is encountered in a module, we currently
blindly branch to whatever would be at its entry in the reloc handler
function pointer arrays. This may be NULL, or if the unsupported reloc
has a type greater than that of the supported reloc with the highest
type then we'll dereference some value after the function pointer array
& branch to that. The result is at best a kernel oops.

Fix this by checking that the reloc type has an entry in the function
pointer array (ie. is less than the number of items in the array) and
that the handler is non-NULL, returning an error code to fail the module
load if no handler is found.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>

---

Changes in v2:
- Use pr_err instead of pr_warn.

 arch/mips/kernel/module-rela.c | 19 ++++++++++++++++---
 arch/mips/kernel/module.c      | 19 ++++++++++++++++---
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/arch/mips/kernel/module-rela.c b/arch/mips/kernel/module-rela.c
index 2b70723..9083d63 100644
--- a/arch/mips/kernel/module-rela.c
+++ b/arch/mips/kernel/module-rela.c
@@ -109,9 +109,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 		       struct module *me)
 {
 	Elf_Mips_Rela *rel = (void *) sechdrs[relsec].sh_addr;
+	int (*handler)(struct module *me, u32 *location, Elf_Addr v);
 	Elf_Sym *sym;
 	u32 *location;
-	unsigned int i;
+	unsigned int i, type;
 	Elf_Addr v;
 	int res;
 
@@ -134,9 +135,21 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 			return -ENOENT;
 		}
 
-		v = sym->st_value + rel[i].r_addend;
+		type = ELF_MIPS_R_TYPE(rel[i]);
+
+		if (type < ARRAY_SIZE(reloc_handlers_rela))
+			handler = reloc_handlers_rela[type];
+		else
+			handler = NULL;
 
-		res = reloc_handlers_rela[ELF_MIPS_R_TYPE(rel[i])](me, location, v);
+		if (!handler) {
+			pr_err("%s: Unknown relocation type %u\n",
+			       me->name, type);
+			return -EINVAL;
+		}
+
+		v = sym->st_value + rel[i].r_addend;
+		res = handler(me, location, v);
 		if (res)
 			return res;
 	}
diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
index 1833f51..f9b2936 100644
--- a/arch/mips/kernel/module.c
+++ b/arch/mips/kernel/module.c
@@ -197,9 +197,10 @@ int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
 		   struct module *me)
 {
 	Elf_Mips_Rel *rel = (void *) sechdrs[relsec].sh_addr;
+	int (*handler)(struct module *me, u32 *location, Elf_Addr v);
 	Elf_Sym *sym;
 	u32 *location;
-	unsigned int i;
+	unsigned int i, type;
 	Elf_Addr v;
 	int res;
 
@@ -223,9 +224,21 @@ int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
 			return -ENOENT;
 		}
 
-		v = sym->st_value;
+		type = ELF_MIPS_R_TYPE(rel[i]);
+
+		if (type < ARRAY_SIZE(reloc_handlers_rel))
+			handler = reloc_handlers_rel[type];
+		else
+			handler = NULL;
 
-		res = reloc_handlers_rel[ELF_MIPS_R_TYPE(rel[i])](me, location, v);
+		if (!handler) {
+			pr_err("%s: Unknown relocation type %u\n",
+			       me->name, type);
+			return -EINVAL;
+		}
+
+		v = sym->st_value;
+		res = handler(me, location, v);
 		if (res)
 			return res;
 	}
-- 
2.7.0

[PATCH v2 2/4] MIPS: module: Make consistent use of pr_*()

[Paul Burton]

From: "Steven J. Hill" <Steven.Hill@imgtec.com>

The module relocation handling code has inconsistent use of printk() and
pr_*() functions. Convert printk() calls to use pr_err() and pr_warn().

[paul.burton@imgtec.com: Do the same thing in module.c]

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>

---

Changes in v2:
- Do the same in module.c.

 arch/mips/kernel/module-rela.c | 8 +++-----
 arch/mips/kernel/module.c      | 7 +++----
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/mips/kernel/module-rela.c b/arch/mips/kernel/module-rela.c
index 9083d63..0570676 100644
--- a/arch/mips/kernel/module-rela.c
+++ b/arch/mips/kernel/module-rela.c
@@ -35,15 +35,13 @@ static int apply_r_mips_32_rela(struct module *me, u32 *location, Elf_Addr v)
 static int apply_r_mips_26_rela(struct module *me, u32 *location, Elf_Addr v)
 {
 	if (v % 4) {
-		pr_err("module %s: dangerous R_MIPS_26 RELArelocation\n",
+		pr_err("module %s: dangerous R_MIPS_26 RELA relocation\n",
 		       me->name);
 		return -ENOEXEC;
 	}
 
 	if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
-		printk(KERN_ERR
-		       "module %s: relocation overflow\n",
-		       me->name);
+		pr_err("module %s: relocation overflow\n", me->name);
 		return -ENOEXEC;
 	}
 
