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From cb1bf2f321b45a06447133b3db00621b7300c456 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Mon, 2 Nov 2015 12:39:28 -0500
Subject: [PATCH] properly access mcontext_t program counter in cancellation
handler
using the actual mcontext_t definition rather than an overlaid pointer
array both improves correctness/readability and eliminates some ugly
hacks for archs with 64-bit registers bit 32-bit program counter.
also fix UB due to comparison of pointers not in a common array
object.
---
arch/aarch64/pthread_arch.h | 2 +-
arch/arm/pthread_arch.h | 2 +-
arch/i386/pthread_arch.h | 2 +-
arch/microblaze/pthread_arch.h | 2 +-
arch/mips/pthread_arch.h | 2 +-
arch/or1k/pthread_arch.h | 3 +--
arch/powerpc/pthread_arch.h | 3 +--
arch/sh/pthread_arch.h | 2 +-
arch/x32/pthread_arch.h | 2 +-
arch/x86_64/pthread_arch.h | 2 +-
src/thread/pthread_cancel.c | 7 ++++---
11 files changed, 14 insertions(+), 15 deletions(-)
diff --git a/arch/aarch64/pthread_arch.h b/arch/aarch64/pthread_arch.h
index 74276f4..b2e2d8f 100644
--- a/arch/aarch64/pthread_arch.h
+++ b/arch/aarch64/pthread_arch.h
@@ -8,4 +8,4 @@ static inline struct pthread *__pthread_self()
#define TLS_ABOVE_TP
#define TP_ADJ(p) ((char *)(p) + sizeof(struct pthread) - 16)
-#define CANCEL_REG_IP 33
+#define MC_PC pc
diff --git a/arch/arm/pthread_arch.h b/arch/arm/pthread_arch.h
index 4a4dd09..8b8a7fb 100644
--- a/arch/arm/pthread_arch.h
+++ b/arch/arm/pthread_arch.h
@@ -27,4 +27,4 @@ static inline pthread_t __pthread_self()
#define TLS_ABOVE_TP
#define TP_ADJ(p) ((char *)(p) + sizeof(struct pthread) - 8)
-#define CANCEL_REG_IP 18
+#define MC_PC arm_pc
diff --git a/arch/i386/pthread_arch.h b/arch/i386/pthread_arch.h
index 1c06c76..7f38a56 100644
--- a/arch/i386/pthread_arch.h
+++ b/arch/i386/pthread_arch.h
@@ -7,4 +7,4 @@ static inline struct pthread *__pthread_self()
#define TP_ADJ(p) (p)
-#define CANCEL_REG_IP 14
+#define MC_PC gregs[REG_EIP]
diff --git a/arch/microblaze/pthread_arch.h b/arch/microblaze/pthread_arch.h
index 259d3d6..08d1ba7 100644
--- a/arch/microblaze/pthread_arch.h
+++ b/arch/microblaze/pthread_arch.h
@@ -7,4 +7,4 @@ static inline struct pthread *__pthread_self()
#define TP_ADJ(p) (p)
-#define CANCEL_REG_IP 32
+#define MC_PC regs.pc
diff --git a/arch/mips/pthread_arch.h b/arch/mips/pthread_arch.h
index 93edbd4..8a49965 100644
--- a/arch/mips/pthread_arch.h
+++ b/arch/mips/pthread_arch.h
@@ -16,4 +16,4 @@ static inline struct pthread *__pthread_self()
#define DTP_OFFSET 0x8000
-#define CANCEL_REG_IP (3-(union {int __i; char __b;}){1}.__b)
+#define MC_PC pc
diff --git a/arch/or1k/pthread_arch.h b/arch/or1k/pthread_arch.h
index ad63169..7decd76 100644
--- a/arch/or1k/pthread_arch.h
+++ b/arch/or1k/pthread_arch.h
@@ -14,5 +14,4 @@ static inline struct pthread *__pthread_self()
#define TLS_ABOVE_TP
#define TP_ADJ(p) ((char *)(p) + sizeof(struct pthread))
-/* word-offset to 'pc' in mcontext_t */
-#define CANCEL_REG_IP 32
+#define MC_PC regs.pc
diff --git a/arch/powerpc/pthread_arch.h b/arch/powerpc/pthread_arch.h
index bb7405d..7c5c4fa 100644
--- a/arch/powerpc/pthread_arch.h
+++ b/arch/powerpc/pthread_arch.h
@@ -15,9 +15,8 @@ static inline struct pthread *__pthread_self()
#define DTP_OFFSET 0x8000
-// offset of the PC register in mcontext_t, divided by the system wordsize
// the kernel calls the ip "nip", it's the first saved value after the 32
// GPRs.
-#define CANCEL_REG_IP 32
+#define MC_PC gregs[32]
#define CANARY canary_at_end
diff --git a/arch/sh/pthread_arch.h b/arch/sh/pthread_arch.h
index 65c389f..2756e7e 100644
--- a/arch/sh/pthread_arch.h
+++ b/arch/sh/pthread_arch.h
@@ -8,4 +8,4 @@ static inline struct pthread *__pthread_self()
#define TLS_ABOVE_TP
#define TP_ADJ(p) ((char *)(p) + sizeof(struct pthread) - 8)
-#define CANCEL_REG_IP 17
+#define MC_PC sc_pc
diff --git a/arch/x32/pthread_arch.h b/arch/x32/pthread_arch.h
index 033bfd6..ecb0bbf 100644
--- a/arch/x32/pthread_arch.h
+++ b/arch/x32/pthread_arch.h
@@ -7,6 +7,6 @@ static inline struct pthread *__pthread_self()
#define TP_ADJ(p) (p)
-#define CANCEL_REG_IP 32
+#define MC_PC gregs[REG_RIP]
#define CANARY canary2
diff --git a/arch/x86_64/pthread_arch.h b/arch/x86_64/pthread_arch.h
index 29e4590..c61509c 100644
--- a/arch/x86_64/pthread_arch.h
+++ b/arch/x86_64/pthread_arch.h
@@ -7,4 +7,4 @@ static inline struct pthread *__pthread_self()
#define TP_ADJ(p) (p)
-#define CANCEL_REG_IP 16
+#define MC_PC gregs[REG_RIP]
diff --git a/src/thread/pthread_cancel.c b/src/thread/pthread_cancel.c
index 0151a1a..6eaf72c 100644
--- a/src/thread/pthread_cancel.c
+++ b/src/thread/pthread_cancel.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
#include <string.h>
#include "pthread_impl.h"
#include "syscall.h"
@@ -61,15 +62,15 @@ static void cancel_handler(int sig, siginfo_t *si, void *ctx)
{
pthread_t self = __pthread_self();
ucontext_t *uc = ctx;
- const char *ip = ((char **)&uc->uc_mcontext)[CANCEL_REG_IP];
+ uintptr_t pc = uc->uc_mcontext.MC_PC;
a_barrier();
if (!self->cancel || self->canceldisable == PTHREAD_CANCEL_DISABLE) return;
_sigaddset(&uc->uc_sigmask, SIGCANCEL);
- if (self->cancelasync || ip >= __cp_begin && ip < __cp_end) {
- ((char **)&uc->uc_mcontext)[CANCEL_REG_IP] = (char *)__cp_cancel;
+ if (self->cancelasync || pc >= (uintptr_t)__cp_begin && pc < (uintptr_t)__cp_end) {
+ uc->uc_mcontext.MC_PC = (uintptr_t)__cp_cancel;
return;
}
--
2.7.0
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