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Commit 377fad3a authored by Jeff Dike's avatar Jeff Dike Committed by Linus Torvalds
Browse files

uml: kernel segfaults should dump proper registers 



If there's a segfault inside the kernel, we want a dump of the registers at
the point of the segfault, not the registers at the point of calling panic or
the last userspace registers.

sig_handler_common_skas now uses a static register set in the case of a
SIGSEGV to avoid messing up the process registers if the segfault turns out to
be non-fatal.

The architecture sigcontext-to-pt_regs copying code was repurposed to copy
data out of the SEGV stack frame.

Signed-off-by: default avatarJeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5d86456d

arch/um/include/common-offsets.h

+2 −0
Original line number Diff line number Diff line
@@ -24,5 +24,7 @@ DEFINE(UM_ELF_CLASS, ELF_CLASS); 
DEFINE(UM_ELFCLASS32, ELFCLASS32);

DEFINE(UM_ELFCLASS64, ELFCLASS64);



DEFINE(UM_NR_CPUS, NR_CPUS);



/* For crypto assembler code. */

DEFINE(crypto_tfm_ctx_offset, offsetof(struct crypto_tfm, __crt_ctx));

arch/um/include/kern_util.h

+2 −0
Original line number Diff line number Diff line
@@ -115,4 +115,6 @@ extern void time_init_kern(void); 
extern int __cant_sleep(void);

extern void sigio_handler(int sig, union uml_pt_regs *regs);



extern void copy_sc(union uml_pt_regs *regs, void *from);



#endif

arch/um/kernel/trap.c

+7 −3
Original line number Diff line number Diff line
@@ -170,8 +170,10 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, 
		flush_tlb_kernel_vm();

		return 0;

	}

	else if(current->mm == NULL)

	else if(current->mm == NULL) {

		show_regs(container_of(regs, struct pt_regs, regs));

  		panic("Segfault with no mm");

	}



	if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))

		err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
@@ -194,9 +196,11 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, 
	else if(!is_user && arch_fixup(ip, regs))

		return 0;



	if(!is_user)

	if(!is_user) {

		show_regs(container_of(regs, struct pt_regs, regs));

		panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",

		      address, ip);

	}



	if (err == -EACCES) {

		si.si_signo = SIGBUS;

arch/um/os-Linux/skas/trap.c

+13 −2
Original line number Diff line number Diff line
@@ -15,6 +15,8 @@ 
#include "sysdep/ptrace_user.h"

#include "os.h"



static union uml_pt_regs ksig_regs[UM_NR_CPUS];



void sig_handler_common_skas(int sig, void *sc_ptr)

{

	struct sigcontext *sc = sc_ptr;
@@ -27,10 +29,19 @@ void sig_handler_common_skas(int sig, void *sc_ptr) 
	 * the process will die.

	 * XXX Figure out why this is better than SA_NODEFER

	 */

	if(sig == SIGSEGV)

	if(sig == SIGSEGV) {

		change_sig(SIGSEGV, 1);

		/* For segfaults, we want the data from the

		 * sigcontext.  In this case, we don't want to mangle

		 * the process registers, so use a static set of

		 * registers.  For other signals, the process

		 * registers are OK.

		 */

		r = &ksig_regs[cpu()];

		copy_sc(r, sc_ptr);

	}

	else r = TASK_REGS(get_current());



	r = TASK_REGS(get_current());

	save_user = r->skas.is_user;

	r->skas.is_user = 0;

	if ( sig == SIGFPE || sig == SIGSEGV ||

arch/um/sys-i386/signal.c

+24 −17
Original line number Diff line number Diff line
@@ -18,6 +18,28 @@ 


#include "skas.h"



void copy_sc(union uml_pt_regs *regs, void *from)

{

	struct sigcontext *sc = from;



	REGS_GS(regs->skas.regs) = sc->gs;

	REGS_FS(regs->skas.regs) = sc->fs;

	REGS_ES(regs->skas.regs) = sc->es;

	REGS_DS(regs->skas.regs) = sc->ds;

	REGS_EDI(regs->skas.regs) = sc->edi;

	REGS_ESI(regs->skas.regs) = sc->esi;

	REGS_EBP(regs->skas.regs) = sc->ebp;

	REGS_SP(regs->skas.regs) = sc->esp;

	REGS_EBX(regs->skas.regs) = sc->ebx;

	REGS_EDX(regs->skas.regs) = sc->edx;

	REGS_ECX(regs->skas.regs) = sc->ecx;

	REGS_EAX(regs->skas.regs) = sc->eax;

	REGS_IP(regs->skas.regs) = sc->eip;

	REGS_CS(regs->skas.regs) = sc->cs;

	REGS_EFLAGS(regs->skas.regs) = sc->eflags;

	REGS_SS(regs->skas.regs) = sc->ss;

}



static int copy_sc_from_user_skas(struct pt_regs *regs,

				  struct sigcontext __user *from)

{
@@ -30,22 +52,7 @@ static int copy_sc_from_user_skas(struct pt_regs *regs, 
	if(err)

		return err;



	REGS_GS(regs->regs.skas.regs) = sc.gs;

	REGS_FS(regs->regs.skas.regs) = sc.fs;

	REGS_ES(regs->regs.skas.regs) = sc.es;

	REGS_DS(regs->regs.skas.regs) = sc.ds;

	REGS_EDI(regs->regs.skas.regs) = sc.edi;

	REGS_ESI(regs->regs.skas.regs) = sc.esi;

	REGS_EBP(regs->regs.skas.regs) = sc.ebp;

	REGS_SP(regs->regs.skas.regs) = sc.esp;

	REGS_EBX(regs->regs.skas.regs) = sc.ebx;

	REGS_EDX(regs->regs.skas.regs) = sc.edx;

	REGS_ECX(regs->regs.skas.regs) = sc.ecx;

	REGS_EAX(regs->regs.skas.regs) = sc.eax;

	REGS_IP(regs->regs.skas.regs) = sc.eip;

	REGS_CS(regs->regs.skas.regs) = sc.cs;

	REGS_EFLAGS(regs->regs.skas.regs) = sc.eflags;

	REGS_SS(regs->regs.skas.regs) = sc.ss;

	copy_sc(&regs->regs, &sc);



	err = restore_fp_registers(userspace_pid[0], fpregs);

	if(err < 0) {