@@ -130,7 +128,7 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 			/* Ignore unresolved weak symbol */
 			if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
 				continue;
-			printk(KERN_WARNING "%s: Unknown symbol %s\n",
+			pr_warn("%s: Unknown symbol %s\n",
 			       me->name, strtab + sym->st_name);
 			return -ENOENT;
 		}
diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
index f9b2936..e16624f 100644
--- a/arch/mips/kernel/module.c
+++ b/arch/mips/kernel/module.c
@@ -73,8 +73,7 @@ static int apply_r_mips_26_rel(struct module *me, u32 *location, Elf_Addr v)
 	}
 
 	if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
-		printk(KERN_ERR
-		       "module %s: relocation overflow\n",
+		pr_err("module %s: relocation overflow\n",
 		       me->name);
 		return -ENOEXEC;
 	}
@@ -219,8 +218,8 @@ int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
 			/* Ignore unresolved weak symbol */
 			if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
 				continue;
-			printk(KERN_WARNING "%s: Unknown symbol %s\n",
-			       me->name, strtab + sym->st_name);
+			pr_warn("%s: Unknown symbol %s\n",
+				me->name, strtab + sym->st_name);
 			return -ENOENT;
 		}
 
-- 
2.7.0

[PATCH v2 3/4] MIPS: Support R_MIPS_PC{21,26} rela-style relocs

[Paul Burton]

MIPS64 code uses rela-style relocs, and MIPS64r6 modules may include the
new R_MIPS_PC21 & R_MIPS_PC26 relocations. We thus need to support these
relocations in order to load MIPS64r6 kernel modules. They are similar
to the existing R_MIPS_PC16 relocation but applying to a wider field.
Implement support for them by genericising the existing R_MIPS_PC16
implementation such that it can be used for different field widths, and
calling it for all 3 reloc types.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
---

Changes in v2: None

 arch/mips/include/asm/elf.h    |  5 +++++
 arch/mips/kernel/module-rela.c | 48 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index cefb7a5..7cec234 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -111,6 +111,11 @@
 #define R_MIPS_CALLHI16		30
 #define R_MIPS_CALLLO16		31
 /*
+ * Introduced for MIPSr6.
+ */
+#define R_MIPS_PC21_S2		60
+#define R_MIPS_PC26_S2		61
+/*
  * This range is reserved for vendor specific relocations.
  */
 #define R_MIPS_LOVENDOR		100
diff --git a/arch/mips/kernel/module-rela.c b/arch/mips/kernel/module-rela.c
index 0570676..b361142 100644
--- a/arch/mips/kernel/module-rela.c
+++ b/arch/mips/kernel/module-rela.c
@@ -16,6 +16,7 @@
  *  Copyright (C) 2001 Rusty Russell.
  *  Copyright (C) 2003, 2004 Ralf Baechle (ralf@linux-mips.org)
  *  Copyright (C) 2005 Thiemo Seufer
+ *  Copyright (C) 2015 Imagination Technologies Ltd.
  */
 
 #include <linux/elf.h>
@@ -65,6 +66,48 @@ static int apply_r_mips_lo16_rela(struct module *me, u32 *location, Elf_Addr v)
 	return 0;
 }
 
