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selftests/seccomp: Remove SYSCALL_NUM_RET_SHARE_REG in favor of SYSCALL_RET_SET 

Instead of special-casing the specific case of shared registers, create
a default SYSCALL_RET_SET() macro (mirroring SYSCALL_NUM_SET()), that
writes to the SYSCALL_RET register. For architectures that can't set the
return value (for whatever reason), they can define SYSCALL_RET_SET()
without an associated SYSCALL_RET() macro. This also paves the way for
architectures that need to do special things to set the return value
(e.g. powerpc).

Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/lkml/20200912110820.597135-12-keescook@chromium.org
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
This commit is contained in:
Kees Cook 2020-09-12 04:08:16 -07:00
parent e4e8e5d28d
commit f04cf78bbf
1 changed files with 23 additions and 10 deletions
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33
tools/testing/selftests/seccomp/seccomp_bpf.c
View File

@ -1753,8 +1753,8 @@ TEST_F(TRACE_poke, getpid_runs_normally)
#elif defined(__s390__)
# define ARCH_REGS s390_regs
# define SYSCALL_NUM(_regs) (_regs).gprs[2]
# define SYSCALL_RET(_regs) (_regs).gprs[2]
# define SYSCALL_NUM_RET_SHARE_REG
# define SYSCALL_RET_SET(_regs, _val) \
TH_LOG("Can't modify syscall return on this architecture")
#elif defined(__mips__)
# include <asm/unistd_nr_n32.h>
# include <asm/unistd_nr_n64.h>
@ -1776,8 +1776,8 @@ TEST_F(TRACE_poke, getpid_runs_normally)
else \
(_regs).regs[2] = _nr; \
} while (0)
# define SYSCALL_RET(_regs) (_regs).regs[2]
# define SYSCALL_NUM_RET_SHARE_REG
# define SYSCALL_RET_SET(_regs, _val) \
TH_LOG("Can't modify syscall return on this architecture")
#elif defined(__xtensa__)
# define ARCH_REGS struct user_pt_regs
# define SYSCALL_NUM(_regs) (_regs).syscall
@ -1804,9 +1804,26 @@ TEST_F(TRACE_poke, getpid_runs_normally)
SYSCALL_NUM(_regs) = (_nr); \
} while (0)
#endif
/*
* Most architectures can change the syscall return value by just
* writing to the SYSCALL_RET register. This is the default if not
* defined above. If an architecture cannot set the return value
* (for example when the syscall and return value register is
* shared), report it with TH_LOG() in an arch-specific definition
* of SYSCALL_RET_SET() above, and leave SYSCALL_RET undefined.
*/
#if !defined(SYSCALL_RET) && !defined(SYSCALL_RET_SET)
# error "One of SYSCALL_RET or SYSCALL_RET_SET is needed for this arch"
#endif
#ifndef SYSCALL_RET_SET
# define SYSCALL_RET_SET(_regs, _val) \
do { \
SYSCALL_RET(_regs) = (_val); \
} while (0)
#endif
/* When the syscall return can't be changed, stub out the tests for it. */
#ifdef SYSCALL_NUM_RET_SHARE_REG
#ifndef SYSCALL_RET
# define EXPECT_SYSCALL_RETURN(val, action) EXPECT_EQ(-1, action)
#else
# define EXPECT_SYSCALL_RETURN(val, action) \
@ -1870,11 +1887,7 @@ void change_syscall(struct __test_metadata *_metadata,
/* If syscall is skipped, change return value. */
if (syscall == -1)
#ifdef SYSCALL_NUM_RET_SHARE_REG
TH_LOG("Can't modify syscall return on this architecture");
#else
SYSCALL_RET(regs) = result;
#endif
SYSCALL_RET_SET(regs, result);
/* Flush any register changes made. */
if (memcmp(&orig, &regs, sizeof(orig)) != 0)