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Bug/syscall clobber #280

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Merged
wipawel merged 3 commits into from
Aug 22, 2023
Merged

Bug/syscall clobber #280

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056d531
usermode: simpler syscall_return
sktt Aug 3, 2023
2623d74
usermode: syscall_handler clobbers rbp
sktt Aug 3, 2023
0de5d78
usermode: clobber all x64 registers.
sktt Aug 3, 2023
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7 changes: 1 addition & 6 deletions common/usermode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -49,12 +49,7 @@ static inline void syscall_restore(void) {
}

static inline long syscall_return(long return_code) {
/* clang-format off */
asm volatile(
"mov %[ret], %%" STR(_ASM_AX) "\n"
::[ret] "r"(return_code)
);
/* clang-format on */
asm volatile("" ::"a"(return_code));
return return_code;
}

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16 changes: 13 additions & 3 deletions include/arch/x86/asm-macros.h
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Original file line number Diff line number Diff line change
Expand Up @@ -266,15 +266,23 @@ name ## _end:
"push %%r9\n" \
"push %%r10\n" \
"push %%r11\n" \
"push %%r12\n" \
"push %%r13\n" \
"push %%r14\n" \
"push %%r15\n" \
::: "memory")

#define RESTORE_CLOBBERED_REGS64() \
asm volatile ( \
"pop %%" STR(r15) "\n" \
"pop %%" STR(r14) "\n" \
"pop %%" STR(r13) "\n" \
"pop %%" STR(r12) "\n" \
"pop %%" STR(r11) "\n" \
"pop %%" STR(r10) "\n" \
"pop %%" STR(r9) "\n" \
"pop %%" STR(r8) "\n" \
::: "r8", "r9", "r10", "r11")
::: "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15")
#else
#define SAVE_CLOBBERED_REGS64()
#define RESTORE_CLOBBERED_REGS64()
Expand All @@ -286,18 +294,20 @@ name ## _end:
"push %%" STR(_ASM_DX) "\n" \
"push %%" STR(_ASM_SI) "\n" \
"push %%" STR(_ASM_DI) "\n" \
"push %%" STR(_ASM_BP) "\n" \
::: "memory"); \
SAVE_CLOBBERED_REGS64()

#define RESTORE_CLOBBERED_REGS() \
RESTORE_CLOBBERED_REGS64(); \
asm volatile ( \
"pop %%" STR(_ASM_BP) "\n" \
"pop %%" STR(_ASM_DI) "\n" \
"pop %%" STR(_ASM_SI) "\n" \
"pop %%" STR(_ASM_DX) "\n" \
"pop %%" STR(_ASM_CX) "\n" \
::: STR(_ASM_DI), STR(_ASM_SI), \
STR(_ASM_DX), STR(_ASM_CX))
::: STR(_ASM_BP), STR(_ASM_DI), \
STR(_ASM_SI), STR(_ASM_DX), STR(_ASM_CX))
/* clang-format on */

#if defined(__x86_64__)
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