+static int apply_r_mips_pc_rela(struct module *me, u32 *location, Elf_Addr v,
+				unsigned bits)
+{
+	unsigned long mask = GENMASK(bits - 1, 0);
+	unsigned long se_bits;
+	long offset;
+
+	if (v % 4) {
+		pr_err("module %s: dangerous R_MIPS_PC%u RELA relocation\n",
+		       me->name, bits);
+		return -ENOEXEC;
+	}
+
+	offset = ((long)v - (long)location) >> 2;
+
+	/* check the sign bit onwards are identical - ie. we didn't overflow */
+	se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
+	if ((offset & ~mask) != (se_bits & ~mask)) {
+		pr_err("module %s: relocation overflow\n", me->name);
+		return -ENOEXEC;
+	}
+
+	*location = (*location & ~mask) | (offset & mask);
+
+	return 0;
+}
+
+static int apply_r_mips_pc16_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+	return apply_r_mips_pc_rela(me, location, v, 16);
+}
+
+static int apply_r_mips_pc21_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+	return apply_r_mips_pc_rela(me, location, v, 21);
+}
+
+static int apply_r_mips_pc26_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+	return apply_r_mips_pc_rela(me, location, v, 26);
+}
+
 static int apply_r_mips_64_rela(struct module *me, u32 *location, Elf_Addr v)
 {
 	*(Elf_Addr *)location = v;
@@ -97,9 +140,12 @@ static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
 	[R_MIPS_26]		= apply_r_mips_26_rela,
 	[R_MIPS_HI16]		= apply_r_mips_hi16_rela,
 	[R_MIPS_LO16]		= apply_r_mips_lo16_rela,
+	[R_MIPS_PC16]		= apply_r_mips_pc16_rela,
 	[R_MIPS_64]		= apply_r_mips_64_rela,
 	[R_MIPS_HIGHER]		= apply_r_mips_higher_rela,
-	[R_MIPS_HIGHEST]	= apply_r_mips_highest_rela
+	[R_MIPS_HIGHEST]	= apply_r_mips_highest_rela,
+	[R_MIPS_PC21_S2]	= apply_r_mips_pc21_rela,
+	[R_MIPS_PC26_S2]	= apply_r_mips_pc26_rela,
 };
 
 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
-- 
2.7.0

[PATCH v2 4/4] MIPS: Support R_MIPS_PC{16,21,26} rel-style relocs

[Paul Burton]

MIPS32 code uses rel-style relocs, and MIPS32r6 modules may include
R_MIPS_PC16, R_MIPS_PC21 & R_MIPS_PC26 relocations. We thus need to
support these relocations in order to load MIPS32r6 kernel modules. This
patch adds such support, which is similar to the rela-style support in
module-rela.c but making use of the implicit addend from the instruction
encoding.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>

---

Changes in v2:
- Unify PC{16,21,26} implementation.

 arch/mips/kernel/module.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
index e16624f..ff5d97d 100644
--- a/arch/mips/kernel/module.c
+++ b/arch/mips/kernel/module.c
@@ -182,13 +182,62 @@ out_danger:
 	return -ENOEXEC;
 }
 
+static int apply_r_mips_pc_rel(struct module *me, u32 *location, Elf_Addr v,
+			       unsigned bits)
+{
+	unsigned long mask = GENMASK(bits - 1, 0);
+	unsigned long se_bits;
+	long offset;
+
+	if (v % 4) {
+		pr_err("module %s: dangerous R_MIPS_PC%u REL relocation\n",
+		       me->name, bits);
+		return -ENOEXEC;
+	}
+
+	/* retrieve & sign extend implicit addend */
+	offset = *location & mask;
+	offset |= (offset & BIT(bits - 1)) ? ~mask : 0;
+
+	offset += ((long)v - (long)location) >> 2;
+
+	/* check the sign bit onwards are identical - ie. we didn't overflow */
+	se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
+	if ((offset & ~mask) != (se_bits & ~mask)) {
+		pr_err("module %s: relocation overflow\n", me->name);
+		return -ENOEXEC;
+	}
+
+	*location = (*location & ~mask) | (offset & mask);
+
+	return 0;
+}
+
+static int apply_r_mips_pc16_rel(struct module *me, u32 *location, Elf_Addr v)
+{
+	return apply_r_mips_pc_rel(me, location, v, 16);
+}
+
+static int apply_r_mips_pc21_rel(struct module *me, u32 *location, Elf_Addr v)
+{
+	return apply_r_mips_pc_rel(me, location, v, 21);
+}
+
+static int apply_r_mips_pc26_rel(struct module *me, u32 *location, Elf_Addr v)
+{
+	return apply_r_mips_pc_rel(me, location, v, 26);
+}
+
 static int (*reloc_handlers_rel[]) (struct module *me, u32 *location,
 				Elf_Addr v) = {
 	[R_MIPS_NONE]		= apply_r_mips_none,
 	[R_MIPS_32]		= apply_r_mips_32_rel,
 	[R_MIPS_26]		= apply_r_mips_26_rel,
 	[R_MIPS_HI16]		= apply_r_mips_hi16_rel,
-	[R_MIPS_LO16]		= apply_r_mips_lo16_rel
+	[R_MIPS_LO16]		= apply_r_mips_lo16_rel,
+	[R_MIPS_PC16]		= apply_r_mips_pc16_rel,
+	[R_MIPS_PC21_S2]	= apply_r_mips_pc21_rel,
+	[R_MIPS_PC26_S2]	= apply_r_mips_pc26_rel,
 };
 
 int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
-- 
2.7.0