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authorYang Zhang <yang.z.zhang@intel.com>2015-08-28 09:58:54 +0800
committerYang Zhang <yang.z.zhang@intel.com>2015-09-01 12:44:00 +0800
commite44e3482bdb4d0ebde2d8b41830ac2cdb07948fb (patch)
tree66b09f592c55df2878107a468a91d21506104d3f /qemu/roms/SLOF/lib/libc/README.txt
parent9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (diff)
Add qemu 2.4.0
Change-Id: Ic99cbad4b61f8b127b7dc74d04576c0bcbaaf4f5 Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
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+
+ Standard C library for the SLOF firmware project
+ ================================================
+
+To use this library, link your target against the "libc.a" archive.
+
+However, there are some prerequisites before you can use certain parts of the
+library:
+
+1) If you want to use malloc() and the like, you have to supply an implemen-
+ tation of sbrk() in your own code. malloc() uses sbrk() to get new, free
+ memory regions.
+
+ Prototype: void *sbrk(int incr);
+ Description: sbrk() increments the available data space by incr bytes and
+ returns a pointer to the start of the new area.
+
+ See the man-page of sbrk for details about this function.
+
+2) Before you can use the stdio output functions like printf(), puts() and the
+ like, you have to provide a standard write() function in your code.
+ printf() and the like use write() to print out the strings to the standard
+ output.
+
+ Prototype: ssize_t write(int fd, const void *buf, size_t cnt);
+ Description: Write cnt byte from the buffer buf to the stream associated
+ with the file descriptor fd.
+
+ The stdio functions will print their output to the stdout channel which is
+ assigned with the file descriptor 1 by default. Note that the stdio
+ functions will not use open() before calling write(), so if the stdout
+ cannel needs to be opened first, you should do that in your start-up code
+ before using the libc functions for the first time.
+
+3) Before you can use the stdio input functions like scanf() and the
+ like, you have to provide a standard read() function in your code.
+ scanf() and the like use read() to get the characters from the standard
+ input.
+
+ Prototype: ssize_t read(int fd, void *buf, size_t cnt);
+ Description: Read cnt byte from the stream associated with the file
+ descriptor fd and put them into the buffer buf.
+
+ The stdio functions will get their input from the stdin channel which is
+ assigned with the file descriptor 0 by default. Note that the stdio
+ functions will not use open() before calling read(), so if the stdin
+ cannel needs to be opened first, you should do that in your start-up code
+ before using the libc functions for the first time.
+