Re: [PATCH 2/2] UML - Fix x86_64 core dump crash

[Andrew Morton]

On Wed, 22 Aug 2007 17:25:30 -0400
Jeff Dike <jdike@xxxxxxxxxxx> wrote:

> --- linux-2.6.22.orig/arch/um/os-Linux/sys-x86_64/registers.c	2007-08-22 16:55:38.000000000 -0400
> +++ linux-2.6.22/arch/um/os-Linux/sys-x86_64/registers.c	2007-08-22 16:56:20.000000000 -0400
> @@ -3,11 +3,27 @@
>   * Licensed under the GPL
>   */
>  
> +#include <errno.h>
> +#include <sys/ptrace.h>
>  #define __FRAME_OFFSETS
>  #include <asm/ptrace.h>
>  #include "longjmp.h"
>  #include "user.h"
>  
> +int save_fp_registers(int pid, unsigned long *fp_regs)
> +{
> +	if(ptrace(PTRACE_GETFPREGS, pid, 0, fp_regs) < 0)
> +		return -errno;
> +	return 0;
> +}
> +
> +int restore_fp_registers(int pid, unsigned long *fp_regs)
> +{
> +	if(ptrace(PTRACE_SETFPREGS, pid, 0, fp_regs) < 0)
> +		return -errno;
> +	return 0;
> +}
> +
>  unsigned long get_thread_reg(int reg, jmp_buf *buf)

This doesn't apply to current mainline in ways which I'm not entirely
comfortable fixing.  (it assumes the presence of queued-for-2.6.24 things).


Does the below still work?


From: Jeff Dike <jdike@xxxxxxxxxxx>

Stop UML crashing when trying to dump a process core on x86_64.  This is the
minimal fix to stop the crash - more things are broken here, and patches are
forthcoming.

The immediate thing to do is define ELF_CORE_COPY_REGS and
ELF_CORE_COPY_FPREGS.  Defining ELF_CORE_COPY_FPREGS allows dump_fpu to go
away.  It is defined in terms of save_fp_registers, so that needs to be added.

Signed-off-by: Jeff Dike <jdike@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 arch/um/os-Linux/sys-x86_64/registers.c |   15 ++++++++
 arch/um/sys-x86_64/ptrace.c             |    6 ---
 include/asm-um/elf-x86_64.h             |   40 ++++++++++++++++++++++
 3 files changed, 55 insertions(+), 6 deletions(-)

diff -puN arch/um/os-Linux/sys-x86_64/registers.c~uml-fix-x86_64-core-dump-crash arch/um/os-Linux/sys-x86_64/registers.c
--- a/arch/um/os-Linux/sys-x86_64/registers.c~uml-fix-x86_64-core-dump-crash
+++ a/arch/um/os-Linux/sys-x86_64/registers.c
@@ -4,6 +4,7 @@
  */
 
 #include <errno.h>
+#include <sys/ptrace.h>
 #include <string.h>
 #include "ptrace_user.h"
 #include "uml-config.h"
@@ -17,6 +18,20 @@
 static unsigned long exec_regs[MAX_REG_NR];
 static unsigned long exec_fp_regs[HOST_FP_SIZE];
 
+int save_fp_registers(int pid, unsigned long *fp_regs)
+{
+	if(ptrace(PTRACE_GETFPREGS, pid, 0, fp_regs) < 0)
+		return -errno;
+	return 0;
+}
+
+int restore_fp_registers(int pid, unsigned long *fp_regs)
+{
+	if(ptrace(PTRACE_SETFPREGS, pid, 0, fp_regs) < 0)
+		return -errno;
+	return 0;
+}
+
 void init_thread_registers(union uml_pt_regs *to)
 {
 	memcpy(to->skas.regs, exec_regs, sizeof(to->skas.regs));
diff -puN arch/um/sys-x86_64/ptrace.c~uml-fix-x86_64-core-dump-crash arch/um/sys-x86_64/ptrace.c
--- a/arch/um/sys-x86_64/ptrace.c~uml-fix-x86_64-core-dump-crash
+++ a/arch/um/sys-x86_64/ptrace.c
@@ -156,12 +156,6 @@ int is_syscall(unsigned long addr)
 	return(instr == 0x050f);
 }
 
-int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu )
-{
-	panic("dump_fpu");
-	return(1);
-}
-
 int get_fpregs(unsigned long buf, struct task_struct *child)
 {
 	panic("get_fpregs");
diff -puN include/asm-um/elf-x86_64.h~uml-fix-x86_64-core-dump-crash include/asm-um/elf-x86_64.h
--- a/include/asm-um/elf-x86_64.h~uml-fix-x86_64-core-dump-crash
+++ a/include/asm-um/elf-x86_64.h
@@ -6,7 +6,9 @@
 #ifndef __UM_ELF_X86_64_H
 #define __UM_ELF_X86_64_H
 
+#include <linux/sched.h>
 #include <asm/user.h>
+#include "skas.h"
 
 /* x86-64 relocation types, taken from asm-x86_64/elf.h */
 #define R_X86_64_NONE		0	/* No reloc */
@@ -64,6 +66,44 @@ typedef struct { } elf_fpregset_t;
 	PT_REGS_R15(regs) = 0; \
 } while (0)
 
+#define ELF_CORE_COPY_REGS(pr_reg, regs)		\
+	(pr_reg)[0] = (regs)->regs.gp[0];			\
+	(pr_reg)[1] = (regs)->regs.gp[1];			\
+	(pr_reg)[2] = (regs)->regs.gp[2];			\
+	(pr_reg)[3] = (regs)->regs.gp[3];			\
+	(pr_reg)[4] = (regs)->regs.gp[4];			\
+	(pr_reg)[5] = (regs)->regs.gp[5];			\
+	(pr_reg)[6] = (regs)->regs.gp[6];			\
+	(pr_reg)[7] = (regs)->regs.gp[7];			\
+	(pr_reg)[8] = (regs)->regs.gp[8];			\
+	(pr_reg)[9] = (regs)->regs.gp[9];			\
+	(pr_reg)[10] = (regs)->regs.gp[10];			\
+	(pr_reg)[11] = (regs)->regs.gp[11];			\
+	(pr_reg)[12] = (regs)->regs.gp[12];			\
+	(pr_reg)[13] = (regs)->regs.gp[13];			\
+	(pr_reg)[14] = (regs)->regs.gp[14];			\
+	(pr_reg)[15] = (regs)->regs.gp[15];			\
+	(pr_reg)[16] = (regs)->regs.gp[16];			\
+	(pr_reg)[17] = (regs)->regs.gp[17];			\
+	(pr_reg)[18] = (regs)->regs.gp[18];			\
+	(pr_reg)[19] = (regs)->regs.gp[19];			\
+	(pr_reg)[20] = (regs)->regs.gp[20];			\
+	(pr_reg)[21] = current->thread.arch.fs;			\
+	(pr_reg)[22] = 0;					\
+	(pr_reg)[23] = 0;					\
+	(pr_reg)[24] = 0;					\
+	(pr_reg)[25] = 0;					\
+	(pr_reg)[26] = 0;
+
+static inline int elf_core_copy_fpregs(struct task_struct *t,
+				       elf_fpregset_t *fpu)
+{
+	int cpu = current_thread->cpu;
+	return save_fp_registers(userspace_pid[cpu], (unsigned long *) fpu);
+}
+
+#define ELF_CORE_COPY_FPREGS(t, fpu) elf_core_copy_fpregs(t, fpu)
+
 #ifdef TIF_IA32 /* XXX */
 #error XXX, indeed
         clear_thread_flag(TIF_IA32);
_

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